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DRAFT
ENVIRONMENTAL IMPACT STATEMENT
on
MANAGEMENT PLAN FOR WASTEWATER SLUDGE
BY METROPOLITAN DENVER SEWAGE DISPOSAL DISTRICT NO. 1
DENVER, COLORADO
EPA Project Number: C0080341
by
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION VIII, DENVER
May 1976
Approved By: John A. Green
Regional Administrate
&
Prepared under Contract Number 68-01-2860 between
Engineering-Science, Inc.
EPA and 600 Bancroft Way
Berkeley, California 94710
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Metropolitan Denver Sewage Disposal District No. 1
Denver, Colorado
EPA Project No. C-0030341
(x) Draft ( ) Final Environmental Impact Statement
1. Name of Action: (x) Administrative ( ) Legislative
2. Description of Action: The Metropolitan Denver Sewage Dispos-
al District No. 1 (Metro) has proposed to construct the necessary
facilities to transport sludge to a site in Adams County for air
drying in earthen basins, stockpiling in above-ground windrows and
distributing to the farming community to be reused on land for grow-
ing crops. It is envisioned that anaerobically digested sludge--
digester construction already being funded by EPA--in the
amount of 107 dry tons per year will be produced in the design
year 1985. The types of lands expected to receive sludge from
Metro include city parks in the metropolitan area, sod farms, mine
spoil sites, irrigated farms, nonirrigated farms and home gardens.
It is assumed that application rates will be consistent with the
nutrient uptake rate of the growing plants and that sludge applica-
tion on a given piece of land will be terminated when the heavy
metal loading limit specified for that particular land will have
been reached.
3. Environmental Impacts:
A. At the sludge drying and distribution center:
(1) Soil, as an agricultural resource, will be lost from
the 600-acre drying basins.
(2) Groundwater quality will gradually be deteriorated by
the leachates from the bottom of the drying basins, carrying salts,
including nitrates, to the water table.
(3) An increased amount of water over that now consumed in the
existing sludge disposal practices of Metro will be carried in sludge,
purge water and additional irrigation water to the Adams County site,
reducing flows in the South Platte River downstream of the Central Plant,
(4) A sizable saving in transport -energy (8 million KWH/
yr) will be realized over the current method of sludge disposal.
In addition, about 20 million KVJH/yr of equivalent energy will be
saved if all the sludge is successfully marketed to replace com-
mercial fertilizer. If the digester gases are converted into
usable energy, another major saving of 50 million KWH/yr will be
realized.
ing
ers
(5) Odors generated in the drying basins—especially dur-
digester upsets--may be objectionable to the surrounding farm-
and other residents.
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(6) Severe effects on soils, plants and the groundwater
would occur if the site were to be used for a disposal area.
B. At the sludge reuse areas:
(1) Introduction of heavy metal elements, particularly cad-
mium, into the soils and the food chain, and their gradual concen-
tration magnification in various tissues, poses a health hazard to
humans and possible reduction in yield of crops. These hazards are
the greatest in home gardens and on irrigated farms.
(2) Longevity of certain parasites such as Ascaris beyond
the drying/storage period comprises a public health hazard, espe-
cially in home gardens and city parks.
(3) Water quality degradation from salt and nitrate movement
below the root zone in home gardens, irrigated farms, city parks and
sod farms is a long-term, cumulative impact.
(4) Air quality may be degraded by particulates and aero-
sols during severe windstorms, especially in dry-farmed areas.
(5) Soil productivity will improve (although salinity will
gradually increase) with the addition of the organic matter in the
sludges, resulting in improved vegetative growth and crop produc-
tion.
(6) Conservation of natural resources, especially fossil
fuels and plant nutrients, is a prime reason for, and the most
salient beneficial impact of, the project.
C. At the Lowry Bombing Range sludge disposal area:
(1) Heavy metal elements are introduced into the food chain
through grazing of livestock on the sludge-amended fields.
(2) A potential public health hazard to the operators at
the Bombing Range is posed by the raw sludges now deposited.
(3) There is a threat to groundwater quality from the move-
ment of salts (particularly nitrates) below the root zone.
(4) Even though soil structure and water-holding capacity
will increase, excessive salt and nutrient loading rates will some-
what limit the increase in productivity.
(5) The sludge drying practices and transport method to carry
sludge to the Bombing Range use large amounts of energy.
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(6) Large amounts of chemicals are used to reduce odors
and dewater the sludge under present operation.
(7) The Metro Central Plant will experience increases in
loadings of suspended solids, BOD and ammonia due to return of
supernatant from the anaerobic digesters.
4. Alternatives: Sixteen alternatives, ranging from no action to
heat treatment-air drying-landfill to vacuum filtration-pipeline
transport and recycling with solid wastes were considered. They
are summarized in Tables 1 and 2.
5. Distribution: The distribution list is presented in Appendix H.
6. Draft Statement Sent to Council on Environmental Quality:
7. Final Statement Sent to Council on Environmental Quality: N.A.
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TABLE OF CONTENTS
List of Figures
List of Tables
Section
I BACKGROUND 1
Introduction 1
The Reason for This Document 2
History of the Project 5
The Proposed Action 7
Financing the Project 10
II ALTERNATIVES TO THE PROPOSED ACTION 11
Introduction 11
Historical Development of Alternatives 12
Comparative Evaluation of Sludge Treatment 14
System Alternatives
Sub-System Alternatives 22
Sub-System Alternatives to the Metro Land 22
Recycling Proposal
Sub-System Alternatives to the Present 32
Lowry Disposal System
III ENVIRONMENTAL SETTING 35
Climate 36
Temperature 36
Precipitation 36
Wind 36
Regional Climatic Variations 41
Topography 41
Geology - 44
Earthquakes 51
Soils 52
Water 54
Groundwater 54
Surface Water 55
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TABLE OF CONTENTS (Continued)
Section Page
Biology 56
Cultivated Lands Unit 58
Uplands Unit 59
Riparian and Aquatic Unit 59
Urban/Residential Unit 60
Rare and Endangered Species 61
Air Quality 64
Odor 68
Archaeology and History 71
Land Use 71
Land Tenure 73
Population 73
Regional Population 73
Metropolitan Denver Sewage Disposal Dis- 75
trict No. 1
Adams County 75
Population Projections 76
Transportation and Circulation 76
Recreation 80
Institutional and Governmental Agency Juris- 80
dictions
Socio-Economic Setting 82
Adams County Agricultural Economy 82
Sources of Fertilizer 82
Urban/Rural Characteristics 84
Land Values 84
Employment 86
Visual Aesthetics 86
Public Health 87
IV DESCRIPTION OF PROPOSED ACTION 39
Sludge Treatment 89
Sludge Transport System 91
Sludge Drying and Distribution Center 92
Sludge Drying and Distribution Center Site 92
Selection
Drying and Distribution Center Operation 93
and Layout
Proposed Land Application of Sludge by Metro 96
Denver
Sludge Recycling Areas 98
Sludge Disposal at Lowry Bombing Range 105
(No Action)
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TABLE OF CONTENTS (Continued)
Section
V ENVIRONMENTAL IMPACTS OF THE PROPOSED ACTION 109
Introduction 109
Impact of Sludge Processing, Transfer, 109
Drying and Distribution
Soil Loss 109
Water 110
Public Health 112
Loss of Habitat 117
Air Quality 117
Noise 120
Energy Use 121
Aesthetics 123
Plant Operation and Plant Effluent 124
Quality
Natural Resources 124
Archaeology and History 125
Land Use 126
Land Tenure 127
Population 127
Transportation and Circulation 127
Recreation 129
Governmental Agency Jurisdiction 130
Employment 130
Land Values 130
Construction Impacts 131
Secondary Impacts 132
Summary of Impacts at the Sludge Drying 135
and Distribution Center
Impacts of Land Application of Sludge on 137
the Recycling Areas
General 137
Food Chain 141
Public Health 143
Water Quality 145
Soil Properties 148
Air Quality 154
Flora and Fauna 156
Noise 162
Aesthetics - 162
Natural Resources 163
Traffic and Circulation 164
Agricultural Economy 164
Land Values 165
Summary of Land Application of Sludge on 165
the Recycling Areas
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TABLE OF CONTENTS (Continued)
Section Page
Impacts of Subsurface Injection of Liquid 166
Sludge at the Drying/Distribution Center
Impact of Sludge Disposal at Lowry Bombing 167
Range
Food Chain 167
Public Health 169
Plant Operation and Effluent Quality 169
Soil Properties 170
Water Quality 170
Flora and Fauna 171
Noise 174
Air Quality 175
Aesthetics 175
Traffic and Circulation 176
Public Reactions 176
Natural Resources 176
Land Use 176
Impact of Sludge Landfill ing at Lowry 177
Landfill
Soil Properties 177
Water Quality 177
Flora and Fauna 178
Air Quality 178
Explosive Gas Production 179
Land Use 179
Resources 179
Summary of Impacts of Sludge Disposal at 179
the Lowry Bombing Range
VI NEGATIVE IMPACTS AND RECOMMENDED MITIGATIVE 181
MEASURES
Processing, Transfer, Drying and Distribution 181
Groundwater Pollution by Nitrates and 181
Salts Leaching from Sludge Drying Basins
Surface Water Pollution from Experimental 182
Plots
Potential Threats to Public Health 182
Proliferation of Insect Vectors on Sludge 182
Drying Basins
Air Pollution from Particulate Matter of 182
Sludge Origin
Production of Nuisance Odors in Drying 182
Basins
Negative Public Reaction to Establishment 183
of the Drying and Distribution Center
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TABLE OF CONTENTS (Continued)
Section Page
Land Application in Sludge Recycling Areas 183
Heavy Metals Accumulation in Soil, 183
Plants, Animals and the Food Chain
Nitrate Pollution of Groundwater, Espe- 185
cially in Irrigated Farms, Sod Farms,
Home Gardens, City Parks
Nitrate Pollution and Eutrophication of 185
Lakes and Other Water Bodies
Air Pollution from Particulate Matter of 185
Sludge Origin
Exposure of Humans to Viable Pathogens 185
and Parasites
Exposure of Animals to Viable Pathogens 186
and Parasites
Odor 186
Adverse Public Reactions 186
Initial Toxicity of Liquid Sludge to 187
Seeds and Young Plants
Ingestion of Sludge from Foliage and Soil 187
Heavy Metals Accumulation in Soil, Plants, 187
Animals and the Food Chain
Possible Loss of Unique Vegetation Type 137
Possible Destruction of Rare and Endan- 187
gered Plant Species
Possible Loss of Black-Footed Ferret Habi- 188
tat
Initial Toxicity of Liquid Sludge to 188
Seeds and Young Plants
Air Pollution from Particulate Matter of 183
Sludge Origin
Reduction of Grazing Resource 138
Lowry Landfill 188
Removal of Uildlife Habitat 188
Groundwater Pollution 188
Explosive Gas Production 189
VII LONG-TERM CONSIDERATIONS 191
Adverse Impacts that Cannot J3e Avoided 191
Sludge Drying and Distribution Site 191
Land Application Sites for Recycling 192
Sludge
Lowry Bombing Range Sludge Disposal 193
Area (No Action)
vn
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TABLE OF CONTENTS (Continued)
Section Page
Irreversible and Irretrievable Resource 193
Commitments
Destruction of Soil Profile- 194
Energy Use 194
Groundwater Use as Receiving Medium 194
Application Site Soil Commitment 194
Relationship Between Short-Term Uses of the 194
Human Environment and the Maintenance and
Enhancement of Long-Term Productivity
Conservation of Non-Renewable and 195
Renewable Resources
Potential Cumulative Long-Term Environ- 196
mental Damage
The Long-Term Environmental Perspective 197
VIII COORDINATION WITH AGENCIES AND PUBLIC INVOLVEMENT 199
Governmental Agencies 199
Public Involvement 199
Public Reaction to Drying and Distribution 202
Site
Public Reaction to Land Application Sites 202
IX REFERENCES 203
Environmental Team 213
APPENDICES
Appendix
A Evaluation of Alternative Sludge Handling and A-l
Disposal Systems
B Soils B-l
C Biology C-l
D Sludge Application to Land D-l
E Environmental Settings of Drying and Distribu- E-l
tion Site and Specific Land Application
Sites for Metro Denver Sludge
F Examples of Approval for or Interest in the F-l
Proposed Project
G Summary of Impacts at Alternative Sludge Drying/ G-l
Distribution Sites
H Distribution List H-l
vm
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LIST OF FIGURES
Figure Page
1 Project area and example sludge application sites 8
2 Potential drying and distribution center sites 24
3 Irrigated and dryland farms, sod farms and parks 26
of the Denver area in relation to the sludge
distribution site
4 Generalized precipitation pattern in the Metropoli- 38
tan Denver region
5 Topography of project area 45
6 Geologic map of areas in the vicinity of Metropoli- 47
tan Denver
7 Soil associations in vicinity of Denver 53
8 Natural vegetation of Colorado 57
9 Summary of biotic community characteristics, Metro- 62
politan Denver area
10 Colorado Air Quality Control Regions 65
11 Annual frequencies of winds of various velocities 67
at Stapleton Airport, Denver, Colorado
12 Metropolitan Denver proposed sludge drying and dis- 94
tribution center
13 Ammonia and total Kjeldahl nitrogen concentration 95
as a percent of the total solids concentration
in three layers in air drying basins
14 Relationship between allowable sludge application 101
rate and uptake of mineralized nitrogen for
sludges containing different amounts of nitrogen
15 Annual sludge application rates 103
16 Summary of impacts at the proposed sludge drying 136
and distribution center for Metro Denver
17 Summary comparison of relative impacts of sludge 138
recycling on various land application sites in
the vicinity of Denver
18 Summary impacts of sludge disposal at the Lowry 168
Bombing Range
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LIST OF FIGURES (Continued)
Figure Page
A-l Process trains for various alternatives A-12
D-l Daily consumptive water use of crops grown near D-21
Denver, Colorado
E-l Sod farm and dryland wheat farm E-6
E-2 Soils on the sod farm and adjoining dryland farms £-7
in Adams County
E-3 Representative mine spoil site E-12
E-4 Representative agricultural reuse areas E-17
E-5 Lowry Bombing Range disposal area E-26
E-6 Soils of tne Lowry Bombing Range sludge disposal E-30
areas
Table
LIST OF TABLES
1 Summary of Sludge System Alternatives Evaluation 16
2 Final Sludge Handling Alternatives Comparison 20
3 Temperature, Precipitation, Snow and Freeze Data, 37
Denver (WB City)
4 Maximum Precipitation Frequency, Thunderstorm and 39
Relative Humidity Data, Denver
5 Wind Data, Denver (WB Airport) 40
6 Temperature, Precipitation, Snow and Freeze Data, 42
Denver (WB Airport) and Fort Lupton
7 Temperature, Precipitation, Snow and Freeze Data, 43
Cherry Creek Dam and Byers
8 Typical Elevations for Sites Within the Study Area 44
9 Stratigraphic Units and Their Water-Bearing Proper- 50
ties in the Vicinity of Denver
10 Population by County, 1970-1975 74
11 Population Growth Rates, Adams County 75
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.1ST OF TABLES (Continued)
Table Page
12 Selected Population Projections for Counties in 77
Vicinity of Metro Denver
13 Population Forecasts for the Five-County Denver 78
Region in the Year 2000
14 Population and Sludge Load Projections for Metro 79
Denver District
15 Value of Crops Produced in Adams County, 1972-1973 83
16 Livestock on Farms, 1 January 1973, Adams County, 83
Relative to All Colorado Counties
17 Contrasting Socio-Economic Characteristics 85
18 Adams County Employment Patterns, 1973 86
19 Changes in Characteristics of Sewage Sludges Through 90
Digestion
20 Survival Times of Pathogenic Microorganisms in 114
Various Areas
21 Estimated Capital Cost and Approximate Allocation 134
to Land, Labor and Materials
A-l Cost of Alternative Systems A-6
A-2 Cost of Alternative Systems Treating the Capital A-7
Cost of Anaerobic Digestion as a Sunk Cost
A-3 Cost Summaries Using 10 Percent Discount - No A-28
Inflation
A-4 Cost Summaries Using 10 Percent Discount and A-29
8 Percent Inflation
B-l Soil Associations in the Vicinity of Denver B-l
C-l List of Plant Species Observed During Field Recon- C-l
naissance, August 7, 1975
C-2 Commonly Occurring Range Species in the Denver Area C-3
C-3 Native Trees and Associated Shrubs in the Denver C-5
Area
C-4 Common Birds of the Denver Region C-6
C-5 Common Mammals of the Denver Region C-10
C-6 Common Amphibians and Reptiles of the Denver Region C-12
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LIST OF TABLES (Continued)
Table Page
C-7 Common Fishes in Streams and Lakes of the Denver C-13
Region
D-l Three Main Categories for Waste Organics Applica- D-3
tion to Land
D-2 On-Farm Fertilizer Used in Denver Area, 1970 D-18
D-3 Reported Nutrient Removal by Crops D-20
D-4 Sludge Heavy Metals Content Computed from Samples D-25
Obtained and Analyzed over a Period of Four
Months in Early 1975
D-5 Comparison of Metro Denver Sludge Heavy Metal Con- D-26
tent with Suggested Limits
E-l Comparative Fertilizer Usage at Selected Sod Farms E-9
in the Denver Region
E-2 Temperature, Precipitation, Snow and Freeze Data, E-13
Berthoud Pass
E-3 Value and Area of Crops Harvested in Weld, Adams E-l6
and Arapahoe Counties in 1973
E-4 Pertinent Characteristics of Selected Soils Under E-19
Irrigation in Weld County
E-5 Pertinent Characteristics of Selected Soils in Dry- E-24
land Farming in Adams County
E-6 Pertinent Characteristics of Soils in Lowry Bomb- E-28
ing Range Sludge Disposal Sites
G-l Summary of Impacts at Alternative Sludge Drying/ G-l
Distribution Sites
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h
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This section provides an introduction to
the problem of sludge handling at Metro and a
brief description of the proposed land-recycling
system. It also explains the role of EPA in the
project and its requirements for fulfilling the
National Environmental Policy Act.
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SECTION I
BACKGROUND
INTRODUCTION
Victor Hugo's Paris was discarding some five million francs
worth of sewage per year, by his estimates, in the mid-19th Cen-
tury. His graphic and prophetic lament on the wastage of this
valuable material was in part motivated by the untenable social
and economic conditions dramatized in Les Miserabies. While many
underlying conditions have drastically changed ana new types of
social problems and technologies have since emerged, it appears
that we nave come full circle back to the realization of the po-
tential resource value of our waste products.
The outbreaks of cholera in Europe in tne early 19th Century
led to the beginnings of sanitation systems. Today, in many de-
veloping countries which have not adopted such systems, the rate
of incidence of enteric diseases is still vivid testimony to the
need for the protection of human health. The potential health
problems of waste application to land have multiplied since
Victor Hugo wrote his masterpiece by the introduction into the
sewers of large quantities of exotic elements and by the sheer in-
crease in the size of our metropolitan areas. Thus, realistically,
waste products of human beings are both a valuable resource and a
potential environmental hazard.
Placement of sludge upon the land is at once the oldest and
the most recent concept in the use and/or disposal of this mate-
rial. It is an old practice in all parts of the world. Before
communities evolved into complex social structures that required
proper sanitation facilities, land disposal of human wastes was
the most logical approach. In many developing countries, these
wastes are even now directly utilized for crop fertilization, and
as such they are traded as a valuable commodity.
Application of sludge to land is a relatively new concept in
the more technologically advanced countries—particularly in the
United States—because of recent concerns over water quality degra-
dation caused by the various other existing sludge disposal prac-
tices. Modern widespread consciousness ot the energy and resource
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values that could be derived from sludges is anotner impetus for
land application. Thus, in a recent revision to EPA's grant regu-
lations and procedures, it is stipulated that:
Grantees must participate in the National Energy
Conservation Program by fostering, promoting, and
achieving energy conservation in their grant programs,
Grantees must utilize to the maximum practical extent
the most energy-efficient equipment, materials, and
construction and operating procedures available.
(Reference 1)
A main Tactor causing the great difference between the "new"
land application ana reuse of sludges and the "old" fertilizer use
of human wastes is the altered chemical properties of the respec-
tive materials involved. Modern plumbing systems, and industrial
inputs into municipal sewers have changed the character of sludges
by introduction of potentially toxic and otherwise dangerous mater-
ials. This, coupled with the ever present microorganisms, includ-
ing pathogens, makes sludge application to land a very sensitive
matter which must be subject to careful design, surveillance and
management control.
The environmental impact of land application of sludge in-
cludes the beneficial impacts (such as conservation of energy and
nutrients and improvement of physical characteristics of the soil)
and adverse impacts (such as potential degradation of ground and
surface water quality ana soil chemical characteristics as well as
human health and the food chain). The degree and extent of these
impacts vary qualitatively and quantitatively from one proposed
application site to another, sometimes in an entirely opposite fa-
shion. Therefore, the impacts of sludge application are clearly
identified with the category of land use to which the sludge might
be applied. For each category, typical sites were selected and
studied in detail, and the conclusions are expected to be typical
for other areas of similar character and use.
THE REASON FuR THIS DOCUMENT
The National Environmental Policy Act (NEPA) requires every
Federal agency to prepare a detailed statement on environmental
impact for each of its major proposed actions significantly affect-
ing the environment. In this case, the Environmental Protection
Agency is proposing to approve a facilities plan tor the management
and disposal of sludge, by the Metropolitan Denver Sewage Disposal
District No. 1.
EPA's responsibility for the approval of a wastewater treat-
ment facility is given to it under Public Law 92-500, known as the
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Water Pollution Control Act Amendments of 1972.
EPA has decided that approval of this plan constitutes a major,
significant action under NEPA and is therefore preparing a detailed
environmental impact statement. An environmental impact statement
(EIS) must consider the environmental impacts of a proposed action,
both short and long term (and especially the irreversible, adverse
kinds), and alternatives to the action.
Under Title II of the Water Pollution Control Act Amendments,
EPA is given authority to distribute construction grant fundings
for municipal wastewater treatment facilities, [his section of the
Act defines a three-step process of planning (Step I), design (Step
II) and construction (Step III] that must be fulfilled for an eli-
gible grant applicant to construct a facility with Federal funds.
Tne Step I process works as follows: an applicant who is cer-
tified through a State priority system prepares a facilities plan.
EPA will pay 75 percent of tne costs of such a plan. Before a plan
can proceed to the design and construction phase, the plan must be
approved by EPA. Design (Step II) review is delegated to the State.
EPA has determined that the approval process ot a facilities plan
constitutes the Federal action under NEPA.
Sludge treatment and disposal units are considered an integral
part of the wastewater treatment process and hence are eligible for
funding. Section 212(A) of the Act defines such facilities to in-
clude land acquisition costs if they are part of the treatment process:
The term "treatment works" means any devices and
systems used in the storage, treatment, recycling, and
reclamation of municipal sewage or industrial wastes of
a liquid nature ... including site acquisition of the
land that will be an integral part of the treatment
process or is used for the ultimate disposal of residues
resulting from such treatment.
The Congressional philosophy for the need to recycle and re-
claim many of the pollutants in sewage, including sludge, in a
beneficial manner is clear in Sections 201(d), (e) and (fj of the
Act:
(d) The Administrator shall encourage water treat-
ment management which results in the construction of
revenue producing facilities providing for—
(1) the recycling of potential sewage pollu-
tants through the production of agriculture, silvi-
culture, or aquaculture products, or any combination
thereof;
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(4) the ultimate disposal ot sludge in a
manner that will not result in environmental
hazards.
(e) The Administrator shall encourage waste
treatment management which results in integrating fa-
cilities for sewage treatment and recycling with faci-
lities to treat, dispose of, or utilize other indus-
trial and municipal wastes, including but not limited
to solid waste and waste heat and thermal discharges.
Such integrated facilities shall be designed and oper-
ated to produce revenues in excess of capital and
operation and maintenance costs and such revenues
shall be used by the designated regional management
agency to aid in financing other environmental improve-
ment programs.
(f) The Administrator shall encourage waste
treatment management which combines "open space" and
recreational considerations with such management.
In addition to the environmental considerations required under
NEPA, EPA must determine whether the facility considered in this
plan meets the goals of the Federal Water Pollution Control Act
Amendments of 1972 stated above.
The Metropolitan Denver Sewage Disposal District No. 1 (re-
ferred to as "Metro") has submitted a facility plan to EPA and the
State of Colorado to process and dispose of its sludge by recycling
it to the land. This EIS considers the effect such a plan would
have with regard to requirements of the following Federal environ-
mental laws, among others:
(1) Federal Water Pollution Control Act Amendments of 1972
(2) Clean Air Act (of 1970)
(3) various legislation regarding noise, solid waste and pesti-
cides
(4) Historic Sites, Buildings and Antiquities Act of 1935
(5) the Endangered Species Act of 1973 and Endangered Species
Conservation Act of 1969 and amendments
Because sludge is being considered for use on products that
could reach the human and animal food chains, the expertise of the
Food and Drug Administration and the Department of Agriculture
will be solicited. All appropriate State standards and regulations
will have to be met, including the Solid Waste Disposal Sites and
Facilities Act requirements. This act is administered jointly by
the State Health Department and the Board of County Commissioners
for the county in which the proposed site is to be located.
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While the Department of Health makes recommendations, the
County must approve specific site locations for any solid waste
disposal area. State law defines sludge as a solid waste for
purposes of this Act.
Agency expertise and public opinion are thus being sought by
EPA for this project. Atter this draft EIS has been distributed
for review, EPA will conduct a public hearing, if necessary, to
solicit additional information. ATter a period of not less than
60 days from release of the draft EIS, a final Elb will be distrib-
uted. This document will contain a resolution of any issues raised
in the course of the review of the draft EIS. Only after EHA has
determined that all of the important issues have been satisfactorily
resolved, and after at least 30 days from tne release of the final
EIS, would this facility plan be approved.
EPA assigned the consultant Engineering-Science, Inc. to assist
the agency in reviewing this very complex plan, to obtain additional
expertise and to help prepare the EIS document. This document rep-
resents the position of the Environmental Protection Agency regard-
ing this plan except where the consultant's own recommendations or
positions are explicitly identified.
HISTORY OF THE PROJECT
The Metropolitan Denver Sewage Disposal District wastewater
treatment facilities were originally constructed in 1966 with a
design capacity of 5.15 cu m/sec [117 mgd]. The overall BOD reduc-
tion goal was 80 percent. Sludge processing involved dewatering
through dissolved air flotation, vacuum filtration, flash drying
and/or incineration. At that time, it was expected that the rela-
tive proportions of raw primary sludge, anaerobically digested
sludge and undigested waste-activated sludge would be such tnat the
vacuum filter would produce a filter cake solids concentration of
22 to 25 percent.
By 1967, the District realized that the proportion of waste-
activated sludge in the mixture was much larger than nad been ex-
pected, giving rise to increased difficulty in dewatering the
sludge mixture (achieving only 14 to la percent solids concentra-
tion of the filter cake). Thus, tne need for chemicals for vacuum
filtration more than doubled, and the increased moisture content
overloaded the design capacity of the flash dryer-incinerator.
Corrosion of the stainless steel components of the dryer-incinerator
resulted from the heavy doses of ferric chloride used in sludge
conditioning, further compounding the problems with the sludge hand-
ling system.
This problem became intolerable in the fall of 1968. More than
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half of the evaporative capacity of the dryer-incinerator had be-
come unavailable because of mechanical problems; and activated
sludge was accumulating in the biological treatment system, rapidly
deteriorating the effluent quality. Therefore, lagoons were con-
structed for the winter months of 1968 and 1969. Odors generated
in these lagoons brought about loud complaints and forced the Dis-
trict to shift to land disposal of the filter cake in May 1969.
Since that time, land disposal, with various types of equipment, at
various rates and under different conditions, has been practiced at
an abandoned portion of the Lowry Bombing Range, some 40 km [25
miles] southeast of the treatment plant.
Some of the land application operations were conducted by
District personnel, while others were performed by contractors.
Odor problems resulting from the method of disposal used by con-
tractors gave rise to adverse neighborhood reactions and complaints
to Arapahoe County Commissioners. A public hearing was held on 20
June 1972 at which the District was committed to a new, revised
land application method aimed at eliminating odor and fire hazards
(Reference 3). The new method has since been utilized during dry-
weather conditions, as described in Section IV under Land Applica-
tion at Lowry Bombing Range. Inclement weather operation is simi-
lar to standard sanitary landfill ing of solid wastes.
In 1971, the District consultants prepared an expansion plan
for the central plant and recommended an agricultural reuse scheme
for the sludges produced (Reference 4). After two public meetings
with residents of the proposed reuse area in the winter of 1972-
1973, some revisions were made, and a new agricultural reuse pro-
gram was prepared by the District (Reference 5). The system has
since been further refined in concept, and in February 1975 a four-
volume sludge management plan was published, comparing alternatives,
describing the recommended agricultural reuse scheme in detail and
assessing the environmental impact of the recommended plan (Refer-
ence 6).
That report comprises a facilities plan, which was submitted
to the U.S. Environmental Protection Agency on 27 February 1975.
Earlier, applications for a Step I grant for the sludge management
plan had been made to the State and to EPA (on 19 November and 22
November 1974, respectively). On 9 June 1975, the Regional Admin-
istrator of the U.S. Environmental Protection Agency sent a "Notice
of Intent to Prepare an Environmental Impact Statement" for the pro-
posed sludge management program of the Metropolitan Denver Sewage
Disposal District No. 1.
On 30 June 1975, EPA authorized Engineering-Science, Inc. to
prepare an Environmental Impact Statement on the proposed action in
6
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the plan in accordance with all relevant legislation and policies
and the regulations of EPA. EPA required an additional evaluation
of the environmental impact to off-site areas being considered by
Metro for land application of sludge. Engineering-Science pre-
sented a preliminary draft EIS to EPA incorporating the analysis
of off-site impacts. This draft EIS was written by Engineering-
Science under EPA management using much of the information in
the preliminary report prepared by Engineering-Science.
THE PROPOSED ACTION
The sludge management plan proposed by Metro involves treat-
ment, pipeline transport, drying, distribution and application on
land of anaerobically digested sludge from the Metropolitan Denver
Sewage Disposal District No. 1 sewage treatment plant in Commerce
City. Figure 1 shows the location of various components of this
plan in the Denver Metropolitan area.
All of Metro's sludge would first receive anaerobic digestion
treatment at the central plant before further disposal. This pro-
cess stabilizes the sludge and reduces odor and pathogens. EPA
recently gave the District a $5.5 million grant to construct anaer-
obic digesters at the central plant.
The sludge would then be transported by pipeline to a drying/
storage center site located in western Adams County near Irondale
Road and about 18 kilometers [11 miles] southeast of Barr Lake.
There the sludge would be dried in open basins and stored for fu-
ture use. This processing site would also be used for marketing,
research and demonstration areas, and as a disposal site on occa-
sion.
Metro contemplates marketing the dried or liquid sludge to
local dryland and irrigation farmers, for municipal parks, for
mine-land reclamation, and perhaps for individual garden use. At
worst, Metro could dispose of the dried sludge in a sanitary land-
fill if no markets were available.
Land areas that might utilize the sludge extend from the AMAX
mine spoils site, near Berthoud Pass, to many of the park areas in
the metropolitan Denver areas.
The impacts of the various processing alternatives and the dry-
ing/distribution center were assessed during the facilities plan-
ning and are summarized in Section V. This environmental impact
statement deals primarily with the land application processes in
such areas as City parks, sod farms, mine spoil sites, irrigated
farms, dryland farms, the Lowry Bombing Range and the Lowry landfill,
-------
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PROJECT AREA
AND EXAMPLE SLUDGE
APPLICATION SITES
-------
It is proposed that air-dried sludge be trucked to application
sites of the types described above and incorporated into the top
layers of soil for ready use of nutrients by plants and improve-
ment in the physical condition of soils. A very important assump-
tion implicit in the environmental analysis of the proposed action
is that sludge application rates (metric tons per hectare per year)
ana quantities (ultimate metric tons per hectare) recommended for
a given piece of land, and other required cultural practices, will
be adhered to by the recipients of the materials. However, the
reliability OT such adherence cannot be guarded or guaranteed, and
to the extent that these recommendations are not followed, the
number and severity of impacts will increase beyond those enumerated
unaer tne basic assumption. Thus a thorough familiarity witn such
basic assumptions, presented in Section IV under Description of
tne Proposed Action, is essential to the understanding of the most
important conclusions of this Statement.
The proposed project will encompass primarily Adams County,
Colorado but will also include the City and County of Denver and
perhaps portions of Arapahoe, Weld, Douglas, Elbert, Jefferson and
Clear Creek counties. In fact, the cost of transport of air-dried
sludge may become the main factor limiting the distance the mater-
ial is shipped for land application.* For the purposes of envi-
ronmental impact analysis, six representative land application
sites are selected, as shown on Figure 1.
The service area contributing wastewaters to the sewage treat-
ment plants, which in turn produce sludges from the wastewaters, is
most of the metropolitan Denver area, comprised of more than 20
political entities. Excluded from the service area at present are
tne separate districts of Commerce City, Rocky Mountain Arsenal,
Glendale, Littleton and Englewood.
In order to construct facilities considered in any one of the
alternatives (excluding the no-action alternative) discussed in
Section II for the full projected sludge generation rate of 150 dry
metric tons [166 tons] per day, a capital expenditure ranging from
$2.2 to $29 million would be required, depending on the alternative
ultimately selected. The currently recommended alternative, de-
scribed in detail in Section IV, has a capital cost of $25.9 mil-
lion.
At a trucking cost of 50.08/cu meter-kilometer [SO.lO/cu yd-mile],
a distance of 100 km [60 miles] would represent the limit at which
transport cost of dried sludge (with 5 percent nitrogen and 50
percent solids content] equals the current price of equivalent com-
mercial chemical fertilizer nitrogen ($0.55/kilogram [$U.25/lb])
alone.
-------
Financing ^the Project
If approved, the U.S. Environmental Protection Agency would
pay 75 percent of the-grant-eligible-portion of the capital cost if
further'Congressional funding became'available, and the District
would bear the remaining5 25 percent-,' as provided by~!the Federal
Water Pollution Cpntrol Act as"amended in 1972.
The local share (25 percent) of the capital cost would have to
be borne proportionately by the users; i.e., the individuals, indus-
tries and businesses' using the District's sewerage facilities. At
present, however,-no further funds are available to Colorado for
construction in the Denver metropolitan area, unless the Congress
authorizes additiona-1 money for wastewater treatment works. Approv-
al of this plan would allow EPA to reimburse Metro for 75 percent
of the eligible design costs of this project.
-------
h
H
-------
This Section considers the alternatives to
the proposed project. It looks at the historical
development of alternatives and provides a com-
parative evaluation of reasonable alternatives,
using environmental, engineering and cost para-
meters. Areas where alternatives were considered
include processing and disposal, site locations
and transportation.
-------
SECTION II
ALTERNATIVES TO THE PROPOSED ACTION
INTRODUCTION
The National Environmental Policy Act requires Federal agencies
to consider "alternatives to the proposed action" in every environ-
mental impact statement. The law does not specify how thorough
the alternatives must be, but courts have interpreted it to mean
that a "reasonable" number of alternatives must he considered,
especially any which may have merit in reducing the negative environ-
mental impacts of the project as originally proposed.
This very broad definition of alternatives suggests that not
only are very broad "total system" alternatives to be considered
but, where particular features of a given proposal may have unusual-
ly severe impact, subalternatives within a system should also be
evaluated. In the case of Metro Denver's proposal, site location
alternatives or drying basin design alternatives might be sub-
alternatives worthy of consideration.
A second factor must be borne in mind in the review of alter-
natives for a construction grants program project. EPA does not
initiate a proposal for construction grant funding; that is the
prerogative of any legal wastewater management district. Upon
certification by the State, a district evaluates alternatives and
develops a plan. The plan is then sent to EPA for final review.
Although EPA has developed guidelines to assist grant applicants
in order to make them aware of EPA's responsibilities in consider-
ing project alternatives, it is inevitable that the applicant will
view the alternatives from a somewhat different perspective than
will EPA.
To overcome this difficulty, EPA will give equal consideration
to all alternatives but will recognize the effort that has been
invested in the development of the proposed project. Only if there
are significant environmental or other objections to the proposed
overall system will a wholly different system be advanced. Even
within a given proposal, however, major changes could be required
if the situation so warranted.
11
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This Section describes the historical background of Metro
District planning leading to the development of alternatives and
to the present proposal; compares total system alternatives; and
reviews subalternatives to both the proposal and the existing sys-
tem.
HISTORICAL DEVELOPMENT OF ALTERNATIVES
The Metro Denver Central Plant, built in 1965, is a secondary
biological treatment facility. The plant not only processes
residual solids from its own aqueous-phase treatment units but
also handles anaerobic digested sludge pumped from the Denver North-
side Plant. Sludge treatment and disposal has always been problem-
atical at the plant, as evidenced by the fact that Metro has re-
ceived a number of research grants to evaluate alternative sludge
treatment processes.
When the Metro plant was built, flash-dry incinerators were
installed to dry sludge for reuse as a soil conditioner in local
parks. Because of operational problems, Metro abandoned the in-
cinerators in 1971 in favor of dewatering on vacuum filters and
disposal by landfill ing at the Lowry Bombing Range. Subsequently,
complaints about odors forced Metro to modify its method of sludge
disposal from landfill ing to landspreading at Lowry.
In 1971, Metro hired the firm of CH2M-Hill to develop plans for
the Central Plant expansion, including an evaluation of alternatives
to the present sludge treatment and disposal system, which was be-
coming increasingly expensive. CH2M-Hi11 studied and evaluated
from an engineering point-of-view three basically different sludge
treatment and disposal systems:
1. The present Metro system.
2. Multiple hearth incineration.
3. Land disposal of digested sludge.
While the incineration and land disposal alternatives were
felt to be close in overall costs and much preferable operationally
to the present system, Metro adopted the recommendation of land
disposal because of an environmental "net benefit" and the possi-
bility of revenue from the sale of agricultural products. In
its land recycling proposal, Metro would have sprayed anaerobically
digested sludge on about 6,000 acres of farmland either owned and
operated outright by Metro or leased to fanners.
When Metro presented this option to the farming community in
western Adams County, it encountered considerable resistance.
Farmers objected to the loading rates, the effect of having Metro
12
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entering the farming business in a large-scale operation and po-
tential effects of odors on land values and health in the area
where the sludge would be stored. As a result, Metro concluded
that more land would probably be needed to accommodate lower load-
ing rates and became less enthusiastic about engaging in a farming
operation itself.
CH2M-Hill was authorized to evaluate in more detail the land
recycling alternatives and in March 1973 produced a study entitled
"An Agricultural Reuse Program" (Reference 5). This study eval-
uated in much more detail a comprehensive approach to land re-
cycling, using the latest information then available. The report
considered issues such as various sludge characteristics and their
effects on the land; water-rights issues; state-of-the-art compost-
ing and landspreading systems; fertilizer considerations; loading
rates for semi-arid areas; and the types of crops most likely to
benefit from sludge applications. A number of land application
alternatives were evaluated in the study. The more promising sys-
tems identified were drying beds with application to agriculatural
land, permanent subsurface injection on Metro-owned land and re-
cycling on private farm land with short-term injection on Metro-
owned land. Two other alternatives (spray irrigation or subsurface
injection on privately owned dry farmland, and irrigation of crop-
land owned by Metro) were eliminated because of high cost and
water-rights problems.
The report included a preliminary site evaluation which served
as a basis for a more detailed site evaluation in the facilities
plan (considered below). A preliminary design configuration for
the most favored alternative, recycling on private land with short-
term injection on Metro-owned land, was presented in the report.
Metro remained committed to the concept of land recycling but
required the facilities planner to develop a more comprehensive re-
view of all alternatives. In the facilities plan, a wide range of
processing and disposal alternatives was evaluated and eight over-
all processing and disposal alternatives were evaluated in detail.
These included:
1. The existing system--"no action",
2. anaerobic digestion—pipeline transport to a drying/dis-
tribution facility—beneficial reuse,
3. dewatering by filter presses—incineration—landfill,
4. heat treatment—dewatering on vacuum filters—landfill,
5. heat treatment—pipel ine transport—drying—landfill,
6. heat treatment—vacuum filtration—incineration—landfill ,
7. anaerobic digestion—dewatering by filter presses—com-
posting—beneficial reuse, and
13
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8. dewatering by filter presses--composting--beneficial reuse.
The facilities planners recommended the second alternative: i.e.,
anaerobic digestion, pipeline transport to a drying/distribution fa-
cility and beneficial reuse. This alternative became Metro's pro-
posed system and is the principal focus of this particular EIS pro-
cess.
In June 1975, EPA retained Engineering-Science (ES) to review
the facilities plan and develop the EIS. Part of Engineering-Science's
task was to evaluate the existing alternatives and to propose addi-
tional alternatives that appeared promising. A total of 17 alterna-
tives for the processing and disposing of sludge were developed and
evaluated for this EIS, including the eight alternatives studied by
CH2M-Hill.
Table 1 shows the 17 alternative systems evaluated by Engineering-
Science. The basic form of disposal is shown next to the process de-
scription. Cost information includes present-worth values with and
without anaerobic digestion as a sunk cost, with and without an eight
percent inflation rate and with and without revenue. Generally, cost
information showed that many of the process options were close in
overall costs, but land recycling became much more cost-effective
when revenues, inflation and sunk costs were considered. Alternatives
in which Metro sludge would be processed together with municipal
refuse also appeared to be economically advantageous.
Further evaluation might be warranted if these latter types of
systems were to be developed. However, the latest information
available indicates that the Colorado legislature has failed to act
on a Denver Regional Council of Governments (DRCOG) bill sponsored
to develop a solid waste recycling system. Therefore, while the
systems are promising, the possibility that an actual system might
be developed in the near future seems unlikely.
Environmental, engineering and cost factors considered, Engi-
neering-Science also concluded that the "apparent best alternative"
involved the Metro land recycling proposal. The Engineering-Science
evaluation is contained in Appendix A, which summarizes the perti-
nent assumptions made in evaluating the alternative systems.
COMPARATIVE EVALUATION OF SLUDGE TREATMENT
SYSTEM ALTERNATIVES
In considering the work performed by the consultants and the
Metro District, a useful perspective can be gained by comparing
the disposal element in each alternative, since this is the ele-
ment of a sludge management system that has the most significant
environmental impact. The processing alternatives generally
14
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have a relatively small environmental impact; the most important
in-plant consideration is the selection of a combination of pro-
cesses that will efficiently and economically produce a treated
sludge with the requisite characteristics for each particular dis-
posal mode. Thus, the comparative evaluation of sludge management
alternatives for the Metro system has as its focus the disposal
elements of the alternatives.
EPA recently proposed tentative sludge management guidelines
(Reference 79) that provide an indication of the way in which the
agency approaches the issue of sludge disposal from an environmental
point of view. The guidelines recognize that disposal of the solid
material in sludge can have significant impact on the environment;
disposal can simultaneously affect air, land and water and may en-
compass such varied considerations as human health, animal health,
plant growth and the protection of ground and surface water from
pollution. A basic distinction made by the guidelines in consider-
ing the final disposal of sludge is the division of management
techniques into those in which sludge is utilized as a resource
and those in which sludge is not used for any beneficial purpose.
Examples of beneficial use include land recycling or incineration
for heat or power, while in the case of nonbeneficial disposal,
landfill ing or incineration would simply dispose of the unwanted
sludge without any return benefit.
Semantic confusion surrounds the word "disposal." In a gen-
erally accepted sense, the word is taken to mean the last step in
the sludge handling process, regardless of whether beneficial reuse
is involved. In the distinction often made, the word "disposal"
is used only to indicate those forms of sludge management where no
beneficial reuse occurs.
The basic intent of disposal is simply to take the sludge, as
an unwanted residual material, out of the sewage treatment process
and put it into some other system where it is relatively "harmless."
An environmental concern that must be kept in mind, however, is
that a residual material like sludge is never destroyed by a dis-
posal process but simply converted to another form of matter and/or
energy that continues to exist in the biosphere.
A distinction between "beneficial" and "nonbeneficial" dis-
posal methods worth noting is that a beneficial method allows
some re-entry of previously unwanted materials jnto the socio-
economic system; the nonbeneficial system simply puts the residual
material into larger environmental systems—air, land or water.
As a way of maintaining this distinction, disposal systems are re-
ferred to in this EIS as beneficial or nonbeneficial.
15
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Table 1.
SUMMARY OF SLUDGE
SYSTEM ALTERNATIVES EVALUATION3
(millions of dollars)
Cost comparisons
Anaerobic digestion costs included Anaerobic digestion not included (sunk cost)
Alter- Description
native of
number alternative
1A Existing system — waste-activated and
other sludges trucked to Lowry Bomb-
ing Range for landspreading
IB Existing system with anaerobic digestion
2 Anaerobic digestion, pipeline transport,
air drying and beneficial reuse (prod-
uct: 100 percent air-dried sludge)
J Filter presses, incineration, landfill
of ash
4 Heat treatment, vacuum filtration,
landfill
5 Heat treatment, air drying, landfill
6 Heat treatment, vacuum filtration, in-
cineration, landfill of ash
7 Anaerobic digestion, filter presses,
compost (product: 100 percent nutrient-
enriched composted sludge)
8 Filter presses, compost (product: 100
percent nutrient-enriched composted
sludge)
9 Anaerobic digestion, centrifugation, com-
post (product: 100 percent nutrient-
enriched composted sludge)
10 Anaerobic digestion, pipeline transport,
air drying, compost (product: 50 per-
cent air-dried sludge; 50 percent
nutrient-enriched composted sludge)
Basic
disposal
method
predominantly
land disposal
(spreading)
with some
landfilling
land disposal
(spreading)
land recycle
incineration
land disposal
land disposal
incineration
land recycle
land recycle
land recycle
land recycle
Unadjusted 82 Unadjusted 8%
for inflation inflation for inflation inflation
Ab Bc A B A B A B
24.1 24.1 34.3 34.3 24.1 24.1 34.3 34.3
24.7 . 24.7 30.1 30.1 18.6 18.6 26.4 26.4
24.0 19.3 17.7 10.8 17.8 13.1 14.0 7.1
24.2 24.2 26.8 26.8 24.2 24.2 26.8 26.8
22.5 22.5 25.9 25.9 22.5 22.4 26.0 26.0
33.3 33.3 30.2 30.2 33.3 33.3 30.2 30.2
23.6 23.7 23.6 23.6 23.7 23.7 23.6 23.6
30.3 19.6 35.1 19.3 24.2 13.5 31.4 15.6
34.0 17.0 45.1 20.1 33.9 17.0 45.1 20.1
33.8 25.9 40.1 28.5 27.6 19.8 36.3 24.8
28.8 '20.5 24.4 12.3 22.7 14.4 20.7 8.6
-------
11 Anaerobic digestion, centrifugation, land disposal
landfill
12 Anaerobic digestion, pipeline transport, land recycle
air drying, landfill, compost (product: and
33 percent air-dried sludge; 33 percent land disposal
nutrient-enriched composted sludge; re-
mainder to landfill)
13 Anaerobic digestion, vacuum filtration, land recycle
compost (product: 100 percent nutrient-
enriched composted sludge)
14 Vacuum filtration, compost (product: land recycle
100 percent nutrient-enriched composted
sludge)
15" Anaerobic digestion, vacuum filtration, conversion
pipeline transport to solid waste re-
cycling plant
16^ Vacuum filtration, pipeline transport conversion
to solid waste recycling plant
26.4 26.4 30.8 30.{
26.9 20.7 24.5 12.4
28.4 20.5 33.8 22.2
27.0 14.5 36.4 18.0
16.8 16.8 17.8 17.8
10.1 10.1 13.3 13.3
20.2 20.1 27.1 27.1
22.8 14.5 20.9 8.7
22.2 14.4 30.1 18.5
30.0 14.5 36.4 18.0
10.6 10.6 14.1 14.1
10.1 10.1 13.3 13.3
By Engineering-Science, Inc.
b,,. ,
Without revenue.
With revenue.
Sludges containing less than 25 percent solid materials would require the expenditure of additional resources for the removal of water.
-------
The Congressional philosophy expressed in the Water Pollution
Control Amendments of 1972 makes it apparent that the Congress was
very much concerned with developing and promoting beneficial ways
to use both sludge and treated wastewater. In the portions of the
Act quoted in the first Section of this EIS, beneficial disposal
of sludge can be accomplished either separately by the wastewater
treatment entity or in combination with municipal solid waste sys-
tems. Because cost, engineering, institutional and, to a certain
extent, environmental considerations differ between these two ap-
proaches, they are distinguished in the comparative evaluation
that follows. A separate wastewater district might find it very
uneconomical to incinerate sludge for power purposes, but, in com-
bination with municipal refuse incineration, the system could prove
attractive.
Table 2 compares environmental impact, engineering considera-
tions, institutional factors and costs"as they relate to a number
of courses of action. The alternative courses of action are or-
ganized in three groups--nonbeneficial disposal, separate beneficial
use and combined municipal refuse and sludge beneficial use. It
should be noted that the ranking shown in the Table is, at present,
simply serving as a guide in the process of comparison; it is not
yet being used as a decisive factor in the selection of alternatives.
The comparative evaluation shows the general preferability of
separate land recycling schemes. Were the DRCOG solid waste re-
cycling alternatives a real possibility, some of these alternatives
would be more attractive. Metro has evaluated air basin drying
versus composting approaches and decided upon the former as the
method of land recycling. There appear to be no outstanding reasons
from EPA's point of view as to why one should be chosen over another
in this case. Recent work on composting sludge shows great environ-
mental and economic promise (Reference 129).
Other disposal and recycling systems do not fare as well for
a variety of reasons. Incineration (whether heat or power benefits
are gained or not) involves air quality problems and is highly en-
ergy-demanding with Metro sludge. Land disposal methods such as
landfill or land spreading do not rate as high overall because of
greater adverse environmental impact, little or no positive bene-
fit and higher costs. Other schemes involve unproven technology
or are associated with higher costs.
It is concluded, from a review of all the available informa-
tion at hand, that some form of land recycling, utilizing air-dried
anaerobically digested sludge, is a generally environmentally sound
and cost-effective alternative for the Metro District. At this
point in time, EPA does not feel that a further evaluation of al-
together novel sludge handling and disposal systems need be con-
sidered.
18
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However, in view of the fact that Metro has an ongoing sludge
handling and disposal system at the Lowry Bombing Range that would
be replaced by a different system, EPA feels that the alternative
of continued use of the Lowry disposal system (perhaps modified to
a certain extent) must be considered in detail. The National En-
vironmental Policy Act requires a Federal agency to review the
null or "no-project" alternative. It seems reasonable for EPA to
question whether a new system, even with the inclusion of environ-
mental improvements, should be funded in lieu of the existing system.
Past evaluations by the Metro District and consultants have indi-
cated problems with groundwater contamination and excessive soil
loadings at Lowry. Therefore, the Lowry system is evaluated further
in this document.
The EPA guidelines recognize that the choice of a disposal
method is not as important as properly evaluating the chosen method
with respect to a wide range of environmental conditions. The EIS
process functions to evaluate in detail any impacted environmental
elements in order to insure the least environmental degradation.
The guidelines indicate that for land recycling schemes the follow-
ing elements must be considered:
1. Soils.
2. Groundwater.
3. Stabilization of sludge.
4. Sludge characteristics (heavy metals, nutrients).
5. Pathogen reduction.
6. Crop suitability.
7. Public access.
8. Surface runoff.
9. Application methods.
10. Application rates (nutrients and trace elements).
11. System operation control.
12. Monitoring.
13. Food chain considerations.
Thus, in the body of this Environmental Impact Statement, EPA
considers in detail the following two sludge management systems.
1. Metro's proposed land recycling system using anaerobic
Digestion, pipe!ine transport, drying beds, storage and distribution
to the land. Metro has proposed that dried sludge could be used on
irrigated areas, dryland areas, sod farm operations, metropolitan
Denver parks and reclamation of some mine spoil areas. It has also
been suggested that dried sludge might be made available to individ-
ual home gardeners. Metro has also indicated the possibility that
the sludge could be bagged and sold commercially.
19
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Table 2. FINAL SLUDGE HANDLING ALTERNATIVES COMPARISON
FOR METRO DENVER DISTRICT
Sludge
handling
alternative
L*rul disposal
Landfill
Lanjspreading
Incineration-
ash disposal
Environmental impacts
Beneficial
None
Can improve soil
structure and add
nutrients
Minimal, material
volume reduced
Adverse
Crounduater leachate
problems, soil sta-
bility, explosive
gas production
Can harm soil quali-
ty by excessive met-
al loadings; can af-
fect grounduater,
food chain
Releases participates
and gases to air; ash
disposal can create
leachate problems in
grounduater; high
energy utilization
Engineering factors
Feasibility
Dlsp
High
High, but requires
large land areas
an& constant moni-
toring
Moderate, moisture
content of sludge
could affect oper-'
ation
Reliability
osal
High, but requires
close control of
deposition and must
be mixed with dry
solid waste and/or
soil
Moderate, requires
standby system for
winter and wet days
High, except air
pollution control
equipment may have
problems
Institutional
ability to
implement
High-existing, but
would require new
disposal sites
High-existing, but
would require new
land spread ing sites
Moderate, because
of air pollution
problems
Costs
All disposal operations
have no revenue, low
capital costs and high
operating, energy and
chemical costs
Low capital costs;
moderate operating
costs; high energy
and chemical costs
High capital and energy
costs; moderate operat-
ing costs; chemical
costs could be high
Overall3
rating
Marginal
Acceptable
Marginal
Recycling — Separately
Land recycling
Air drying
Composting
Incineration
Drying-
recycle
Improves soil
structure; adds
nutrients; mini-
mizes energy use
Improves soil
moisture; high
nutrient value;
minimum energy
use
Cattle feed;
soil amendment
Localized groundwater
problems at drying
site; pathogen prob-
lem; control of final
use difficult
Same as air-drying
Odor problems; ash
disposal; low inten-
sive energy use
High, but requires
complex coordina-
tion for recycling
Moderate, requires
good market for re-
cycled material
Low with past Metro
experience; could be
higher with anaero-
bic sludge
High, except for
occasional digest-
er failure
High, except for
potential contam-
inants
Low to moderate be-
cause of incinerator
breakdowns
High, except for
farming community
resistance to land
i se aesthetic de-
terioration
Limited Metro ex-
perience or re-
search in this
area
Low, Metro exper-
ience with drying
unfavorable
High capital coats and
low operating, energy
and chemical costs;
high revenue likely
Same as air-drying;
revenue could be high.
uncertain at this time
Same as air-drying;
revenue could be high,
uncertain at this time
Most fa-
vorable
Favorable
Acceptable
-------
Ash-heat
production
Conversion
Pyroly«i«
Cattle feed
Land recycle —
composting
Incineration —
power production
Conversion
Supplemental
boiler fuel
Synthetic gas
production
The overall rating
Produce* useful
heat
Useful carbon-
black produce
Valuable cattle
feed supplement
Large amounts of
fertiliser and
soil amendment*
Useful heat or
steam energy
produced in
large amounts
Energy source
for Industrial
uae
Synthetic natural
gas for indus-t
trial/domestic uaa
scale (unacceptable,
Disposal of ash and
leachate to ground-
water problems
Heavy metal contam-
inants; releases
gases
Unknown, potential
metal contaminant!
in food chain
Control of patho-
gens difficult;
odor problems
Ash disposal; re-
lease of gases to
air
Air pollution, ash
residue
Ash residua
marginal, acceptable,
Low a* a separat* Low
system
Experimental Unknown
Experimental Unknown
Combined Recycling with Municipal Solid Wastes
Probably high High
Potentially high; Vrobably high
water content in
sludge lowers heat
value; past oper-
ating problems
with CO from in-
cinerators
Very low, imprac- Low
tlcal with DRCOG
proposal
Moderate, caloric High, if sludge
and high water con- quality constant.
tent of Metro but unknown re-
sludge somewhat liability for
unfavorable overall system
favorable and most favorable) was developed through
Moderate.
Low; untested
Low; untested
Low; lack of leg-
islative support
f c r financing sol-
id waste systems
Low; lack of leg-
islative/financial
support
Low; lack of leg-
islative/financial
Low; lack of leg-
islative/financial
support
a semi-quantitative
ranking and evaluation of the alternatives on the bail* of parameter presented la this Table. The subjective nature of this method
High capital, operating
energy and chemical
costs; low revenues
High capital, operating
energy and chemical
costs; revenue unknown
Same as pyrolysls
Costs unknown to a
great extent for all
combined options
Costs unknown, could
be low for Metro
Costs unknown, could
be low for Metro
Costs unknown, could
be low for Metro
! relative
is shared
Unaccept-
able
Unaccept-
able
Acceptable
Marginal
Marginal
Unaccept-
able
Acceptable
by all such attempts at numerical evaluation.
-------
2. Metro's existing disposal operation of landspreading and
occasional burial at the Lowry Bombing Range. The system will be
modified by the addition of anaerobic digesters at the Metro plant.
Other possible modifications are also discussed.
The analysis of the alternative systems is prefaced in this
Section by a discussion of the sub-system alternatives within each
of the major alternatives.
SUB-SYSTEM ALTERNATIVES
Many environmental impacts can be lessened by careful attention
to the design details of the chosen system. The National Environ-
mental Policy Act requires that consideration be given to lessening
environmental impact of a project by evaluation of alternatives and
selection of an environmentally sound option and then by mitigation
of negative impacts through careful attention to design details.
This Section of the EIS discusses the basic components of the major
alternatives, their environmental impacts and the means by which
their impacts might be mitigated.
Sub-System Alternatives to the Metro Land
Recycling Proposal
Stabilization--.
Some form of sludge stabilization is necessary before sewage
sludge can be applied to the land. Stabilization involves the des-
truction of volatile matter in the sludge. If sludge were applied
to the land unstabilizeds odiferous conditions would result.
The most commonly applied stabilization process is digestion,
either aerobic or anaerobic. Based on many years experience with
both digestion processes, Metro has selected the latter for this
project, for the following reasons: (1) Anaerobic digestion is a
well-established process in the sewage treatment technology field;
it has very low energy use requirements, whereas aerobic digestion
requires considerable energy to supply air to the mixed sludge,
(2) The methane gas from anaerobic digestion can be used to power
the digestion process and perhaps other units, and (3) Aerobic
sludge must be very well digested in order to avoid odor problems,
if the sludge becomes septic.
An issue within the general choice of anaerobic digestion is
whether the process should be mesophilic (operating at temperatures
between 21°C and 39°C [70°F and 103°FJ), or thermophilic (operating
between 40°C and 54°C [104°F and 130°F]). Thermophilic digestion
results in a better stabilized sludge that can be more easily de-
22
-------
watered. Pathogen reductions are also reported to be more effective
with this process. The principal negative aspects of thermophilic
digestion are the high additional costs for insulation and extra
heating. Metro has decided to operate the system in the mesophilic
range.
The actual range of choice for the digestion sub-systems is
extremely limited because EPA has already provided the Metro Dis-
trict with funds for anaerobic digesters. EPA intends to evaluate
whether operation in the thermophilic range is desirable and within
reasonable cost limits, given the present design of the anaerobic
digesters.
Transportation--
The principal means of conveyance to a sludge drying/storage
facility in the Metro proposal is by pipeline. Two pipes (25 and
30 cm [10 and 12 in.]) will carry the sludge, with a pumping station
at the Central Plant and an intermediate pumping station. Although
design of the pipeline is not completed at the time of this writing,
the lines would be sized to carry the expected sludge volume pro-
jected for 1985 at a speed required to keep the solids in suspension.
A more detailed description of the pipeline design is given in
Volume III of the facilities plan (Reference 55) and Section IV of
this EIS. Generally, EPA has not had any outstanding conceptual
problems with the pipeline design and, hence, no design alternatives
are offered here at this time.
Pipeline routes were also considered to be of minor importance.
CH2M-Hill considered two pipeline alternatives depending on the sites
for the distribution center. Since Site B-2 is preferred, the route
along Irondale Road is the corresponding alternative for the pipe-
line. Because the pipeline will follow roadway right-of-ways, min-
imum environmental or social impact is expected.
Sites for Drying and Distribution Center —
The most controversial element in Metro's proposed system is
the location of the drying and distribution center. When Metro first
proposed its spray irrigation system for sludge disposal in 1972,
the agricultural areas to the northeast of Denver in Adams County
were felt to be best for this type of system. At that time, it was
anticipated that dryland farming would be the principal user of the
sludge. Six sites in this general area were evaluated (See Figure 2)
and a site near the present B-2, although much larger in area, was
selected.
Metro modified its land recycling proposal after meetings with
23
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LEGEND
I [ORIGINAL 6 SITES DESIGNATED
I | IN PHASE I REPORT
REVISED POTENTIAL SITES
(AGRIC. REUSE PROGRAM REPT.)
ALTERNATIVE SITES SELECTED
[FOR FINAL CONSIDERATION
(AGRIC. REUSE PREDESIGN REPT.)
[^RECOMMENDED
~ SITE
SLUDGE CONVEYANCE
PIPELINE TO SITE
I IRONDALE RD
ROCKY
MOUNTAIN
ARSENAL
METRO
CENTRAL
PLANT
SOURCE: CHgM HILL
POTENTIAL DRYING
AND
DISTRIBUTION CENTER SITES
-------
local farmers who felt the loading rates for nutrients were too
high and that sludge directly applied to crops could have detri-
mental effects. The 1973 study (Reference 5) recommended a drying
system whereby Metro would dry and store the sludge and make it
available to private farms. A preliminary site evaluation for a
drying/processing/storage site was made in the same general area
of Adams County. Eleven sites were evaluated, as shown in Figure 2.
A rating system was used to compare factors such as distance from
the Metro plant location with respect to markets, nearness to exist-
ing populations, soil suitability, number of homesites that would
have to be removed, visibility, elevation and land costs. No eco-
logical factors were evaluated. The evaluation led to the selec-
tion of three sites to be studied in more detail. Figure 2 shows
the location of the original six sites, the eleven sites under the
modified proposal and the three preferred sites—A, A-2 and B-2.
An environmental assessment of the three preferred sites was in-
cluded in the facilities plan and is reproduced in summary here in
Appendix G.
The environmental assessment included an ecological comparison
of the three sites and an archaeological investigation. The archaeo-
logical investigation identified only one prehistoric site of pos-
sible concern located on site A-2. The ecological evaluation con-
cluded that sites A-2 and B-2 were floristically rich areas with a
greater potential as wildlife habitat. This was in large part due
to the presence of "relictual prairie areas" within the sites. On
the basis of this information, Metro redefined the sites to avoid
the relictual prairies. Detailed information on soil conditions
and groundwater depth and quality is not available; thus these
factors, although important, played only a minor role in the eval-
uation.
Metro's reasons for preferring site B-2 are described in
Chapter 6 of Volume III of the facilities plan. Environmentally,
only land-use considerations were felt to be significantly dif-
ferent for each site. Metro's overwhelming reason for selection
of the B-2 site was to stay as far away as possible from concen-
trated population areas to avoid any further controversy. This is
candidly admitted to be the principal reason for the selection
indicated in the facilities plan. From the point of view of prox-
imity to markets and ease of land acquisition, B-2 compares un-
favorably with the other sites. Figure 3 shows the relationship
of the three sites to the expected principal users of the dried
sludge: irrigation farms, sod farms and Denver park areas. The
cost of construction and operation at the preferred site is also
estimated to be greater than at the other sites. More information
is provided on the relative merits of the three sites on pages 92 and 93.
On 8 May 1975, EPA, recognizing the controversial nature of
-------
FIGURE 3
S'arnesv.ne DENVER CITY MAP
GITY PARKS ARE APPROXIMATE" LOCATIONS,
IRRIGATED AND DRYLAND FARMS, SOD FARMS AND PARKS
OF THE DENVER AREA IN RELATION TO THE
SLUDGE DISTRIBUTION SITE
-------
site selection, requested that the Metro District Board of Direc-
tors refrain from any actions to acquire the B-2 site until the
National Environmental Policy Act process was completed. EPA feels
that the work done to date by the District and CH2M-Hill represents
a reasonable effort at evaluating the sites considered so far; how-
ever, it is necessary to evaluate a wider range of sites, which have
been suggested by others. For example, suggestions have been made
to use the Rocky Mountain Arsenal or the Lowry Bombing Range as a
drying/distribution site. The facilities plan did not discuss
these possibilities. Others have expressed a desire to know why
the site could not be located further north in Weld County or fur-
ther to the southeast in the vicinity of Lowry Bombing Range.
The Metro District has indicated to EPA that the Defense De-
partment is opposed to any use of the Arsenal site for a sludge
drying/distribution center. At this point, it would be difficult
to say how favorable or unfavorable the Arsenal would be from a
soils or groundwater standpoint. It is likely that unless the
Defense Department has developed a definite plan for the long-
range use of this facility, it would be reluctant to provide a por-
tion of the Arsenal on a piecemeal basis. The site does contain
significant wildlife and natural areas; it also contains sites
where very toxic materials are stored. It has recently been indi-
cated that the Army will have to exhaustively search any
part of the Arsenal that becomes open to public access for stored
poisons or weapons. The Army Department also informed Metro that
no Arsenal land could be used until the nerve gas detoxification
program is completed in 1977.
The Lowry Bombing Range would seem to be an ideal site for the
proposed sludge drying and distribution operation since Metro has
already been operating there. However, the pipeline would have to
traverse a developed urban area with a consequent increase in cost
and inconvenience. A second consideration is that the elevation
of the Lowry site is about 150 m [500 ft] higher than the B-2
site which would approximately double the pumping costs. In addi-
tion to the above disadvantages, there is a rapidly developing
urban fringe in the southeastern Denver area within eight km [five
miles] of the site, which may cause a future land-use conflict.
There are also institutional problems in acquiring the site.
Finally, the site is remote from most potential markets, as shown
on Figure 3.
The principal way to avoid some of these conflicts is to obtain
some part of the Lowry Bombing Range that would not involve popula-
tion conflicts. The institutional arrangement at present does not
allow an easy transfer of land within the range. Metro District
utilizes a portion of the bombing range that has been leased to
27
-------
the City and County of Denver from the U.S. government. Again, it
is premature to develop any detailed comparison of the benefits and
costs of this site unless indications could be obtained from the
Defense Department that such land could potentially become avail-
able. Were this the case, environmental and engineering informa-
tion would be required to evaluate the merits of sites in the gen-
eral vicinity. Finally, it would appear that the site would be
located at some distance from its potential markets, especially
irrigated farms. However, sod farms and Denver parks would per-
haps be somewhat closer than with the B-2 site.
Lands to the north and west of the Platte River would generally
be unfavorable because of their proximity to populated areas. Weld
County has already indicated a lack of interest in having the Metro
District locate their sludge distribution center within the county.
However, the presence of large amounts of irrigable lands and sod
farms makes this area attractive from a potential market standpoint.
Lands lie at lower elevations in this general direction and would
result in lower pumping costs; land values are higher, however, and
would increase the capital costs of the project.
The principal conclusions of EPA at this time with regard to
site locations would be the following:
1. There appears to be no site that is overwhelmingly superior
from an overall standpoint.
2. It is generally true (at least in the predominantly dryland
areas selected for site consideration) that there are no significant
environmental issues involving vegetation or wildlife areas that
could not be avoided.
3. There is a lack of specific soils and groundwater data in
all areas either studied or suggested to indicate the beneficial and
adverse impacts of locating there.
4. Cost differentials between sites considered are small. The
cost implications of some of the suggested sites are unknown.
5. A potential health risk may be associated with actual phys-
ical contact with the sludge. However, no significant health risk
exists as a result of the presence of members of the public living,
working or merely visiting within the environs of the sludge drying
and distribution center as long as appropriate precautions are ob-
served.
6. No matter which site is selected, there will be public con-
troversy about the location of a facility of this kind. A possible
exception could be one of the two Federal areas--Lowry or the Ar-
senal . However, it does not appear that these areas will be easy
to acquire.
7. Selection of an area that is reasonably close to market
areas could be important if trucking costs are high. However,
28
-------
with the range of potential uses suggested for the dried sludge--
from sod farms to parklands--and with no definite information about
the preponderant users of the sludge, the optimal location of the
site from this viewpoint is impossible to determine at this point.
At this time EPA tentatively accepts the Metro District's
judgment for the B-2 site; however, no final determination will be
made until the EIS process is complete. The principle which was
advanced in the discussion of overall alternatives pertains here
as well: it may be more important to evaluate a given site in de-
tail and suggest design features to minimize effects on the natural
and human environment, rather than try to select an optimum site.
Those factors which could be important from, a locational standpoint-
distance from market, soils, groundwater conditions—are either in-
significantly different from a cost and environmental standpoint,
or else not enough is known about particular characteristics of the
entire area to make a judgment.
Drying Basin Design Alternatives--
Although there are a variety of design alternatives that could
be of potential interest, only one at this point has been identified
as an environmental issue: control of percolation waters from the
drying sludge that could result in groundwater contamination.
At present, Metro is planning to take the supernatant from
anaerobic digestion that is usually treated at the wastewater treat-
ment plant to the drying site. In order to pump sludge the distance
called for in this plan, a sludge of two to three percent solids is
necessary. This involves the use of some of the supernatant which
normally runs at about one percent solids. There is an agricultural
advantage to pumping the supernatant with the sludge, since it con-
tains considerable amounts of nitrogen and phosphorus.
A difficulty occurs when the sludge is applied to the drying
basins. With the sludge in a liquid form, most of the free water
will percolate downward toward the water table. Some water will
be lost to evaporation and some will stay in the dried sludge, but
most will move downward where it will likely result in degra-
dation of water quality to a degree that would make the groundwater
unacceptable as a source of drinking water. High nitrate concentra-
tions in drinking water can cause infant methemoglobinemia. High
concentrations of dissolved solids will deteriorate groundwater
quality for both potable use and irrigation.
Nitrate concentrations in the percolating water may be reduced
by bacterial denitrification, a process that occurs under aerobic
or least depressed dissolved oxygen conditions. It is not known
29
-------
to what degree the process might occur in the drying basins.
Metro believes that the likelihood of groundwater contamination
is low and proposes to monitor groundwater quality in order to
rapidly detect any deterioration. If deterioration occurs, Metro
would install a system to collect and treat percolating waters.
Alternatively, the drying basins could be lined. Both mitigation
measures would be extremely expensive.
Before the design of the drying basins is finalized, the issue
of the potential for groundwater contamination must be resolved.
To this end, Metro's on-going experimental work at a test site near
Greeley might be expanded to include studies of denitrification in
ponds.
Alternative Design Capacities —
The presently proposed system is designed to handle the sludge
loads from the Metro system projected to occur in 1985. The facili-
ties plan indicates that the sludge loads will increase from 30,000
dry metric tons [33,000 tons] in 1974 to 55,000 dry metric tons
[61,000 tons] per year in the early 1980's. These sludge quantities
are proportional to the wastewater flow volumes to be treated at the
Metro central (and possibly satellite plant) facilities.
EPA has become sensitive to the possible secondary impact of
funding large excess capacities for utilities such as sewage treat-
ment facilities. The issue becomes especially critical in air
quality priority areas such as Denver where water quality benefits
obtained from providing treatment to future residents conflict with
the additional air quality degradation from the automotive habits
of these newer residents. EPA has funded a Section 208 study under
the Federal Water Pollution Control Act Amendments of 1972 that will
evaluate and guide population projections of facilities plans in the
Denver area. The designated planning agency is the Denver Regional
Council of Governments(DRCOG). At present, DRCOG has been working
with facilities planners to reduce the somewhat inflated earlier
individual Districts' population projections, to conform with the
planned growth figure of 2.35 million persons in the overall Metro
area by the year 2000. The latter goal has been adopted by the
DRCOG and approved by its members.
The sludge loads projected by the Metro District and its
facilities planning consultant were developed as far back as the
1972 predesign study. The values presented in Volume III of the
facilities plan (Reference 55) on page 4-1 are essentially un-
changed from earlier projections. The annual rate of population
growth and hence growth in sludge loads is estimated to be at
30
-------
5.5 percent per annum over the 1975-1985 period. While this rate
did occur in the early seventies, current growth rates in the metro-
politan area are much closer to the recommended DRCOG growth rates
of 2 to 2.5 percent per annum. Thus it appears that at least the
amount of excess capacity designed into the sludge handling system
may be beyond that necessary to support the aqueous stream treat-
ment facilities sized on the basis of the lower population projec-
tions. Whether this excess capacity will have an influence on
secondary growth impacts and whether this capacity is "excessive"
should be evaluated further.
There appears to be little direct correlation between the
addition of sludge handling capacity and induced growth. That is
to say, additional capacity will not in itself induce individuals
to settle in the metropolitan Denver area. However, EPA has gener-
ally tried to coordinate its planning efforts for wastewater facil-
ities with other plans in a given area for consistency. Because
additional capacity accommodates additional growth, it can still
contribute toward excessive growth that may be inconsistent with
other planning efforts. In this case, the planning involves EPA's
own responsibilities under the Clean Air Act.
"Excessive" capacity is also exceptionally difficult to define
in the case of the design of this project. The only 'average'
figures available for design purposes are the projected sludge
loads. Design values for most of the equipment are based on peak
flows that vary with the particular unit. Anaerobic digestion
equipment is already under construction and therefore not really
an issue. Pipeline sizing and pump sizing is based on peak flows
for limited time periods. These can be related to an average flow,
but sizing requirements are not very sensitive to average changes.
The basin sizing is a function of the amounts of sludge and waste-
water to be dried, but two constraints apply. First, an average
value of wet sludge, about three percent solids, is assumed, but a
change in consistency to say 2.5 percent solids might be more im-
portant than the actual solids amounts involved. Secondly, the
actual time needed for drying in the basins is not precisely known.
A year's time is assumed for design purposes, but longer or shorter
drying times might be needed. Construction of basin volume can be
staged to meet needs as demonstrated in the early years of the
project. Metro District has indicated that no more than 180 hec-
tares [450 acres] of the proposed 240 hectares [600 acres] drying/
storage area need be developed immediately.
The principal alternative to the present sizing may be to
limit the monies spent on the drying/storage system. From the
point of view of secondary impacts, since control of the size of
aqueous stream treatment facilities will accomplish control of the
31
-------
rate of wastewater utility growth, control for sludge management
facilities may not be necessary.
Sub-System Alternatives to the Present
Lowry Disposal System
In a sense, sub-system alternatives to a null alternative are
a contradiction in terms. However, the null alter-
native may be improved by certain changes which can be regarded as
mitigation measures or sub-alternatives. This may be important be-
cause, although the proposed system appears most advantageous, some
modified version of the existing system is the most likely option
in the event that the proposed system proves infeasible.
Variations to the present Lowry system presented here are
tentative; they have had neither the benefit of a cost evaluation
nor an engineering and environmental evaluation. EPA simply sug-
gests these alternatives at this time as somewhat less preferable
alternatives that may have to evaluated in more detail if funding
is not available for the more capital-intensive land recycling sys-
tem now proposed by Metro.
Sludge Conditioning and Digestion--
It has already been mentioned that Metro has received a Federal
grant to construct facilities at the Central Plant to anaerobically
digest all Metro sludges. Part of the problem at the Lowry site
has been the deposition of large amounts of unstabilized sludge con-
taining large quantities of chemicals used for conditioning. These
chemicals include ferric chloride, lime and polymers. While they
have not been considered to be deleterious to the soil, it would be
preferable to keep them out of the sludge if possible.
The performance of anaerobic digesters on the raw and waste
activated sludges now treated at Metro must be considered an un-
known area at present. Anaerobic digestion can improve the dewater-
ing characteristics of sludges (resulting in less chemicals for
conditioning). However, digestion of secondary waste activated sludge
may not perform in the same fashion. It might be expected that odor
and chemical-related problems at the Lowry site will be reduced by
the measures already under construction. Conversion of the diges-
ters to the thermophilic mode might further improve sludge dewater-
ing characteristics.
Transport—
CH2M-Hill indicated in its evaluation of the present alterna-
tive that it might become more economical for Metro to purchase its
32
-------
own fleet of trucks to haul sludge to Lowry. A pipeline would
appear to be a reasonable alternative only if Metro were guaranteed
long-term use of the Lowry site.
The Lowry Site--
As discussed previously, use of the Lowry Range is contingent
upon Federal (Defense Department) approval and possibly the granting
of a long-term lease for some part of the bombing range to Denver
or the District. The present operation is predominantly a land-
spreading operation where sludge is being loaded onto the land at
annual rates considered highly excessive for good land recycling
practices on dryland. As long as the area involved is small, the
use of a "sacrifice area" is probably reasonable. Some plant species
including wheat will grow on the site even with the high loading
rates. The sacrifice would generally be in the potential contamina-
tion of groundwater supplies and food chain hazards posed by grazing
animals. A modification might involve restriction of grazing ani-
mals from direct contact with sludge-amended areas.
If grazing were to be permitted but controlled, additional
forage growth might be provided for cattle. This could be expensive
for Metro since large land areas would be involved and Metro would
have to purchase sludge spreading equipment.
A second alternative might be to develop some modified type of
drying/windrowing operation to store anaerobically digested-vacuum
filtered sludge at Lowry for sale or distribution to local farmers,
sod farms, etc. This would involve a substantial change of the use
of the bombing range that would need approval by the Federal mana-
gers. The alternative suggested here differs from the site alter-
native consideration for the Metro proposed system in that minimal
capital investment for new facilities would be required. Metro could
store some sludge and landspread the remainder until a market de-
veloped. Such a system would need large amounts of land available
in order to remain flexible.
33
-------
ivx-.
*****.
* '••-«•
., '^mm
:P$'&-- -V-
C-- r . .>.<
-------
w
wm
H
-------
This section contains a description of the
general setting for the project. The environ-
mental and social areas covered are ones that
might reasonably be expected to affect or be
affected by this project or its alternatives.
Because sludge applications could occur
almost anywhere in the Metropolitan Denver area,
it is necessary to broaden the focus of study to
include the overall environment. EPA is partic-
ularly concerned about impacts that could occur
after the sludge has left the drying and distri-
bution site and is finally applied to the land.
Therefore, the environmental settings for actual
use sites (Denver parkland, sod farms, mine-
spoil reclamation sites, irrigated and dryland
farms) are described to the extent that there
are recognizable differences in the way the im-
pacts might occur at different sites and with
different uses of the land. These site-specific
descriptions are found in Appendix E, which also
contains a description of the Lowry Bombing range
since that site is considered a basic alternative
to the project proposed.
-------
SECTION III
ENVIRONMENTAL SETTING
The study area is comprised of several sites, which are
highly diverse in natural and artificial characteristics. The
service area of the wastewater management system and the City
parks are in a highly urbanized setting; most of the proposed
sludge reuse sites are rural, and the mine spoil reclamation
sites are extremely remote and isolated from public access.
While most potential land application sites are within 50 km [30
miles] of the proposed sludge drying and distribution site and
to the east of the site, the mines are generally much farther
away, to the west.
The environmental setting for the proposed action comprises
the entire Denver region. The general discussion of the region
in this Section is supplemented in Appendix E by descriptions of
environmental settings in five specific sites, providing examples
of possible agricultural reuses of anaerobically digested, air-
dried sludge. For each category of reuse potential, a represen-
tative site was selected—mainly by virtue of the interest ex-
pressed by the owner and/or operator of the site in the use of
sludge in the operation—for detailed investigation of the envi-
ronmental setting and the probable impacts.
The representative sites serve to pinpoint the impacts which
can be expected from sludge application to all areas of similar
characteristics. For those areas which have very different char-
acteristics, the impacts may vary widely. Therefore, it is impor-
tant that, prior to drawing generalizations from assessments made
here, one compare the environmental characteristics of the pro-
posed sites with those of the representative sites. Clearly,
some extrapolations and approximations will be possible in many
cases; but, in some cases, it may be necessary to reevaluate the
impacts and adjust application rates and management conditions to
match the requirements of the particular site._
A discussion of the environmental setting at the Lowry Bombing
Range sludge disposal area is presented, also in Appendix E, to
serve as a basis for the evaluation of impacts of the "no-action,"
present alternative.
35
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CLIMATE
The Metropolitan Denver region, lying on the western edge of
the Great Plains, near the foothills of the Rocky Mountains, is
an area of transition from the climate of the plains to the cli-
mate of the foothills. The region has a high-elevation continen-
tal climate that has been characterized as semi-arid, Steppe-type
clime (Reference 9).
Temperature
Temperatures are generally moderate, with a mean annual tem-
perature of 11.3°C L52.3°F]. Ranges in extremes have been recorded
from -34°C [-30°F] to 40°C [|Q5°F]. Mean monthly temperatures for
Denver are presented in Table 3.
Precipitation
Monthly precipitation data for Denver are shown in Table 3,
Generalized precipitation patterns for the Denver region and sur-
rounding areas are shown in Figure 4. Precipitation is relatively
light ^average annual depth: 31 cm [12 in.]), with a large pro-
portion of the rain falling during the growing season from April
to September. Much of this summer precipitation occurs as a re-
sult of thunderstorm activity. Table 4 shows the seasonal occur-
rence of thunderstorms. Heavy thunderstorms in the eastern foot-
hills and plains area occasionally cause damaging flash floods.
Maximum expected precipitation frequencies as flood-producing
events are also shown in Table 4, together with relative humidity
data. The generally low relative humidity is a major factor in
the areal potential evapotranspiration rate of 610 mm [24 in.]
per year (Reference 9). This amount is twice the average precipi-
tation and is an indication of the aridity of the area. Periods
of drought one to two years in length are fairly common in portions
of Adams County (Reference 10).
Snowfall is generally not heavy, with most snow occurring
between November and April. Mean monthly snowfall data for Denver
are shown in Table 3. Extensive flooding caused by snowmelt in
the mountains occurs only at times when there has been either a
heavy accumulation of snow or a sudden increase in high-elevation
temperatures (Reference 11). The growing season is approximately
five to six months long, from April to September, when the temper-
ature does not fall below freezing.
Hind
Wind data for the Denver airport are presented in Table 5.
36
-------
Table 3. TEMPERATURE, PRECIPITATION, SNOW AND FREEZE DATA, DENVER (WB CITY)
CO
Mean
Temperature
°C
[°F]
P re c ip it at ion
trim
[in.]
Snowfall
^m
[ia.]
Freeze
Jan
1.2
34.1
8.6
0.34
15.7
6.2
Feb
1.8
35.3
16.3
0.64
23.6
9.3
Mar
3.6
38.5
20.6
0.81
29.7
11.7
Apr
8.8
47.8
36.8
1.45
27.2
10.7
May
14.7
58.4
65.0
°.56
3.0
1.2
Jun Jul
20.8 23.6
69.4 74.5
25.9 37.3
1.02 1.47
0.3 T
0.1 T
Aug Sep
22.9 18.4
73.2 65.1
30.5 19.3
1.20 0.76
T 3.3
T 1.3
Oct
12.1
53.7
24.4
0.96
8.1
3.2
Nov
4.7
40.5
14.2
0.56
17.5
6.9
Dec
2.6
36.6
10.7
0.42
17.0
6.7
Annual
11.3
52.3
309.6
12.19
145.5
57.3
No. days with 25 22 21 10 1 +a 0 0 + 5 18 24 126
temperature
< 0°C [32°F]
Freeze threshold
°C [
0 [
-2.2 [
-4.4 (
-6.7 [
-8.9 [
temperature
°F ]
32 ]
28 ]
24 ]
20 ]
16 ]
Mean number of days between
spring occurrence and first
166
192
212
231
239
date of last
fall occurrence
"+ - 0 > .5
Source: Decennial Census of United States Climate,
-------
»- ,-;'
FbRT'LUPTON
CITY1 ' 355
(14)
RY CJREER DAW A I
380 ', :
\ (is) : i
© SL7LECTED REPORTING WEATHER STATION
ISOHYET , mm (inches)
| SOURCE' WATCH QUALITY MANAGEMENT PLAN REPORT
GENERALIZED PRECIPITATION
PATTERN IN THE
METROPOLITAN DENVER REGION
-------
Table 4. MAXIMUM PRECIPITATION FREQUENCY, THUNDERSTORM AND RELATIVE HUMIDITY DATA, DENVER
Maximum amounts of precipitation to be expected within different time periods
(frequencies)
Frequency, 6-hour total 24-hour total
years mm [in.] mm
2 36 to 41 [ 1.4 to 1.6 ] 46 to 56 [1
5 46 to 51 [ 1.8 to 2.0 ] 61 to 71 [2
10 56 to 64 [ 2.2 to 2.5 ] 66 to 86 [2
25 71 to 76 [ 2.8 to 3.0 ] 86 to 97 [3
50 76 to 86 [ 3.0 to 3.4 ] 97 to 117 [ 3
100 86 to 97 [ 3.4 to 3.8 ] 107 to 127 [ 4
ir> Thunderstorms, mean number of days
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0+a +16 10 12 8 4 1 + 0
Relative humidity
percent percent of time
0 to 29 27
30 to 49 28
50 to 69 23
70 to 79 10
80 to 89 9
90 to 100 4
[in.]
.8 to 2.2 ]
.4 to 2.8 ]
.6 to 3.4 ]
.4 to 3.8 ]
.8 to 4.6" ]
,2 to 5.0 ]
Annual
43
The symbol + indicates a range between 0 and .5.
Source: Water Quality Management Plan, Denver Regional Council of Governments.
-------
Table 5. WIND DATA, DENVER (WB AIRPORT)
Wind speed Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mean hourly speed
mps 4.3 4.5 4,8 4.7 A. A A. A 4.0 3.7 3.7 3.8 A. 3 4.5
[niph] 9.6 10.1 10.7 10.6 9.9 9.8 9.0 8.3 8.3 8.5 9.7 10.0
Prevailing direction SSSSSSSSSSSS
Fastest speed
mps 18 22 2A 23 19 21 20 18 21 18 18 23
[raph] Al A9 53 52 A3 A7 AA AO A7 AO AO 51
Direction NW NW NW SE NW S SE SW NW SW NE NE
o Frequencies of wind speed percent
0 - 1 aps [ 0 - 3 mph] 9.6 9.2 8.6 8.0 9.1 9.8 11.6 1A.3 13.1 13. A 10.1 10.2
2 - 3 mps [ A - 7 mph] 25.6 25.1 23.2 23.5 2A.8 25.2 28.2 27.6 30. A 33.5 26.9 25.8
A - 5 nips [8-12 mph] 3A.A 33.0 33.5 31. A 33. A 3A.O 35. A 35.6 3A.1 33.0 33.6 3A.2
6-7 mps [13 - 18 mph] 2A.2 2A.1 22.7 2A.3 2A.2 23.0 20.5 19.3 18.9 16.6 23.1 22.2
8-10 mps [19 - 2A mph] A. 6 5.8 7.0 7.9 6.3 3. A 2.6 2.9 2.9 2.7 A. A 5.2
11 - 13 mps [25 - 31 mph] l.A 2. A 3.6 3.9 1.6 1.5 0.8 0.7 0.6 0.6 1.4 1.8
14 - 16 mps [32 - 38 mph] 0.2 O.A 1.1 0.7 O.A 0.3 0.1 +a 0.1 0.3 O.A 0.5
17 - 20 mpo [39 - 46 mph] 0 + 0.2 0.2 + + + 0 0 0.1 + 0.2
> 21 mps [ > A7 mph] 000 + 00 + 00000
+ •» < 0.5 percent.
Source: Water Quality Management Plan, Denver Regional Council of Governments.
Annual
mean
4.2
9.5
S
24
53
NW
10.6
25.7
-------
Air- quality is adversely affected by low wind speeds and special
atmospheric gradients. Air pollution in Denver can occur when wind
speed is 1 mps [3 mphj or less. A wind blowing at 2 mps [4 inph]
will usually clear polluted air out of the city in about two hours
(Reference 9). At the airport (see Table 5), wind speeds of 1 mps
[3 inph] or less occur 10.6 percent of the tine; winds blowing at
3 inps [7 mphj or less occur 36.3 percent of the time.
Chinook winds periodically blow from the mountains with great
turbulence. This phenomenon results from high-elevation westerly
winds being warmed in their rapid descent through a shallow layer
of cool air covering the plains. Sudden rises in temperature ac-
companying these gusty winds exert a moderating influence on winter
temperatures.
Regional Climatic Variations
Additional climatic data are presented for the six weather
stations whose locations are snown in Figure 4. Climatological
data for the city of Denver was presented previously in Table 3.
Information from this table is applicable to the city's parks.
Data provided by the Denver Airport and Fort Lupton weather sta-
tions (Table 6) are applicable to sod farms, irrigated farms and
dryland farms. The Cherry Creek Dam and Byers weather stations
(Table 7) are at the western and eastern extremes, respectively,
of the Lowry Bombing Range. Data from these stations also pertain
to some of the sod farms south of the Denver Metropolitan Area.
These five weather stations fall within the Denver region, an area
that is generally uniform climatically, although there are some lo-
cal variations.
The sixth selected weather station, at Berthoud Pass, is lo-
cated on the crest of the Continental Divide and experiences a dif-
ferent climate altogether. Discussion is deferred to a separate
heading under Mine Spoil Site in Appendix E, as data from this sta-
tion are applicable to that area only.
TOPOGRAPHY
The Metropolitan Denver region is located along the western
periphery of the high plains of Colorado, which slope gently up-
ward for almost 300 km [186 miles] from the eastern border of the
state to the base of the foothills of the Rocky Mountains. The
relief can be characterized as rolling prairie, with some hills and
ridges intersected by nearly flat floodplains along watercourses.
Much of the land currently under cultivation, mostly to the east
and northeast of Denver, is nearly flat ana level. Most of the
land in Adams and Arapahoe counties has a slope equal to or less
41
-------
Table 6. TEMPERATURE, PRECIPITATION, SNOW AND FREEZE DATA,
DENVER (WB AIRPORT) AND FORT LUPTON
Mean
Teaperature
Denver AF
•c
[•FJ
Ft. Lupton
•c
I'll
Precipitation
Denver AP
ma
[in.]
Ft. Lupton
na
[in.]
Snowfall
Denver AP
ca
r 4 i
[in.]
Ft. Lupton
CO
[in.]
Freeze
No. days with
teaperature
i O'C [32*F]
Denver AP
Ft. Lupton
Jan Feb Mar Apr
-0.3 0.7 2.9 8.1
31.5 33,3 37,3 46.6
-1.2 -0,3 3.1 9.3
29.8 31.4 37.5 48,8
13. Q 23.4 34,5 45.5
0,51 0.92 1.36 1.79
12.2 14.5 23.4 26.7
0.48 0.57 Q.92 1.05
19.8 27.9 38.9 30.2
70 Tin 111 1 1 Q
, O .LJ.aU JL3,J 1.1. * 7
21.8 18.5 12.2 6.4
8.6 7.3 4.8 2.5
29 25 25 13
30 27 28 15
Freeze threshold
temperature
•C [ -F 1
0 32
-2.2 28
-4.4 24
-6.7 20
-8.9 16
May Jun Jul Aug
14.1 20,2 23.1 22.3
57.4 68,3 73,5 72,2
14,9 20.5 23,4 22.2
58.8 68.9 74.1 72.0
77.0 25.4 50.8 39.1
3.03 1.00 2.00 1.54
54.1 16.8 32.5 36.6
2.13 0.66 1.28 1.44
3.3 0.3 T 0.3
0.8 0 0 0
0.3 0 0 0
1 +a 0 0
2 + 00
Sep Oct Nov Dec
17.8 11.3 3.7 0.9
64,0 52,4 38.6 33.7
17.6 10.9 3.1 -0.2
63,6 51.7 37.5 31.6
23.6 29.7 20.3 14.7
0.93 1,17 0.80 0.58
23.6 24.6 11.4 10.7
0.93 0.97 0.45 0.42
4.3 9.4 23.4 19.3
0 0.3 5.3 8.6
0 0.1 2.1 3.4
+ 7 23 29
1 13 27 30
Annual
10.4
50.7
10.3
50.5
397.0
15.63
287.0
11.30
177.0
£Q -J
07./
73.9
29.1
153
173
Mean nuuber of days between date of last
spring occurrence and firs
Denver AP
160
184
198
222
230
jt fall occurrence
Ft, Lupton
143
175
196
213
226
+ - 0 > .5
Source: Decennial Census of United States Climate.
42
-------
Table 7. TEMPERATURE, PRECIPITATION, SNOW AND FREEZE DATA,
CHERRY CREEK DAM AND BYERS
Mean
Temperature
Cherry Cr. Daa
•c
t'F]
Byers
•c
IT]
Precipitation
Cherry Cr. Daa
na
[in.]
By era
IBS
[ln.1
Snowfall
Cherry Cr. Daa
ca
[la.]
Byer»
ca
[in.]
freeze
No. days with
teaperature
< O'C [32'F]
Cherry Cr. Daa
Byers
Jan Feb Mar Apr
-0.3 0,6 2,8 8,1
31,5 33.1 37.1 46,6
-1.1 0.2 2.6 7,9
30.1 32.4 36.6 46.2
7.9 16.3 20.1 41.4
0.31 0.64 0.79 1.63
11.2 13.0 22.1 34.0
0.44 0.51 0.87 1.34
22.1 21.6 28.7 22.9
8.7 8.5 11.3 9.0
20.1 22.6 26.9 19.3
7.9 8.9 10.6 7.6
29 27 28 17
30 27 28 17
Freeze threshold
temperature
•c [ •? 1
0 32
-2.2 23
-4.4 24
-6.7 20
-8.9 16
Kay Jun Jul Aui? Sep
13.5 19,7 21,9 21,3 17.3
56,3 67.4 71,5 70.3 63,2
14.0 20.1 23.0 22,1 17.8
57.2 68.2 73.4 71.8 64,1
78.7 28.4 43.7 30.7 18.3
3.10 1.12 1.72 1.21 0.72
65.3 30.7 58.2 40.9 20.8
2.59 1.21 2.29 1.61 0.82
3.0 0 0 0 1.5
1.2 0 0 0 0.6
3.0 I T I 2.3
1.2 T T T 0.9
3 +a 0 0 1
2 + 0 0 1
Oct Hoy D«c
11,2 3,7 0.7
52,2 38,6 33.3
11.2 3.1 0.1
52,1 37.6 32.1
26.9 13.7 11.2
1.06 0.54 0.44
21.8 14.0 8.9
0.86 0.55 0.35
16.0 15.7 22.9
6.3 6.2 9.0
4.8 18.5 12.7
1.9 7.3 5.0
10 26 29
9 25 30
Annual
10.1
50.1
10.1
50.2
337.3
13.28
341.4
13.44
154.4
60.8
130.3
51.3
170
169
Kean cumber of days between o-te of last
spring occurrence and first fall
Cherry Creelt Daa
135
155
190
211
222
occurrence
Byers
133
168
133
204
222
•*• • Q > .5
Source: Decennial Census of United State* Climate; Cliantologicil Dau for th« U.S.:' Colondo.
43
-------
than nine percent, as shown below (References 10,14).
Percent of total land area In county
County
Adams
Arapahoe
<. 5% slope
63.7
55.7
1 9% slope
75.5
73.0
Elevation in the eastern plains section of Colorado ranges
from 1,020 m [3,350 ft] at the lowest point in the state (where
the Arkansas River crosses the border] to about 1,600 m [5,280 ft]
around the Denver area. West of Denver, the plains give way abruptly
to the foothills, with elevations of 2,100 m to 2,750 m [6,890 ft
to 9,025 ft]. Typical elevations for sites within the study area
are shown in Table 8. General elevations for the region are shown
in Figure 5.
Table 8. TYPICAL ELEVATIONS FOR SITES WITHIN THE STUDY AREA
Study site
City park
Sod farm
Sou farm
Sod farm, irrigated farm,
dryland farm
Irrigated farm
Dryland farm
Lowry Bombing Range
Lowry Bombing Range
Nearby city or
weather station
Denver
Littleton
Brighton
Fort Lupton
Platteville
Wat kins
Cherry Creek Dam
Byers
Elevation
m
1,609
1,634
1,518
1,497
1,469
1,685
1,721
1,584
[ft]
[ 5,280 ]
[ 5,362 ]
[ 4,982 ]
[ 4,914 ]
[ 4,820 ]
[ 5,530 ]
[ 5,649 ]
[ 5,200 ]
Many rivers and creeks flow out of the mountains and foothills,
mostly in a south-to-north direction through the Denver region, in
the Platte Drainage watershed. The South Platte River and Cherry
Creek flow through the heart of Denver.
Separate discussion of the topography of the mine spoil sits
is presented under that heading in Appendix E.
GEOLOGY
he Metropolitan Denver area is located in the Denver Basin
T
44
-------
j
'
A , R A ,P A
-------
near its boundary with the Front Range. The strata of the Denver
Basin dip slightly toward the east, while the strata of the Front
Range have a steep dip. The two geologic regions are separated by
a zone of sharp, almost vertical folds. Thus the dip of a forma-
tion several kilometers west of Denver would be high (>90 percent),
while the dip of the same formation several kilometers east of
Denver would be slight (
-------
FIGURE 6
GEOLOGIC MAP
OF AREAS IN THE VICINITY OF
METROPOLITAN DENVER
FOR EXPLANATION OF SYMBOLS
SEE THE FOLLOWING 2 PAGES
SOURCE: GENERALIZED SURFICIAL GEOLOGIC MAP
OF THE DENVER AREA,COLORADO
OCKY MfN.
ARSENAC WELL
47
-------
FIGURE 6 (cont.)
EXPLANATION
Loess, eolian sand, colluvium
undifferentiated
Wind-deposited silt, sand: sand and cvbbtfs on
foothill slopes. Silt and sand deposits 0-$0
feet thick, sand and cobbles as much as 10
feet thick. Saturated sand and yraref may
yield 1 to 5 gpm to tcells
Post-Piney Creek alluvium, Piney Creek
Alluvium, pre-Piney Creek alluvium,
Broadway and Louviers Alluviums
Sand, grartl. Kilt, and clay. Deposits range
from 0-60 feet thick. Saturated sand and
grartl yield ox much a,s J,OfjO gpm to icells.
Chemical quality of teat er generally good
Slocum, Verdos, and Rocky Flats
Alluviums
Reddish-brown silty clay. silt, sand, pebble
lenses, and /w.s-s. Course gravel and sand
and rolcanic axh underlie high terract
re tn Hants. L'nit may exceed 50feet in thick-
ness locally. Yields J to 5 gpm to irells
tcher? material* are saturated. Gravel and
sand near Barr Lake yield as much as 200
gpm to icflh. Water generally of poor
quality.^ contains excess ire concentrations
of fluoride
L
TKcd
Castle Rock Conglomerate, upper p£-t
of Dawson Formation, and upper
part of Denver Formation
Gray, broicn. tan. and greenish-gray shale.
clay, and siltstone. and numerous lenticular
beds of light-colored conglomerate and
Hand* tone. .\ndesitic mudflotc breccias
common in vicinity of Table Mountains
and Green Mountain. Beds of sandy lime-
stone, lignite, coal, and carbonaceous shale
are common. L'nit ranges in thickness from
3Wt to 1,+ 00 feet. Yields lefts than 25 gpm
to u'eils in mr.xt of the area, but as much a*
150 gpm in southeast part. Locally u-ater
contains high concentrations of ditsoh'ed
solids, iron, radioactive constituents, and
hydrogen suljlde gas
I
Kdl
Lower part of Dawson Formation, Arap-
ahoe Formation, and lower part of
Denver Formation
White to yelion- arkotic sandstone and con-
glornfrate interbedded irith gray, green.
and red .thole and claystone. Contain*
all u rial and mudflotc ande^itic detritn*.
CoH'jfornerrtte hrdx thicken itt xpper f»irt.
and nrt> thtckvr nnd mure nttititrmut ton-(ird
avuthir .if part of the tmm'n. L'nit ranyex
from ±wtn l, + 'mfftt thifk. Yittd* to irellt
areruye 100 up m and arena much ax^OfJgpm.
Water generally nfad quality
Upper part of Laramie Formation
Blxe-gmy nilty shale, thin xilty Hdnd-itnne.
limestone, and coal: cvxi/ thickest in fa>rtr
part. Yield* 1 to 2 QP^ of poor quality
water to trflft. Witter contains hydrr^jen
sulfide. iron, and methane
Volcanic rocks
Lai-afloirson Table Moun-
tains, rent source near
Kalstoit Creek, and ask
flow tuffs neur Castlt
Rock. Ash jloir tuffs
underlie Castle Rock
Conglomerate. AV
knou-n to be saturated
Ift
D
o
LJ
"
u
u
Geological map of areas in the vicinity of Metropolitan Denver (cont'd)
-------
FIGURE 6 (cont.)
I
Klf
Lower part of Laramie Formation and
Fox Hills Sandstone
Medium-grained sandstone (60-80 feet),
orerlying and grading into finer grained
thin-bedded sandstone interbedded with
siltstone and shale fJO-100 feet}. fine
grained qitartzost sandstone, siltstone,
shale (80-230 feet). Wells penetrating en-
tire unit generally yield 100 gpm and a few
yield as much as $00 gpm. At places water
may contain objectionable amounts of
methane, hydrogen sulfide, iron, and fluo-
ride
Kpb
Pierre Shale, Xiobrara Formation,
and Benton Shale
Gny, blue, and black shale, sandy shale, and
thin limestone; some silty sandstone, ben-
to/iite seams, chalky marl, and lijrustone.
Units may total S,000 feet in Denver Basin.
Fractured zones in shale may yield 1 to 2
gpm of poor quality water to icetlt
[ Kd
Dakota Group
Upper 100 feet gray-tchite fine- to medium
grained sandstone, thin-bedded, to massive.
Middle 350 feet dark-gray silty carbona-
ceous shale, contains refractory clay.
Lou-er60feet gray coarse sandstone, locally
conglomeratic. cros.f bedded. Sandstone
yields 5 to 30 gpm ta u-ellx near outcrop.
Water contains excessive iron locally
Sedimentary rocks undifferentiated
Includes Upper Jurassic Morrison (300 feet)
and Ralston Creek 1120 feet) Formations;
Triajssic(f) and Permian Lykins Formation
(£00 feet); Permian Lyons Sandstone (200
feet); and Lower Permian and L'pp€r and
Middle Pennxylranian Fountain Forma-
tion (1,200 feet). Lyons Sandstone, shotrn
by stipple, generally yields 5 to 10 gpm, and
as much as 80 gpm to u~ells near outcrop
areas. Fountain Formation sandy conglom-
erate may yield 1 to 5 gpm to icells. H'afer
may contain extexstire iron and fluoride
Igneous and metamorphic rocks
undifferentiated
Granite, gneisx. schist, quartzite, pegmatite.
quartz reins, intruaire igneous rocks. Yield
1 to 5 gpm of generally good quality u-ater
to veils that tap fractures or it-fathered
xnnes
Contact
Fault
y
ZU)
•I
I-
f
o
UJ
tr
Geological map of areas in the vicinity of Metropolitan Denver (cont'd)
49
-------
in
o
Table 9. STRATIGRAPHIC UNITS AND THEIR WATER-BEARING PROPERTIES IN THE VICINITY OF DENVER
System
Quaternary
Tertiary
Cretaceous
Series
lecent «nd
Pleistocene
Pleistocene
Paleocene
Upper
Cretaceous
Subdivision
Dune sand
Slope wash
Valley-fill
deposits
Upland
deposits
arkose
Dawson
Denver
formation
Arapahoe
formation
Laramie
formation
Fox
a
Hills
andstone
Thick-
ness
ma
0-15
0-9
0-40
0-5
0-60
0 - 185
0 - 185
0-75
Fine to medium sand and minor amounts of clay
and silt.
Poorly sorted clay, silt, sand and gravel;
grades into val ley-f ill deposits*
Interbedded clay, silt, sand and gravel that con-
tains some cobbles and boulders and beds of al-
tered volcanic ash. Underlies the flood plain
and terraces on the South Platte River valley and
underlie floor of Bccbe Draw and Bex Elder Creek
Valley, Include some slope wash along the edges
of Beebe Draw and Box Elder Valley.
Deposits of sand, gravel, conglomerate and vol-
canic ash that mantle the bedrock in the upland
arens. Include colluvium, r -siduum and remnants
of pediment and terrace deposits.
Varicolored clay, soft shale and siltstone con-
with lenticular poorly sorted generally moder-
ately indurated yel lowish-hrown sand s tone and
conglomerate. Local ly contains andesitic mate-
rial and beds of weathered volcanic ash and ben-
tonltlc clay .
Upper part (120 m) : Soft predominantly blue or
lenticular boils of sandstone.
Lower part (60 m) : White to yellow sand, gravel
and conglomerate, variously Indurated and in-
cluding minor amounts of shale and clay.
Upper part (120 m) : Chiefly olive-gray silty
shale and si'ltstone and lenticular sllty sand-
stone; contains numerous carbonaceous clay
beds and 1 ignit Ic s earns .
Lower part (60 m) : At top, a sequence of thin
beda of blue-gray ailty shale, sandstone and
thin beds of sandstone, fairly thick beds of
a ubb 1 1 urn 1 nous coal, and several other thinner
sandstone units that locally coalesce with the
thick basal sandstone.
Uniformly bedded buff to pale-yellow friable
medium-grained sand atone interbedded with gray
to black sllty shale and sllty sandstone. About
15-18 m of massive sandstone at top.
Water-bearing
properties
Serves mainly as medium for recharge from pre-
cipitation . Local lv vie 1 ds srr.,i 11 quantit_tjs of
vatrr to donrst ic and sti-r- vM ] s .
Yields small to arderat**
domestic and stock wells
we 11 s .
quantities of water to
and to a f ft. irrigation
The most important aquifer In the report area and
the source of groundvater for nearly all the
large-capacity wel Is. Yield r.oderat e to large
quantities of water to many Jcnestic, stock,
irrigation, public-supply and industrial veils.
Topographically high and
medium for recharge from
Yields small quantities
of water to domestic
and stock wells In the
southern part of the
report area.
Yields small to moder-
ate quantities of water
to domestic, stock, pub-
lic-supply and inJustri-1
al wells in the southcrr
UP 1 1 drained. Not a
precipitation.
The Pawscn arkose.
stratipraphically
equival pni tc part
of the Denver and
Ar 3 pa hoe f orir,at 1 ons ,
yields srr.al 1 to
moderate quantities
of water to domestic,
sfc c'r- , puM I c- supply
and industrial veils
in the southeastern
part of the report
area .
Some of the sandstone unl ts in the upper part
yield smal 1 to modera ', e quantities of water to
domestic, Etock and industrial wells through-
out the report area.
The basal sandstones in the lower part yield
small to moderate quantities of water to domes-
tic, stock, public-supply and industrial wells
throughout the area.
Yields small to moderate quantities of water to
domestic , stock , public-supply and industrial
wells throughout the report area.
Water y le1. d ,
litc-rs per s*-cc r- j
0.1 - 0.3
!
I
1:5
125
0.3 - 13
1 - 9
1 - °
6-25
upp^r : 0.1
lower: (, - :5
6-25
i
*l nwter - 3,261 feet
1 liter per second * 15.85 gallons per minute
S-iurce: Ground Water Resources of the South Platte River Basin in Western Adams and Southwest Weld Counties, Colorado
-------
The Dawson Arkose and Denver formations, unlike the Arapahoe, have
poor groundwater yield and serve as an aquitard. The upper parts
of these formations outcrop in southeastern Arapahoe County.
Most of the surface of the study area is covered by unconsoli-
dated Quaternary deposits which range in thickness from 0 to 20 m
[0 to 66 ft].
Early in the Quaternary, before the Wisconsin glaciation, de-
bris from the Front Range formed large deltas in the Denver Basin.
The deltas included layers of silt, sand and gravel as well as some
volcanic ash. The pre-Wisconsin Quaternary deposits are designated
as Qsi on the geologic map presented on Figure 6. The water yield
of these deosits is small and generally of poor quality.
During the Wisconsin glaciation, the Denver Basin, particularly
the western portion near the city of Denver, served as an outwash
area for the glaciers in the mountains to the west. The torrential
flow of the outwash streams eroded the underlying deltas and depos-
ited as much as 20 m [66 ft] of sand, gravel, silt and clay over
them. Thus outcrops of the Qsr formation represent topographic
highs which v/ere not destroyed by the outwash streams. The allu-
vium from the glacier forms an aquifer with good water quality and
yield as high as 125 Ips [2,000 gpm]. The Wisconsin alluvium is
depicted as Qpl on the geologic map. Strong winds capable of car-
rying heavy bedloads also characterize outwash areas. The winds
shift the unconsolidated alluvium. These eolian deposits, depicted
as Qs on the geologic map, cover more of the surface than does any
other deposit in the study area. They range in tnickness to about
three meters [10 ft] and have a small yield (about 0.3 Ips [5 gpm]).
The proposed sludge reuse sites, except for the irrigated farms
in Weld County, are plotted on the geologic map. In general, water-
bearing formations used intensively as a groundwater source, are
less suitable for sludge disposal. Many other factors are impor-
tant, however; the geologic character of an area cannot be the only
criterion for site selection.
Earthquakes
During the history of Denver, only one earthquake of damaging
proportions has been reported near Denver. In the mid-1960's, how-
ever, several mild earthquakes occurred. These earthquakes centered
around the Rocky Mountain Arsenal well, where millions of gallons
of contaminated water were injected into the highly faulted pre-
Cambrian bedrock (Reference 19). In the future, it is unlikely that
major earthquakes will occur in the Denver area. It will probably
not be necessary to incorporate earthquake lateral force considera-
51
-------
tions into design features for the sludge disposal systems.
SOILS
Soils in the study area have been surveyed by the U.S. Soil
Conservation Service (SCS) in recent years. Final reports on de-
tailed soil surveys have been published for Adams County (Refer-
ence 10) and Arapahoe County (Reference 14). As for Weld County,
a detailed survey has been completed, but no published report is
available. Official soil series descriptions and interpretations
for the Weld County soils which may be subjected to sludge appli-
cation were obtained from the SCS field office in Greeley (Refer-
ence 22).
Soils in most of the potential areas of sludge application
are for the most part calcareous. They fall within about 20 dis-
tinct associations with characteristics typical of their geographic
setting. The topography, drainage, texture and parent materials
of these soils are presented in Appendix B and are shown graph-
ically on Figure 7. Specific characteristics of soils in each
typical site under investigation are presented separately under
the discussion of the environmental setting of the particular site
in Appendix E. The published soil surveys are indispensable as a
tool tor planning sludge use in agriculture on a regional basis.
However, for application on a specific field, this information
should be augmented with additional field investigations by soil
scientists and/or agronomists.
An important soil property which should be carefully consid-
ered in sludge application is the micro-community inhabiting the
soil. Microbial populations living in the soil include viruses,
bacteria, actinomycetes, fungi, algae and protozoa. Soil aeration,
acidity, temperature, moisture content, organic matter, inorganic
nutrient supply and other parameters determine the relative popula-
tions of the various microbial groups. Some of the important func-
tions of soil microorganisms, insofar as sludge application is con-
cerned, are (1) uptake of nutrient elements and their conversion
to organic matter, (2) production of growth factors stimulating
other organisms, (3) breakdown of complex organic molecules to
simpler, more readily usable forms, (4) production of antibiotics
which inhibit some organisms, (5) symbiotic relationships between
certain organisms, (6j predation and parasitism between organisms,
(7) nitrogen fixation from the atmosphere under certain conditions
and (8) production of enzymes which promote many different biochem-
ical reactions.
52
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FIGURE 7
SOIL ASSOCIATIONS IN
VICINITY OF DENVER
0 468
KILOMETERS
02468
SOURCE : WATER QUALITY MANAGEMENT PLAN
U.S. SOIL CONSERVATION SERVICE
ADAMS COUNTY
RAPAHOE "COUNTY
53
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WATER
The Metropolitan Denver area is water-deficient. It is
through large-scale transmountain diversions that the demands of
the area are balanced with imported supplies. Intricate and long-
standing water rights and allocations dictate ownership and use of
the existing and developed supplies. Municipalities, irrigated
farms, industries, recreation projects, fisheries and stream aes-
thetic requirements impose cumulative and sometimes conflicting
demands upon quality and quantity of water in the study area.
Even though sludge-handling is an important phase of the to-
tal water management picture in the region, it neither demands nor
supplies significant quantities of water to the total system. How-
ever, sludge must be viewed as a potential threat to the quality
of waters, both in the ground and on the surface. Thus, the dis-
cussion that follows is not aimed at" being a comprehensive eluci-
dation of the water supplies of the region; rather, it is meant to
provide the basic background for the impact statements which are
presented in the succeeding sections.
Groundwater
The water-bearing properties of strata underlying the study
area are presented in Table 9 under Geology. Valley fill deposits
of Recent and Pleistocene series, ranging in thickness from 0 to
40 m [0 to 125 ft] comprise the most important aquifers in the
area. These aquifers underlie various thicknesses of dune sand
and slope wash. The valley fill deposits yield moderate to large
quantities of water to the domestic, stock, irrigation, public
supply and industrial wells. Depth to water table ranges from a
meter [a few feet] to 30 m [100 ft]. Detailed data on groundwater
occurrence and movement are not available.
Below this aquifer formation, strata with low permeability
(aquitards) separate the upper aquifer from the important Laramie-
Fox Hills aquifer, which lies at considerable depths (90 m [300
ft] at Platteville; 520 m [1,700 ft] at Lowry Bombing Range; 400 m
[1,300 ft] at the proposed sludge drying and distribution center)
from the land surface. Wells penetrating the full thickness of
this aquifer can yield from 6 to 60 liters per second [100 to 900
gallons per minute].
Water quality in the upper aquifer is generally good, although
scarcity of data preclude adequate evaluation. The Laramie-Fox
Hills aquifer water quality varies from one place to another. Near
its recharge sites, to the south and east, the quality is superior
to that at some other locations, where objectionable amounts of
54
-------
methane, hydrogen sulfide, iron and fluorides are encountered.
Surface Water
Even though the study area is interlaced with many of the trib-
utaries of the South Platte River, most of the creeks in the east-
ern part of the study area are dry during most parts of the year.
Some streambeds are wet only on rare occasions: once every several
years. Streams draining the western parts of the Metropolitan
Denver area flow during most of the year and include St. Vrain
Creek, Boulder Creek, Coal Creek, Big Dry Creek, Clear Creek, Sand
Creek, Cherry Creek, Bear Creek, Plum Creek and many smaller creeks.
Many diversion structures across streams on the western slopes of
tne Continental Divide have been constructed to transfer water
through the mountains to the eastern slopes and to discharge the
water in the above-mentioned streams. These water diversions, res-
ervoirs built on the creeks themselves, groundwater withdrawals,
irrigation diversions and their return flows have drastically
changed natural flow patterns in these streams. A discussion of
the quantities and quality of water in the streams, as well as a
model of stream water quality in the Denver Basin, are presented in
the recently published Water Quality Management Plan (Reference 9).
During the period 1966 through 1970, annual stream flow into
the Metropolitan Denver area totaled 450 million cubic meters
[185,600 cfsd], 95 percent of which was diverted from the streams.
Fully 38 percent of the streamflow into the Denver Area in that
period was wastewater treatment plant effluents from upstream areas,
and over half of the water leaving the metropolitan area was gen-
erated within the area (Reference 9).
The lakes in and around the metropolitan area are of special
significance. Most of the lakes were used for irrigation before
the area became heavily urbanized. Most are now used for recreation
and as centers of real estate development. There are some 50 lakes
with surface areas greater than 10 hectares [25 acres], with a total
combined area of 3,686 hectares [9,103 acres] and a total shoreline
of 185 km [115 miles]. The three largest lakes are:
Lake
Barr
Stand! ey
Chatfield
Surface area
hectares L acres J
708 [ 1,750 ]
492 [ 1,216 ]
465 [ 1,149 ]
There are another 113 lakes of 2 to 10 hectare [5 to 25 acre] sur-
face area, with a total area of 526 hectares [1,300 acres] and a
shoreline of 110 km i63 miles] {.Reference 23).
55
-------
Water quality in the lakes nas deteriorated progressively
over the past decades with chemical and biological pollutants
emanating from the increasingly heavy use and development of the
surrounding area. A recent investigation of the present quality
of waters in these lakes, including parameters such as salinity,
pH, transparency and coliform bacteria, is reported by the U.S.
Geological Survey in graphic format (Reference 23).
BIOLOGY
The Metropolitan Denver region is part of the high plains area
that extends from the Great Plains to the foothills of the Rocky
Mountains. The elevation of the study area ranges from 1,400 m to
1,800 m [4,600 ft to 6,000 ft], placing it within the Upper Sonoran
life zone (Reference 24). This zone begins at the Transition zone
of the foothills of the Rocky Mountains and extends beyond the
eastern border of Colorado. The growth and distribution of vegeta-
tion is largely dependent upon climate, relief, substrate, fire and
the occurrence of human activities such as grazing and agriculture.
With an average annual precipitation rate of only 30 to 40 cm [12
to 16 in.], water availability is the chief limiting factor leading
to the low growth of grasses and forbs on the plains.
Prior to settlement, the plains supported a mixed prairie which
v/as made up primarily of perennial bunchgrasses. Short grasses such
as blue grama and buffalo grass dominated on drier sites, and taller
grasses (western wheatgrass ana little bluestem) occurred on sites
with higher moisture, such as along eastern stream courses and to-
ward the mountains to the west. Prior to settlement, a very complex
mosaic of steppe communities existed in the Denver area in response
to the numerous soils (Reference 9). Under natural conditions, the
three major plant communities probably were (1) upland prairie or
short-grass plains, (2) meadow and (3) cottonwood-willow. The
plains did not support tree growth except along the watercourses,
which were fringed with cottonwoods and willows. Dense thickets of
wild plum and ciiokecherry, with scattered clumps of hackberry and
box elder, occurred sometimes in gulches and arroyos (Reference 24).
The original distribution of natural vegetation in the Denver region
(Reference 25) is shown in Figure 8.
Human activities, mainly in the form of cultivation and live-
stock grazing, have altered the natural vegetation considerably.
Sixty-five percent of Adams County is currently under cultivation,
and 35 percent of Arapahoe County is similarly utilized. The remain-
ing uncultivated lands are generally used for pasture and range or
urban and residential purposes (References 10,14).
The present biotic communities can be classified according to
56
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NATURAL VEGETATION OF COLORADO
LEGEND
1-GRASSLANDS OF THE PLAINS-Blue gramma is the dominant
grass.
2-GRASSLANDS OF THE PLAINS-Blue grama, sand dropseed,three-
awn, sand reed, bluestem, sideoats grama, and yucca,
3-GRASSLANDS OF THE PLAINS-San reed, bluestem, sand drop-
seed and sand sage on sandhills,
4-GRASSLANDS OF THE FOOTHILLS-Wheatgrass, needlegrass, sand
reed, bluestem, and blue grama mixed with areas of
shrub and occasional ponderosa pine,
5-WOODLANDS OF THE LOWER MOUNTAINS-With stands of ponder-
osa pine (and often Gambel Oak) with Douglas-fir, blue
spruce, white fir and occasional aspin mixed with
fescue, muhly, bluegrass, shrubs and forbs,
6-WOODLANDS AND GRASSLANDS OF SUBALPINE AREAS-With stands
of spruce and fir or lodgepole pine, or aspen.
Thurber's fescue grassland parks intermingle with
timbered areas.
7-GRASSLANDS AND MEADOWS OF ALPINE REGIONS ABOVE TIMBERLINE
With sedges, grass, willow, birch and forbs.
SOURCE: SOIL CONSERVATION SERVICE, OCTOBER 1972
METROPOLITAN
DENVER SEWAGE
DISPOSAL DISTRIC
(MDSDD-I)
c
-R
m
CD
-------
the following general vegetation units; (1) Cultivated, (2) Uplands
Vegetation, (.3) Riparian and Aquatic and (4) Urban/Residential. A
listing of common plants and animals in these units is given in Ap-
pendix C.
TYPICAL UPLAND VEGETATION UNIT WITH
COTTONWOOD TREES INDICATING SEASONAL
RIPARIAN ZONE
Cultivated Lands Unit
Cultivated vegetation includes sod farms, irrigated farms and
dry farms. Thousands of hectares of the plains are devoted to irri-
gated farming along the South Platte River, and to dryland farming
on adjoining uplands. In some areas, such as in Arapahoe County,
irrigated farmland has decreased significantly in the past 30 years
because of community development and the diversion of water from
the South Platte River for domestic purposes.
Agricultural lands are typically cultivated as monoculture
units. The allocation of large parcels of land to only a few plant
58
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species leads to a simplified environment with low animal diversity.
Animal populations are generally characterized by numerous small
burrowing rodents, seed-eating birds and a few wide-ranging preda-
tor species. Although a monoculture yields little variety in habi-
tat, the crops provide an important food source for wildlife. This
is particularly significant in migratory bird wintering areas near
Riparian-Aquatic habitats. The stubble, fence rows and unharvested
remains are often vital to wildlife for sustenance and cover during
the winter months.
Uplands Unit
Uplands vegetation includes pasture and range lands whose spe-
cies composition varies with soil character and past use. Current
Upland vegetation on uncultivated soils is typically a weedy grass
type that has suffered from too heavy grazing. The two major short-
grass species of the mixed prairie, blue grama and buffalograss, are
hardy perennials that can withstand heavy grazing since they grow
close to the ground and form a cover of bunchy sod. Both of these
grasses increase when tall-grass associations are overgrazed. When
overgrazing occurs on the short-grass units, the sod mats weaken and
are invaded by annual grasses and annual and perennial weeds (Refer-
ence 26). Good examples of the tall-grass prairies and mixed-grass
prairies are now becoming scarce in the Denver region (Reference 9).
Wildlife patterns have also changed in response to prairie suc-
cession and alterations in land use. Formerly abundant animals such
as the prairie dog, American buffalo and pronghorn antelope have be-
come limited in distribution because of human intervention and changes
in the short-grass prairie habitat. The black-footed ferret, which
had a nistoric range dependent upon that of the prairie dog, is con-
sidered an endangered species (Reference 27). The greater and the
lesser prairie chicken are examples of species which are endangered
by the diminishing size of the mixed prairie habitat. The Uplands
vegetation area is now primarily inhabited by jackrabbits, rodents
and many reptiles which are tolerant to change and can coexist with
human activities.
Riparian and Aquatic Unit
Riparian and Aquatic units occur along major watercourses, such
as the South Platte River and Cherry Creek. Associated with most
watercourses are wide, nearly flat floodplains. Many of the creeks
in the study area seldom flow for more than two weeks, generally in
March and April and during heavy storms in the summer. Most of the
suitable terrace soils along streams have been cultivated, and other
Kiparian zone sites, which have not been utilized for gravel mining
or occupied by industrial sites, have been grazed for 100 or more
years. In bottom lands where there is no current grazing, there is
59
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a greater variability in vegetative cover (Reference 9).
Colorado's semiarid Front Range Urban Corridor has many lakes
of high value. In the past, they were used to store water for irri-
gation and domestic uses, with occasional use for recreational acti-
vities. As a result of rapid suburban development, their importance
at present is as recreational areas and centers of real estate de-
velopment. The major lakes of the Denver region are Cherry Creek
Lake, Chatfield Lake, Marston Lake, Standley Lake and Barr Lake.
The network of smaller lakes, ponds and reservoirs also plays an im-
portant role in the natural ecosystem.
Riparian and Aquatic units include some of the most important
wildlife habitat in the area. The Platte River Valley and its trib-
utaries produce one-third of Colorado's annual water fowl crop and
provide winter habitat for tens of thousands of migrant birds. The
trees of the floodplain supply nesting and roosting areas for large
numbers of birds of many kinds, including small numbers of bald
eagles. In the metropolitan area, most marshlands have been elimi-
nated, although many floodplain oxbow lakes, ponds and marshes per-
sist in the more rural areas. Marshes provide a valuable wildlife
habitat, serving as home for amphibians and aquatic mammals, and as
nesting and feeding grounds for waterfowl. The dense vegetation
provides excellent winter storm cover for pheasants, rabbits and
many other kinds of wildlife (Reference 9).
The larger lakes of the Denver region are stocked with gamefish
such as brown trout and rainbow trout. All lakes generally contain
several species of roughfish, which provide important food supply
for wildlife as well as maintaining the aquatic ecosystem. Lakes
and ponds that are less disturbed by human activities comprise the
necessary aquatic habitat for migrant waterfowl.
Urban/Residential Unit
Tne original site of Denver was a virgin prairie traversed by
two tree-lined streamcourses. With urban growth and development, a
large variety of non-native shrubs and trees have been introduced
into the Denver area. A vast City park system interlaces the city,
providing a wealth of greenery, open space and artificial lakes and
ponds. Denver has more than 100 parks covering more than 1,100 ha
[2,800 acres], as shown on Figure 3.
The present vegetation is a cross-section of many plant types
from midwestern and eastern United States. Parks and residential
areas are lined with shade ana fruit trees, ornamental shrubs and
flower gardens. Many large areas are landscaped with grasses and
other ground covers for recreational use. This wealth of foliage
60
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ha? attracted several midwestern birds, such as the red-eyed vireo
and bronzed grackle, unknown within the area before 1910 (Reference
28). Thus, in the past century, the urbanization of Denver has re-
sulted in the creation of v/oodland, shrub and aquatic habitats in
formerly barren areas.
A summary of the major biotic units, with their characteristic
plant and animal species, is shown in Figure 9.
Rare and Endangered Species
The Federal Register for rare or endangered plant species was
reviewed for the State of Colorado (Reference 34). No plant species
were considered to be threatened in the Denver Region.
The Nongame and Endangered Species Conservation Act (Reference
35) for the State of Colorado is consistent with Title 50, Part 17
of the U.S. Conservation of Endangered Species Act. The Colorado
Division of Wildlife further protects several wildlife species not
covered by the Federal Conservation Act. The Wildlife Division has
recognized the stress on wildlife caused by a growing population and
changing land use, and endeavors to protect wildlife habitat as well
as endangered wildlife species. Animals protected by State and Fed-
eral regulations (Reference 34) that may occur within the study area
include the black-footed ferret, peregrine falcon, white pelican,
and river otter.
Black-Footed Ferret—
The black-footed ferret (tiusteia nigripe] occurs within snort-
grass prairies. Its historic range coincides closely with that of
its prey species, the prairie dog. The population has been dras-
tically reduced and its range decreased due to changing land uses
and programs to control or eliminate prairie dogs. Scattered re-
ports of the black-footed ferret indicate nearly statewide distri-
bution, with tendencies toward the eastern grasslands. The lands
within the study area are largely cultivated or grazed and probably
represent a marginal habitat for the black-footed ferret.
Peregrine Falcon—
Colorado has two recognized subspecies of the peregrine falcon:
a winter nesting resident, the American peregrine (Faico peregrinus
anatum), and the arctic peregrine (raico p. tundrius), a migratory
visitor during the spring and fall (Reference 36). The resident
subspecies is of greater concern within the Rocky Mountain area. Hu-
man activities such as road-building, forest- and sagebrush-clearing,
game-hunting and outdoor recreation have deteriorated the quality of
61
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Unit
Location and examples
Characteristic vegetation
Characteristic birds
Characteristic animals
titivated
Lands
Flat or rolling farm-
lands; east and
north of Denver.
Major portions of
Weld and Adams
counties.
Rural dwellings;
farm buildings.
Steep dirt banks;
along ditches and
seasonal streams.
Alfalfa, corn, sugar beet,
vegetables, wheat, oats,
barley, rye, forage sor-
ghum.
Sunflower, prickly let-
tuce, Russian thistle,
tansy mustard, dande-
lion, garden escapes.
Brewer's blackbird,
western vesper
sparrow, ring-
necked pheasant,
western meadow-
lark, lark bunt-
ing.
Barn swallow, Say's
phoebe, housefinch.
Bank swallow, king-
fisher.
Meadow vole, pocket
gopher, ground
squirrel, harvest
mouse, western jump-
ing mouse, weasel,
bullsnake, garter
snake.
House mouse, raccoon,
feral cat, spade-
foot toad, garter
snake.
Fence lizard.
Uplands
Vegetation
Arid plains region;
typically found in
eastern Adams and
Arapahoe counties.
Blue grama grass, buffalo
grass, western wheat-
grass, little bluestem,
Junegrass, needle-and-
thread, red three-awn,
locoweed, sunflower,
aster, fanweed, prickly
pear, plantain, yucca.
Burrowing owl, desert
horned lark, moun-
tain plover, turkey
vulture, red-tailed
hawk.
Jackrabbit, prairie
vole, -pocket mouse,
Ord kangaroo rat,
coyote, pronghorn
antelope, prairie
rattlesnake, bull-
snake, central
plains milksnake,
sagebrush lizard,
horned liaard.
Bluffs and cliffs
Cliff swallow, prairie
falcon, ferruginous
roughleg hawk.
Summary of biotic community characteristics, Metropolitan Denver area
-------
CO
Unit
Riparian and
Aquatic
Urban/Resi-
dential
Location and examples
Cottonwoods; along
rivers and streams
such as South
Platte River and
Cherry Creek.
Shrubbery; along
streams and creeks
and intermittently
between stretches
of cottonwood.
Lakes and ponds ;
storage reservoirs
such ao Barr Lake
and ponds through-
out farming region
and urban areas.
Marsh areas and
swamps ; along the
floodplain of
South Platte
River.
Greater Denver Metro-
politan area; in-
cludes residential
environs , City
parks and other
recreational faci-
lities.
Characteristic vegetation
Plains cottonwood, box
alder, willow, narrow
leaf cottonwood.
Chokecherry, wild plum,
buffaloberry , hawthorn,
rabbitbrush, willow.
Willow, rushes, cattail,
sedge, salt grass and
aquatic plants.
Salt grass, bulrush and
other rushes, sedge.
Ornamental shrubs, flow-r
ers , lawn-type grasses,
soft maple, elm, weep-
ing willow, Carolina &
Lombardy poplar, ash
sycamore, Norway pine,
Russian olive, and
several varieties of
fruit trees.
Characteristic birds
Red-headed woodpeck-
er, Rocky Mountain
screech owl, Swain-
son's hawk, crow,
Bullock's oriole,
kingbird, western
mockingbird, white-
rumped shrike.
Black-headed gros-
beak, catbird,
brown thrasher,
yellow warbler,
song sparrow.
Grebe, gull, tern,
goose, green heron,
mallard, pintail,
shoveler and other
ducks, shorebirds.
Rail, coot, heron,
bittern, duck, red-
winged blackbird,
ycllowthroat .
Robin, starling,
mockingbird, house
sparrow, black-
capped chickadee,
chipping sparrow,
rock dove, red-eyed
vireo , bronzed
gracklc.
Characteristic animals
Raccoon, fox squirrel,
shrew, weasel, bat,
barred tiger sala-
mander, yellow-
bellied racer, gar-
ter snake.
Striped skunk, rac-
coon, eastern wood-
rat, deer mouse,
yellow-bellied ra-
cer, garter snake.
Snapping turtle, box
turtle, boreal
chorus frog, carp,
brown. trout, chub,
minnow, shiner, cat-
fish.
Musk rat, coyote, bull-
frog, leopard frog,
boreal chorus frog,
garter snake, nor-
thern watersnake.
House mouse, Norway
rat, pocket gopher,
feral cat,
Source: References 28, 29, 30, 31, 32 and 33.
Summary of biotic community characteristics, Metropolitan Denver area (contined)
-------
the environment for this species. The peregrine falcon requires
high cliffs for nesting sites and a food supply of small birds.
Accurate information about breeding pairs has been difficult to
obtain. However, the plains area may still have some value as a
feeding range for this species (Reference 36).
White Pelican--
The white pelican (peiicanus erythrorhynchos) is common in
portions of the United States and is not considered endangered on
a national basis. Within Colorado, it is presently considered en-
dangered as a nesting summer resident. White pelicans may be found
at several reservoirs along the South Platte River drainage; how-
ever, they nest and rear young only at Riverside Reservoir, outside
of the study area.
River Otter—
The river otter (Lutra canadensis) formerly ranged over many
of the rivers and lakes of North America. Due to hunting and human
encroachment, otters have been eliminated or their numbers reduced
over much of their range. However, the river otter is not consid-
ered endangered on a national basis. The otter has probably always
been rare in Colorado I Reference 36). Scattered sightings have
been reported in the South Platte River drainage in Weld County,
and it is unlikely that a breeding population is present. Because
this species is usually limited to wilderness areas, it is unlikely
that it could ever exist in any numbers in the study area. Most of
the streams and lakes are influenced by adjacent homes, industry or
other incompatible human developments.
AIR QUALITY
The project study area is located within Air Quality Control
Region 2 (AQCR2)--Metropolitan Denver (see Figure 10). Air pollu-
tion control priorities for this region have been determined by the
Colorado Air Pollution Control Division and the U.S. Environmental
Protection Agency on the oasis of the following five considerations:
1. existing air quality data
2. population status and trends
3. degree and type of industrialization (emission inventory)
4. amount of vehicular traffic
5. topographic and meteorologic factors
On the basis of these criteria, pollutants are given priority
rankings of 1, II or III, with Priority I as the most severe. Par-
ticulates, carbon monoxide and reactive hydrocarbons and oxidants
64
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LOGAN
i SEDGWICK
__ JRAWNEEf5
PHILLIPS
i j
WASHINGTON |YUMA I
J Y A M PA — ;
— -I
_______
' "" '
METR_0
DENVER
/ METRO
X \ \ \
fDELTA
emf- "GRAND"; MESA
_
COMANCHE
SAN ISABEL
\ \ \
PUEBLO
I ^^ JUMN
'RIO GRANDE lALAMOSA
SAN LUIS
ii
rnuF.inc; '—
I MONTEZUMA
I
I {'"""1 1 J ARCHULETA 1 CONEJOS ' '
j /FOUR CORNERS k
SOURCE: COLORADO DEPARTMENT~OF HEALTH, ~
AIR POLLUTION CONTROL COMMISSION.
STATE AIR POLLUTION CONTROL
DESIGNATED AREAS.
COLORADO AIR QUALITY CONTROL REGIONS
-------
are ranked Priority I and sulfur dioxides and nitrogen oxides are
ranked Priority III; Priority II ranking has not been assigned to
any pollutant (Reference 37). These pollutants mentioned are gen-
erally related to human activity and thus decrease markedly as one
leaves the urbanized regions. Carbon monoxide in AQCR2 is due al-
most entirely to vehicular traffic. It is currently felt that com-
pliance with Federal carbon monoxide standards will not be achieved
in AQCR2 by the 31 May 1977 target date (Reference 37). Reduction
in vehicular traffic will be needed to achieve the standard, par-
ticularly during the winter months when frequent inversions occur.
The very small traffic flows in rural Adams County preclude carbon
monoxide pollution problems.
Ozone, produced as a product of reactions between oxides of
nitrogen and reactive hydrocarbons in the presence of sunlight, is
one of the photochemical oxidants which cause the unpleasant effects
of "smog." Federal standards for ozone levels are commonly exceeded
in AQCR2. Control of these levels is achieved by reducing the pri-
mary pollutants, hydrocarbons and NOX. In order to meet Federal
standards, hydrocarbon emissions must be reduced by about 80 percent
(110,000 metric tons/yr [120,000 tons/yr]) by 31 May 1977. It is
not expected that this reduction will be attained. In the rural
setting of the project area, however, ozone concentrations are not
as high as in urban areas, although sporadic violations may occur.
The Federal primary and secondary standards for particulates
are exceeded in AQCR2. The primary standard is set to protect the
public health at 75 yg/m3, geometric mean. Levels in the urban
Denver area are generally over 100 ug/m3, diminishing to two-thirds
this level in outlying areas. Contaminants previously discussed
are monitored at only six stations in the Metropolitan Denver area.
The particulate concentrations are sampled more widely (22 stations).
The monitoring station nearest the project is in Brighton, about
16 km [10 miles] northwest of the sludge drying sites. In 1974, a
year of average meteorological conditions, the annual arithmetic
mean particulate level was 103 yg/m3. The State standard is 70
yg/m3. Hhile rural areas may experience high particulate levels
due to agricultural operations, these levels are generally lower
than those of urban areas. For tnis reason, particulate levels
around the project site are not presently considered significant.
Wind transport of pollutants into or away from the project area
can be surmised from wind speed and direction, as described on Fig-
ure 11. The data used in this figure, from Stapleton Airport on
the northeast edge of Denver, are representative of wind patterns
in the study area. The average wind speed and direction is 15 km
[9.5 miles] per hour from the south. Infrequent strong, destructive
winds generally come from the northwest.
66
-------
FIGURE I
N
NNW
NNE
NW
NE
WNW
157.
W
WSW
ENE
ESE
SW
SE
SSW
SOURCE: BASED ON 10 YEARS OF DATA
(DECENNIAL CENSUS), 1951-I960, BY
JOHN BENCI, DEPT OF ATMOSPHERIC
SCIENCE, COLORADO STATE UNIVERSITY
(REFERENCE 38).
SSE
LEGEND
SYMBOL WIND SPEED
H.8-5.4 mps (4-l2mph)
5.4-11.0 mps (13-24 mph)
> 11.0 mps (> 24 mph)
ANNUAL FREQUENCIES OF WINDS OF VARIOUS VELOCITIES
AT STAPLETON AIRPORT, DENVER COLORADO
67
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The average annual temperature is about 10°C [50°F], with the
highest temperatures usually occurring in July and the lowest in
January. Daily differences fn temperature extremes (high-low) are
usually about 17°C [30°F] in most months (Reference 8). The summer
temperature conditions are favorable for smog formation, while win-
ter conditions cause frequent inversions. The mean morning mixing
height is relatively low in Denver, averaging only about 60 m [200
ft]. This limits the dilution of air pollutants. However, this
low mixing height rises quickly in the afternoon due to the sun's
heat. During the summer months, the afternoon mean mixing height
is about 1,000 m [3,300 ft].
Precipitation is relatively mild, averaging about 41 cm [16
in.] per year, as discussed under Climate. These dry conditions
cause additional particulate emission problems.
Odor
Background odors generally associated with the study area are
those normally associated with urban, suburban and farming communi-
ties. The petroleum refineries east of Denver emit characteristic
odors which are especially noticeable at distant locations during
calm periods when mixing with the upper air layers is minimal.
Other odorous materials are those commonly associated with farming
operations in the area. For example, a chicken farm may heat-
pressurize chicken manure, producing very offensive odors. These
fertilizer and manure odors are generally accepted as part of normal
farm operations and are therefore tolerated.
Odors are regulated by Odor Emission Regulation No. 2 of the
Colorado Department of Health, Air Pollution Control Commission
(Reference 37). This regulation sets forth three types of odor
limits. For residential or commercial areas, odorous substances
must be undetectable from beyond the property line of the emission
source after being diluted with seven volumes of odor-free air. A
scentometer allows this dilution and measurement to be taken. For
other areas, a dilution of 15 volumes of odor-free air must render
the odor undetectable. A special regulation exempts agricultural
and manufacturing processes, provided the best practicable methods
have been employed to control odors. For all odor sources, however,
there is an upper limit which must not be exceeded: they must not
be detectable after having been diluted with 127 volumes of odor-
free air.
Because of the potential for emission of odorous air contami-
nants from the drying and distribution center, an emission permit
from the Air Pollution Control Division of the Colorado Deparcment
of Health will be required.
68
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CTl
-------
' •
I
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ARCHAEOLOGY AND HISTORY
Transient and sedentary Indian tribes once associated with
eastern Colorado and the general Great Plains complex include the
Ute, Cheyenne, Arapaho, Comanche, Kiowa, Pawnee and Plains Apache
(Reference 42). Because of the locational association with the
proposed project, an archaeological survey was undertaken and was
completed in August 1974 (Reference 8). The primary survey area
was the proposed drying basin site, where major excavation activi-
ties would take place.
During its investigation, the archaeological team found no
surficial evidence of existing archaeological sites on the proposed
drying basin site; a single, isolated mano, probably of Ute origin,
was discovered immediately to the northeast of the site. The team
determined that, since the proposed site has been under long-term
cultivation, any artifacts lying on or near the surface would have
been scattered during plowing and seeding activiites. During the
course of the survey, the team did discover evidence of a nearby
archaeological site, approximately 8 km [5 miles] to the northeast
of the proposed drying basin site.
While land beneath the Metro Denver Plant may contain a con-
cealed archaeological site, the land has undergone development,
and any surficial evidence would have been scattered or destroyed.
As indicated on Figure 1, the proposed pipeline route lies be-
neath various roadway rights-of-way. Consequently, any evidence of
associated archaeological sites would have been obliterated through
adjacent road-building activities.
Representative off-site distribution areas have also been dis-
turbed in the last century by human activities such as cultivation,
mining and park-building. Surface archaeological remnants would
not be present on these areas.
In terms of historical importance, no known historical site
has been officially designated on or near project sites which lie
in Adams County (Reference 43). Since the proposed project opera-
tion will not disturb any existing historical sites on or near
sludge recycling areas, no historical survey was conducted for
this project.
LAND USE
Areas in the proximity of the proposed project are presently
used for a variety of urban and rural land use purposes. Those
areas which are entirely urban in function include land in the
71
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immediate vicinity of the Metro Denver Central Plant and various
parks in the Denver area which will become project distribution
sites. Areas which are rural include the drying basin site, the
Urad Mine and the sod, irrigated and dryland farms. Other project-
related areas consist of the proposed pipeline route and the Lowry
Bombing Range site, which also contains the landfill site.
The Metro Denver Plant facility which will house the anaerobic
digesters is located within the Denver urban core area. Use of the
lands immediately surrounding this facility is industrial and in-
cludes a rendering plant, a refinery and a variety of factories.
The site proposed for the drying basins is rural in character.
Hhile some of the site and the land adjacent to it is used for pas-
turing, the majority is under dryland cultivation, with wheat as the
principal crop. Buildings within one kilometer of this site include
a farmhouse and two structures related to agriculture, all of which
are located 0.4 km [1/4 mile] east of the site. Subdivisions in the
vicinity are located on five four-hectare [10-acre] lots to the north-
west of the site, but none is closer than six km [four miles] (Refer-
ence 44), The area is zoned for agriculture and large subdivision
lots. County land use plans would continue agriculturally related
uses but also propose an airport facility for this area (References
45,46). As proposed, the Adams County General Aviation facility
will be in excellent conformity with the drying basin site since the
facility will be flat, low and sparsely populated (Reference 47).
The Urad Mine, under consideration for sludge application, lies
in a rural area of Clear Creek County approximately 13 km [8 miles]
west of the city of Empire. While the mine is not presently used,
evidence of mining operations remains, including deforested land
and large volumes of tailings and other mining wastes deposited near
the vacant mines. Amax, Inc. plans eventually to revitalize the
area by application of its "Comprehensive Plan for Land Reclamation
and Stabilization at the Urad Mine" (Reference 48). In time, the
area will be restored through reforestation and revegetation activi-
ties (Reference 48).
The sod farm chosen as representative for sludge recycling lies
close to the drying basin site and, like that site, is part of a
rural, agricultural area where wheat is the primary crop. Because
of its proximity to Box Elder Creek, turf and river bottom grasses
are also grown here. The only structures on the property are a few
farm buildings.
The representative irrigated farm also lies in an area which is
devoted to farming activities. It is located approximately 0.8 km
[0.5 mile] east of Platteville, which is a small, rural community.
72
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Buildings lying on the property include a farmhouse, barn and stor-
age shed.
Dryland farms to be used for sludge application are coterminous
with the representative sod and irrigated farm areas and therefore
have common environmental characteristics.
The pipeline proposed for transport of the processed sludge
from the Central Plant to outlying drying basins will traverse both
urban and rural land. Initially the line will pass through the in-
dustrialized area surrounding the Central Plant. It will then cross
into Commerce City, a suburb of Denver, and skirt the Rocky Mountain
Arsenal. From that point it will run beneath the Irondale Road
right-of-way, through land which is rural in character, until it
reaches the drying basin site in Adams County.
Because the area surrounding the Lowry Bobming Range is sparse-
ly developed and lightly populated, it may be characterized as rural.
No change from its present use as a sludge deposition and landfill
site is proposed at present. However, potentially detrimental levels
of heavy metals may have accumulated in the soils (Reference 45),
and this situation may force a change or limitation in land use.
LAND TENURE
The Metro Denver treatment plant facilities are situated on
publicly owned lands. Various roadway right-of-way areas which will
accommodate the proposed pipeline are also publicly owned, as are
the project-related parks in the Denver area. The Lowry Bombing
Range, which contains the Lowry Landfill site, is part of a U.S. Air
Force military reservation. Privately owned lands include the pro-
posed 800-hectare [2,000-acre] drying basin site, the Urad Mine area
and the representative sod, irrigated and dryland farms.
POPULATION
Regional Population
The service area where the sludge originates and the areas to
receive the dried sludge are located within the jurisdiction of the
Denver Regional Council of Governments (DRCOG). Recent DRCOG popu-
lation trends, disaggregated according to county, -are given in
Table 10.
In common with major metropolitan areas throughout the country,
there has been a recent shift in population from the central city
to the suburbs. During the year 1974-75, while Denver County's
population remained essentially static, two of the three counties
73
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Table 10. POPULATION BY COUNTY, 1970-1975
County
Adams
Arapahoe
Boulder
Clear Creek
Denver
Douglas
Gllpin
Jefferson
Region
1970
183,000
161,000
130,000
4,600
514,000
8,000
1,200
231,000
1,232,800
1971
191,600
166,800
136,700
5,500
518,600
9,700
1,500
245,700
1,276,100
1972
202,800
179,000
145,200
5,700
523,700
10,900
1,600
264,500
1,333,400
1973
213,200
196,000
156,300
5,700
528,000
13,100
1,900
292,300
1,406,500
1974
225,600
211,300
164,200
5,700
529,600
15,800
1,900
310,800
1,464,900
1975
232,100
224,800
171,500
5,900
529,700
18,000
2,000
322,800
1,506,800
Note: All estimates as of January 1 of each year.
Source: "Population Change in the Seventies."
-------
which contain the suburban communities around Denver grew at a rate
faster than that for regional annual population growth, which was
2.97 percent: Arapahoe County, 6.4 percent, and Jefferson County,
3.9 percent; the third, Adams County, grew at a rate of 2.9 percent,
nearly equal to the regional rate (Reference 49).
Regional growth reached a peak rate of 5.5 percent per year in
1972-73 and has since declined to a rate close to the 1960-1970
average of 2.6 percent. This decline in growth rate is attributed
to declining fertility rates, restrictions on new gas and water con-
nections which began in 1972 and a general economic slowdown, which
has reduced the rate of immigration into the region and has brought
new residential construction almost to a standstill (Reference 49).
Metropolitan Denver Sewage Disposal District No. 1
The population within Metropolitan Denver Sewage Disposal Dis-
trict No. 1 (Metro Denver) in 1975 was 1,081,000 (Reference 50).
The District serves most of the population of Adams, Arapaho, Jef-
ferson and Denver counties.
Adams County
Adams County, a rapidly growing section of the Denver Metropoli-
tan area, had the highest growth rate among the DRCOG counties from
1940 to 1950. In the 1950's it almost tripled its population. This
growth has leveled somewhat over the past two decades, as shown in
Table 11.
Table 11. POPULATION GROWTH RATES, ADAMS COUNTY
(percent per year)
Growth period
1940-1960
1960-1970
1970-71
1971-72
1972-73
1973-74
1974-75
1970-1975
Growth
Annual
4.7
5.8
5.1
5.8
2.9
rate
Average
6.8
4.4
- -
4.9
Source: Reference 49.
75
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Almost two-thirds of the population of Adams County is concen-
trated in the cities of Aurora, Northglenn, Commerce City, Thornton
and Westminster. About 95 percent of the population is in urban
areas. The sewage from 78 percent of the population of Adams County
is generated and treated within the Metro Denver district. Adams
County accounts for 17 percent of the population in the Metro Denver
service area.
Population Projections
Projections of population for the counties of concern are given
in Table 12.
DRCOG population estimates were adjusted by Metro Denver staff
for use in their Long Range Planning Study. These figures give a
total District projection for the year 2000 which is 16 percent
higher than that projected by DRCOG for the same area for that year
(Reference 9). Table 13 shows a range of eight projections for the
five-county Denver region for the year 2000. On the basis of the
16 percent difference mentioned, it would appear that Metro Denver's
projections fall somewhere near the middle of the range of projec-
tions made by various agencies.
The projected sludge load increases used to estimate the 1985
levels are given in Table 14 along with Metro Denver and DRCOG popu-
lation growth assumptions for a similar time period.
TRANSPORTATION AND CIRCULATION
Roadway, railroad and air travel are the primary modes of trans-
portation used in the region of the proposed project. While road-
ways serve most areas, railroad travel is concentrated on lines pass-
ing through Denver and airplane travel facilities are interspersed
throughout the region.
Roadways of a variety of types serve the region. Minor streets
and arterials are found in urbanized areas, particularly those sur-
rounding the City and County of Denver, along with state, interstate
and federal highways (Reference 56). In rural and sparsely populated
areas, roadways are limited to minor streets and arterials, which
are variously classified, depending on surface composition character-
istics and design width (Reference 57). In general, these roads are
infrequently travelled, with average daily travel (ADT) ranging from
90 to 230; however, many are adequate in design to carry heavy, agri-
culturally related trucks and can accommodate an ADT as high as 6,200
(Reference 59),
Railroads in the region are concentrated around Denver. These
76
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Table 12. SELECTED POPULATION PROJECTIONS FOR COUNTIES
IN VICINITY OF METRO DENVER
County
Denver
Adams
Arapahoe
Jefferson
Weld
Population,
1975a
529,700
232,100
224,800
322,800
114,000
State of Colorado
low
392,000
314,000
322,000
483,000
138,000
projections5, 1995 DRCOG proiections0
high
538,000
432,000
443,000
664,000
160,000
1990
602,000
295,000
345,000
515,000
(not
2000
709,100
326,000
413,000
658,000
in DRCOG)
Source: Reference 51 for Weld County, Reference 49 for all others.
Source: Reference 51.
"Source: Reference 52, Denver Regional Council of Governments.
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Table 13. POPULATION FORECASTS FOR THE FIVE-COUNTY DENVER REGION IN THE YEAR 2000
Agency Population estimate
U.S. Department of Commerce, Office of Business and 1,981,000
Economic Research Service (OBERS)
Colorado Land Use Commission 2,175,000
Denver Regional Council of Governments (DRCOG) 2,350,000
(policy forecast)
Denver Research Institute (DRI) 2,675,000
Colorado Division of Planning (county total) 2,886,000
Colorado Division of Planning (city total) 2,892,000
Metropolitan Denver Water Study Committee 2,000,000
Colorado Division of Planning (adjusted city total) 3,399,000
Source: "Appraisal of the DRCOG Policy Population Forecast."
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Table 14. POPULATION AND SLUDGE LOAD PROJECTIONS FOR METRO DENVER DISTRICT
Projections
DRCOG population projection
for Metro Denver district ,
persons
Metro Denver population pro-
jection , persons
Metro Denver sludge load
projection0, dry metric
tons/day
Time period
1970-1985
1970-1985
1977-1985
Year Average
1970 1977 1985 growth
1,074,775 1,469,420 2.
1,080,032 1,683,400 3.
68 97 4.
annual
rate, %
1
0
8
Source: Reference 9.
Source: Reference 47.
£
Source: Reference 55.
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include the Union Pacific and Burlington-Northern Railroad lines.
Although there is variation in routes, most of the lines pass
through Denver (Reference 56). The line closest to the proposed
sludge drying basin site lies 11 km [7 miles] to the south.
Airport facilities located within the region include Stapleton
International Airport in Denver and a variety of noncommercial pri-
vate facilities in Adams, Arapahoe, Weld and Denver counties (Ref-
erence 60). The proposed Adams County General Aviation Airport is
located in the proximity of the area slated for the sludge drying
basins.
RECREATION
The State of Colorado is divided into several recreational
regions. Denver, Adams, Held and Arapahoe counties are included
in Metro Region No. 9, while Clear Creek County lies in the North-
Central Colorado Region No. 7 (Reference 43). There are a number
of officially designated recreational areas within these two re-
gions. They include reservoirs, rivers and streams, natural lakes,
cold springs, forests the parks (Reference 43). Recreational areas
of several types are found near the proposed project. The proposed
South Platte River recreational area is located approximately 1.6 km
[one mile] east of the Metro Denver Plant; Barr Lake and Barr Lake
Duck Club lie 18 km [11 miles] northeast of the proposed drying basin
site. In the vicinity of sludge recycling sites are the Big Bend
Picnic Grounds, about 1.6 km [one mile] northeast of the Urad mine;
the Old Fort Vasquez site, about 1.6 km [one mile] southwest of the
Platteville sod farm; and 120 developed neighborhood parks in Denver
County (Reference 40).
INSTITUTIONAL AND GOVERNMENTAL AGENCY JURISDICTIONS
The jurisdictional issue of principal concern for the proposed
project is the conflict between Adams County and Metro Denver over
final approval of the drying and distribution center. Since the
proposed site for this operation is within unincorporated County
territory, and therefore under the jurisdiction of the Adams County
Planning Commission, the County feels it should have the power to
accept, modify or veto the operation. Very recent litigation has
determined that Metro Denver needs a Certificate of Designation
from the Adams County Board of Commissioners in order to proceed.
The application for Certificate of Designation, including support-
ing documents (such as this Draft EIS), would be reviewed by the
Colorado Department of Health, who would recommend approval or dis-
approval to the County Commissioners (Reference 61). If approval
is not forthcoming, the District can attempt to exercise its power
to condemn property required for its operations (Reference 62).
80
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There is also a possibility that the law will be amended to ex-
clude requirement of approval by the Board of Commissioners.
Most of the farmlands affected by the proposed project are
within unincorporated County territory and are under the jurisdic-
tion of the Adams County Planning Commission.
The Colorado Land Use Commission is the Statewide planning
body responsible for the management of State lands. The State of
Colorado owns about 130 hectares [320 acres] of the recommended
site (B-2).
The regional planning body with jurisdiction in the study area
is the Denver Regional Council of Governments (DRCOG). This is a
planning agency whose purpose is to coordinate plans of local and
county governments and to ensure, through the A-95 review process,
that federally funded projects are in harmony with these coordi-
nated plans. DRCOG is presently studying the feasibility of coor-
dinating a solid waste management program with Metro Denver's
sludge management system. The plan under consideration would com-
bine the Metro Denver sludge with solid waste from the City of
Denver to provide fuel feedstock for generation of electricity.
As of March 1976, the Colorado legislature has let die proposed
legislation which would have made regional solid waste management
possible.
The U.S. Environmental Protection Agency is the Federal body
charged with managing the Federal funds provided for construction
of the proposed project. Another Federal agency with jurisdiction
and interest in the proposed project is the U.S. Food and Drug
Administration (FDA). The FDA generates and enforces regulations
for the application of sludge on crops which enter the human food
chain if they are to be used in interstate commerce. Jurisdiction
over the immediate health concerns associated with the project is
held by the Tri-County District Health Department. This Department
oversees the present operations at Lowry Bombing Range and would
also be responsible for checking the proposed operation in Adams
County.
The City of Denver uses a small portion of the Lowry Bombing
range for the disposal of its solid wastes. Metro Denver Sewage
Disposal District also uses this area on an interim basis for its
sludge disposal operations; however, the City maintains jurisdic-
tion over the area, and no long-term or written agreement is in
effect between the two entities. The City may have need_of the
additional Lowry space for its own future sanitary landfill opera-
tions (Reference 63).
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SOCIO-ECONOMIC SETTING
Adams County Agricultural Economy
Agriculture has been the mainstay of the Adams County economy
since homesteaders first arrived in the 1860's (Reference 45). Al-
most 95 percent of the area of the county is presently in agricul-
tural use.
In 1973, Adams County ranked seventh among the 65 counties in
the state in winter wheat production, tenth in barley, seventeenth
in sugar beets, nineteenth in corn for grain, twentieth in sorghum
for grain and eleventh in total crop production.
Truck farming activities in western Adams County are concen-
trated along the Platte River. The main irrigated crops are alfal-
fa, corn, barley, sugar beets, oats and rye. Greenhouses and turf
farms are increasing, and this trend is expected to continue (Ref-
erence 45). Dryland farming is carried out primarily in the east-
ern part of the County (including the vicinity of the proposed dry-
ing and distribution center site). The main nonirrigated crops are
winter wheat, forage sorghum and barley. The values of the various
crops produced in Adams County are shown in Table 15.
Livestock population in Adams County is shown in Table 16.
Sources of Fertilizer
Nitrogen fertilizers are manufactured using nitrogen from the
atmosphere and hydrogen from fossil sources (coal, petroleum and
natural gas) within the state. Phosphorus is imported from other
states. Adequate sources of potash exist in southwestern Colorado;
additional supplies are available from southeastern Utah, where it
is mined exclusively.
The main source of organic fertilizer in Colorado is livestock
manure. Dried manure comprised about 83 percent of the total or-
ganic commercial fertilizer sales in 1972 in the Mountain States;
about 10 percent consisted of activated sewage sludge; the other
two percent was composed of other sewage organics and tankage, and
dried blood. Similar percentages are assumed to hold for Colorado
(Reference 5).
There were 281,000 metric tons [309,551 tons] of fertilizer
sold in Colorado in 1972, up from about 175,000 metric tons [193,000
tons] in 1965. During the same period, the commercial sale of natu-
ral organic materials dropped from 16,000 metric tons [18,000 tons]
to 6,600 metric tons [8,000 tons].
82
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Table 15. VALUE OF CROPS PRODUCED IN
ADAMS COUNTY, 1972-1973
Crop
Wheat
Corn, grain and silage
Barley
Sorghum grain
Sugar beets
All other crops3
TOTAL
1972
Value
$ 6,752,900
2,310,000
832,000
25,100
744,400
4,529,300
$15,193,900
%
44
15
6
—
5
30
100
1973
Value
$13,768,000
2,467,100
763,500
35,700
—
5,590,500
$22,624,800
%
61
11
3
—
—
25
100
o
Includes dry beans, rye, hay, potatoes, oats, broomcorn, fruits
and vegetables.
Source: Comprehensive Plan: Adams County.
Table 16. LIVESTOCK ON FARMS, 1 JANUARY 1973,
ADAMS COUNTY, RELATIVE TO ALL COLORADO COUNTIES
Livestock
Cattle and calves
Milk cows
Hogs and pigs
Stock sheep
Cattle on feed
Number
70,000
5,000
22,500
4,300
40,000
Ranking
13
3
4
_25
5
Source: Comprehensive Plan: Adams County.
83
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The fertilizer required for the agricultural economy of the
state is presently in short supply, and these shortages are ex-
pected to continue (Reference 5). This situation is linked to
fuel and natural gas shortages and to increased demand in this
country and abroad.
Urban/Rural Characteristics
The socio-economic characteristics of the Metro Denver service
area differ greatly from the characteristics of the area proposed
for the sludge drying and distribution center. This difference re-
flects the urban/rural contrast: Metro Denver serves the urbanized
Metropolitan Denver area, while the proposed site is situated in
rural eastern Adams County. There are perhaps even greater differ-
ences between the eastern and western parts of Adams County than
between Denver County and Adams County, as indicated in Table 17.
Table 17 shows some of the contrasts among socio-economic
characteristics of the three areas (Reference 43). In 1972, about
95 percent of the population of Adams County was urban rather than
rural, with approximately 65 percent of the population concentrated
in five cities in the far western part of the county adjacent to
Denver (Aurora, Northglenn, Commerce City, Thornton and Westminster).
Census Tract 084 consists of that part of Adams County east of Box
Elder Creek (roughly the eastern two-thirds of the county), the
area in which the sludge drying and distribution center would be
located.
Land Values
The site under consideration for the drying and distribution
center has a present market value of approximately $1 million for
the 810 hectares [2,000 acres] required (Reference 55). This pre-
liminary cost estimate thus sets the market value of the site at
about $1,200/hectare [$500/acre].
Market values fluctuate considerably, but the current market
for land bought by a farmer in large tracts in the general area of
the proposed project site is approximately $500/hectare [$200/acre]
for dry farmland and $l,000/hectare [$400/acre] for farmland with
wells adequate for irrigation (Reference 66).
Through speculation, often in anticipation of a special demand
for a particular parcel, property values may rise as high as $5,000/
hectare [$2,000/acre], or prices may be increased because of a trans-
action which involves a low downpayment (Reference 66). The recent
trend in land values in the area is one of sporadic increases in
property value. The general trend in Colorado shows a 25 percent
84
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Table 17. CONTRASTING SOCIO-ECONOMIC CHARACTERISTICS
Characteristic Criterion
Total population Numbers of people
Mobility/ stability Lived in same house, 1965-1970
Commuting patterns Work in county of residence
Education High school graduates, 25+ yrs old
College graduates, 25+ yrs old
co Family size Children born/women married, 35-44
01 yrs old
Income Median family income
Age Median age
Farm population Number of farm-related jobs: farmers,
mgrs, foremen, workmen
Farm and related jobs/100,000 population
1
r\
Approximately the eastern two-thirds of Adams County.
Source: 1970 Census of Population and Housing (Reference 64);
(Reference 65) .
Denver Adams Census
County County tract 084a
514,678 185,789 2,233
44.0% 46.6% 50.6%
78.1% 32.7% 69.4%
61.5% 62.7% 58.0%
15.5% 8.6% 5.2%
3.0 3.0 2.7
$ 9,654 $10,409 $ 6,374
28.6 22.8 28.2
1,020 1,613 277
198 868 1189
1970 Census of Population
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increase in land value from 1972 to 1973, a 14 percent increase
from 1973 to 1974 and a seven percent increase from 1974 to 1975
(Reference 66). Land values may change near the proposed site in
response to a number of currently unpredictable factors, including
changes in farm prices and the rate of growth of the Denver region.
Employment
The employment-generating facilities associated with the pro-
posed project will be located in Adams County. The major employ-
ment classifications in Adams County are given in Table 18.
Table 18. ADAMS COUNTY EMPLOYMENT PATTERNS, 1973
Employment category Number employed
Retail trade 3,700
Manufacturing 7,300
Contract construction 5,100
Services 4,900
Farm-related jobs (farmers, man- 1,800
agers, foremen, workmen)
Wholesale trade 1,600
Transportation and other public 1,600
utilities
Finance, insurance, real estate 1,200
Source: 1970 Census of Population (Reference 65); Adams County In-
formation Service (Reference 43).
The Urad mine is one of the sites being evaluated as a sludge
recycling area. The mine is one of three owned by Climax Molybdenum
Company, which is the largest private employer in Colorado, employ-
ing 3,500 workers (Reference 41).
The unemployment rate in the eight-county Denver-Boulder Labor
Market Area in September 1975 was 5.7 percent; the Adams County rate
was 5.8 percent (Reference 67). The national rate at that time was
eight to nine percent.
VISUAL AESTHETICS
The rural regions within the study area are characterized by a
86
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broad, rolling topography. While there are generally no particu-
larly striking features in this agricultural area, an expansive
and restful atmosphere gives the area a pleasant contrast to the
urbanized areas to the west. Dryland farms bear relatively few
signs of agricultural activity and thus do little to disturb the
area's original prairie impression. Irrigated farms are more ac-
tive; their green crops exist in greater variety and provide a
more stimulating rural backdrop.
The Denver Parks provide a variety of well-maintained, attrac-
tive areas within the city. The 1,800 acres of parkland range from
quiet, secluded neighborhood parks to the spacious City Park, which
includes a number of lakes and provides a setting for many culutral
and recreational activities.
To reach the mine reclamation site farther to the v/est, one
leaves the flat, rural regions and climbs into the rugged, moun-
tainous terrain more commonly associated with the Rocky Mountain
region. The Urad Valley is one of the many high, scenic valleys
along U.S. Highway 40, but its scenic value has been impaired by
mine tailings deposited on the floor of the valley.
Specific descriptions of the environmental setting of the
various representative sludge application areas are presented in
Appendix E.
PUBLIC HEALTH
The agency charged with maintenance of the public health in
Adams, Arapahoe and Douglas counties is the Tri-County District
Health Department. This agency monitors the present Metro Denver
sludge disposal operations at Lowry Bombing Range in Arapahoe
County and would also monitor the health impacts of the proposed
project. A project requiring a Certificate of Designation is sub-
ject to review by the Colorado Department of Health, who would
have veto power over the project (Reference 78).
The U.S. Environmental Protection Agency takes public health
impacts into consideration in awarding grant monies. These consid-
erations are contained in the tentative guidelines presently being
circulated for review before being formally released by EPA (Ref-
erence 79).
The Agricultural Research Service of the U.S. Department of
Agriculture sets down criteria to ensure that heavy metals in
sludge (zinc, copper, cadmium, etc.) will not harm plants or the
soil. The U.S. Food and Drug Administration has yet to promulgate
guidelines for control of levels of possibly harmful substances in
sludge applied to crops which enter the human food chain.
87
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h
-------
The principal features of Metro's proposed
sludge management plan are described in this
Section. Main features include anaerobic di-
gesters, pipeline and pumping facilities, the
drying/storage/distribution center and proposals
for on-site irrigation and disposal. Metro is
planning to market the sludge to farmers and
other users. The type of uses considered and
their general locations are described here.
Discussion of recommended loading rates and
limits based on research in each type of land
use is presented.
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SECTION IV
DESCRIPTION OF PROPOSED ACTION
Metro Denver's proposed sludge management plan involves
treatment of sewage sludge at the District's Central Plant and
pipeline transport to a sludge drying and distribution center 40
km [25 miles] east of the Metro Denver Central Plant. Air-dried
and liquid sludges will be taken from the center and applied to
the land in various ways. Each component in the proposed sludge
management system is described in this Section. A predesign and
site selection study was conducted for Metro Denver in 1974-75.
The recommended plan is discussed in detail in the "Metro Denver
District Sludge Management, Volume I - Summary Report and Volume
II - Agricultural Reuse Predesign" (References 55 and 118). Ex-
cerpts from these reports are used extensively in this Section
for the description of the proposed action.
SLUDGE TREATMENT
Raw sewage sludge is generally unacceptable for land appli-
cation due to the problems of odors, vectors and disease trans-
mission. These aesthetic and public health problems can be al-
leviated by stabilization of the putrescible organic material in
the sludge. Sewage sludge at the Metro Denver Central Plant will
be stabilized by anaerobic digestion. The Denver Northside Plant
sludge is digested prior to conveyance to the Central Plant. This
process will involve the decomposition of most of the organic ma-
terials by micro-organisms in the absence of oxygen. The sludge
will be processed in mesophilic digesters with a constant temper-
ature maintenance at 35°C [95°F] and continuous gas-diffusion
mixing.
The digesters are designed for loadings of 2.1 kg of volatile
suspended solids (VSS) per day per cubic meter of digester [0.13
Ibs/day/cubic foot] and a 22 day digestion period. _At the end of
this detention period, 50 percent volatile solids destruction and
three percent solids concentration should occur. Most of the organic
material will be converted into water, methane, carbon dioxide
and other gases. A comparison of changes in sewage sludge char-
acteristics through anaerobic digestion is given in Table 19.
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Table 19. CHANGES IN CHARACTERISTICS OF
SEWAGE SLUDGES THROUGH DIGESTION3
Concentration from treatment nreceedine analysis
Primary settling
Constituents
Total solids, Z
Suspended solids, Z
Volatile sollda,
Z of T.S.S.
Chemical oxygen
demand, ppm
Total nitrogen, ppm
Organic nitrogen,
ppm
Phosphate, ppm
Grease, ppm
Alkalinity, ppm
Cadmium , ppra
Nickel, ppra
Lead, ppm
Sliver, ppm
Zinc, ppm
Copper, ppm
Arsenic, ppm
Chromium, ppm
Typical ranges and
Range
4.25- 8.90
-
72.0 -94.5
36,800-98,280
1,070- 2,734
340- 2,626
1,237- 2,257
8,544-13,916
1,000- 2,420
Dissolved
0.02
0.67
Total:
Total:
1.55
11
0.01
0.09
Mean
6.4
-
80.2
61,267
2,066
1,874
1,795
11,080
1,603
Suspended
2.48
10.43
8.00
2.40
119
52
1.0
45
means were obtained from
Primary to secondary sludge solids ratio 15:
Activated
sludge
Calculatedb Mesophilic
Secondary settling Combined sludges digestion
flange
0.44- 0.89
0.10- 0.79
57.3 -92,0
4,224-11,408
481- 799
462- 580
963- 1,360
248- 528
330- 520
Dissolved
0.03
0.38
0.25
0.30
0.25
0.50
0
0.07
data at the City
Mean
0.69
0.58
73.1
7,106
541
512
1,148
400
430
Mean
4.02
-
79.8
38,699
1,431
1,30:
1,525
6,630
1,114
Suspended . Dissolved
0.77
1.42
2.25
2.00
12.8
11.5
0.14
16
of Los Angeles
1; primary to secondary sludge
0.02
0.55
Total:
Total:
1.01
6.6
0.006
0.08
Range
1.15- 2.98
1.04- 3.23
35.8 -71.5
12,900-42,400
1,840- 2,173
720- 969
1,250- 1,734
1,576- 2,672
4,900- 6,700
Suspended Dissolved
1.77 0.02
6.68 0.36
5.71 0.50
2.36 Total:
75 0.06
35 11
0.64 0.01
33 0.06
Mean
2.12
2.22
59.9
24,195
2,000
869
1,570
1,981
5,520
Suspended
2.98
9.14
7.5
3.30
77.3
32
0.08
50.3
Thermophilic
digestion
Range
1.67- 3.64
1.06- 3.67
37.8 -70.5
19,200-47,200
1.516--2.079
320- 790'
1,101- 1,697
2,468- 3,264
5,190- 7,900
Dissolved
0.02
0.45
0.45
Total:
0.20
0.27
0.04
0.15
Mean
2.35
2.49
62.0
33,420
1,992
697
1,604
2,820
6,190
Suspended
2.78
11.1
7.55
2.40
67.8
36.7
0.87
52.5
Hyperion Wastewater Treatment Plant.
flow ratio
1.4:1.
-------
The example data are drawn from the Hyperion Wastewater Treatment
Plant in Los Angeles which treats sludges with higher metal content
than Metro Denver's and utilizes thermophilic digestion. While
the changes in characteristics of sludges occur at a faster rate
in thermophilic digestion, the change in characteristics is gener-
ally similar to that from a mesophilic process. However, it is
expected that microorganisms (pathogens in particular) will not be
reduced in numbers as effectively with the mesophilic process.
At the anticipated design loading, ten digesters would be re-
quired with a total volume of 2.4 million cubic feet. First, eight
concrete anaerobic digesters with a total volume of 54,000 cu m
[1.9 million cu ft] would be built to accommodate 1977 sludge load-
ings at the Central Plant of 2,047 cu m/day [547,000 gal/day].
These digesters are now being constructed as part of the present
Central Plant expansion. Two additional digesters would be con-
structed sometime prior to 1980 to handle the 1985 design capacity
of 3,100 cu m/day [824,000 gal/day].
In the predesign study, it was assumed that all initial eight
units would operate as primary digesters. Four of these units,
however, have been designed with the flexibility of operating as
secondary digesters for gravity thickening of the digested sludge.
Three existing sludge holding tanks at the Central Plant
would be used in the sludge digestion and agricultural reuse sys-
tem. One tank would provide storage for the undigested Central
Plant sludge. Another tank would store the Central Plant sludge
after it is digested as well as the Denver Northside digested
sludge. The sludge in this latter tank would be pumped to the
sludge drying and distribution center. The third tank would be
used for storage of the liquid sludge in the event of some emer-
gency in the system.
SLUDGE TRANSPORT SYSTEM
The liquid sludge would be transported from the Central Plant
to the distribution center through two pipelines, 25 cm [10 in.]
and 30 cm [12 in.] in diameter. Each pipe would be capable of
handling 40 I/sec [600 gal/min] of sludge or secondary effluent.
Secondary effluent would be pumped tnrougn the force mains to
clean out solids deposits. At the distribution center the efflu-
ent would be used for irrigation, dust control and fire protection
of on-site facilities.
The proposed pipeline route to the sludge distribution center
site is shown on Figures 1 and 2. The criteria used for locating
the route were length of route, elevation along the route and
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proximity to estaolished rights-of-way for easy access to power
lines. These criteria were used to minimize costs and environ-
mental impacts. The pipeline will run parallel to the railroad
tracks heading northeast from the District's plant and then turn
eastward along the northern boundary of the Rocky Mountain Arsenal.
From there the pipelines will turn east to the distribution center
along Irondale Road.
A system of Central Plant pumps and booster pumps at an inter-
mediate pump station would be used to produce the required head of
240 m [800 ft] to pump the material from the Central Plant to the
distribution center. The Central Plant pumps would develop 120 m
[400 ft] of head, and the additional 120 m [400 ft] would be sup-
plied by the booster pumps.
All transport system pumps would be controlled from the Cen-
tral Plant. Gauges and meters at both the Central Plant and dis-
tribution center would monitor the operation of the transport
system.
SLUDGE DRYING AND DISTRIBUTION CENTER
Drying and Distribution Center Site Selection
The three potential sites for the drying and distribution
center, shown on Figure 2, were compared to determine the best
location on the basis of economic and environmental considerations.
Factors examined in making the site selection are shown in an ap-
pendix to the Environmental Assessment for the Metropolitan Den-
ver Sewage Disposal District Sludge Management (Volume IV) (Ref-
erence 8) and reproduced here in Appendix G.
The environmental factors investigated in comparing the sites
included historic value of each site, climate, plant and animal
ecology, traffic and aesthetic impacts, economic investment and
land use. Land use was found to be the most distinguishing factor
among the three sites. The least amount of project impact on pres-
ent and potential land use would occur at site B-2. Both sites A
and A-2 have the disadvantage of being located near an existing
housing subdivision which is scheduled for future expansion. Be-
cause site B-2 is near the fewest number of private homes, loca-
tion of the facility at that site would be more acceptable to the
local community.
In an economic comparison conducted in Appendix A of "Agri-
cultural Reuse Predesign" (Volume III), the present worth for 10
years of design, construction and operation for sites A, A-2 and
B-2 is $11,948,000, $11,695,000 and $12,899,000, respectively.
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Thus, on the basis of the economic comparison, site A-2 would be
the preferred location, and site B-2 the least desirable location.
However, site B-2 was recommended as the best location for the
drying and distribution center primarily because it was not near
any major residential development. The potential social problems
associated with locating the distribution center near a subdivision
far outweighed all other differences among the three sites. Solu-
tions or compromises could be worked out for most of the environ-
mental and economic problems. However, strong public opposition
to the project would be difficult to resolve and could be detri-
mental to the success of the project. Locating the distribution
center at site B-2 would minimize this problem. Furthermore, the
projected location of a new regional airport near site B-2 com-
prises a highly compatible land use.
Drying and Distribution Center Operation and Layout
The sludge drying and distribution center would operate as a
drying, storage, marketing and research and demonstration center.
Facilities which would be used for these functions are illustrated
on Figure 12 and are described in the following paragraphs. Sludge
could be purchased at the distribution center in both dry and liq-
uid forms. Liquid sludge could also be distributed from the Cen-
tral Plant and booster pump station.
The sludge would be air-dried in earthen drying basins which
would occupy about 240 ha [600 ac] at full development of the pro-
ject. The open, unlined basins would be separated by earth berms.
The drying basins could process about 33,000 dry metric tons
[36,000 short tons] of sludge per year. Sludge applied to the
basins in layers of 60 cm [24 in] can be expected to dry to 40 to
50 percent solids in about twelve months. It should be noted that
during the drying process further changes occur in sludge charac-
teristics. The probable changes over 50 days in nitrogen content,
for example, are shown in Figure 13, as measured at the Colorado
State University Agricultural Experimental Farm at Fort Collins
using anaerobically digested liquid sludge in the winter of 1974.
Dried sludge will be removed from the basins when tests in-
dicate that the required solids content has been achieved. Front-
end loaders will load dried sludge into special trucks (not yet
specifically determined) for transport to the stockpjle area. Jhe
stockpile area will serve as the storage area and as the distribu-
tion point where users could obtain dried sludge. The dried
material will be stored between the drying beds as shown in
Figure 12. Fences will be erected around the drying_basin and
stockpile area to keep out grazing animals and wildlife. The
capability for manual wetting of the stockpiles will be provided
93
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FIGURE 12
SOURCE^ SLUDGE MANAGEMENT PLAN FOR
METRO DENVER DISTRICT.
METROPOLITAN DENVER PROPOSED
SLUDGE DRYING AND DISTRIBUTION CENTER
94
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FIGURE 13
16
15
14
13
CO
S ii
o
CO
10
15
o
u_
o
f- 8
Z
UJ
O
o: 7
UJ '
CL
LU 6
O
O
a:
J- 5
LEGEND AND NOTES
-N
TKN
—B-
TOP LAYER S-——
MIDDLE LAYER A
BOTTOM LAYER -<•>-
I. BASIN DEPTH = I METER (40 INCHES)
^ 2. BOTTOM OF BASIN WAS LINED
\
\
-X--^.
SOURCE: METROPOLITAN DENVER SEWAGE DISPOSAL DISTRICT NO. I
J_
0 5 10 15 20 25 30 35 40 45 50
TIME .DAYS SINCE LIQUID SLUDGE WAS INTRODUCED INTO DRYING BASIN
AMMONIA AND TOTAL KJELDAHL NITROGEN
CONCENTRATION AS A PERCENT OF THE TOTAL SOLIDS
CONCENTRATION IN THREE LAYERS IN AIR DRYING BASINS
-------
as a means of preventing air pollution during strong windstorms.
Dried sludge will be transported by truck to agricultural users'
farms and to other land application areas.
On-site subsurface and surface application areas would be used
to test and illustrate the effects of using liquid or dried sludge
for agricultural purposes. The subsurface injection area would show
the effect of Metro Denver's sludge on crop production. In the
later stages of operation, Metro proposes to inject up to ten per-
cent of the liquid sludge into the soil at the sludge injection
areas unless a market develops for additional dry or liquid sludge.
These injections would be at very high rates of 875 tons/ha [390
tons/acre].
Land application of sludge on the research and demonstration
plots would test the effects of various sludge loading rates on
crop production. Both irrigated and dryland crops would be grown
on these plots. Various control features would ensure reliable
and efficient operation and maintenance of the distribution center.
A control and administration building, a maintenance building, and
liquid sludge and secondary effluent storage tanks would be parts
of the on-site control complex. All of the automatic controls and
monitoring devices for operating the distribution center would be
housed in the control and administration building. Another control
feature would be the collection and impoundment of the on-site sur-
face runoff water by a system of earthen channels and dams to pre-
vent possible contamination of surface waters, as shown on Figure
12. Offsite runoff would be diverted around the site. Also, soil
and groundwater would be monitored continually to provide informa-
tion for research purposes and for protection against potential en-
vironmental damage.
PROPOSED LAND APPLICATION OF SLUDGE BY METRO DENVER
The Metropolitan Denver Sewage Disposal District No. 1 pro-
poses to make sludge available for recycling on various agricultural
areas in the vicinity of Denver. The agricultural reuse program
would involve controlled seasonal applications under careful nutri-
ent and toxin management. Disposal landfill ing would probably occur
only under emergency conditions at the Lowry Bombing Range Sanitary
Landfill. High-rate sludge application, as proposed by Metro Den-
ver, would be conducted in the open lands of the Lowry Bombing
Range if the proposed sludge recycling plan is not implemented.
Controlled sludge application areas may include Denver Parks, sod
farms, mine spoil areas, irrigated and dryland farms and possibly
some home gardens.
96
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It is envisioned that no single type of application will be
used for the ultimate disposal of the entire sludge generated in
Denver. More likely, a combination of two or more types of land
application, with varying proportions from year to year (and
greater variety in the years following the initial few years) will
take place. Because of the varying environmental settings of the
different sites and the different possible impacts of each type of
land application, separate discussions of each type and the methods
of application envisioned for those types are presented. Figure 3
shows potential areas for each category of sludge application.
No definite contractual arrangements have yet been made for specific
sludge recycling areas.
SPECIALLY EQUIPPED TRUCK SPREADS SLUDGE ON FARMLAND
In the following paragraphs, the proposed sludge recycling
areas and the present disposal operations at Lowry Bombing Range
(the no-action alternative) are discussed with a view to recom-
mended methods and rates of application and operation.
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Sludge Recycling Areas
Denver Parks--
Over the past few years, some dried sludge (containing 20 to
30 percent solids) has been used in preparing topsoil for estab-
lishment of new city parks in Denver and other cities in the area.
The stockpiled and air-dried sludge has been incorporated into top-
soil at about 112 metric tons/ha [50 tons/ac] prior to spreading
the topsoil on new park areas for seedbed preparation.
In the future, if the proposed reuse scheme becomes operational,
anaerobically digested and air-dried sludge will be spread during
winter months on already established parks. It is expected that the
sludge will be applied to the grass at the same total rate (112
metric tons/ha [50 tons/ac]) during the wintertime. The City and
County of Denver Parks Department has received sludge free of charge
in the past and expects to utilize up to a maximum of 4,500 metric
tons [about 5,000 short tons] per year on that basis. However, if
a charge is imposed or if the delivery responsibility is shifted to
the recipient, a change in this projection may occur.
Other communities indicating interest in sludge application to
park areas are Northglenn, Commerce City and Aurora. Parks in the
Denver area which are potential sludge candidates are graphically
shown in Figure 3.
Sod Farms—
Application of anaerobically digested air-dried sludge on sod
farms will probably be conducted by broadcasting of the dry material
using manure spreaders or similar equipment. The relatively fre-
quent sprinkler irrigation, typical of such farms, will provide the
necessary mechanism for moving sludge particles and soluble mate-
rials into the soil root zone.
With the cyclic removal of thin layers of soil during the har-
vest operations, residual sludge and its components—not used by
plants—are also removed from the site and transported to the con-
sumer. At the final destination, sludge materials in the sod root
network and the soil carried with it are gradually dispersed into
the soil and eventually taken up by plant root systems.
Representative locations of major sod farms in the Denver area
are depicted in Figure 3.
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Nine Spoil Sites—
In many parts of the Rocky Mountains, the natural landscape
has been marred by large piles of mine tailings created in the pro-
cess of extracting molybdenum and other elements from mined ores.
Without a deliberate effort to reclaim these spoil areas and im-
prove their potential productivity, these inert heaps may remain
unvegetated for many decades. On some sites, where particle sizes
are uniformly coarse (large gravel, boulders and rocks), larger
particles may have to be crushed or finer materials imported before
attempting to add organic materials.
For the example mine spoil site—the URAD mine near Berthoud
Pass—it is expected that Climax Molybdenum will furnish the neces-
sary trucks and other equipment needed for transporting and applying
dried sludge. Sludge will be mixed with wood chips in equal pro-
portions and applied at an initial rate of 45 metric tons/ha [20
tons/ac] of the sludge (90 metric tons/ha [40 tons/ac] of the mix-
ture). It is planned to add another 22 metric tons/ha [10 tons/ac]
of sludge within the first two years after the initial application.
Thus, a total of 67 metric tons/ha [30 tons/ac] of sludge will be
added to reclaimed spoil areas. It is expected that this applica-
tion rate will prove to be lower than optimal for spoil reclamation.
With a total spoil area of 50 ha [125 ac], this will amount to a
total sludge dry solids utilization of 3,400 metric tons [3,800
tons] at this particular mine.
Another area of potential sludge usage is the Watkins Project,
approximately 17 miles east of downtown Denver on Highway 70. The
Watkins Project is a conceptual plan to develop largely untapped
reserves of lignite coal near Denver. Under this scheme, the coal
resource would be combined with solid wastes and converted (gas-
ified) into pipeline quality natural gas. The energy source for
operation of the coal mine, the coal gasification plants and re-
clamation and restoration programs, as envisioned by the Mintech
Corporation, may potentially be derived from Denver sewage sludge
and solid wastes. Briquettes pressed from mixtures of solid waste
(garbage) and liquid sludge could supply approximately 20 percent
of the fuel feedstock. Dried sludge may also be used as an alter-
nate energy source.
The earliest projected date for project completion is 1981,
depending upon various financial arrangements and approvals by
State and Federal regulatory agencies.
Irrigated Farms--
Sludge application on irrigated farms will be the most sensi-
99
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tive of the agricultural reuse schemes, because of the intensive
food crop production on such farms. It is important to note that
the sludge application procedures and rates described here are those
best suited for the specific site studied. Impacts discussed in
Section V are similarly site specific. Therefore, an examination
of the characteristics of each site is necessary prior to embarking
upon a sludge application program. Such examination should include
analyses of soil cation exchange capacity (C.E.C.), pH and back-
ground heavy metals.
At the present time, barnyard manure is used on many irrigated
farms, particularly in sugarbeet fields. Conversion to use of
sludge or supplementation of this material can be readily accom-
plished with existing equipment and procedures.
Annual Application Rate Limitations — It is expected that an-
nual sludge application rates will be limited to the quantity which
provides nitrogen in amounts that can be taken up by the crops
grown on the farm. A formula of this general character requires
a number of assumptions, regarding the basic parameters determining
nitrogen balance. The more significant of these parameters are:
1. potential annual uptake of nitrogen by each crop, U, in
kilograms per hectare per year
2. total nitrogen content of applied sludge, N as percent
of sol ids
3. proportion of crop nitrogen removed from the land at
harvest, Cj
4. percent of nitrogen which is mineralized (made available
to plants) in a given year, c2
5. total background nitrogen in soil, p, in metric tons
per hectare
Using these values, annual application rate, R, in metric tons
per hectare, is given by the formula:
C, U
R = 1 ,000 C2 M " P (Equation!)
A plot of this equation is shown on Figure 14, in which p is
assumed to be zero. Under most conditions this is a reasonable
assumption for the first year of sludge application. On a farm
which has received sludge or other nitrogenous organic materials
in past years, p can be approximated by assuming that 30 percent
I U'J
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FIGURE 14
UJ
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o:
Q_
QL
UJ
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Q
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O
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o
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o
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o
'C
1
800
Ib/acre/year :
i • i i
I
100
200
300
800
900
400 500 600 -700
Kg/ha/year
UPTAKE OF MINERALIZED NITROGEN BY PLANTS
NOTE : ASSUMING C, = 95%; C2 = 30?^; p = 0
RELATIONSHIP BETWEEN ALLOWABLE SLUDGE
APPLICATION RATE AND UPTAKE OF MINERALIZED
NITROGEN FOR SLUDGES CONTAINING DIFFERENT
AMOUNTS OF NITROGEN - PLOT OF EQUATION I
o
(U
o
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o
o
QJ
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o
101
ENGINEERING-SCIENCE, INC.
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of the nitrogen in applied sludge becomes mineralized (made availa-
ble for plant uptake) in the first year, 15 percent in the second
year, 10 percent in the third year and 5 percent in the fourth and
succeeding years. While controlled experimental data in this area
are rather sparse, this decay series provides a tentative and con-
servative guide for protection against over-application. Using
these assumptions and further assuming that sludge contains 3.5
percent nitrogen on a dry weight basis, allowable application rates
over time are graphically portrayed in Figure 15. For other sludges
with different sludge concentrations (other than 3.5 percent) the
plots should be adjusted proportionately, i.e.,
RN = IT* R3.5 (Equation 2)
to obtain the proper application rate, RN-
Sludge application rates which are greater than the rates
given in Figure 15 for a given crop will result in leaching of ex-
cess mineralized nitrogen beyond the root zone and eventually to
the groundwater table. It has been estimated by Pratt that it
takes from 10 to 50 years for excess nitrogen to travel 30 m [100
ft] vertically in an unsaturated medium, depending on the inter-
vening soil types present (Reference 96). The nitrogen balance
is discussed more fully in Appendix D.
Total Sludge Application Surface Rate Limitation—The total
sludge quantity which may be permitted on a piece of land is lim-
ited by the heavy metals which can safely be tolerated in the soil.
A quantitative guide on the tolerable amount of sludge which can
be allowed is that the total amount of heavy metals introduced
therewith should not exceed ten percent of the soil cation exchange
capacity. A formula proposed by the EPA (modified to metric units)
in the tentative guidelines (Reference 79) suggests:
Total Sludge (dry solids, metric tons per hectare) =
73,000 x Cation Exchange Capacity (meg/100 g soil)
Zinc (mg/kg) + 2 Copper (mg/kg) + 4 Nickel (mg/kg) - 200
(Equation 3)
The implicit assumption of this formula is that copper is twice as
toxic as zinc and nickel is four times as toxic. Soils that might
receive Denver sludge in Arapahoe or Adams County may have a cation
exchange capacity of 20 meq/100 g. Typically, Denver sludge con-
tains 1,145 mg/kg zinc, 808 mg/kg copper and 282 mg/kg nickel
102
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FIGURE 15
200
- IOO
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O)
1_
o
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c
o
o
10
100
TIME , years
NOTES:
1. ASSUMING 3.5% N IN SLUDGE WITH 0.30, 0.15, 0.10,
0.05--" DECAY SERIES FROM YEAR 1 ON.
2. RATES NECESSARY TO MINERALIZE (MAKE AVAILABLE)
CONSTANT NITROGEN QUANTITIES FOR VARIOUS CROPS
AND/OR LEACHING OF EXCESS N TO GROUNDWATER.
3. 1 Kg/ha = 0.892 Ib/ac
ANNUAL SLUDGE APPLICATION RATES
103
ENGINEERING-SCIENCE, INC.
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(chemical characteristics of Denver sludge are given in Appendix D).
Equation 3 yields a total permissible sludge application of about
400 metric tons/ha [180 short tons/ac]. Comparing this representa-
tive total loading with annual rates given earlier for irrigated
farms, it appears that sludge application can be conducted on a
given piece of land for 20 to over 100 years (depending upon ap-
plication and uptake rates) before the limit is reached.
It is very important that the limit should be computed for
each soil on each farm. Average values and representative condi-
tions can be deceiving with respect to actual field implementation
of a project. For the purposes of this environmental impact state-
ment, values found on the farms studied are used as a means of
assessment of impact on those sites as reported in Section V. The
specificity of the impacts to the site cannot be overemphasized.
The applicability of these impacts to the entire study area is
valid only insofar as planning is concerned. Design and implemen-
tation should be viewed from an entirely site-specific point of
view. Using safe average application rates, if all the 1985 pro-
jected sludge quantities were to be applied to irrigated farms, a
total of about 3,000 ha [7,000 ac] of irrigated farms would be
needed.
Dryland Farms--
As noted in Figures 14 and 15, wheat grown under dryland
farming practices uses very little nitrogen due to the lower pro-
duction rates, compared with irrigated crops. Therefore, sludge
application rates consistent with nitrogen uptake are rather low,
ranging from less than one to three metric tons/ha [0.3 to 1.5
tons/ac] per year. At such low rates, rather extensive areas of
application and, consequently, greatly increased operation expendi-
tures are involved. On the other hand, due to the lower applica-
tion rates, the dryland farms can be utilized for sludge reuse over
a much prolonged period (over 300 years) before the total limit of
heavy metals loading is reached. Furthermore, impacts would occur
at a proportionately slower rate, providing greater opportunity
for mitigation and amelioration.
Experimentation with methods of direct injection of liquid
sludge at various depths has been conducted in the Denver-Boulder-
Fort Collins area and equipment is available from commercial manu-
facturers (References 97 and 98). These methods have promise par-
ticularly for dryland farms with the lower application rate re-
quirements. The effort involved in such methods is about equal to
land scarification procedures widely utilized by farmers for water
conservation. Sludge injectors achieve both functions in the same
operation (Reference 97).
104
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Application of air-dried sludge with manure spreaders or other
similar equipment can be controlled to achieve proper application
rates. Due to the relatively low rainfall rates and minimal culti-
vation processes in the dry-farmed areas, it is expected that in-
corporation of sludge within the soil root zone will be a rather
slow process; loss of nitrogen to volatilization would be greater
and the rate of breakdown of organic matter would be accelerated.
If all the 1985 projected sludge quantities were to be ap-
plied to dryland farms within safe application rates, a total of
about 43,000 ha [100,000 ac] of non-irrigated farmland would be
needed. If non-cultivated range land is to be included in sludge
application, adequate areas exist within reasonable distances from
the proposed distribution center.
Home Gardens—
The dried sludge could possibly be made available to the gen-
eral public for use in home gardens. Users would purchase the
sludge at the distribution center and apply it to ornamental plants,
such as lawns and flowers. Although highly unadvisable, home gar-
deners may choose to apply sludge to vegetable gardens. Metro
Denver could recommend appropriate usages of the sludge, similar to
the criteria for irrigated farmlands, but would not be able to con-
trol or restrict ultimate uses of the sludge by the home gardener
once the material is in his or her possession. Metro Denver also
contemplates marketing the dried sludge (presumably fortified and
sanitized) in bags for use by home gardeners in a similar fashion
to the Milwaukee "Milorganite" and the Rhode Island "Organiform."
Sludge Disposal at Lowry Bombing Range (No Action)
The present sludge disposal practice involves a large-scale
trucking operation from the Metro Denver Central Plant 40 km [25
mi] southeast to the Lowry Bombing Range.
For the high-rate sludge applications, the transfer trucks
are unloaded on a special ramp at the Bombing Range into an en-
closed hopper which in turn drains into smaller spreader trucks.
The spreader trucks convey the dewatered (10 to 16 percent solids)
sludge to the application areas where sludge is dumped in a uniform
layer (about 15 cm [6 in.] thick) atop the ground surface and left
to dry partially. The sludge is later plowed into the topsoil
using moldboard plows pulled by a track-type tractor along the
contours. Alternate contour strips are used to plow in the sludge
while the intervening strips are cropped and used for pasture.
A given contour strip receives sludge in this manner once every
nine months until a total of 392 metric tons/ha [175 tons/ac] are
105
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added. The operation then moves on to a new tract. It is expected
that if the agricultural reuse plan is fully implemented, disposal
operations in the Lowry Bombing Range will be phased out.
SLUDGE IS SPREAD ON LOWRY BOMBING RANGE BEFORE DISCING
During winter months when land application becomes impeded by
ice and snow on the ground, this operation is temporarily replaced
by direct dumping of the sludge into pits in a manner similar to
solid waste landfilling.
Sludge Landfill ing--
Landfilling sludge along with other municipal solid wastes is
a widely accepted practice, generally used for ultimate disposal
of the solid wastes. Typically, partially dried sludge is dumped
into the landfill and covered with other refuse. However, under
well-managed sanitary landfill ing procedures—increasingly in use
in communities across the country—strict operating techniques are
followed. Foremost among these techniques is a sound site selec-
tion process in which the environmental implications of candidate
sites are exhaustively researched and compared. The U.S. Environ-
mental Protection Agency has published a recent design and opera-
tion manual incorporating site selection, construction, operation
and maintenance procedures (Reference 98). The methods and pro-
visions standard on truly sanitary landfills are aimed at odor
control, protection of public health, groundwater quality protec-
tion and prevention of various hazards. Monitoring provisions are
aimed at determination of long-term impacts and early warning of
106
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adverse impacts. At the Lowry landfill, sludge disposal is expected
to occur only during emergency periods when the normal operations
are temporarily disrupted. Also, if the proposed sludge recycling
plan is somehow aborted, and if Metro Denver is also barred from
landspreading at the Lowry Bombing Range, it is possible that sani-
tary landfill ing would be the reasonable alternative.
107
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w
h
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This Section is the core of the Draft EIS.
It is here that the impacts of the proposed action
are presented and discussed.
Because of the highly site—specific nature
of the impacts, this Section is organized to empha-
size the most important issues likely to arise at
the most vulnerable sites. It is divided into
three main parts. First, impacts expected during
the processing, transfer, drying and stockpiling
of the sludge are analyzed. Second, impacts at
the land application sites (sludge recycling areas)
are presented. Finally, impacts at the Lowry land
disposal and landfill—which comprises the "no-
action" alternative—are discussed.
Throughout, an attempt has been made to pre-
sent the impacted environmental parameters and
criteria in descending order of importance and in-
tensity of impact, as perceived under the existing
state of knowledge and as judged from the perspec-
tive of overall human welfare. A great deal of
research in the field of land application of sludge
is currently in progress and is planned for the
future. Therefore, many of the stated impacts must
necessarily be considered tentative in intensity
and, in some cases, in magnitude and direction, as
well.
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SECTION V
ENVIRONMENTAL IMPACTS OF THE PROPOSED ACTION
INTRODUCTION
The Metro Denver sludge management plan, proposing the re-
cycling of organic solids on land, is a relatively complex scheme
involving several treatment subsystems and numerous different
types of application sites. Such complexity and diversity gives
rise to different types and intensities of impact, necessitating
separate and distinct evaluation in the decision-making process.
The reader who is interested in only one type of application site,
under a given local condition, is cautioned to read this draft EIS
with a special view to the specific sites and conditions discussed
under each impact category. In the present draft, impacts are ar-
ranged in order of general severity and with particular reference
to the sites of sludge application where they will be encountered.
IMPACT OF SLUDGE PROCESSING, TRANSFER,
DRYING AND DISTRIBUTION
The environmental impact of the proposed action was partially
assessed in the facilities planning process and reported in Febru-
ary 1975 (Reference 8). A summary of environmental impacts of
sludge drying and distribution activities at the alternative sites,
prepared by the facilities planners (CH2M Hill) is presented in
Appendix G. Impacts attributable to the reocmmended sludge drying
and distribution site (B2) are summarized in this Section.
Impacts of processing and transfer (pipeline) will be rather
temporary and slight compared to those of the sludge drying/distri-
bution site and those at the application sites.
Soil Loss
The excavation of Z40 hectares [600 acres] of land to 1.5-m
[5-ft] depth for the drying basins would effectively disturb all
soil in this large area. Even though the disturbed soil mass
would remain at the drying/distribution site, soil profile charac-
teristics, structure and other physical properties would be so
thoroughly destroyed or modified that an agricultural substratum
109
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would no longer exist. Furthermore, the soil mass thus removed
would cover over other soil areas, gradually changing their physi-
cal, chemical and microbiological characteristics. Thus, an irre-
trievable loss of the soil resource from the site would occur.
Soils in the proposed drying/distribution site are largely
in soil capability unit Ill-e (irrigated) or IV-e (nonirrigated).
This indicates that, with a moderate degree of management control
(especially to prevent erosion), the soils can be generally produc-
tive (particularly under irrigation). Soil impacts arising from
experimental programs on the distribution site will be highly vari-
able due to the wide range of application rates and methods typi-
cally used in a controlled experiment. It is expected that these
experiments will be conducted with adequate monitoring of the vari-
ous sludge components and environmental parameters during and be-
yond the experimental period. Results obtained from monitoring
programs should provide the necessary information for minimizing
and mitigating adverse impacts. The size of the experimental
areas will be generally limited, and accumulations of excess quan-
tities of heavy metals in plots receiving high application rates
will eventually be dispersed, in part to surrounding soils (by cul-
tivation practices) and in part to underlying strata.
The impacts of sludge reuse on agricultural land per se are
discussed in later parts of this Section. Many of the statements
made with reference to off-site impacts are equally applicable to
conditions on the distribution site insofar as irrigated crop pro-
duction is concerned.
Water
Groundwater Quality—
Due to the low permeability of soils in the distribution site,
it is expected that water movement toward the groundwater reservoir
will be very slow, notwithstanding the slow initial rates of water
(and sludge leachate) movement and the further clogging of soil
particles, salt-laden water will eventually move past the upper
soil strata. In time, this drained water and the solutes it car-
ries will percolate into the water table and deteriorate ground-
water quality. It is expected that the extent of groundwater pol-
lution from this source will be significant considering the
proposed 240 hectares [600 acres] of unlined sludge drying basins.
With a total dissolved solids concentration of about 6,000 mg/1,
the percolate is a threat to groundwater quality. Both the inor-
ganic components and the stable organic portion of this leachate
can damage the groundwater quality and thus gradually reduce per-
missible uses of the water. The contamination of groundwater by
no
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nitrates is discussed under Public Health, below.
The soils in the proposed drying basins have a permeability
of 0.02 to 0.08 cm/hr [0.008 to 0.03 in./hr]. Assuming that the
soil permeability to sludge leachate will eventually decrease to
0.0001 cm/hr [0.00004 in./hr] by clogging of soil pores, and as-
suming that half of the drying basins will be wet enough to re-
lease water to percolation at any given time, it can be computed
that 27,000 cu m [nearly one million cu ft] of leachate per year
will move toward the groundwater table. With a total dissolved
solids concentration of 6,000 mg/1, this amounts to 160 metric
tons [180 tons] of salt per year moving toward the water table.
The rate of movement will be slow; it would take 20 to 100 years
for the water to reach the groundwater table. It would take a
similar length of time to terminate pollution from this source at
the end of a long-term use of this land area. Thus, a lack of
evidence of water pollution in the initial decades of operation
cannot be viewed as a sign of absence of impact. The groundwater
mound eventually created will move horizontally and will affect
wells in the vicinity.
In light of these calculations—recognizing the limitations
implicit in their assumptions—it may be necessary to line drying
basins with (pigmented) bentonite or some other effective barrier.
Other, partial, solutions include separation of decant, use of
underdrains, pumping leachate from the ground and vacuum filtration
of the sludge at the site before air drying. Mitigation measures
against this severe impact are discussed in Section VI. Monitoring
of leaching water quality and movement rates will be necessary
whether or not basins are lined.
Surface Water Quality--
Surface water protection will be effectively provided with
the provision of drainage channels and earthen dams with adequate
impoundment areas. These features have already been incorporated
into the facilities plan for the drying and distribution area.
Provision is made for analysis of impounded water for BOD, COD,
biological indicators, nitrogen, total dissolved solids and other
parameters, as set forth by agencies regulating discharges to sur-
face water. Contaminated water would not be discharged to streams
but would instead be used for surface irrigation (see above for
groundwater quality effects).
Water Rights—
In the process of transporting liquid sludge to the drying
and distribution center, and during tne periods of purging the
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pipelines with secondary effluent and any additional irrigation water
beyond what is now consumed in the sludge disposal process will be
carried from the Central Plant to the Adams County site. It is anti-
cipated that this removal of water will have some impact on appropria-
tions downstream of the Central Plant discharge into the South Platte
River. Under the existing system of appropriations, the treated and
discharged sewage would belong to senior consumptive users downstream.
However, under Colorado Supreme Court decisions, water transferred
interbasin belongs to the diverter and can thus be reused. In this
particular case, the Denver Water Board is the owner of the water
transferred from the western slopes and will presumably allow Metro
to use these additional waters as part of the treatment process.
Public Health
General--
Biological health hazards associated with sludge include patho-
genic bacteria, viruses and parasites which may have survived the ini-
tial treatment process. The major bacterial diseases have been con-
trolled well by traditional treatment processes. Statements about
viral health problems must be more guarded and uncertain because of
the difficulty in measuring viruses and the lack of standards for vi-
rus levels. In general, however, viruses are more short-lived than
bacterial pathogens (References 39,80). Intestinal parasites may
also be present in various forms in the sludge. Parasites and their
eggs or cysts are only partially destroyed by traditional treatment
processes. Other biological hazards associated with sludge are such
disease-carrying vectors as flies, mosquitoes and rats.
Threats to health from chemicals within the sludge are generally-
chronic and indirect. Before the chemicals can reach the human body,
they usually pass through at least two biological systems (plants and
livestock); acute effects can be noted at these intermediate stages.
The treatment process itself is a relatively sensitive biological sys-
tem which can be upset at the activated sludge or anaerobic digestion
stage if high concentrations of certain elements enter the system.
Chemicals applied to the soil would affect the crops if they built up
to dangerous levels. Present standards for heavy metals are based on
determinations of the levels at which there is toxicity to plants (Ref-
erence 79). The human health effects of long-term, low-level consump-
tion of these materials cannot be determined at this time. Therefore,
potential adverse effects on human health cannot be overemphasized.
Traditional sludge treatment processes do not reduce hazards to human
health from heavy metals in the sludge. An interim primary standard
has been established by the EPA for nitrates at 45 ppm (as nitrate)
in drinking water supplies. If levels are kept below this thresh-
old, a safe water supply is generally presumed. Regulations also
exist to control the levels of persistent organic chemicals in certain
112
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components of the food chain,
Health Protective Factors Associated
with Sludge Management—
There are a number of factors which help to ensure that the
potential health hazards associated with sludge will not be real-
ized to the extent of creating actual health problems. The an-
aerobic digestion process destroys most of the human pathogens.
Fecal coliforms, an indicator of pathogens, are reduced by 97 per-
cent or more in a well-run anaerobic digester (Reference 79). An-
aerobically digested sludge is generally considered biologically
safe to use on farm crops without further treatment (Reference 81).
Eggs and cysts of enteric parasites are able to survive the diges-
tion process and remain alive for relatively long periods of time.
The subsequent drying and soil incorporation processes are deadly
to pathogens due to the exposure to ultraviolet light, desiccation
and unsuccessful competition with the indigenous soil organisms.
However, many parasites have long survival periods in the soil in
cyst form or in the egg stage. Long-term storage of sludge is an
effective reducer of pathogenic organisms (Reference 82). Storage
of liquid digested sludge for 60 days at 20°C [68°F] or 120 days
at 4°C [40°F] has been reported to be a successful pathogen reduc-
tion measure (Reference 79).
Pathogens--
Because potential hazards exist in the use of recycled, di-
gested sludge, proper precautionary measures must be provided to
assure that no significant harm to human health will result from
this practice (Reference 39).
Pathogenic microorganisms will not pose a significant public
health threat at the distribution site if the proposed project is
operated as designed. The project will include a soil and ground-
water monitoring system to monitor environmental quality. Six on-
site wells around the perimeter of the drying site and other near-
by wells will be used to monitor approximately 15 biological and
chemical parameters.
The survival times of various pathogens as_sociated with sew-
age sludge are given in Table 20. Ascaris ova (eggs of a para-
sitic worm) are particularly long-lived and thus are good indica-
tors for monitoring the general sanitary quality of the sludge.
salmonella, relatively common pathogenic microorganisms, are also
113
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Table 20. SURVIVAL TIMES OF PATHOGENIC MICROORGANISMS IN VARIOUS MEDIA
Organism
Ascaris ova
Cholera
vibrios
Endamoeba
histolytica
cysts
Enteric viruses
H'.okwona larvae
Leptospira
Salmonella typhi
Medium
soil
soil
plants and
fruits
spinach, lettuce
cucumbers
non-acid vegeta-
bles — onions ,
garlic, oranges,
lemons, lentils,
grapes
rice and dates
river water
soil
tomatoes
lettuce
roots of bean
plants
soil
tomato and pea
roots
soil
river water
soil
dates
harvested fruits
apples, peats,
grapes
strawberries
soil
soil
soil
pea plant stems
radish plant
stems
soil
lettuce and
endive
Type of application
not stated
sewage
ACb
AC
AC
AC
infected
f eces
AC
AC
AC
AC
AC
AC
AC
infected
feces
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
Survival time
2.5 years
up to 7 years3
1 month
22 - 29 days
7 days
2 days
hours to
3 days
8-40 days
8 days
18 - 42 hours
18 hours
at least
4 days
12 days
4-6 days
6 weeks
5-6 days
15 - 43 days
68 days
3 days
24 - 48 hours
6 hours
74 days
70 days
at least
5 days
14 days
4 days
up to
20 days
1-3 days
114
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Table 20 (continued). SURVIVAL TIMES OF PATHOGENIC
ORGANISMS IN VARIOUS MEDIA
Organism
Salmonella,
other than
typhi
Shi gel Jt a
Tubercle bacilli
Medium
soil
soil
lettuce
radishes
soil
soil
soil
cress, lettuce,
and radishes
lake water
soil
vegetables
tomatoes
soil
potatoes
carrots
cabbage and
gooseberries
streams
harvested fruits
market tomatoes
market apples
tomatoes
soil
grass
sewage
soil
Type of application
AC
AC
infected
f ecps
infected
f eces
infected
f eces
AC
AC
AC
AC
AC
AC
AC
sprinkled with
domestic sewage
sprinkled with
domestic sewage
sprinkled with
domestic sewage
sprinkled with
domestic sewage
not stated
AC
AC
AC
AC
AC
AC
•>
?
Survival time
2 - 110 days
several months
18 days
53 days
74 days
5-19 days
70 - 80 days
3 weeks
3-5 days
15 - 70 days
2-7 weeks
less than
7 days
40 days
40 days
10 days
4 days
30 minutes -
4 days
minutes -
5 days
at least
2 days
at least
6 days
2-7 days
6 months
14 - 49 days
3 months
6 months
warm, moist conditions not encountered in the Denver area.
AC = Artificial Contamination
Source: Evaluation of Municipal Sewage Treatment Alternatives (Reference 80).
115
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fairly hardy and therefore good indicators for monitoring the
safety of the sludge.
Because of the remoteness of the site, human exposure to the
drying sludge will be limited, further ensuring that no significant
health impacts will result from the proposed project. However,
public access to the drying beds should be curtailed while the
sludge is drying, and special periodic medical examinations and
preventive treatment by qualified physicians should be made avail-
able to project personnel and to consumers who come to the site to
collect sludge.
An adequate soil barrier/filter exists for protection of the
groundwater from any pathogenic microorganisms in the sludge. Sur-
face water runoff will be contained behind earthen dams on a site
about 15 m [50 ft] above the water table, and access to this water
will be controlled to bar potential health and safety problems.
Nitrates--
It is probable that significant quantities of nitrogen, in the
soluble nitrate form, will move with the leachate water from the
bottom of the sludge drying basins toward the groundwater table.
The precise quantity and rate of movement of the nitrates depend
on several factors (denitrification rates under anaerobic condi-
tions, mineralization of organic nitrogen forms by microorganisms,
oxidation of the ammonia form under aerobic conditions, etc.), each
of which may be occurring at different times and places in the ba-
sins at different rates. Once nitrate begins to migrate beneath
the basins, it will remain unchanged and may gradually increase in
concentration in the groundwater reservoir, eventually exceeding
the 45 mg/1 standard. High nitrate (NO^) concentrations in drink-
ing water supplies have been linked to methemoglobinemia, a rare
"blue baby" disease resulting from reduction of the oxygen-transfer
capacity of blood in infants. The problem of nitrate, coupled with
the other salts discussed above under groundwater quality, can be
handled by lining the basins and other measures enumerated.
Vectors--
Gnats, flies and mosquitoes are the most common vectors of
pathogens expected to be present in the vicinity of the drying ba-
sins. It is important that qualified specialist entomologists be
consulted for the identification of specific species of insects
that will emerge in the basins. While gnats and flies will remain
within one km [O.6 mile] of the basin boundaries, mosquitoes can
travel (even under severe wind conditions) UD to 40 km [25 miles]
116
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away. Mosquitoes and some species of flies can transmit certain
diseases; hence, it is important that integrated insect control
measures be instituted with a view to maximizing natural control
mechanisms. The drying basins (240 hectares [600 acres] in size)
will provide a large, permanent ecosystem with a wide range of
moisture, food supply, breeding environments and surrounding vege-
tation. It is difficult to predict the actual invertebrate spe-
cies that will inhabit this new ecosystem. However, it is possible
that a few species will predominate in the absence of natural ene-
mies. Only after accurate identification of the prevalent species
can proper control measures be recommended. Hence, consultation
with specialist entomologists is important at the initial stages
of operation of drying basins. It may be necessary to add safe
insecticides (such as organophosphates) to sludge at the treatment
plant.
Experimental sites for liquid sludge application may also at-
tract some insects and require control measures. Vectors such as
rats and mice are usually not attracted to drying basins or to
stockpile areas. The proposed activities in the experimental areas
are therefore not expected to influence either the presence or the
size of population of such vectors.
Loss of Habitat
Animal species diversity at the proposed site will be greatly
reduced due to the removal of habitat during the construction of
facilities and the excavation of vast areas for the sludge drying
basins. Some species, including mice, voles and rabbits, may re-
turn to cultivated portions of the site when crops are growing.
Some of the birds presently found on the proposed site may return
if the level of human activity and the types of crops grown in
these areas are not incompatible with their resting and feeding
requirements. At the time of facilities planning investigations,
consultants found "no nesting areas which might be disturbed" (Ref-
erence 8). The disturbance to vegetation along the 40-km [25-mile]
pipeline and within the 300-hectare [2,000-acre] distribution site
would not be of a drastic nature because most native vegetation
has long been replaced by farming. Vegetation will be readily re-
stored along the pipeline. At the distribution center, all vege-
tation at the site of the drying basins and stockpile area will
be removed for the indefinite duration of the -project. At the
experimental areas, a presumably well-managed farming operation
will replace the existing dryland farms.
Air Quality
The proposed project is not expected to cause a significant
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air quality impact on the alternative drying and distribution cen-
ter sites during any but the most severe windstorms. (Odors are
discussed as a separate topic in the pages following.)
During operation of the sludge drying center, dust will origi-
nate primarily from vehicles driving on the dirt roads of the site.
A problem lesser in magnitude but perhaps greater in offensiveness
is the dust which will be blown from the dried sludge piles. Be-
cause the sludge particles will have been thoroughly dried before
becoming airborne, little odorous, volatile material will be pres-
ent and pathogenic organisms will have been largely desiccated.
However, spores and certain parasite eggs can survive in dry con-
ditions for relatively long periods.
Normal winds will not spread significant amounts of dried
sludge, though the strong (over 11 mps [24 mph]) winds which oc-
casionally occur (during about two percent of the year) will
spread the dried material, probably to the east or south (see Fig-
ure 9 for wind distribution patterns). It is difficult to esti-
mate the amount of material blown during such winds. During most
wind storms, the contributions from the sludge piles probably will
not be quantitatively or qualitatively significant because of the
cohesive, fibrous nature of the dried stockpiled material.
Air pollutants generated during transport and delivery of
the dried sludge will not be of great enough quantity to signifi-
cantly affect air quality. Impacts on air quality were determined
assuming "worst case" conditions during peak periods: 30 truck
trips/day and 200-km [120-mile] maximum roundtrip (Reference 77).
From these figures and emission factors appropriate for the trucks
(Reference 99), it is calculated that the maximum amounts of air
pollutants generated during the spring and fall peak delivery per-
iods are: hydrocarbons, 10 kg/day [23 lb/day]; carbon monoxide,
70 kg/day [150 lb/day]; nitrogen oxides, 110 kg/day [240 lb/day].
This will not cause a significant air quality impact, being about
0.03 percent of the pollutants emitted daily in Air Quality Con-
trol Region 2 (see Figure 8) (Reference 38).
Ammonia nitrogen (as N) accounts for three to four percent
of the dry weight of the liquid sludge (Reference 55); 50 percent
of this will be lost to the atmosphere during drying (Reference
88). On the basis of design sludge quantities, this amounts to
approximately 620 metric tons [633 tons] per year of nitrogen-
containing gases emitted. Liquid sludge loses about one-fourth
as much ammonia nitrogen and therefore will emit less of this ma-
terial to the air. These emissions have caused no knov;n air qual-
ity problems in sinilar operations in Los Angeles County, Califor-
nia (Reference 100). It is doubtful that this loss in ammonia
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nitrogen will have a significant effect on air quality (Reference
101).
Because there is no air quality standard in Colorado for am-
monia emissions, odor is the only parameter of concern with regard
to this gas. An emission permit is required from the Air Pollution
Control Division of the Colorado Department of Health under Regula-
tion No. 2, promulgated by the Colorado Air Pollution Control Com-
mission. Included in this permit would be a definitive plan for
the control of odorous emissions. In addition, a complete inven-
tory of quantities and rates of emission is required for all odor-
ous compounds being emitted from the site. (Odor conditions are
described separately, below.)
The Department of Health further stipulates that significant
emissions be modeled to estimate maximum concentrations and their
locations downwind of the site. Similarly, it will be necessary
to include a plan for the control of fugitive dust.
Odor—
Tv/o sets of observations have been gathered on odors which
might possibly enter the environment surrounding the proposed
sludge drying and distribution center. One test was carried out
by the Metro Denver staff in cooperation with Colorado State Uni-
versity on a system similar to the proposed new system. A second
set of observations of interest was gathered by the Tri-County
District Health Department on the sludge drying system presently
operating at the abandoned Lowry Bombing Range.
In the first test, the Metro Denver District staff constructed
and monitored six 8-m by 9-m [25-ft by 30-ft] sludge drying basins
at the Colorado State University research farm at Fort Collins. A
panel of Colorado State University faculty members and wastewater
treatment plant operators was assembled. The odor tests were taken
within a few meters of the ba~sins over a period of 6 to 12 months.
The panel was asked to describe the odor level in terms of the fol-
lowing numerical rating system:
0 - undetectable
1 - faintly detectable
2 - detectable
3 - objectionable
4 - very objectionable
The basins took from 6 to 12 days to reach the No. 1 level. The
panelists noted that the odors did not carry very far beyond the
basins.
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The results of the tests were confirmed by Metro representa-
tives during a field trip to drying basins in Sioux Falls, South
Dakota; Topeka and Wichita, Kansas; and Tulsa and Oklahoma City,
Oklahoma. None of those facilities had serious, continuing odor
problems. However, odors were a problem where inadequate diges-
tion occurred due to system failure (Reference 3).
The present Metro Denver operation at Lowry Bombing Range is
monitored for odors and other factors by the Tri-County District
Health Department. The Department also receives any complaints
concerning odor problems of the operation. There are about 10
complaints a year concerning odors emanating from the site. These
complaints come from areas up to 10 km [six miles] from the Lowry
site. However, complaints coming from this distance were found by
the Health Department to be unjustified ones: "The range of what
were considered justified complaints was one or two miles [two to
three km] from the Site" (Reference 39). The complaints usually
conincided with unusual meteorological conditions and/or system
failure.
Some past odor problems (such as the one occasioning the pub-
lic hearing of 20 June 1972) were due to system inadequacies which
were subsequently corrected. About 80 percent of the complaints
were found by the Health Department to be due to other odor sources
in the area, such as the landfill operation at Lowry and the gas
processing plants in the vicinity. The remaining 20 percent of
the complaints occurred during unfavorable weather or operation
breakdown (Reference 39).
It should be noted that the anaerobically digested sludge to
be dried as part of the proposed project will be less odorous than
the material presently deposited at the Lowry site. After the
sludge has been dried prior to distribution to sludge recycling
areas, almost all of the volatile, odorous materials will have
left the sludge. During digester malfunctions (souring), severe
odor problems may be expected if sludge were to be pumped to the site.
Noise
Traffic, aircraft and farm equipment comprise the main sources
of existing background noise in the vicinity of the proposed drying
and distribution center, with an average noise level of 35 decibels
on the A scale (35 dB-A) and a maximum of 60 dB-A (Reference 3).
It is expected that the site will be designed in such a way that
most of the noise-generating activities will occur at the center of
the 800-hectare [2,000-acre] site and thus be surrounded by experi-
mental fields. Further, it is possible to equip all internal com-
bustion engines with noise mufflers, reducing noise to 80 dB-A at
15m [50 ft].
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Noise levels are expected to rise on Irondale Road with in-
creasing truck traffic, particularly during the heaviest periods
of sludge application. These noises, as well as all others dis-
cussed above, would occur only during the least noise-sensitive
daylight hours and would not disturb the comfort of residences or
pose a health threat to operators or other persons on the site.
Energy Use
Metro Denver Sewage Disposal District No. 1 used about 50 mil-
lion kilowatt hours (KWH) of electricity for its total operations
in 1975 (Reference 73). On a per capita basis, this amounts to
about 50 KWH/person/year, which compares to a total per capita
energy consumption in the United States of about 100,000 KWH/year
(References 74,75). The current sludge handling and disposal sys-
tem has total energy costs, for electrical power and fuel, equiva-
lent to roughly 20 million KWH of energy (References 8,55,70), or
20 KWH/person/year.
Viewing the energy required for sludge handling and disposal
in the perspective of the total energy use within the District's
service area, sludge accounts for about 0.02 percent of the total
energy consumption in that region. Viewed in absolute terms, it
is roughly equivalent to the total annual energy consumption of
200 people.
Energy Value of Sludge Nutrients—
An energy parameter of significance is the amount of energy
required to produce and ship fertilizer in the area. For produc-
tion of the three macronutrients essential for fertilizers: ni-
trogen, phosphorus and potassium, costs to the consumer that are
due to energy costs are estimated to be 50, 25 and 30 percent,
respectively (Reference 76). Assuming that the nutrient elements
are available in proportions of two nitrogen, one phosphorus and
no potassium in Metro Denver sludge, the weighted average energy
equivalent of the nutrient value of the sludge becomes 40 percent.
If recycling of nutrients in the sludge is successfully
achieved, a saving will be realized that is equivalent to the en-
ergy requirement for mining, manufacture and transport of commer-
cial chemical fertilizers which otherwise would have been needed.
Assuming (a) a nutrient value benefit of $28/metric ton [$25/ton]
for Metro Denver sludge (on the basis that nitrogen is the only
nutrient of value, with five percent of the dry matter in the
sludge worth $0.55/kg [$0.25/lb]); (b) design production of 97
metric tons [107 tons] of dry sludge per day, and (c) an energy
factor of 40 percent of the total fertilizer cost, an energy equiv-
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alent of about $400,000/yr is obtained. At $0.02/KWH, this trans-
lates into energy savings of about 20 million KWH per year.
Energy Produced in the Digestion Process—
Methane gas is generated in the anaerobic digestion process
at the rate of nearly one cu m/kg [15 cu ft/lb] of volatile mater-
ials destroyed in the digesters. The energy value of methane thus
produced will be almost 70 million KWH/yr using conservative as-
sumptions in basic production rates. Since an equivalent of about
20 million KWH will be used annually for heating the digestors, a
net gain of about 50 million KWH/yr would be realized if energy-
conversion equipment (boilers, steam turbines, etc.) were to be
available for utilization of the excess energy. At this point,
however, such equipment is not envisaged in the facilities plan;
therefore, this rather large energy item is not included in the
total energy picture.
Energy Used in Transport of Sludge—
Another major energy economy can be achieved through the more
efficient transportation system (in comparison to the Lowry dispos-
al operations) designed for the recycling project. About 680,000
liters [180,000 gallons] of diesel fuel per year are consumed in
the Lowry operation, assuming 35 truck trips/day, 80-km [50-mile]
round trip and 1.5 km/1 [3.5 miles/gal] (References 55,77). This
energy is equivalent to nine million KWH/yr and is included in the
total energy figure given above for the present operation of the
sludge handling and distribution systems.
By contrast, only about 80,000 liters [20,000 gallons] of
fuel per year would be required to deliver the present sludge load
to the land application areas. Net savings accomplished by the new
transport system (including the sludge pumping energy requirement)
over the Lowry operation amount to about eight million KWH/yr.
Energy Balance in Sludge Transport to Farms—In order for the
shipping of sludge, from the drying and distribution center to re-
use areas, to be economical, the cost of shipping must not exceed
the price of equivalent fertilizer delivered at the reuse site.
This assumes no value for the soil-structure-enhancing benefits of
sludge recycled to land. Assuming further that nitrogen is the
only constituent of value in sludge, maximum distance—beyond which
shipment of sludge would be uneconomical — is obtained by:
U = F
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in which: D = distance from the distribution center to the
ultimate application area,
F = fertilizer cost,
N = fraction of nitrogen in the sludge dry solids,
W = fraction of total solids in the sludge shipped,
S = specific weight of stockpiled sludge, and
Y = volumetric unit transport cost.
With: F at $0.55/kg [$0.25/lb] of elemental nitrogen,
N at 0.05, i.e., five percent of the dry matter,
U at 0.50, i.e., 50 percent of the sludge,
S at 560 kg/cu m [35 Ib/cu ft], and
Y at $0.08/cu m-km [$0.10/cu yd-mile],
the breakeven distance, D, is calculated to be nearly 100 km [60
miles].
In summary, it can be seen from the discussions presented
above that a total energy saving of at least 28 million KWH/year
could be realized if a successful sludge recycling program were
instituted to replace the present system: eight million through
abandonment of the Lowry operation and 20 million from fertilizer
recycling revenues. This is equivalent to the average annual en-
ergy consumption of 280 people, or about 0.03 percent of the total
energy consumed within the District boundaries in a year.
Aesthetics
The visual impact of the proposed sludge drying site, as de-
signed, will be perceptible mainly from within the site and from
above (from aircraft). The demonstration plots will be visible to
the passing motorist from Irondale Road, the most heavily travelled
road bounding the site (though even this road carries only about
210 vehicles per day). It is expected that the sight of_the drying
basins may be unpleasant to those associating the site with the
fecal origin of sludge. Otherwise, the distinctive geometric pat-
terns formed by the basins (schematically presented on Figure 13)
and stockpile windrows could provide an interesting visual contrast
(particularly from the air) to adjacent farmland patterns. The
association of the project with energy and resource conservation
will further improve its aesthetic status in the minds of people
who are aware of the limits of our planet.
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Plant Operation and Plant Effluent Quality
Because Metro is installing anaerobic digesters at the Metro
Central Plant, a different strength waste stream will result com-
pared to the present system. In a wastewater treatment plant using
digesters, supernatant from the digesters is often recycled to the
plant. This recycle stream can put an additional treatment burden
on the plant operation from addition of suspended solids, BOD, am-
monia and other substances.
With the Metro land recycling proposal, the digester super-
natant would be pumped along with the digested sludge to the drying
and distribution site. This proposal would therefore leave the re-
cycle situation at the Metro plant comparable to what it is now.
However, if the use of the Lowry Bombing Range were continued for
disposal (and presuming that the present operation of vacuum filter
and truck haul were also to be continued with digested sludges) the
Metro Central Plant would experience additional loads on the liquid
treatment portion of the plant. A rough estimate of the additional
load would be as follows: suspended solids: 10 to 15 percent, BOD:
3 to 6 percent, and ammonia: 4 to 8 percent, assuming both Metro
and the Northside plants were to recycle or add supernatant to the
plant. The first two constituents would probably be further treated
in the plant process and might not affect effluent quality. Ammonia,
however, could pass through existing plant treatment units unchanged
and increase ammonia loadings to the South Platte River. Any alter-
native involving recycled supernatant to the wastewater plant would
have this effect.
The tradeoff between the Metro proposal and any alternatives in-
volving recycle to the plant involves the additional treatment that
may be necessary at the drying site to handle the supernatant and
additional excess water in the digested sludge. No cost estimate
has yet been made for controls which may be necessary to prevent mi-
gration of soluble nitrate in the sludge water into the groundwater.
Natural Resources
While the proposed action will conserve a presently wasted re-
source of significant potential value, it will require use of fuel
for transport and application of sludge to land and will necessi-
tate disturbance of the soil resource on some 240 hectares [600
acres] of the proposed drying basins and stockpile areas.
Organic Matter and Plant Nutrients —
The single most important impact of the proposed action is
the conservation of the soil-conditioning/fertilizing capability
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of sludge. Within the framework of limitations discussed in Sec-
tion IV, sludge comprises a valuable resource whose magnitude is
only now becoming apparent to the general public. Depending on
process train and application type, the total nitrogen value alone
of Denver sludge can range from $4 to $4.6 million per year under
present prices and values. Sludge contains phosphorus in abundant
quantities as well as minor amounts of all other essential ele-
ments. It also has the ability to improve soil conditions for
plant growth. However, it lacks adequate potassium. It is ex-
pected that the money-equivalent value of sludge will increase
snarply in future years as fossil fuels (primary sources of com-
mercial nitrogen fertilizers) become ever more scarce and other
shortages of natural resources become more apparent than at
present.
Use of Fuel for Transport of Sludge—
As discussed above under Energy Use, the fuel required under
the proposed action is far less than that used for present opera-
tions at the Lowry Bombing Range site. Nevertheless, it is a sig-
nificant commitment of resources.
Soil —
Disturbance of soil profiles at the sludge drying basins has
already been discussed in the early part of this Section, under
Soil Loss, and need not be restated here.
Archaeology and History
The proposed project should not have an adverse impact on
either the archaeologic or the historic characteristics of land
affected by the proposed project. Land underlying the site of
the anaerobic digesters has already been developed, as has the
land adjacent to the proposed pipeline route. Furthermore, there
was no surficial evidence at the proposed drying basin site to
indicate underlying archaeologic sites (Reference 3), and no his-
toric sites have been designated in that area (Reference 43).
While all evidence indicates that the proposed project_will
not jeopardize archaeologically or historically important sites,
the remote possibility exists that heretofore unknown sites will
be discovered during construction activities connected with exca-
vation of areas for the installation of anaerobic digestors, with
laying the pipeline and with construction of the drying basins.
In the event of such a discovery, the Colorado State Antiquities
Law should be reviewed and its provisions implemented. Jhe par-
ticular significance of this law in relation to the National
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Historic Preservation Act of 1966 and the Archaeological and His-
toric Preservation Act of 1974 should be recognized in making pro-
vision for the possible discovery of archaeological and historic
resources.
Land Use
Land uses within the immediate boundaries of sites to be used
for the installation of the anaerobic digesters, pipeline route
and drying basins will change as a result of implementation of the
proposed project. These changes will be compatible with surround-
ing land use activities and will not conflict with relevant land
use plans or zoning regulations.
Installation of anaerobic digesters at the Metro Denver Cen-
tral Plant facility will cause an internal land use change. This
change will be compatible with the present use since plant opera-
tion will not change and use of the land will continue to be for
sewage processing.
The proposed pipeline route, lying beneath the roadway right-
of-way areas, will not precipitate adjacent land use changes. Ex-
cept for other utility and municipal service lines which lie be-
neath these areas, the land is presently vacant; addition of the
pipeline will leave the status of the land unchanged.
The agricultural area to accommodate the sludge drying and
distribution site will change in use, but this change will be com-
patible with surrounding land uses since the project will provide
fertilizer for agricultural use. Because of this function, the
proposed location of these basins is consistent with Adams County
land use plans and with County zoning regulations which seek to
perpetuate both agricultural and agriculture-related land uses
(References 45,46). A potential impact of benefit would result
from reduction of pressure for future large-lot subdivision in
the vicinity of the sludge drying and distribution center.
It is not likely that the proposed storage and distribution
system will provide the stimulus for any significant land use
changes in the surrounding area. At this time it appears that the
major cause of future land use changes in the area will be the pro-
posed Adams County General Aviation Airport. Sites to the west of
the proposed sludge drying and distribution center are being con-
sidered for the airport. A "growth corridor" running from the pro-
posed airport northwest to Brighton is likely. The drying and dis-
tribution center might limit growth which would otherwise extend
eastward from the proposed airport. However, in general there ap-
pear to be no major negative land use impacts associated with the
proposed drying and distribution center (Reference 44).
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Land Tenure
Should the proposed project be implemented, there will be
varying effects on land associated with the sludge processing,
transfer and drying facilities. In terms of the Metro Denver Cen-
tral Plant, there will be no impact on land tenure since no trans-
fer of ownership is anticipated. Likewise, no tenure change is
anticipated for the roadway right-of-way areas for the pipeline
since an easement will probably be obtained. However, ownership
of the drying basin site will be transferred from private into
public ownership.
No other impacts on land tenure will be incurred by the pro-
posed project. The Lowry Bombing Range and landfill site will re-
main in public ownership whether or not the project is implemented.
Population
The project will not have a significant impact on the popula-
tion growth rate in Adams County or in the Metro Denver service
area as a whole. It seems likely that the project would encourage
the continuation of agricultural activity and sparse population in
the region surrounding the drying site. This impact on population
distribution is predicated on two factors: (1) The proposed proj-
ect would provide a conveniently located source of fertilizer/soil
conditioner, to the benefit of farmers; and (2) the project may
inhibit residential development in the immediate vicinity of the
sludge drying site.
The impact on population distribution is uncertain and will
probably be diffuse. It would tend to maintain a sparsely popu-
lated rural area in its present state and thus aid in limiting
sprawl radiating from the Denver area.
The 18 new jobs generated by the drying/distribution center
will not significantly affect population growth or distribution
in the area. It is expected that the project will have no signifi-
cant growth-inducing impacts.
Transportation and Circulation
The proposed project could have a variety-of direct impacts
on transportation facilities which will serve the proposed drying
basin site. Average daily traffic (ADT) will increase, roadways
will deteriorate, highways might become littered and dust will be
generated as a consequence of sludge trucking. No impacts are ex-
pected on transportation facilities located in the area surround-
ing the Metro Denver Plant or along the proposed pipeline route.
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Average Dally Travel —
Average daily travel will increase on roadways serving the
proposed sludge drying and distribution center as a result of
trips made by facility employees traveling to and from work and
trucks using various roadways to deliver dried sludge. The ma-
jority of this traffic will be concentrated on such roadways as
Irondale Road, Bromley Lane and Hacksmount Road, which will serve
the drying and distribution center. The impact declines as road-
way travel radiates toward destination points. This increase in
average daily travel will not adversely affect traffic flow since
the roads in question are infrequently traveled and have design
capacities adequate to carry the additional traffic.
Assuming an average daily sludge production of 190 metric
tons [210 tons] and a truck capacity of 14 metric tons [15 tons],
annual truck traffic will total about 5,000 trips. Assuming a de-
livery period of four months (tv/o months during the spring and two
months during the fall), five days per week, daily truck trips
will total 60 to 65. Further assuming a delivery radius of 100 km
[60 miles] from the sludge drying site, this number of truck trips
distributed over an area of over 31,000 sq km [11,000 sq miles]
will not cause a significant impact on traffic.
Highway Bridge Capacity—
A potential problem is inherent in the fact that highway
bridges in some areas have posted capacity limits below 14 metric
tons [15 tons], the assumed average truck load. County Road 30,
for example, which serves the representative irrigated farm in
Weld County, includes two bridges, 30/25A and 30/258, the former
with a posted limit of 4.5 metric tons [five tons] and the latter
with a capacity of seven metric tons [eight tons] (Reference 105).
The routing of trucks will therefore require consideration of
bridge capacities in order to avoid accidents and bridge damage.
Traffic Dust—
Unpaved sections of roadway, on Weld County Road 30, for ex-
ample, can lead to dust problems under conditions of heavy traffic.
Because many areas in which deliveries will occur are under the
jurisdiction of an air pollution control district, Colorado's Fugi-
tive Dust Law will apply, requiring a dust abatement plan to be
filed prior to the start of deliveries over unpaved roads (Refer-
ence 104).
Dust generated by increased traffic could annoy residents of
the area. This problem would be minor, however, since most of the
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roadways are paved except for a six-km [four-mile] segment of
Hacksmount Road (Reference 103).
Damage to Roadways—
It is expected that deterioration of road conditions will
accelerate as a consequence of increased average daily traffic
associated with the conveyance of three-axle trucks carrying
dried sludge loads estimated at 14 metric tons [15 tons] (Refer-
ence 77). Hacksmount Road, Bromely Lane and Irondale Road have
design capacities adequate for such loads and presently are used
by agriculture-related trucks carrying similar loads.
Sludge Spillage in Transit—
Load spillage on these roadways is another potential problem
related to the distribution operation. However, spillage_occur-
ring on roadways related to the Lowry Bombing Range facilities,
whose operation is similar to that of the proposed delivery sys-
tem, has been minor, with only two sludge-carrying trucks having
overturned during three years of operation (Reference 77). There-
fore, it can be assumed that spillage and littering will not be a
major problem in the operation of the proposed project.
Recreation
Odors produced by operation of the proposed project represent
the only potential impact of the project on recreational areas and
their users. Impact would be limited to the vicinity of the Metro
Denver Plant, which will house anaerobic digesters. Should those
digesters fail, odors produced would radiate for a distance of 1.5
to 3 km [one to two miles] from the Central Plant facilities. Jhe
only recreational area located within that distance is a ten-mile
segment of the South Platte River area proposed for boating, bi-
cycling and picnicking activities (Reference 106). Although some
users would be affected by odors once the recreational area had
been developed, the impact would not be a major one.
The probability of anaerobic digester breakdown is small; de-
sign features appear to be adequate, and operational precautions
will presumably be incorporated. If a system failure does occur,
the impact period will be limited to the time required for repair.
The potential impact of such a failure is considered minimal be-
cause the Metro Denver facilities are located in an industrial cor-
ridor. Other odors generated in this area would tend to mingle
with and hence lessen the perceptible intensity of those produced
by anaerobic digester failure. There are no recreational areas
within the odor range of the pipeline facilities or drying basin
areas.
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Governmental Agency Jurisdiction
The proposed project has precipitated a jurisdictional dispute
between Adams County and Metro Denver. The relative authority of
these two bodies over the proposed project has become the subject
of litigation. The proposed project would remove the Metro Denver
sludge management operations from the Lowry Bombing Range and
therefore from the jurisdiction of the City and County of Denver.
While the present working arrangement has been satisfactory, the
District has no written guarantee for its continuance.
The project does not appear to be in conflict with any acti-
vities of planning agencies concerned, with regard to jurisdiction
in the study area. However, an important question remains as to
which agency will have the necessary authority, responsibility,
funding (for monitoring, surveillance and enforcement of proper
application restrictions) and administrative structure to regulate
the proposed project.
Employment
A full-time staff of 18 people will be required for operation
of the distribution center facilities at full development (1985).
This will not have a significant effect on employment in the area.
Land Values
If the proposed drying and distribution center is operated
according to accepted sanitary engineering principles, it is not
expected to have a significant ultimate effect on surrounding land
values (References 66,52).
Some impact, over and above the various physical impacts de-
scribed elsewhere in this report, would probably be felt on the
value of land surrounding the proposed project. A psychological
impact, which would make people reluctant to live near such a cen-
ter, would inhibit residential development around the site. This
could limit future increases in property values associated with
such development. On the other hand, agricultural activity might
be intensified in the proximity of the fertilizer storage and dis-
tribution system, and secondary development associated with such
increased activity might also occur. Each of these events would
be likely to raise property values.
While it is difficult to generalize fro-n other sludge recy-
cling operations, land values near other such Drojects have not
decreased and it is therefore considered unlikely that decreases
would occur in the vicinity of this operation (Reference 103).
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Therefore, the net effect of the proposed project on the value of
property surrounding the site is likely to be minor.
Construction Impacts
Transportation and Circulation--
Transportation facilities associated with the Metro Denver
Central Plant facility, the proposed pipeline route and the dry-
ing basin site may be affected during the construction phase of
the proposed project. However, these impacts will be of short-
term duration and in most cases insignificant.
In order to construct anaerobic digesters, large equipment
will be moved in over roadways surrounding the Central Plant fa-
cility. This activity may cause a disruption of normal traffic
flow patterns and may even necessitate traffic diversion. How-
ever, such impacts will be of a temporary nature and will be in-
significant since the transport of heavy equipment into the in-
dustrialized corridor surrounding the plant is a normal occur-
rence.
Pipeline construction activities may be of longer duration than
those associated with the digester construction. Traffic patterns
on adjacent travelways such as Irondale Road and Colorado State
Highway 2 could be affected. Construction impacts associated with
Irondale Road should not be a problem since activity will concen-
trate on right-of-way areas and should disrupt traffic on this
infrequently traveled rural roadway to only a minor extent. Con-
struction activities adjacent to 104th Street may have a more se-
vere impact because this travelway accommodates large volumes of
daily traffic. Impacts incurred, including delay periods and pos-
sible detours, will be temporary.
Activities of 80 to 100 construction employees, deliveries,
inspections, etc. associated with construction at the drying ba-
sins will increase average daily traffic on servicing roadways by
360 (Reference 55). These roadways have the capacity to accommo-
date the temporary increase. Because current average daily traf-
fic on these travelways is low, temporary slowing of traffic over
tnem will not be significant. Therefore, any impact incurred
will be negligible.
iio other construction-related impacts on transportation or
circulation are anticipated as a result of the proposed project.
131
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Flora and Fauna/Habitats—
The temporary nature of the construction activities at the
Centra] Plant, along the pipeline and at the drying/distribution
site tends to minimize impacts upon flora, fauna and wildlife
habitats. With successful quick revegetation and adequate plan-
ning, construction impacts can be kept below significant thresh-
olds.
Soils—
Soil profile along pipeline route will be completely de-
stroyed and replaced by a blending of underlying materials and
the initial soil layers. The linear nature of this impact makes
it of relatively little concern, especially since most of it will
take place along the previously disturbed soils of road easements,
Utilities —
In order to extend electricity and telephone service to the
drying basin site, easements will be obtained along farmlands and
roadway right-of-way areas (Reference 72). During construction
activities, farming operations and even travel on adjacent road-
ways may be disrupted. However, the impact would be of short du-
ration and the area of disruption small in scale.
Air Quality--
During construction of the drying and distribution facility
and the pipeline, dust will be generated and pollutants emitted
by construction equipment. However, the effect on ambient air
quality will be insignificant. While much dust will be stirred
up on the project site, this impact will be temporary and will be
localized to a very sparsely populated area.
Employment—
During construction of the pipeline and distribution center,
80 to 100 people will be employed. These workers will be re-
cruited from the local Denver area work force.
Secondary Impacts
Economy—
The construction of a large public facility inevitably has
impact on the local economy as a result of both the construction
process and the subsequent operation of the facility.
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Direct economic impacts, including employment and potential
impacts on agricultural activity, are discussed elsewhere in this
volume, both with regard to temporary construction employment and
to permanent employment. With respect to the operation of the fa-
cility, there appear to be virtually no significant secondary im-
pacts other than those associated with agricultural activity.
The small volume of permanent employment and the relatively small
demand on community resources—when the facility is fully opera-
tional—suggest that secondary impacts of the operation will be
negligible or nonexistent.
The same conclusion cannot be drawn with respect to secondary
impacts of construction. The total capital cost of the proposed
facility is approximately $26 million. The maximum construction
employment will be approximately 130 persons. In addition, a sub-
stantial portion of the capital cost will be accounted for by
items other than direct labor, with a fraction of this amount ex-
pended for local materials and services.
Two steps are used for estimating secondary impacts. First,
an attempt is made to make preliminary allocation of capital costs
among labor and materials and to provide an estimate of the allo-
cation of the material costs between local and imported components.
The second step uses an employment multiplier dealing exclusively
with construction employment to estimate the potential indirect
employment that will be created.
The estimates are based largely on experience with other,
similarly capital-intensive projects in Devner and elsewhere,
using the lower end of estimates to formulate possible minimum
dollar impact on the local economy. The results of the initial
step are shown on Table 21.
It is assumed that only half of the "materials, expenses,
fees, etc." component will be spent in the Denver Standard Metro-
politan Statistical Area. This assumption is not as completely
conservative as it may seem; while many of the materials and ser-
vices may be purchased in the Denver metropolitan area, their
original sources lie elsewhere, and the value added in distribu-
tion within the local metropolitan area may be relatively small.
Employment--
The foregoing analysis suggests that approximately $5.2 mil-
lion in total payrolls may be generated locally by the project
along with approximately S9.35 million in local expenditures for
material expenses, professional services, etc.
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Table 21. ESTIMATED CAPITAL COST AND APPROXIMATE
ALLOCATION TO LAND, LABOR AND MATERIALS
Amount,
Cost estimate and allocation 1974 $
Capital cost (.including digesters) 26,000,000
Less estimated land cost (800 ha @ 1,000,000
$l,250/ha)a
Total cost of improvements 25,000,000
(including contingencies, process-
ing costs and engineering and other
professional costs)
Approximate allocation
Direct labor (20 percent) 5,000,000
Indirect labor (5 percent) 1,250,000
Materials, expenses, fees, etc. (75 percent) 18,750,000
Spent in Denver SMSABr $9,375,000
Imported: $9,375,000
a[2,000 ac @ $500/ac].
Denver Standard Metropolitan Statistical Area.
These estimates of expenditures may in turn be subjected to
further analysis to develop estimates of indirect employment and
economic impacts on the local economy. The purpose of this exer-
cise is to determine the order of magnitude of such impacts.
Quantification on any more precise basis would require disaggrega-
tion of capital cost, which is not now available.
As suggested above, gross payrolls associated with construc-
tion of the project are approximately $5.25 million. It is a rea-
sonable inference that approximately 70 percent would be directly
reflected in the local retail purchases. This would amount to ap-
proximately $3.7 million, an amount well under one percent of the
retail sales in Adams County.
Based on an approximate up-date of the 1972 Census of Business
estimates, the retail sales per employee are approximately $52,000.
Thus, the introduced $3.7 million would create the annual equiva-
lent of approximately 70 additional person-years of new employment.
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The nonlabor expenditures associated with the capital cost
of the project would be spread over a wide range of materials and
services, probably concentrating in the building and construction
materials and transport services areas. A tentative approxima-
tion of sales per employee in these sectors suggests that they
are perhaps $60,000 to $70,000 per employee. On that basis, the
employment impact of these materials and other expenditures would
be approximately 140 employees.
On the basis of preliminary and rough analysis, it is possi-
ble that the aggregate impact of construction of the project
would be 210 person-years of employment. Since the additional
employment impact will spread over the entire Metropolitan Denver
area, the relative impacts will be fairly trivial, amounting to
less than l/20th of one percent of the areawide employment.
Other Secondary Impacts--
Infrastructure investments discussed above can have serious
negative secondary impacts on air quality, urban runoff, sensitive
areas, etc. from population growth induced or accomodated by the
proposed project. The sludge processing and disposal project is
necessary for the efficient operation of the overall Metro waste-
water system. Furthermore, the issue of secondary impacts will be
analyzed in detail in an EIS on Metropolitan Denver Facilities Plans.
Therefore, discussion of secondary impacts are deferred to that EIS
process. It is apparent that control over population cirowth pat-
terns can be more directly effected through the individual waste-
water facilities plans and N'PDES permits.
Impacts of Sludge Disposal at the
Drying and Distribution Center--
Because the disposal portion of the operations at the processing
site involves land application of sludge, the discussion of its im-
pacts is presented on page 166 after the discussion of recycling im-
pacts and prior to disposal impacts.
Summary of Impacts at the Sludge Drying
and Distribution Center
The most serious negative environmental impacts at the sludge
drying and distribution center are on soil properties, groundwater
quality and the public health through nitrate pollution of ground-
water and pathogen problems. Positive impacts are energy and re-
source conservation. The impacts are schematically represented on
Figure 16 in a summary format to indicate the rough order of impor-
tance EPA places on the various impacts surrounding the drying/
processing operation.
135
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FIGURE 16
SUMMARY OF IMPACTS AT THE PROPOSED SLUDGE DRYING AND
DISTRIBUTION CENTER
FOR METRO DENVER
Impact parameter
Direction and potential
intensity
Soil loss
Groundwater quality
Surface water quality
Water rights
Public health—Pathogens
Public health—Nitrates
Public health—Vectors
Loss of habitat
Air quality (including odors)
Energy use
Natural resources
Construction impacts (overall)
Secondary impacts (economy/employment)
o
o
Symbols signify relative impacts, as defined below:
Positive (beneficial) impacts:
Negative (adverse) impacts:
High Moderate Low
O
O o
This schematic representation of impacts should only be interpreted within the
context of analyses of impacts presented in the main body of the EIS. It is
neither an attempt at quantifying the impacts nor reducing the diverse environ-
mental parameters to common bases for comparison. However, it does provide a
rough ranking of the relative importance of the various impacts. The scales
denoted by symbols used above are not intended to be compared with those used
on Figures 17 and 18.
136
ENGINEERING-SCIENCE, INC.
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IMPACTS OF LAND APPLICATION OF SLUDGE ON THE RECYCLING AREAS
General
A large body of new data is being developed in various parts
of the country on impacts of sludge reuse in agricultural and re-
lated activities under a wide variety of conditions. A single
salient conclusion of the collective evidence to date is that the
impacts are site specific. Thus, statements made in the following
paragraphs are necessarily applicable to the types of sites which
are described in Section III and Appendix E under Environmental
Setting. Even though a finite number of sites were investigated
for the purpose of impact analysis, it is recognized that dried
anaerobically digested sludge may be used for a rather large
variety of applications. It is expected that the city parks, sod
farms, mine spoil sites, irrigated and dry farms and home gardens
will provide examples of the entire range of application site pos-
sibilities and provide the information necessary to evaluate the
advisability of using the material on proposed sites.
As an introduction to impacts of sludge application on land
recycling areas, a graphic representation of the severity of the
various impact parameters on the representative types of applica-
tion sites is presented in Figure 17. All of the subjective impact
levels assigned can be qualified depending upon prevailing condi-
tions, management practices and other mitigating circumstances.
These qualifications are presented below with particular emphasis
on site specificity. An overview of the major concerns and advan-
tages of each type of land application site is presented prior to
the presentation of the impact parameters.
City Parks —
The application of sludge to city parks is potentially prob-
lematic because of the high rate of public use of the parks for
recreation. Although sludge has been used as fertilizer on the
parks in the past, publicity resulting from the large scale of the
proposed project may engender some concern, if not opposition.
Public involvement is important, and the Denver Department of Parks
and Recreation should promote a program of public awareness to in-
form the public as fully as possible of the benefits and potential
effects of sludge application. Additionally, the use of sludge on
the City parks should be rigorously monitored to ensure the success
of the program. The viability of pathogens (especially Ascaris
ova) is perhaps the most crucial issue and should be closely moni-
tored. The use of additional methods for pathogen reduction, as
described in detail in Section VI and Appendix D, would provide
additional protection to the public.
137
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FIGURE 17
SUMMARY COMPARISON OF RELATIVE IMPACTS3 OF SLUDGE RECYCLING ON VARIOUS
LAND APPLICATION SITES IN THE VICINITY OF DENVER
Sludge application site
Impact
parameter
Mine Irri- Home gardens
City Sod spoil gated Dry Orna- Edible
parks farms sites farms farms mentals plants
Food chain
Public health
Water quality
Soil productivity
Soil salinity
Soil heavy metals
Air quality
Vegetation
Wildlife
Habitats
Odor
Noise
Aesthetics
Natural resources
Traffic and
circulation
o
© •
ooQ
•vsjpr -^iagr-
O O
o o o o o o o
()
• • o •
o O O O O o o
Symbols signify relative magnitude and direction of impacts, as defined
below:
High Moderate Low None
Positive (beneficial) impacts:
Negative (adverse) impacts:
O o
This schematic representation of impacts should only be interpreted within
the context of analyses of impacts presented in the main body of the EIS.
It is neither an attempt at quantifying the impacts nor reducing the diverse
environmental parameters to common bases for comparison. However, it does
provide a rough ranking of the relative importance of the various impacts
and a comparison of sites vis-a-vis each parameter.
138
ENGINEERING-SCIENCE, INC-
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Sod Farms--
The sod farms of the Denver area represent a specialized type
of irrigated farm. While impacts are evaluated specifically for
one specific sod farm, many of the impacts may be extended to oper-
ations in similar situations. Generally, sod farms represent the
best type of land recycling sites for sludge from the environmental
viewpoint. The applied sludge and its constituents are transported
away from the sites and distributed thinly over a very wide area.
Mine Spoil Sites--
The proposed mine spoil sites for sludge application are
heavily disturbed unnatural areas. The proposed action represents
an initial step towards reclamation of these "waste areas" and,
thus, all impacts are evaluated in this perspective. No food crops
are assumed to be grown on such spoil sites. Public access and
exposure to the sites, especially during the reclamation period,
will be limited. Thus, mine spoil sites are generally the least
problematic for sludge reuse purposes.
Irrigated Farms--
Irrigated farms represent the type of land application candi-
date sites which may become major users of the Metro sewage sludge.
Allowable annual application rates are fairly high, as shown in
Figures 14 and 15 in Section IV. Consequently, the number of years
of safe application is relatively short. Thus, the opportunity for
corrective action, if indicated, is more limited than in the non-
irrigated applications. On the other hand, irrigated farms are
generally more intensively and carefully managed because of the
higher value of crops grown on these farms. In fact, many irrigated
farms have highly sophisticated irrigation equipment capable of
automatic control with sensors connected to tensiometers and other
devices determining plant-soil moisture status.
The availability of a competent and well-equipped management
system tends to give better assurance of (a) proper control of
application rates, (b) careful monitoring of soil, crop and water
quality responses to applications of sludge to land and (c) accu-
rate recording and mapping of areas receiving measured quantities
of sludges from the very first application until the limit is
reached, and beyond.
Application of lime, supplemental phosphorus and potassium,
if needed, and irrigation water are common practices on these
farms and can be readily adjusted to meet the additional require-
ments imposed by the sludge application.
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Therefore, while irrigated farms will be potentially the most
extensively and intensively affected by the sludge reuse scheme,
they are also the areas that offer the greatest opportunity for
control and mitigation.
Non-Irrigated Farms--
Non-irrigated farms abound in Weld, Adams and Arapahoe Coun-
ties, surrounded by extensive areas of drylands used as non-culti-
vated pasture. These areas generally have very low fertility, as
shown by production rates per unit surface area, reported by the
Colorado Department of Agriculture (Reference 95 and shown on
Table E3 in Appendix E). The low fertility is in part due to con-
tinuous cropping with little fertilization or amendment. It is
expected that dry farms will also become extensive users of the
Denver sludge at low surface application rates over large areas
and over a much prolonged period of time.
Use of liquid sludge will probably be more successful on dry-
lands and non-irrigated farms with subsurface injection tools than
use of the air-dried material. This is because the injectors can
serve the double function of soil water conservation through scar-
ring the land surface while applying sludge at a safe depth below
the soil surface.
In general, impacts of sludge application on non-irrigated
farms and drylands will be far less intensive than the other agri-
cultural reuse candidate sites discussed in this volume. Further-
more, the low application rates provide a safety mechanism and
greater opportunities for corrective action should unforeseen neg-
ative impacts become evident in the future.
Home Gardens--
A significant number of gardeners, organic growers and others
raising crops on relatively small scales have expressed interest
in and enthusiasm for the use of anaerobically digested dried
sludge for application to their soils (see Appendix F). Due to
the potentially large numbers and wide separation of sites in this
type of use of the sludge, it could be very difficult for any
jurisdiction to provide the supervision, control and monitoring
that is essential to the success of (including prevention of
environmental hazards from) sludge recycling on the land. Further-
more, the potential for direct human exposure to the material
would be great because automated and mechanical application is im-
practical on small-scale operations. Some home gardeners would
use the sludge for amending soils supporting ornamental plants;
others would use it on edible crops. There are far fewer potential
140
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hazards associated with ornamental than edible (especially leafy
vegetable) crops growing on soils amended with wastewater sludge.
Regulating proper use of the sludge and maintaining public health
protection in home gardens would require a very determined public
education effort including clear labelling, instructions, warnings,
spot checks and, perhaps, provision of legal constraints.
Food Chain
The impact of sludge application in irrigated farms and home
gardens upon the food chain is largely dependent upon the types of
food crops or feeds grown for direct and eventual human consump-
tion. Leafy parts of vegetables, beets, mint, vine, lettuce and
chard are examples of crops which accumulate cadmium in greater
concentrations (sometimes up to ten times) than found in the soil.
The animals eating such crops and ingesting sludge-amended soil
will further accumulate cadmium in the kidneys, liver and some
other organs and tissues. Eating these tissues could give rise to
kidney diseases and hypertension in humans. Some people tend to
consume these less expensive tissues as a substantial part of their
diets. The irrigated crops grown in the area are mainly wheat,
corn, barley, sorghum, beans, beets, oats, hay and potatoes. None
of these crops is usually consumed unprocessed and/or raw and none
is known to be a particularly heavy accumulator of metal elements
in their usually edible parts. On the other hand, leafy vegetables
grown in home gardens such as Swiss chard, spinach and lettuce
tend to magnify cadmium concentrations in their edible tissues.
Cadmium is the most important element of concern in the Denver
situation, while copper and zinc are far less important due to very
low concentrations. Mo standards have yet been established for the
limitation of cadmium in foods. The U.S. Food and Drug Administra-
tion proposes to establish such standards for cadmium in the near
future. Generally, as long as sludge cadmium content is below one
percent of the zinc concentration, and as long as recommended ap-
plication rates are not exceeded, cadmium toxicity in the food
chain will not be expected. Recent analyses (Table D-4 in Appen-
dix D) indicate that even though cadmium levels are far below aver-
age for municipal sludges, average cadmium in the Denver sludge is
about 1.7 percent of the zinc content. Although this is a rather
high percentage compared with the one percent limit stated above,
existing mitigating circumstances are expected to adequately com-
pensate for this ratio. The favorable circumstances are (1) highly
calcareous conditions, particularly in the lower soil horizons on
most of the irrigated farms; (2) the conservative nature of the
ultimate sludge loading rate, given in earlier sections; (3) the
relatively high phosphorus content of Denver sludge, which tends
to help make both zinc and cadmium less available to plant species;
141
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and (4) the poorly defined concept of "reversion," in which heavy
metal elements gradually become combined into stable, unavailable
compounds. This latter process is most rapid in calcareous, alka-
line soils such as encountered in most of the study area. Possible
lowering of pH during the first few years after sludge application
may lead to release and uptake of these elements.
Another important consideration is the possibility of reduc-
tion of the quantities of heavy metals in the wastewater system
from industrial and other sources in the future years. It is
probable that significant reduction will be accomplished before
the ultimate surface application limit is reached on most irri-
gated farms.
The other elements of major concern to the food chain, in-
cluding copper, zinc, molybdenum, selenium and lead, are of suf-
ficiently low concentration in the Denver sludge so that they are
not expected to produce an adverse impact upon the food chain.
The favorable soil conditions discussed above also protect against
most other metals. Most toxic metals sharply reduce crop yields
before they become high enough in concentration to pose a food
chain hazard. This phenomenon constitutes a safety valve in the
food chain. Additionally, organic compounds in sludge are able to
chelate heavy metals, making them even less available.
Crops grown on non-irrigated farms are primarily winter wheat
and barley with lesser areas of grain, corn, sorghum, oats and
spring wheat. From the point of view of preventing heavy metals
accumulation in the food chain, more suitable cropping patterns
would be hard to accomplish. The parts of these plants which are
used for animal feed and/or processed for human consumption are not
known to be accumulators of cadmium or any other heavy metals. It
is not expected that cropping patterns will change appreciably in
the future years; hence, it is expected that no significant food
chain hazards will exist with sludge reuse on non-irrigated farms.
Sludge application, in excessive amounts on rangeland may re-
sult in accumulation of cadmium and other heavy metals in the
leafy parts of some weeds. Domestic animals feeding on these
rangelands will in time accumulate these elements in their tissues
and pass them along to humans who eat the meat (especially liver
and kidneys) thus produced. As long as recommended application
rates are not exceeded, excessive accumulations are not expected
to occur. However, direct ingestion of sludge-amended soils by
livestock (ten percent of whose diet is soil particles) can sig-
nificantly increase heavy metal magnification along the food chain.
The present operations at the Lowry Bombing Range are most conducive
to this sort of heavy metals assimilation by grazing animals.
14;
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The most effective and long-lasting solution to heavy metal
magnification problems in the food chain is removal--or reduction—
of discharges containing toxic elements from the sev/er system, as
mentioned above. This can be achieved through an extensive program
of source identification, promulgation of standards, regulation
and intensive enforcement of the discharge quality standards on
industrial dischargers.
Public Health
Although no documented cases exist in the United States that
associate the use of digested sludge on land with human disease,
two major factors require that the possibility of such an occur-
rence be considered. First, City parks are heavily utilized by
the public who may come in contact with sludge in a number of
accidental and unforeseen ways. Secondly, although sludge proces-
sing destroys a significant number of pathogens, some may survive
over long periods of time (see Table 20 on page 114). The use of
sludge on City parks is practiced in many parts of the country
with no reported public health problems.
Pathogens--
The greatest areas of concern are home gardens where the pos-
sibility of direct human contact with pathogens on the soil, orna-
mental plants and edible crops is quite high. The long survival
time observed for viruses and Ascaris ova makes it imperative that
(1) no food crops be raised on sludge-amended soil to be eaten
directly (unprocessed, raw) by humans, (2) long field re-entry
periods be established and strongly enforced on areas where sludge
is applied, (3) cases of disease contracted from sludge sources be
identified, documented and followed through and (4) a very rigor-
ous public health monitoring program be established as an integral
part of the reuse of sludge on food crops of all types.
The pathogen problems associated with the dried sludge de-
livered to sludge recycling sites will be somewhat less intensive
than the material at the drying and distribution center because
of the natural die-off of the pathogens with time. However, the
greater possibilities for human contact bring up additional pos-
sible public health impacts. If sludge is used to fertilize crops
or home garden vegetables which will be eaten raw within the first
year of application, adverse health impacts will result. If the
one-year wait is observed, no significant health impact is ex-
pected. Recommended waiting periods of from one year (Reference
81) to three years (Reference 79) between sludge application and
growing of crops to be eaten raw have been suggested. However,
Metro plans presently call for a one-year drying period in the
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drying basins only, before release of sludge to the consumer.
The EPA preliminary proposed wait of three years before rais-
ing crops to be eaten raw (Reference 79) is a cautious waiting
period for a cool, dry region like the Metropolitan Denver area.
Table 20 indicates that Ascaris ova are the limiting factor in
setting a safe period for pathogen die-off. The EPA document is
nation-wide in scope, however, and the Ascaris problem is primarily
of concern in moist tropical regions, such as some southern states
(Reference 111).
Ascaris is not of great enough importance in Colorado to be
listed among the 22 diseases on the Colorado State communicable
disease report; the disease ordinarily has mild--often almost un-
noticeable--symptoms. This disease has a very low incidence in
the area, and the long survival time for the parasite's eggs,
applies only under conditions favorable to the roundworm. The
arid, cold seasons common to this area do not provide this en-
vironment.
The next hardiest pathogens are tubercle bacilli, which can
survive only six months. Continued application of sludge to park-
lands will have no significant adverse health impacts. The anaer-
obically digested sludge will have fewer pathogens than the ma-
terial presently being applied to the parks. If a two-year drying
period is instituted, it will ensure that no significant impacts
will result from park application of sludge. This safety margin
will be necessary because particles of sludge will probably be in-
gested by some picnickers, children playing in the dirt, etc.
In view of the differences in pathogen viability and concentra-
tion in the different types of sludges (liquid, air-dried and stock-
piled for various lengths of time), their respective uses should be
limited appropriately. For example: (1) liquid sludge should be
applied only by deep injection into the soil, with no possibility
of surface exposure; (2) as the level of human contact becomes more
probable for each use (dry farms, irrigated farms, home gardens,
vegetable crops, in increasing order), required length of storage
time in the drying and stockpile areas should be increased.
Nitrates--
Potential pollution of groundwater will not pose a significant
public health hazard. The primary chemical constituent of concern is
nitrate. Nitrate levels over 45 ppm (measured as nitrate) in drink-
ing water are considered to be harmful to infants (Reference 112).
However, as indicated below under Water Quality, groundwater contam-
ination under most land recycling schemes would be less than or the
same as from use of commercial fertilizers.
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Health Services--
A significant impact upon the public health department serv-
ices is foreseen as a result of the proposed project. The public
health department's monitoring activities will need to be ex-
panded to cover all the land recycling areas receiving sludge.
This will increase the manpower requirements of the public health
services.
Water Quality
Two important water quality hazards posed by sludge amendment
of soils are the total dissolved salts (TDS) and the nitrate form
(NO^) of nitrogenous compounds found in the sludge and supernatant
liquid. If the supernatant is excluded from the land application
project, salt problems will largely be prevented. The nitrate
pollution of groundwater and surface water remains as long as there
is a supply of nitrogenous compounds over and above the amount
which plants can take up and denitrifying bacteria in the soil can
denitrify. Water pollution hazards posed at the six typical sites
studied are presented separately below, in order to emphasize the
specificity of impacts to sites and conditions as well as the
typical management practices employed.
City Parks--
Of the approximately 500 known wells within the City of Denver
in 1964 (Reference 21) fewer than 50 were used wholly or in part
for domestic purposes. Most wells are used for irrigation, cooling
water, industrial and other purposes.
It is expected that at the proposed annual sludge application
rates of 56 metric tons/ha [25 tons/ac] per year and with the
typical irrigation practices on park lands, significant quantities
of dissolved salts, including nitrates, will leach toward the
groundwater reservoir. In about 20 to 100 years these salt-laden
seepage waters will arrive at the groundwater table and will
gradually increase TDS and nitrate concentration of waters with-
drawn from the wells. It is probable—though supportive data are
lacking—that even under past and present commercial fertilizer
regimes, downward movement of nitrates have been and are proceed-
ing. Therefore, earlier arrival of nitrates in the well waters
should be expected.
If domestic uses of groundwaters (for drinking and culinary
purposes) are altogether prohibited or otherwise terminated, the
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recommended limit of 45 mg/1 of nitrate nitrogen may be permitted
to be exceeded in the groundwater. If, on the other hand, domes-
tic uses of groundwater in parts of the Denver area are indispen-
sable, sludge and fertilizer application rates should be limited
to levels recommended in Section IV. Curtailment of sludge ap-
plication, particularly in those parts of the City and County of
Denver and other cities using groundwater for drinking purposes,
is very important and necessary for public health protection.
Pollution of surface waters, such as streams and lakes in
the City, through leaching and/or runoff is a distinct possibility.
It can be minimized through erosion control and judicious choice
of sludge application rates and methods to balance uptake of salts
by plants.
Sod Farms--
It is expected that with adherence to the recommended sludge
application rates (in Section IV) negligible nitrate leaching to
the groundwater will result. Other soluble salts, however, will
gradually move downward with the irrigation waters applied over
and above the evapotranspiration needs of the grass. The amount
of these salts applied with the sludge is expected to be relatively
moderate (about 350 kg/ha [300 lb/ac] per year) and significant
only from a long-range cumulative point of view.
Surface water contaminations from portions of the sod farm
that are actively growing grass will be insignificant, because of
the highly effective cover that sod provides against runoff and
erosion. The soil in the sod farm studied, Truckton sandy loam,
is erodible unless it has adequate cover. Therefore, without some
provision for catchment of surface runoff, pollution of streams
may be expected from portions of the sod farms which have just been
harvested or which have been left unplanted.
Mine Spoil Sites—
The thickness of spoil materials heaped on top of the natural
ground surface ranges from a few meters at the minimum to about
80 m [250 ft] at the top of the spoil banks. Irrigation water and
rainfall can travel through these highly porous materials with
relative ease after the rocks reach saturation moisture content.
It is expected that the more successful the reclamation of spoil
banks is, the less excess water will be available to leach through
the acidic spoil materials and the less mine spoil drainage will
take place. Irrespective of pollutant constituents of applied
sludge, mine spoil drainage is generally a severe contaminant of
surface waters. Hence, use of sludge to slow down such drainage
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through entrapment and evapotranspiration of precipitation will
help mitigate an existing major water quality hazard.
At the modest application rates proposed, especially with the
use of wood chips (with high C:N ratio, helping immobilize nitro-
gen from the sludge), it is expected that nitrate movement below
the root zone will be minimal, if any. Heavy metals will probably
remain within the developing soil and become immobile and unavail-
able if pH is maintained above 7.
Irrigated Farms--
Irrigated farms generally possess some tail water control
provisions and are designed to achieve high water application uni-
formities and efficiencies, resulting in minimal wastage and con-
trol of excessive deep seepage. With the use of sludge on these
farms, these controls are even more important. Otherwise, (1)
excessive seepage will result in groundwater contamination with
nitrates and soluble salts, and (2) runoff could lead to direct
transport of sludge solids and soluble materials to the surface
water courses.
It is difficult to quantify the precise impact of sludge
application on water quality. The impact is not only a function
of how well the recommended application rate limits are followed;
it is also determined by the manner in which other standard farm-
ing practices (irrigation, drainage, tillage, etc.) are performed.
It can therefore be surmised that the more sophisticated and suc-
cessful a farming operation is, the less are the chances for
sludge application on that farm to pollute water resources. The
converse would hold true for poorly managed and operated farms.
Therefore, it is important that a judicious selection procedure
be set up and the material not be given simply to whoever asks
for it. Binding agreements, permitting the District representa-
tives to conduct monitoring and inspection services, will help
guarantee against large-scale contamination of the water supplies.
Home Gardens--
If large numbers of homeowners and gardeners adopt sludge
amendment practices, water pollution hazards, orr a large scale,
will be inevitable. Ornamental plants and vegetables are typically
heavily irrigated and very often over-irrigated. Therefore, both
deep seepage into the groundwater reservoir and runoff toward sur-
face streams occur on a regular basis. Opportunities for improper-
ly high application rates and consequent degradation of water sup-
plies are thus abundant in this type of recycling of the sludge.
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Soil Properties
Once sludge enters the soil , its impacts upon the various
components of the environment become indistinguishably interde-
pendent. Thus, while this discussion is divided into separate
topics for clarity of presentation, the interdependence of the
physical, chemical and biological properties of the soil and crop
responses, as well as animal and human reactions to eating the
crops and animal tissues, should be clearly recognized.
Soil Productivity--
It can be expected that soil productivity will increase with
properly controlled and managed sludge application to any of the
proposed sites. Many experiments with sludge application to soil
have borne out this conclusion (References 121, 122 and 123 to
cite a few), and some have shown increased productivity even above
that which could be expected from equivalent chemical fertilizer
applications (References 81 and 124). The short-term annual in-
creases in yield, attributable to annual and residual releases of
sludge nitrogen, phosphorus and other essential elements, are by
no means the only contributions to soil productivity. A long-
lasting impact of sludge application to soils is the gradual in-
crease in the organic matter content of the soil root zone. As
rn M
SOIL STRUCTURE IS ENHANCED BY SLUDGE
described below under Soil Structure, the increase in organic con-
tent leads to improved root penetration and other enhanced condi-
tions for plant growth, ultimately resulting in increased yield and
productivity.
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If application procedures do not guard against uneven spread-
ing and variable incorporation of the sludge into the topsoil, the
same types of problems as are associated with uneven fertilizer
application may be expected. A typical problem is non-uniform
soil fertility, resulting in uneven growth, maturation and yield.
The commercial equipment available, if properly operated and main-
tained, can provide reasonably uniform spreading of the dry sludge.
Liquid sludge injectors which concentrate applications in a band
along the cutting "knife" will tend to produce a corrugated growth
and yield pattern during the first few years unless successive in-
jections are performed in a criss-cross fashion.
Liquid sludge usually has a higher nitrogen content than dried
sludge and should be applied at correspondingly lower surface load-
ing rates. Furthermore, liquid sludge tends to inhibit germina-
tion and to impose initial toxicity to young plants. Damage can
be caused by excessive concentrations of ammonia, salts and organic
compounds or by creation of anaerobic conditions in the root zone
which reduce soil microorganisms and deplete oxygen in the soil.
The precise cause of initial organic toxicity has not yet been es-
tablished. At recommended application rates, this initial toxicity
will be limited to the immediate areas of application for only
short periods of time. If injection of liquid sludge is limited
to periods far enough in advance of the growing season, the toxi-
city problem and related reduction,in productivity will be mini-
mized.
Phosphorus content of Metropolitan Denver sludge averages
about three percent of the dry solids (Reference 5). Within the
recommended range of sludge application rates on irrigated farms,
8 to 35 metric tons/ha [3 to 16 tons/ac], about 240 to 1,050 kg/ha
[180 to 960 Ib/ac] of phosphorus (as P) is applied to the soil.
These excessive amounts of phosphorus would be potentially toxic
to plants were it not for two important considerations. First,
phosphates in the sludge are primarily in the precipitated form
and thus are not immediately available for plant uptake. Second,
the calcareous nature of soils in the irrigated farms, for the
most part, provides a ready mechanism for formation of insoluble
calcium phosphate forms which release available phosphorus to
plants over a long period of time. An important advantage of the
high phosphorus content of the sludge is its reported ability to
reduce the availability of zinc and nickel in the soil (Reference
124).
An important aspect of increased fertility—particularly
nitrogen availability--is that continuous nitrogen availability
may make certain management practices more difficult. For ex-
ample, in sugar beet culture, farmers have learned that by with-
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holding nitrogen and water in the last stages of growth, prior to
harvest, they can increase sugar content of the crop. With the
use of sludge, this type of ready control of available nitrogen
may become difficult, if not impossible. The Great Western Sugar
Company of Longmont, Colorado is presently conducting controlled
experimentation with the use of sludge on sugar beet farms (Ref-
erence 125). Other effects of continuous availability of nitro-
gen, such as plant lodging, delayed maturation, color development
of certain fruits, etc. generally do not apply to the types of
crops commonly grown in the study area.
Soil Structure--
The anaerobically digested sewage sludge contains stable
humus-like organic compounds which resist decomposition, particu-
larly under irrigated farming conditions. These molecules, when
well incorporated into the soil , tend to bring about changes in
soil structure which have long-term beneficial effects upon the
physical properties of the soil. The importance of organic mat-
ter to soil conditioning has long been recognized by farmers who
have been applying barnyard manures, compost and other organic
wastes to soils since time immemorial.
The principal change occurring as a consequence of organic
matter additions to the soil is the gradual formation of a loose,
friable soil structure, contrasted with the massive structure of
clayey soils and the granular character of sandy soils. Increased
organic content reduces the possibility of formation of shrinkage
cracks in clay soils and gives a more cohesive character to sandy
soils. Epstein (Reference 126) found a doubling of the percent of
stable aggregates in a soil amended with sludge over a period of
175 days. Organic matter increases the water-holding capacity of
the soil; organic soils can retain more than their own weight of
water against gravity drainage, while a sandy loam soil may hold
less than ten percent water. Thus, successive applications of
sludge over the years slowly builds up the water-holding capacity
of the soil so that irrigation intervals may be increased, un-
wanted leaching of excess water reduced and plant growth and yield
generally increased.
The improved soil structure enhances root penetration and
vigorous growth throughout the soil profile, leading to generally
healthier, more vigorous plant growth and increased crop produc-
tion.
Soil Permeability--
Movement of water through the soil is governed principally
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by soil texture, structure, organic matter content, and the degree
of aggregation of clay particles. Application of sludge to soil
can change the latter three parameters drastically, giving rise to
significant changes in permeability of the soil. Epstein (Reference
126) reported an initial increase in permeability of a sludge-
amended soil followed by a return to initial values. Presumably,
the initial increase occurred due to improved soil structure, and
the subsequent decline was caused by clogging of pores. Although
unsaturated hydraulic conductivities were not measured, it is sur-
mised from increases in water content at all soil-water tension
ranges that these conductivities probably increase with addition
of sludge to soil. The increase in unsaturated conductivities
is important vis-a-vis water availability to plant roots because,
commonly, unsaturated conductivity is the limiting factor in
moisture transport within the root zone.
Soil Erodibility—
Formation of stable aggregates, discussed above, helps increase
soil resistance to both wind and water erosion. Additions of sludge
over a number of years gradually reduces soil erodibility and thus
provides a self-correcting mechanism against contamination of sur-
face waters in addition to conserving topsoil. Many of the soils in
irrigated areas are naturally moderately to highly erodible in the
absence of plant cover. Over the years, sludge application can
significantly reduce soil erodibility in these areas.
Salt Accumulations—
Liquid sludge from the Metro Denver Central Plant contains
about 6,000 mg/1 total salts, with only 180 mg/1 sodium and 140 mg/1
chloride. Salt accumulation in the topsoil can be regulated with
proper irrigation and drainage practices. As long as the necessary
leaching fraction of the total irrigation water requirement is pro-
vided, there should be no excessive salt buildup.
Given a total dissolved solids concentration in liquid di-
gested sludge of about 6,000 mg/1, it can be calculated that on
the average about 350 kg/ha [300 Ib/ac] of salts will eventually
move into the groundwater reservoir. These salts will be trans-
ported horizontally to downstream areas until the water is pumped
out again for irrigation or other uses. Thus, over a very long
period of years (perhaps centuries), it can be expected that salt
buildup in the whole ecosystem will be inevitable. Therefore, ir-
rigation water salt contents will increase gradually. Even though
specific areas of sludge reuse will presumably be returned to non-
sludge culture after the limit surface application rates are reached,
the salt content of the whole region will inevitably rise over the
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long term, as new areas are brought into sludge application cul-
ture.
Soil Impacts on Specific Sites —
The general effects of sludge application on soils, presented
above, are applicable to nearly all types of sites, but are most
representative of the irrigated farms and home gardens, whether
ornamental or food crops are raised. Specific variations from
these generalities can be expected at other sites due to the dif-
fering water regimes and other management differences. These var-
iations are summarized for city parks, sod farms, mine spoil sites
and non-irrigated farms.
City Parks—As discussed under Environmental Setting, most of
the City parks are constructed upon fill material from other areas,
landfill covers, construction debris and imported topsoil. There-
fore, there is practically no indigenous soil profile to be af-
fected, directly or indirectly, by the sludge application and reuse
scheme. The pre-planting use of sludge and the proposed annual
additions will aid in the formation and improvement of supportive
substrata for City park plantings. Improvements in soil structure,
water-holding capacity, root penetration, erosion resistance and
permeability will occur, in similar fashion to those discussed
above.
It is expected that much higher total ultimate loadings of
heavy metals can be allowed in City parks "soils" than in areas
intended for food production. Grasses and other plantings on park
sites are generally more tolerant to higher concentrations of
heavy metals in the soil. Maintenance of high pH through a regu-
lar liming program along with sludge application may be indicated
through testing of soil pH on individual parks. Use of sludge on
City parks subjected to a great deal of foot traffic and compac-
tion can be particularly effective in improving soil aeration and
water penetration.
Sod Farms—The unique harvesting operations at sod farms in-
volve the removal of a thin layer of soil (2 to 3 cm [0.8 to 1.2
in.]) every year. With this layer, most of the added organic
matter and its constituents contributed by sludge are removed to
their ultimate location of use. Thus, most of the direct soil-
building potential of the applied sludge is transferred to the
ultimate consumer of the sod. Since the amounts of sludge in-
volved in one cycle of sod production are relatively low, it is
not expected that the effect upon soil structure, permeability,
and other physical characteristics will be significant unless the
consumer also applies sludge or other humic matter to the lawns.
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The short-term impact on productivity is quite significant and can
exceed that of equivalent quantities of commercial fertilizers.
No significant salt buildup in the soil is expected.
Mine Spoil Sites—Since at present there are no soils on the
surface of the mine spoil sites, no soil impacts are associated
with sludge application to these sites. Natural soils are buried
beneath a great thickness of mine spoil materials. Considerations
for soil building and reclamation of the sites to permit the nat-
ural succession of plant species are presented below under Flora
and Fauna.
Non-Irrigated Farms—The relatively low sludge application
rates recommended for non-irrigated farms and drylands make the
soil impacts relatively minor. The amount of organic matter con-
tributed by sludge will average less than 0.1 percent of the plow
layer mass per year. Furthermore, because of the dry conditions,
organic matter will be oxidized and destroyed more rapidly than
under irrigated conditions. Hence, it is not expected that any
perceptible improvement in soil physical conditions will material-
ize as a result of sludge reuse. Short-term soil fertility, how-
ever j will increase dramatically due to rapid availability of
adequate quantities of nitrogen and other essential nutrients.
Use of liquid sludge usually gives rise to an initial toxicity
whose basic mechanisms are not yet well defined. Special tools for
placement of liquid sludge in separate bands below the soil surface
have been developed and tested. This type of liquid sludge appli-
cation, while conserving the maximum nutrient potential of liquid
sludge, minimizes initial toxicity by permitting roots to grow
around the sludge areas rather than be confined thereby, and therein.
It is expected that future experimentation at the drying and dis-
tribution center will increase knowledge of soil fertility/toxi-
city tradeoffs of the various application tools.
Heavy metals accumulation in soil will proceed at a rate far
lower than that of irrigated farms. These metals will have ade-
quate opportunity to "revert" to unavailable forms in the cal-
careous soils typical of non-irrigated farmlands. It is expected
that long before critical limits of these metals (defined in
Section IV) are reached, industrial effluent exclusion or reduc-
tion schemes will have been instituted and implemented in the
Denver area, permitting almost unlimited periods'of sludge reuse.
Salt accumulation in the topsoil may become a problem after
many decades of sludge application. Although annual salt accrual
rates are much lower than in irrigated farms (less than 20 kg/ha
[20 lb/ac]), lack of irrigation water, paucity of rainfall and
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the predominance of evapotranspiration rates all help keep salts
in the root zone of the soil. It would take about 200 years, at
the recommended sludge application rates, for soil salt content
to reach levels which would reduce crop yields significantly.
Thus, it appears that, instead of heavy metals, soluble salts im-
pose the upper limit on ultimate surface application rates of
sludge in non-irrigated farms and other drylands.
Air Quality
If dried sludge is left on the surface and subjected to blow-
ing in the wind, hazardous air pollution conditions could occur.
Lead content of sludge is the most important constituent in the
airborne assimilation of sludge particles by humans, conceivably
causing cumulative toxicity to frequent passersby. Other heavy
metals in sludge, as well as any surviving microorganisms, in-
cluding spores and egge of parasites, could also be transmitted
by aerosols. It is expected that proper application timing, sup-
plemental sprinkling, and mechanical incorporation of sludge into
the soil will effectively eliminate the air pollution potential
of sludge reuse.
Odors--
Air-dried digested sludge, taken from the stockpiles, is ex-
pected to be nearly odorless. When broadcast at the recommended
surface application rates and incorporated into the soil, it is
not expected that odor from the sludge will be detected at the
boundaries of the application sites except by those most sensitive.
Liquid sludge, if applied with subsurface injectors (equip-
ment is manufactured by at least two companies in the Denver area),
will have no noticeable odor even at close proximity to the ap-
plication equipment. Spraying of the liquid sludge on the surface
with special spreaders behind tank trucks will produce temporary
odors at close proximity to the application areas. The higher the
application rate and the longer the sludge remains on the surface
before incorporation, the worse the odors produced will be. On
the whole, however, anaerobically digested sludge is stable enough
so that the odors produced are not very strong or offensive.
The city parks and home gardens would be potentially the most
odor-sensitive application sites. However, the fact that sludge
has been applied to the parks for years with no significant com-
plaints is a good indication that continuation with digested sludge
will have no significant odor impacts.
There may be some odors the first day or so after a large
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amount of sludge is spread on parkland. This smell, which most
do not find particularly offensive, may carry for about a block.
The past practice of applying the sludge during low-activity per-
iods in the park reduces the airing-out period. Similarly, ap-
plying the major portions in the winter when people tend to be in-
doors has effectively limited the number of complaints.
If any publicity is given this application practice, past
experience has shown that there will be a temporary increase in
odor complaints following the publicity. Lately, sludge use has
become more commonly accepted as a positive conservation-minded
practice.
It is expected that odor produced by sludge application to
such other sites as sod farms, mine spoil sites and other farms
will be of minor significance due to the relative isolation of
such sites and the presence of other normally associated odors
(e.g. manure on farms).
Air Quality Impacts on Specific Sites--
Each site offers special opportunities and limitations insofar
as air quality impacts are concerned.
City Parks — It is expected that quick incorporation of sludge
into the seed bed, at the initial stages of park establishment,
and into the turf during the annual winter applications will mini-
mize air pollution hazards from this source. The high accessibility
of these parks to human beings and the proximity of residences
make the potential impact on air quality quite significant. Dried
sludge, blowing from the trucks as it is hauled to the City parks,
could, if not controlled, have highly undesirable air quality im-
pacts.
Sod Farms—Small quantities of particulate material may be
released to the air during and immediately after application of
the dreid sludge material. These effects may be heightened in the
presence of strong winds, especially during seed bed preparation
in the spring. The frequent irrigation associated with sod farm-
ing would reduce the effect of dust blowing to insignificant levels.
The remoteness of sod farms further mitigates air quality impacts.
Mine Spoil Sites—The proposed reclamation of mine spoil areas
is typically relatively short term. Small quantities of dust may
be released to the air during and immediately after the laying of
fine rock material and composted sludge. This effect may be in-
creased if winds are strong. However, subsequent operation of an
irrigation system and growth of plants will mitigate this effect.
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The quantities of dust thus generated would only be a short-term
contribution to the air quality of the mine operations and would
be relatively insignificant, especially in view of the remoteness
of these sites from human exposure.
Irrigated Farms—Sludge application on irrigated farms is not
expected to give rise to deterioration of air quality if soil in-
corporation of sludge and proper mixing are achieved immediately
upon application. A significant threat from improper application
procedures, i.e. leaving dried sludge on the land surface, especial-
ly in windy conditions, can arise with the dispersal of particulate
matter on and beyond the farms. Immediate mechanical incorporation
of sludge into the soil, followed by irrigation (or a fortuitous
rainfall), can control or minimize air pollution from this source.
Non-Irrigated Farms--The threat of particulate dispersal from
non-irrigated farms and other drylands treated with dry sludge is
rather severe. No matter how well dry sludge is incorporated with
the soil, the dry nature of these lands will permit dust blowing
during severe winds.
Application of liquid sludge, on the other hand, with deep in-
jectors, will alleviate this problem altogether. This is particu-
larly important as dryland farms generally have soils whose deeper
strata are highly calcareous and can rapidly make heavy metals un-
available. The binding effect of sludge on soil particles pro-
motes aggregate formation and reduces the potential for the soil
to become easily airborne in moderate winds.
Flora and Fauna
Impacts of sludge application to land on vegetation and wild-
life is so highly site-specific that no attempt is made here to
make any generalizations. At the risk of a few repetitions, im-
pacts are qualitatively described for each site under a separate
subheading. Impacts on vegetation are further discussed in more
detail in Appendix D.
City Parks and Home Gardens--
Vegetation—Application of sludge to vegetation in the City
parks and home gardens should have beneficial impacts by stimu-
lating plant growth. Sludge contains all of the elements that are
essential for plant growth, and with proper application will serve
as an effective fertilizer.
Any adverse impacts resulting from sludge application would
be caused by excessive rates of application. Grasses are tolerant
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of heavy metals and have a high rate of nitrogen uptake. The per-
iodic mowing of grass will remove appreciable quantities of salts
and nutrients that have accumulated in the plant tissue. The salts
thus removed will probably be deposited in contained sanitary land-
fills.
Grasses are effective in the control of erosion and runoff.
Surface runoff from the land would be minimized with a vigorous
cover of grass.
l-Jildl ife--Broad scale sludge applications would probably occur
in the late fall and winter during periods of minimal park usage.
Sludge application, even on snow-covered areas, followed by further
snowfall, minimizes the direct contact time for wildlife and humans.
Overall bird populations are lower during the fall and winter, with
the exception of wintering species and semi-domesticated species
such as rock doves.
Sludge incorporation into the soil would probably have simi-
lar effects on burrowing and ground-dwelling rodents, as discussed
further below under wildlife impacts at the Lowry Bombing Range.
The effects may be less pronounced due to the controlled sludge
application rates and rodent control programs.
Seed bed preparation with sludge supplement occurs generally
in the spring and late fall. Bird species which forage on the
ground — such as robins and towhees--and feed upon terrestrial in-
sects and seeds are exposed to the sludge mixture the most. These
birds may be exposed to a slight concentration of sludge components
along the food chain. However, these birds are not confined to
the City parks area and range throughout the urban areas. Ani-
mals, including dogs, may be exposed to pathogens and parasites
by direct exposure and ingestion.
Sod Farms--
Vegetation--The use of sludge as a fertilizer and soil condi-
tioner on sod farms will have beneficial impacts on sod production.
Sludge contains all the essential plant nutrients, and in some cases
sludge has been shown to generate higher crop yields than commercial
fertilizer. Grass is a good crop for sludge fertilization because
it is tolerant of heavy metals, is not used as feed or food, has
a high rate of nitrogen uptake and minimizes problems from runoff
and erosion.
VJildl ife--Due to the intensive management of a sod farm, di-
rect effects of sludge application upon wildlife would be few and
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probably limited to spring and fall during times of seedbed prep-
aration. Bird species which forage on the ground—such as meadow-
larks and sparrows—feeding upon terrestrial insects and grass
seeds, are exposed greatly to the sludge mixture. Heavy metals
and other sludge constituents accumulated by insects may be further
concentrated by bird predation. On a well-maintained sod farm,
however, thick sod growth effectively minimizes uptake of sludge
constituents by insects. The monoculture of selected short grass
species also represents an unbalanced ecosystem with only a few
insect and bird species. Small rodent problems on a sod farm are
also minimal due to the poor burrowing quality of a thick, fibrous
turf and constant disturbance and "grazing pressure" of mowing
equipment. Thus, incorporation of sludge constituents by small
rodents would not be a problem on this type of site.
Mine Spoil Sites--
Vegetation—The land application of stabilized sludge mixed
with wood chips to mine spoil sites will have very beneficial im-
pacts on vegetation. Since mine spoil sites are typically devoid
of a substrate capable of supporting plant growth, the land appli-
cation of composted sludge would essentially be a soil building
process.
Climax Molybdenum proposes to transport a total of 90 metric
tons/ha [40 tons/ac] of sludge mixed with wood chips (in a 1:1
ratio) to the mine spoil sites. Assuming that this material has
a density of 400 kg/cu m [25 Ibs/cu ft], the total amount of com-
posted sludge to be applied will have a depth of 2.3 cm [0.9 in.]
before incorporation. Proper substrate building procedures for
vegetation establishment should include: (1) application of
smaller rocks above larger rocks; (2) application of well-graded
materials such as finely crushed rock and sand to a depth of 25 to
30 cm [10 to 12 in.]; (3) application of the sludge-wood chip mix-
ture and (4) incorporation into the top 15 cm [6 in.] of the finer
material. In this way, the top layer of "soil" will contain ap-
proximately 13 percent organic matter after total composted sludge
application. This is a high percentage of organic material and
should provide a good substrate for plant growth.
The establishment of a ground cover would probably follow the
basic pattern of plant succession. Hardy pioneer species would
first become established and would slowly build up the depth of
the soil profile over time through decomposition of dead material,
thus permitting the growth and establishment of a more diverse
plant community.
Plant succession is generally an extremely slow process. The
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rate of succession would depend on such factors as the amount of
sludge and other materials applied and the types of plant species
that are initially planted. Grasses are relatively easily estab-
lished, but they do not provide large amounts of organic material
to be decomposed. Some native shrubs such as bear berry and buf-
falo berry, which are presently growing on the Urad Mine spoil
site, might be planted with some success. These would provide
more substantial amounts of detritus in the form of leaf litter
than would grasses, although their rates of growth might be in-
hibited at first by the penetration of the roots deeper into the
soil profile. Trees might also be planted, although the penetra-
tion of their roots through the top layer into the coarse and
acidic spoils might limit their growth potential for many years.
Because the total amount of sludge to be applied is relatively
low, the uptake of hazardous heavy metals, such as cadmium, zinc,
copper and nickel, should not present problems to plant growth.
Plant growth might be inhibited, however, by the uptake of heavy
metals present in the underlying spoil material, although this
situation should be alleviated over time as the soil profile in-
creases in depth.
The establishment of a complete groundcover of vegetation is
highly desirable since it can result in (1) earlier soil stabili-
zation and reduction of erosion; (2) earlier mitigation of acid
drainage in surface runoff through increased water holding capa-
city and through increased water use by evapotranspiration; (3)
acceleration of the accumulation of organic residues which will
chelate or otherwise make unavailable the soluble iron, manganese
and aluminum. Organic residues also provide the necessary seed-
bed for plant germination.
Wildlife—Mine spoils areas are typically rocky, barren and
devoid of normal signs of life. Application of sludge with in-
corporated wood residues would be an initial step towards the re-
clamation of these wastelands. The successful establishment of
vegetation over a period of time would help to restore some of
the habitat that had been destroyed by mining activities.
Wildlife habitat would be minimal due to the severity of the
terrain and presence of limited types of vegetation. However, the
distinct transition from forested slopes to a broad open swale with
grass and shrub vegetation would provide an "edge" habitat favor-
able to wildlife. Animals feeding upon vegetation in the re-
claimed mine spoils area are subject to accumulations of trace
elements as discussed under Food Chain, above.
Limited sludge applications for only two years at relatively
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low rates greatly reduce the potential for hazard. Within 3 to 5
years, a permanent ground cover could be established. Although
this habitat will not be very diverse, the variation it provides
in the heavily-forested woods and Clear Creek Canyon is an impor-
tant ecological consideration. With the decay of the mine spoils
and long-term formation and maturation of soils on the site, larger
and more sensitive vegetation forms may become established. Thus,
in the long term, partial or full reclamation of the mine spoil
sites would provide new wildlife habitats and an overall benefit
to wildl ife.
Irrigated Farms--
Vegetation--Areas of irrigated farmland that are subject to
the application of sludge are necessarily under cultivation and
contain no native vegetation. In general, sludge will have bene-
ficial effects on plant growth by supplying all of the essential
plant nutrients. The accumulation of hazardous heavy metals in
plants reduces the yield significantly before these metals become
a danger to the food chain if the cadmium/zinc ratio is less than
one percent. In the Denver sludge, this percentage is about 1.7
and poses a potential hazard.
Selection of crops suitable for growth on sludge-enriched
soils should be made in consultation with the local extension
service of the U.S. Department of Agriculture. Plants vary widely
in their reactions to sludge application, and these reactions are
site-dependent. Crops that are grown for their seeds or fruit
rather than for their vegetative tissue and crops whose younger
rather than older vegetative tissue is utilized are more desirable
in terms of trace element accumulation.
Wildlife--Insect populations and scavenging wildlife will con-
stitute a problem on sludge-amended farms, depending on the type
of crop grown. Large stands of monoculture represent a greatly
simplified ecosystem with a preponderance of only a few insect and
animal species.
Plants differ widely in accumulation of heavy metals and other
materials. Zinc and copper in very small amounts are micronutrients
beneficial to the animal and human diet (Reference 127). Evalua-
tion of potential effects of sludge on wildlife and on domestic
animals requires individual analyses of farms and of crop types
and their ability to accumulate trace elements. The greatest con-
cern is for grazing animals who will consume forage crops such as
hay and alfalfa grown on sludge-aided soils. Copper would be a
special hazard to grazing animals if sludge of high copper content
were sprayed on established pastures (Reference 128). Leaf surface
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copper is rapidly washed off with rain or irrigation water but re-
mains a hazard until removed. "Dietary copper and molybdenum in-
teract in the ruminant. When the molybdenum content of forage is
known to be low, expected increases in copper content of some for-
ages could be hazardous to sheep, while in forages of normal molyb-
denum content copper can be considerably higher" (Reference 128).
Insects and small mammals dwelling in or feeding upon ir-
rigated croplands are also subject to accumulations of trace ele-
ments and other materials. Foliage-eating insects and burrowing
rodents such as gophers are particularly susceptible. These
secondary consumers in turn support upper levels of the food
pyramid.
Non-Irrigated Farms--
Vegetation--The impacts to vegetation on dryland farms are
the same as those discussed under Irrigated Farms. Agricultural
effects of sludge application are discussed in detail in Appendix
D. In general, dryland farms will sustain a lower rate of sludge
application than irrigated farms because the rate of nitrogen up-
take of dryland crops is much lower than that of irrigated crops.
Seed germination can be inhibited if planting operations are con-
ducted too soon after liquid sludge application. If planting
is done from two weeks to one month after low-rate sludge applica-
tion, seed germination is uninhibited.
VJild1ife--Sludge application would occur in the spring or fall
during seedbed preparation. Application rates are generally much
lower than on irrigated farms or sod farms. Sludge constituents
are less likely to accumulate in the wheat and barley crops typ-
ically grown in dryland farming. Thus, the hazards of high con-
centrations of trace elements are less significant. The minimum
supervision and low maintenance required for a dryland farm allow
the fields to remain relatively undisturbed for long periods of
the year; thus, dry fields are easily incorporated into the eco-
system and are suitable for wildlife habitat. Mice, gophers and
jackrabbits particularly utilize this environment and will be
constantly in contact with the sludge-treated ground. Acute ef-
fects of grazing upon the vegetation are discussed above under
irrigated farm impacts. The low application rates and low uptake
of trace elements generally do not constitute a great hazard to
wildlife on a dry farm.
Grazing animals and wildlife may be exposed to pathogens and
parasites by direct exposure and ingestion. Pathogen survival is
greatly reduced by stabilization; however, some parasite ova such
as Ascaris may remain viable for many years in the soil.
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Noise
Noise generated by sludge application (broadcasting, injec-
tion or spreading) equipment is expected to be similar to that
produced by similar farm and landscaping equipment, such as trac-
tors, trucks and manure spreaders. Therefore, no particular noise
impact is anticipated. Some reduction in noise may be expected
to the extent that sludge application replaces fertilizer and/or
manure application on these operations.
In city parks, equipment and heavy machinery for applying the
sludge would generate noise levels that may be incompatible with
residential areas. This noise generation is unavoidable, but is
generally limited to short durations a few times per year. The
sludge application process is only a fraction of the parks main-
tenance program and, to some degree, is acceptable in consideration
of the benefits to vegetation and overall maintenance of the City
parks system. Use of mufflers on such equipment can inexpensively
mitigate this minor problem.
In sod farms, irrigated farms and dryland farms, continual
operation of farm equipment and the attendant machine noises during
the growing season are an integral part of the farming operations.
Some additional noise will be introduced by sludge transport trucks
delivering the sludge to remote plains areas. In perspective,
sludge transport and application would only be a small fraction
of farm operations. The local climatological conditions and open-
ness of the plains help to disperse sound well. In addition, the
low population density and isolation from other noise sources
make contributions from this part of the project insignificant.
In mine spoil sites, noise generated from sludge transport
and application operations would by typically on a one-time basis.
The narrow valleys, steep grades and heavily forested slopes tend
to confine noises within the local area. Noise generated during
sludge application and area seeding and planting would be greatly
masked by the noise from ore processing machinery at the molyb-
denum mine. Therefore, noise contributions from sludge transport
and mine spoil reclamation would be relatively insignificant.
In home gardens, sludge application would probably be per-
formed with small hand-operated equipment. Noise from such
machines as rototillers might disturb neighbors for short periods
of time.
Aesthetics
Since people generally accept the fact that fertilizer must be
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applied to the lawns and gardens of the parks, and since the dried
sludge does not have a particularly offensive appearance, no sig-
nificantly adverse visual impacts are expected from the continued
application of the material to the parks. As an added precaution
to avoid offending anyone's aesthetic sensibilities, the Park De-
partment attempts to apply the material during seasons and times
of the week when park use is low. Applying the black material to
snow-covered lawns in winter would make it highly visible until
the next snow.
Application of sludge to mine tailings has a beneficial
aesthetic impact since it prepares the barren spoil areas for
the grass and tree plantings, examples of which are now success-
fully in progress.
It is expected that the inert appearance and the nearly odor-
less characteristics of the dried sludge will help overcome the
psychological image associated with the fecal origin of the mate-
rial. Positive experience with sludge over a period of several
years might reduce the negative aesthetic impact.
Natural Resources
The resource value of sludge
is discussed at length above, un-
der the drying/distribution site
impact analysis.
Intensive farm operations
(such as sod production and
other irrigated agriculture)
can deplete natural resources
over large areas. The rapidly
growing plants extract large
quantities of nitrogen and
other elements from the soil.
In addition, thin layers of
soil material are removed from
the sod farms during harvest-
ing. Without soil supplements
or some form of compensation,
a sod farm could deplete the
soil resource in a relatively
short time. Sludge applications
would serve not only as a
fertilizer but also as a soil
•
- .
DRIED SLUDGE
163
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conditioner. Dried sludge is high in nitrates and contains other
macronutrients and trace elements required for plant growth. Per-
iodic cropping and annual harvesting can remove some accumulations
of trace organic materials. However, the long term accumulation
of salts and trace elements may preclude sludge applications after
a finite period of time, as discussed in Section IV. Therefore,
with controlled applications over a long period, sludge reuse on
farms can help maintain the soil resource.
Mine spoil areas are generally highly disturbed areas with
effectively few resources. The application of sludge to these
waste areas is the initial step towards reclamation of the areas.
Establishment of ground cover will eventually lead to the buildup
of a stable ecosystem. While the reclaimed areas may never be
able to duplicate the original ecosystem, they would constitute
a vast habitat improvement for wildlife resources and the natural
system. Thus, the proposed action would accrue an overall benefit
by partial restoration of natural resources.
Traffic and Circulation
Most of the sludge application sites will not be significantly
affected insofar as traffic and circulation patterns are concerned.
For example, if the City and County of Denver Park Department
ultimately utilizes 4,500 metric tons [5,000 short tons] of dried
sludge as anticipated, average daily trips will increase annually
by 200 (References 40, 77). Since travelways such as Irondale
Road and connecting major highways near the Denver urban core are
adequate in design to accommodate this minimal increase, no sig-
nificant impact on transportation and circulation patterns will
ensue should the proposed project be implemented.
Agricultural Economy
The agricultural economy in the area will be aided by the pro-
posed project, since it will provide a local source of fertilizer/
soil conditioner, a resource in increasingly short supply. The
nutrient benefit value of the design production capacity of 97
metric tons/day [107 tons/day] of dried sludge solids is worth at
least one million dollars per year at present prices.
The productivity increases resulting from sludge application
will undoubtedly vary among the individual farms using the material.
However, field tests by Metro Denver have verified the general in-
creased productivity results achieved elsewhere with agricultural
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use of sludge. For example, in well-managed sludge application
programs there have been 2- to 4-fold increases in forage pro-
duction, 2.5-fold increases in wheat production, and 20 percent
higher corn yields than were achieved by commercial fertilizer
(Reference 81). Mismanagement of the sludge application on farms
could have adverse economic impacts. Application rates in excess
of those recommended by the soil scientists and agronomists could
limit productivity due to high nitrate or heavy metal levels.
A small benefit to the farmers in this somewhat arid region
is the fact that the "dried" sludge will be about 50 percent water.
Assuming design capacity production at 97 metric tons/day [107 dry
tons/day] of dry matter in the sludge, there would be about 36,000
cu m [30 ac-ft] per year water in the sludge. This is a relatively
small amount of water and will be distributed very thinly over a
relatively large area.
Land Values
The proposed project is expected to provide a free or inex-
pensive fertilizer/soil conditioner for agricultural operations
within the delivery area of the sludge drying/distribution center.
This will probably have a positive impact upon land values, based
on the assumption that the sludge will improve the productivity
of the lands which receive it. This assumption seems justified
by the evidence from other areas which have used anaerobically
digested sludge as fertilizer.
Chicago and Orlando are two of a number of cities which have
demonstrated the agricultural benefits of controlled land applica-
tion of sludge for crop production. Denver, San Francisco, San
Diego, New York, Las Vegas, Miami and other cities have used
wastewater treatment plant sludge for park and lawn development.
In other countries too, sludge is used for agricultural purposes
(examples are Melbourne, Australia; Leipzig, Germany: and the
West Hertfordshire Main Drainage Authority in London, England).
Increases in land values in sludge application areas are in part
attributable to improved productivity of the land.
Summary of Land Application of Sludge on the Recycling Areas
The most severe negative impacts are in the food chain due to
heavy metals uptake by plants and animals. Public health hazards
and water quality problems also rank quite high in potential adverse
impact. The worst application sites vis-a-vis reuse of sludge are
home gardens, city parks and irrigated farms, while the best sites_
are mine spoil sites, sod farms and dry farms. The greatest benefi-
cial impacts are in improved soil productivity and conservation of
resources. A schematic representation of the impacts at various
sites is presented on Figure 17 (page 138).
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IMPACTS OF SUBSURFACE INJECTION OF LIQUID SLUDGE
AT THE DRYING/DISTRIBUTION CENTER
The Metro facilities plan calls for the injection of some of the liquid sludge on a
24-ha [60-acre] portion of the proposed site (located at the eastern end of site B-2).
The area is contemplated by Metro to be both a demonstration area and a possible secon-
dary disposal area for excess sludge.
Metro indicates that if the market for sludge does not develop, excess sludge could
be subsurface injected. Metro proposes to apply 175 dry tons/ha [78 dry tons/acre] fol-
lowed by a "rest" period of three years. This process could be repeated five times for
a total soils loading of 875 dry tons/ha [390 dry tons/acre] (Reference 55, page 4-5).
Metro plans to raise dryland crops on this site during the three-year resting periods.
The facility plan document recognizes that problems with heavy metals, nitrogen and
salts could occur. The loading rates contemplated for this portion of the site are
considerably in excess of recommended application rates of sludge for this region of
the country. Heavy metals levels in this range of application could have inhibitory
effects on some plants and pose a danger to animals consuming these plants. Cadmium,
in particular, would be available to such an extent as to warrant prevention of any food
or feed from this site from reaching consumers. The area would generally have to be
considered as a "disposal area for sludge."
The salt and nitrogen loads on the soils at this application rate would have an
'adverse effect on plant growth. At a rate of 175 tons/ha/yr [78 dry tons/yr/acre], ap-
proximately 2,500 cu m/ha [2 acre-feet/acre] of liquid sludge having a salt content of
6,000 rag/': would leach through the soil profile. At these concentrations, a rapid
buildup of soil salinity will result and will give rise to significant yield reductions.
The fate of the soluble nitrogen forms at such high application rates in the soil
is an extremely important question. The ammonia in sludge would partially be tied up
on clay particles, making it available for longer periods of time for plants. But with
dryland crops and some inhibitory effects, very little of the,nitrogen would be used by
crops. Gradually some of this nitrogen would be converted to the nitrate form and would
migrate to the groundwater. Severe localized effects could be expected in groundwaters
receiving the nitrate slug with the leachates. Since the application area is located
on higher ground to the west of the upper Lost Creek drainage, some of the nitrate and
salts could seep into this drainage. Without more definitive groundwater information,
these estimates are conjectural at this point.
The prinicpal limitation of the severity of effects from this method of sludge ap-
plication is the fact that only 24 ha [60 acres] of the site are involved. Although
Metro suggests use of this area as a secondary disposal site, the amount of sludge that
could be put on it in any one year (assuming the need for continuous use of this area)-
would be only about 1,100 metric tons [1,200 tons] per year. This amount represents
only about three percent of the total amount of sludge that must be handled at the site.
Thus, this area has only minimal value as an ultimate disposal site for Metro's sludge.
Metro would still need to develop a contingency plan (such as landfilling) for dis-
posing of sludge if no markets were to develop for sludge.
If sludge injection is carried on at the drying/distribution site, very little in
the way of mitigating measures could be applied to lessen the impacts. Irrigation water
could be applied to flush the soil profile of excess salts. This might lessen some of
the severe inhibitory effects on plant growth. Heavy metals would still remain in the
soil profile. The flushing of the soil profile would have negative impacts because of
the more rapid movement of salts and nitrogen toward the groundwater; The most realis-
tic measure would be to limit the amount of sludge applied at this site, largely for
demonstration purposes. Very little benefit would be gained by using this area as a
disposal site.
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IMPACT OF SLUDGE DISPOSAL AT LOWRY BOMBING RANGE
The disposal of sludge to the Lowry Bombing Range represents
the "no-action" alternative and would be continued if agricultural
reuse of sludge is not implemented. Since sludge is currently being
applied at a relatively high rate on the bombing range, this area
provides the opportunity to assess the effects of sludge applica-
tion. The Metro Denver Sewage Disposal District No. 1 is currently
engaged in several research programs to determine some of these
effects (Reference 114). Various types, rates and methods of
sludge application are being used to measure the precise impacts.
The results of Metro Denver's research project should provide
quantitative data on high-rate sludge application at this site.
The District's history of experience with land application of
sludges, gained at the bombing range, will be a valuable asset in
future reuse programs when the results are published. A summary of
impacts of the present operation is graphically shown on Figure 18.
CONTOUR STRIP SLUDGE APPLICATION AT LOWRY
Food Chain
The entry of heavy metals into the food chain is a potentially
adverse impact on areas of high-rate sludge application. Animals
accumulate heavy metals not only from eating the plants, but also
through direct ingestion of soil and sludge on the pasture areas.
The composition and amount of sludge that is applied as well as
soil conditions and plant characteristics are crucial factors in
the availability of heavy metals. These relationships are dis-
cussed in detail in Appendix D. The Metro Denver research project
should provide quantitative data on food chain parameters.
Of all the land application areas studied, the present opera-
tion at the Lowry Bombing Range comprises the greatest potential
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FIGURE 18
SUMMARY IMPACTS OF SLUDGE DISPOSAL AT THE LOWRY BOMBING RANGE
LANDSPREADING OPERATIONS
Impact parameter Direction and intensity5
Food chain
Public health
Soil productivity ( j
Soil salinity
Soil heavy metals
Water quality
Flora and fauna
Odor
Noise
Air quality
Plant operation and effluent quality
Aesthetics
Public reactions
Natural resources
Land use 9
o
Symbols signify relative impacts, as defined below:
High Moderate Low
Positive (beneficial) impacts: ( j
Negative (adverse) impacts:
This schematic representation of impacts should only be interpreted within the
context of analyses of impacts presented in the main body of the EIS. It is
neither an attempt at quantifying the impacts nor reducing the diverse environ-
mental parameter to common bases for comparison. However, it does provide a
rough ranking of the relative importance of the various impacts.
168 ENGINEERING-SCIENCE,
-------
hazard to the food chain with cattle, destined for the slaughter-
house and the grocery store, grazing unrestricted on sludge-amended
areas.
Public Health
In the past, no significant health problems have been associ-
ated with the Lowry Bombing Range sludge disposal operations. If
these operations continue, it is expected that, under most condi-
tions, the public health situation will not change. However, the
relative longevity of pathogens in soil (especially enteric para-
sites and their eggs or cysts, such as Ascaris ova) and the daily
proximity of workers and other project personnel with the sludge-
loaded soil would continue to present a health hazard that must
not be underestimated.
Effects on Personnel--
The present landspreading system in use at Lowry presents an
operating hazard to workers on the site. The high concentration
of lime used to disinfect the sludge makes the material to be ap-
plied very caustic (pH 11-12). Injuries to skin and eyes of
workers have resulted on occasion. Application by truck of a
semi-solid sludge also poses an operating hazard with the danger
of overturning or losing control of the truck. With the advent
of anaerobic digesters, the pH of the sludge would be nearer a
neutral value (7) and would present less of a hazard to workers.
Plant Operation and Effluent Quality
If the present Lowry operation is continued, with the addi-
tion of anaerobic digesters, recycle of supernatant from the di-
gesters is expected to have a negative impact on the Metro Central
Treatment Plant (see discussion on page 124).
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Soil Properties
As long as soil incorporation of sludges at the currently
heavy rates are kept below the conservative guidelines (presented
in Section IV under irrigated farms and in Appendix D), it is ex-
pected that soil conditions and properties at the Lowry Bombing
Range disposal site will improve with increased fertilizer levels
and organic matter. Obviously, nitrogen and other fertilizer com-
ponents of the applied sludge will be far in excess of that
needed for the weeds and grasses growing on the site. The organic
matter content of soils will rise to about 1.75 percent in the top
15 cm (6 in.) of the soil, at the current 400 metric ton/ha [175
ton/ac] total loadings. This is a significant increase over the
background levels of less than 0.5 percent. Thus, great immediate
benefits to the soil structure, permeability, water availability,
root penetration and erosion resistance will accrue.
The relatively high natural pH in these soils will help keep
heavy metals concentrations from becoming toxic to plants and a
threat to the food chain. The main difference between the bombing
range condition and that of the irrigated farms is that the impact
occurs over a much shorter period of time in the case of the bomb-
ing range. Thus, salt accumulation in the root zone will occur
rather rapidly, especially with the low rainfall levels and lack
of a significant additional water source limiting downward move-
ment of soluble compounds. At current application rates, total
soluble salt content of the soil plow layer will be increased to
0.2 percent of the soil mass, assuming that initial salt content
is nearly nil. This level of salt concentration is not expected
to cause more than a 30 percent plant yield reduction (Reference
115), given the existing vegetation. In fact, the yield reduction
will probably be overshadowed by increases arising from enhanced
fertility levels and soil conditions.
Hater Quality
The Lowry Bombing Range sewage sludge disposal operations pro-
vide a unique opportunity for a quantitative assessment of impact
of sludge reuse on water quality. Already, a network of catch
basins, spring stations and monitoring wells have been established
by the Metropolitan Denver Sewage Disposal District No. 1 in the
immediate areas of past and present sludge disposal. Sampling and
analysis of waters from these stations started in 1973 and are
expected to continue on a regular basis for an indefinite period
of time. The groundwater conditions are monitored through a large
number of shallow and deep wells in the areas of soil incorpora-
tion of sludge. The cooperative program was started in late 1974
by the U.S. Geological Survey and Metro Denver District and is
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continuing at the present time.
Preliminary raw data from the surface water analyses are still
not enough to help assess actual impacts. It can be surmised from
the trends that nitrate nitrogen is already finding its way into
surface waters and the shallower groundwater reservoirs. Individ-
ual catch basin concentrations of 29, 88 and 95 mg/1 nitrate nitro-
gen (as NO^) measured recently are alarming though not necessarily
indicative of wholesale contamination. Most of the analyses indi-
cate concentrations below 5 mg/1.
Preliminary data from the groundwater analyses show vertical
nitrate migration in areas downstream of the older land disposal
areas (8 to 44 mg/1 N03-N) and in the vicinity of the landfill
(13 to 23 mg/1 N03-N). Although these are single-sample prelimi-
nary results they may indicate real trends. Despite certain doubts
about the origin of the nitrogenous materials these trends may
continue. Nitrate levels in groundwater could rise over the com-
ing few years to levels above 45 mg/1 (as NOs), the limit at which
their use for drinking water would be inadmissible.*
As expected, heavy metals concentrations have not yet increased
in groundwaters, whereas preliminary measurements in the topsoil
have confirmed their accumulation. These metals are not expected
to move downward in these calcareous, relatively high-pH soils.
The continuing monitoring programs are an important advance warning
system in this regard.
Flora and Fauna
Vegetation—
Continuation of high-rate sludge application on the Lowry
Bombing Range will cause similar impacts to the vegetation that
can now be observed on that portion of the bombing range that has
received sludge. This site is referred to as Site A and is shown
in Figure E5. The sludge application process itself results in
the complete displacement of the existing vegetation. However,
no rare and endangered species have been reported on this site
(Reference 34), and relictual mixed-prairie units, which are be-
coming scarce in the Denver area, do not occur at the disposal area.
This conclusion was made from a field reconnaissance and should be
verified by more thorough site surveys if land application is to
*Recommended limit for nitrate nitrogen in domestic waters is
45 mg/1 as NOg.
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continue. The original mixed-prairie unit has long been exposed
to heavy grazing and presently contains many introduced annual
grasses and annual and perennial weeds.
The immediate impact of sludge application would be to stimu-
late the growth of weeds. The major weedy species found on Site A
(common sunflower, Russian thistle, summer cypress and tumble pig-
weed) are fast-growing colonizers of bare soil whose growth has
been enhanced by the nutrient value of the sludge. Over a long
period of time, certain grass species would become established in
the absence of grazing. Other management inputs, such as weed
control and planting, would accelerate this process. As long as
the site is grazed, however, cattle will selectively crop grasses
and the weeds will continue to be dominant.
The establishment of a vegetative groundcover is essential to
control soil erosion and surface runoff. Although grasses are
superior to weeds in checking erosion, the dense weedy growth on
Site A does serve to limit problems resulting from soil erosion and
runoff.
Site A is being used for a research project by Metro Denver
Sewage Disposal District No. 1 on the effects of high-rate sludge
application on vegetation and cattle (Reference 114). Two major
areas of concern are the high nitrate levels and the accumulation
of heavy metals in plants and in the food chain. Many common
weeds have high nutrient requirements (nitrogen, phosphorus and
potassium) which limit to some extent the amount of nitrates that
can be leached into the groundwater. Perennial grasses also have
a high nitrogen requirement. The movement of heavy metals into
plant tissue depends on many factors. The high phosphorus content
of the sludge tends to make zinc, cadmium and nickel unavailable
to plants. This property might be somewhat reduced by the cal-
careous nature of the soils. Calcareous soils have a high pH and
tend to make phosphorus unavailable and immobile. Cadmium is po-
tentially hazardous in the food chain, and its movement within
the soil-piant system can be controlled by limiting the amount
applied to less than one percent of the zinc content applied. In
this way, excess zinc would injure the crop before the zinc or
cadmium content of the crop constituted a health hazard (Reference
116). This relationship is explained more fully in Appendix D.
Seed germination is inhibited if planting operations are con-
ducted too soon after the application of liquid sludge. If plant-
ing is done from two weeks to one month after sludge application,
seeds germinate successfully.
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The impacts of high-rate sludge application to this site will
presumably be quantified when the Metro Denver research report is
available.
Wildlife—
High-rate application of sludge upon the Lowry Bombing Range
produces a distinctive plant community as described above. The
resultant plant growth would exhibit a tendency towards a variety
of herbaceous annuals. These fast-growing "weeds" can compete
with the existing grasses and are often thick-stemmed, fibrous,
and in some cases bearing thorns. They are generally less suit-
able than the short grasses for animal forage, but may be grazed
upon in the tender stages or during periods of food scarcity. The
ability of various plant species to accumulate sludge constituents,
such as heavy metals, depends upon many factors as discussed in
Appendix D. High concentrations of zinc, copper and cadmium in
forage could have deleterious effects upon animals. However, se-
vere toxicity injury from metals normally occurs in vegetation at
lower concentrations than those toxic to animals. Some grazing
animals, particularly sheep, are unusually sensitive to copper and
could be injured by eating some forages enriched in copper by
sludge. Few studies have been conducted on particular animal
avoidance by taste or odor of vegetation grown on sludge (Refer-
ence 117). In general, when suitable grass forage is available,
grazing animals will eschew the tough and unpalatable "weed"
species. Cadmium and zinc are accumulated generally in the foliage
and are found only in low concentrations in fruit, root and grain
parts. Wild grains, seeds and fruit from grasses and "weeds",
particularly sunflowers, would provide a satisfactory food sup-
plement for seed-eating birds and small mammals. This would be
particularly beneficial to wildlife in the fall and winter.
The shift in plant species would also result in a change in
the microclimate on the surface and several centimeters below the
surface. The broad-leafed herbaceous plants with relatively
deeper root systems would contrast sharply with the groundhugging
short grasses with shallow, fibrous root systems. The combination
of reduced insolation and semi-moist organic material in the soil
would lead to decreased surface and substratum temperatures with
slight increases in humidity. This micro-environment may be par-
ticularly favorable to invertebrate species and may encourage the
establishment of new species as well. The low-diversity and un-
balanced plant ecosystem may also lead to the preponderance of
only a few species.
High-rate sludge application and mixing into the upper soil
zone would probably have the greatest direct effect upon burrowing
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and ground-dwelling rodents. Initial sludge application would
temporarily destroy the uplands vegetation habitat and cause a
displacement of local rodent populations to adjacent areas. With
the re-establishment of vegetation and aging and maturation of the
organic-laden soil, some rodents—such as pocket gophers and ground
squirrels--may return to the area. Ground squirrels are generally
seed-eating and use the underground burrows chiefly as retreat and
nesting areas. Pocket gophers, on the other hand, reside almost
exclusively underground, burrow continuously and feed upon sub-
terranean root stocks and other material. The gopher may actually
accumulate sludge constituents such as heavy metals through direct
ingestion as well as digestion of plant material. A decrease in
rodent numbers may not be significant to humans, but nevertheless
is important to the ecosystem balance. Gopher populations within
an area may have a contributing effect upon the food chain, as
these small animals are preyed upon by hawks, eagles and coyotes.
Grazing animals may be exposed to pathogens and parasites by
direct exposure and ingestion during feeding. Pathogens will be
greatly reduced over time and by thorough incorporation. However,
parasite ova such as Ascaris may remain viable over many years,
potentially causing serious animal diseases.
The ecosystem shift and effects upon wildlife are localized
to the sludge application areas and are generally short-term.
Without further sludge applications, the altered vegetation com-
munity would gradually change to an upland vegetation unit in
three to five years. With continuing periodic sludge application,
this altered and unbalanced ecosystem could be perpetuated over
the long term.
Large-scale sludge application at the Lowry Bombing Range may
affect the habitat of the endangered black-footed ferret. If the
project destroys any prairie dog towns on the site, it may affect
the main food source of the black-footed ferret.
Noise
Continuation of the present landfilling and high-rate sludge
application methods would perpetuate the existing noise levels
from machinery and associated activities. As stated under the
environmental setting, the climatological conditions and openness
of the prairie would disperse sound well. In addition, the low
population density and isolation from other noise sources make
the noise contribution from the project almost insignificant.
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Air Quality
The application of sludge to the bombing range should not ad-
versely affect air quality if the sludge is promptly incorporated
into the soil. The potential for particulate matter to rise and
be dispersed exists if the sludge is stockpiled or not incorporated
soon after optimum moisture condition is reached. Particulate
matter can contain heavy metals and microorganisms that might be
ingested by people. Lead, particularly, is a health hazard. When
the sludge is well mixed in the soil, the potential for dust and
particulate dispersal is reduced by the soil-binding character of
the organic matter in sludge.
Odor--
The present operation's odor problems are not now serious and
are not expected to be significant in the future. Under present
operations, with largely undigested sludge, odors are easily per-
ceived at close proximity to the application areas, especially
when digester problems are encountered. The small amount of air-
dried anaerobically digested sludge currently stockpiled is almost
free from odors.
Aesthetics
Continuance of operations at Lowry Bombing Range would have no
significant adverse aesthetic impact. The isolated area and neigh-
boring landfill operations place the operation in an unobtrusive
setting. Even at the close-range view, the application areas re-
semble newly-plowed fields.
SLUDGE ON LAND BEFORE PLOWING
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Traffic and Circulation
Should the proposed project not be implemented, truck traffic
to and from the Metro Denver Central Plant facility and the Lowry
Bombing Range will continue at a rate of 35 to 40 truck trips per
day until such time as the land can no longer accommodate additional
increments of heavy metals associated with Metro Denver sewage sludge
(Reference 39).
Public Reactions
Earlier adverse public reactions concerning Lowry operations
resulted from system inadequacies which have since been remedied.
The number and validity of the complaints about odor have been
dealt with in the section devoted to that topic. Continued use of
the Lowry site would probably result in continuance of these com-
plaints. Complaints have averaged about one per month, with 80
percent found to be due to some other source, and the remaining
20 percent due to inclement weather or operations breakdown (Ref-
erence 39).
Natural Resources
The lands on the Lowry Bombing Range are currently utilized
as range and pasturelands and, thus, this area exists as a grazing
resource. As such, the potential for grazing has been reduced in
areas of sludge application by the lack of range management prac-
tices that would ensure adequate forage species composition. Al-
though these areas have been reseeded with wheat and forage grasses,
the continuation of grazing combined with the absence of weed con-
trol has produced a site that is dominated by weeds and has margin-
al value as rangeland. Continuation of sludge application in the
absence of sound range management techniques would thus constitute
a reduction in the grazing natural resource.
High-rate sludge application could beneficially affect this
natural resource if a weed control program was implemented and if
the potential for hazardous heavy metals to enter the food chain
were recognized.
The application of excessive amounts of sludge under a high-
rate application program constitutes a loss of nutrient resources.
Land Use
Should the proposed project not be implemented, the Lowry
Bombing Range may continue to be the application site for Metro
Denver sludge. There is evidence that heavy metals are building
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up in the soils as a direct result of intensive sludge application
(Reference 118). This would reduce the types of uses which the
disposal area could otherwise offer.
IMPACT OF SLUDGE LANDFILLING AT LOWRY LANDFILL
The landfill ing practice near the Lowry Bombing Range is es-
sentially a winter-weather and emergency practice which comprises
a portion of the "no-action" alternative. During the winter, when
it is difficult to perform the regular soil incorporation practices,
sludge is dumped at high rates on prepared bench-and-terrace areas.
Sludge is emptied from the backs of trucks to a depth of 60 cm [24
in.] and mixed at a 5:1 ratio with soil. This amounts to a loading
rate of 670 dry metric tons/ha [300 dry tons/ac] per year. Winter
landfill ing during December, January and February has been prac-
ticed since 1971 but is expected to cease if the proposed agri-
cultural reuse plan is implemented.
Soil Properties
Native soil is removed from the landfill areas prior to dump-
ing sludge. The soil is stockpiled and used to mix with the sludge
during dumping and for final cover. At the very high rates used,
sludge components will saturate the cation exchange sites of the
soil and increase its salt content, making it a practically unpro-
ductive material for crop production or pasture. The increased
water-holding capacity caused by increased organic content will
help delay leachate formation but will not prevent it in the long
term. Overall, the impact upon the soil from landfill ing will be
destructive and extremely long lasting.
Hater Quality
Nitrates and heavy metals will gradually be leached by perco-
lating rain water and carried toward the groundwater reservoirs.
Already, concentrations of nitrates in well waters in the vicinity
of the landfill area are significantly above background levels;
i.e., 13 to 23 mg/1 in contrast to background levels of 0.01 mg/1
or less. These trends are expected to continue unabated unless an
impermeable layer is placed on top of the old fill areas and be-
neath the new ones.
It is expected that heavy metals will gradually move downward
toward the water table from the landfill unless leachate-prevention
mechanisms are implemented. Cadmium is the most mobile of metal
elements and will serve as an indicator of incipient arrival of
other heavy metals to the groundwater reservoir.
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Surface v/ater pollution from the landfilling operation is ex-
pected to be minimal because of the soil cover provisions and prior
site preparations minimizing runoff from the sites.
Flora and Fauna
Vegetation—
The impacts of a landfill on vegetation are of a complete and
long-term nature. Existing vegetation is removed with the excava-
tion of trenches for sludge disposal. At the completion of dis-
posal operations, the District plans to overlay the area with a
topsoil material and revegetate with annual grasses. The success
of the revegetation program depends primarily on such factors as
soil conditions and management inputs, such as weed control.
Grasses are generally tolerant of heavy metals in the soil, and the
establishment of a permanent groundcover in this area would prob-
ably not encounter any severe problems. Heavy metals accumulating
in plant tissues should be recognized as a reality, particularly
if the site is to be grazed by livestock.
Wildlife—
Long-term disposal of sludge at the Lowry Bombing Range by
landfilling would cause a definite change in the local plant com-
munity and a probable shift in wildlife species.
Landfilling, which would probably be a seasonal activity, in-
volves complete destruction of the existing habitat by excavation,
trenching, and deposition of sludge and placement of soil cover
over the mound. Wildlife, particularly small mammals such as mice,
ground squirrels and jackrabbits, would be displaced to adjoining
areas, causing temporary population stresses. The completed land-
fill cover would be relatively barren because of poorer soil con-
ditions, rapid runoff, poor v/ater retention capability and greater
exposure. This anomaly in the landscape would be difficult to
incorporate into the upland vegetation habitat and is effectively
lost to wildlife usage. Landfilling as a method of sludge disposal,
however, does not disturb as great an area as does broad-scale
surface application because the material is concentrated in a
smaller area.
Air Quality
Because the landfill ing operation is restricted to the winter
season and adequate final cover is provided, no air pollution po-
tential is expected from this operation. Safeguards against ero-
sion and removal of the final cover are essential , to maintain the
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sludge under constant cover and to prevent it from drying and blow-
ing in the wind.
Odor--
Similarly, if the final cover is maintained, no odors will
emanate from the site. Otherwise, the landfill can be expected to
produce disturbing odors, detected at considerable distances, as
past experience with unauthorized dumping has indicated.
Explosive Gas Production
Solid waste landfills in general, and sludge landfills in par-
ticular, produce significant quantities of combustible gases such
as methane during the process of anaerobic decomposition. Mhen
mixed with air (5 to 15 percent combustible gas in the mixture),
they are explosive and can pose a safety hazard to humans in the
vicinity. Special provisions for venting such gases are necessary.
Land Use
Whether the proposed project, i.e., beneficial agricultural
reuse of sludge, is implemented or not, general uses of the Lowry
landfill will be unchanged since the area will remain a disposal
site for the Denver urban area.
Resources
Burying the sludge in a landfill constitutes wastage of a re-
source of potentially high fertilizer and soil-conditioner value.
The extent of this loss can be visualized from the discussion of
impacts of sludge application on the soil, discussed in this
Section and in Appendix D.
Summary of Impacts of Sludge Disposal at the
Lowry Bombing Range
As currently practiced, the land spreading operation at the Lowry
site exerts the greatest negative impact on the food chain through
pasturing of domestic animals on sludge-amended fields. Heavy metals
accumulation in the soil, salinity of the soil and groundwater quality
problems are other negative impacts of the current practices. Improved
soil productivity and a partial conservation of natural resources are
among the beneficial impacts of the present disposal operations. These
impacts are schematically represented in Figure 18.
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This section contains recommendations for
possible modification of the original project
proposal (or in the case of land application- on
reuse areas, additional controls that were not
contemplated in the facilities plan) to reduce
or eliminate environmental impacts. Negative
impacts of major elements of the land applica-
tion plan—processing, off-site application
and the Lowry operation—are listed, and miti-
gative measures are recommended.
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SECTION VI
NEGATIVE IMPACTS AND RECOMMENDED MITIGATIVE MEASURES
Key negative impacts identified and discussed in Section V are
listed in this Section with possible mitigative measures which may
be selected during the review process of this Draft EIS for final
implementation. These tentative mitigation measures are recommenda-
tions by EPA and its consultant (Engineering-Science, Inc.) for con-
sideration by the reviewing agencies and the public. Through the
review process, acceptable effective measures will be selected from
those presented here and those which may be offered by the reviewers
of this document. The measures thus selected will become an inte-
gral part of the design and operation of the facilities planned by
Metro before Step 3 grant monies are extended for the construction
of the facilities. The final EIS will include the selected mitiga-
tion measures.
It is extremely important that whatever mitigative measures are
adopted be integrated with the planned monitoring and surveillance
activities so that symptoms detected by the monitoring system can
lead directly into specific mitigative action.
PROCESSING, TRANSFER, DRYING AND DISTRIBUTION
Groundwater Pollution by Nitrates and Salts Leaching
from Sludge Drying Basins
Lining the bottom and sides of basins with impermeable materials
is the only fully effective way to mitigate nitrate and other salt
accumulations in the groundwater. Nitrate movement can probably be
slowed by maintaining anaerobic conditions in the bottom layer of the
drying beds (this possibility has not been fully demonstrated as a
guarantee against nitrate movement). Provision of drainage networks
below the basins can be effective against nitrates and other salts
but will not stop all leachates from moving to the water table.
Furthermore, the collected drainage water must also somehow be safe-
ly disposed.
Return of the supernatant from the digesters to the treatment
plant headworks (rather than pumping it along with the sludge to the
sludge drying and distribution center) would be a great help in re-
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ducing salt pollution of the groundwater. Drying of the superna-
tant in separate, lined drying basins and containment of the dried
salts would also be a suitable—though partial—alternative mitiga-
tion measure against salt buildup in the groundwater.
Surface Water Pollution from Experimental Plots
Impoundment of runoff water in reservoirs at the lowest parts
of the center and treatment or proper disposal (e.g. irrigation of
experimental plots and wetting the sludge stockpiles on windy oc-
casions) of the waters gathered can adequately mitigate surface
water pollution.
Potential Threats to Public Health
Pathogen transmission through the air and through surface run-
off waters and nitrate contamination of groundwaters are two main
threats to public health which can be detected through continuous
monitoring of pathogen longevity and groundwater quality under the
drying and distribution site. Mitigation measures for public health
hazards could include: (1) lining the drying basins with impermeable
materials, (2) provision of special medical services for the employees
at the center, (3) restriction of public access to the site, (4) main-
tenance of optimal digestion conditions in anaerobic digestors, (5)
provision of special medical monitoring and preventive treatment to
persons frequenting the site for taking delivery of sludge loads and
(6) a strict ban against pumping of undigested sludge at all times.
Proliferation of Insect Vectors on Sludge
Drying Basins
A qualified entomologist should be retained at the early stages
of full utilization of the drying basins to identify specific insects
colonizing the basins. Control measures defined through the identifica-
tion process should be implemented.
Air Pollution from Participate Matter of
Sludge Origin
Sprinkling of the stockpile areas during windy periods and stor-
age in gently sloping heaps (in contrast to high abrupt mounds) would
help minimize dried sludge being blown in the wind. However, with
above-ground storage it will not be possible to completely prevent loose
material from being blown.
Production of Nuisance Odors in Drying Basins
Odors can be minimized with proper digestion of sludge and main-
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tenance of an adequate buffer zone between the basins and site bound-
aries. Odor production on the site itself cannot be wholly prevented.
Negative Public Reaction to Establishment of
the Drying and Distribution Center
A proper public relations campaign with full disclosure of all
environmental, economic, political and social considerations involved
with the project should provide a healthy atmosphere of open dialogue.
This will help improve the acceptability of the drying and distribu-
tion center to the neighboring farming community.
LAND APPLICATION IN SLUDGE RECYCLING AREAS
Lands which will be the ultimate repositories of dried sludge
will be the most critical impact areas in the sludge handling process.
This is due to the fact that many of the impacts discussed are of a
cumulative, long-term nature. Therefore, mitigative measures are es-
sential for success of the beneficial reuse scheme. The most import-
ant overall mitigative measure would be limitation of land application,
in the initial years, to the sites with the least severe adverse im-
pacts (such as mine spoil sites and sod farms).
Heavy Metals Accumulation in Soil, Plants,
Animals and the Food Chain
(1) Removal or reduction of sources contributing heavy metals to
the wastewater management system will mitigate many of the adverse im-
pacts on soils, plants, animals and the food chain. This can be done
by promulgation of a special wastewater ordinance, setting tolerable
limits on concentrations of exotic substances entering the sewer sys-
tem, thus forcing industries to adopt in-plant measures to curb dis-
charge of heavy metals.
Exclusion of industrial and other heavy metal discharges from the
wastewater treatment system will allow prolonged use of sludge on the
various sites.
(2) Control of cadmium:zinc ratio is another important mitigat-
ive measure. If this ratio is kept below one percent, acceptability
of sludge for use on feed crops and foods will be greatly enhanced
through the plant yield reduction effected by zirrc, long before either
element accumulates in toxic concentrations.
(3) Record-keeping, inspection of sludge application operations
on individual sites and monitoring of environmental parameters are
functions which must be carried out by the District or another res-
ponsible agency in close cooperation with individual farmers and oper-
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ators. These functions will prevent inadvertent aggravation of im-
pacts by excessive, non-uniform or careless applications of sludge
and will mitigate the adverse impacts. It may be necessary to ob-
tain binding agreements with recipients of sludge to permit inspec-
tion and monitoring and to provide for cessation of sludge supply
in cases of noncompliance with recommended management practices.
(4) In many cases, it may be necessary to subsoil the farmland
prior to or during the first sludge application pass, in order to
bring to the surface some of the calcareous material in the lower
soil horizons. Alternatively, lime amendment would also help in-
crease soil calcium content, if necessary. This will help hasten
the "reversion" of heavy metal elements to unavailable forms.
(5) Crop selection to favor non-foliar edible parts and younger
rather than older plant parts can help reduce magnification of cad-
mium and other heavy metals in the food chain.
(6) Surface spraying of liquid sludge should be avoided, espec-
ially on pasture areas where it may be directly ingested by livestock.
(7) Exclusion, at the slaughterhouse, of kidneys and livers from
the meat of animals having grazed on--or having been fed hay and
other feeds raised on--sludge-amended farms and the disposal of these
organs at a sanitary landfill would be an excellent mitigation mea-
sure. The ability of these organs to concentrate heavy metals would
thus be benefically used as a device to eliminate them from the food
chain.
LIVESTOCK GRAZING ON SLUDGE-AMENDED FIELD
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Nitrate Pollution of Groundwater, Especially In
Irrigated Farms, Sod Farms. Home Gardens, City Parks
While the active process of leaching of nitrates into the
groundwater table cannot be avoided, the extent and duration can
be substantially reduced. Periodic monitoring should be conducted
on groundwater assoicated with each site that is receiving sludge.
Before nitrate concentrations reach 45 mg/1 N as N03, usage of slu-
dge should be curtailed, and the groundwater should be restricted
from potable use.
Nitrate Pollution and Eutrophication of
Lakes and Other Water Bodies
(1) The pollution of surface waters can be mitigated by strict
control over application rates so that a balance between nitrogen
uptake by plants and available nitrogen content of sludge is adhered
to as closely as possible. Water quality should be monitored to de-
tect any buildup of nitrates.
(2) Control of the tailwater in irrigation systems and use of
standard runoff and erosion control practices on the farm can reduce
the threat of surface water pollution.
(3) Riverbeds, flood plains and steep slopes should be categor-
ically excluded from sludge application.
(4) Use of liquid sludge injectors, applying sludge at greater
depths, should be preferred over application of dried sludge.
Air Pollution from Particulate Matter
of Sludge Origin
Particulate matter from dried sludge applied to soils can be
reduced by several means: (1) deep incorporation of sludge into the
soil by mechanical means as soon as possible after application; (2)
subsequent irrigation to keep particulate matter in the soil; (3) ap-
propriate scheduling to avoid or minimize sludge application during
windy conditions—particularly in the springtime; (4) opportunistic
timing to apply sludge immediately prior to forcasted rainstorms and;
(5) injection of liquid sludge deep below the surface wherever this
is a feasible practice.
Exposure of Humans to Viable Pathogens
and Parasites
(1) The use of sludge which has been air-dried for at least two
years would greatly reduce the numbers of viable pathogens. Addit -
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ional methods of pathogen reduction in sludge include: (a) pasteur-
ization for 30 minutes at 70°C [158°F]; (b) high pH treatment, typi-
cally with lime, at a pH greater than 12 for three hours; (c) long-
term storage of liquid digested sludge (if applicable) for 60 days
at 20°C [68°F] or 120 days at 4°C [40°F]; (d) complete composting at
temperatures above 55°C [131°F] for at least 30 days; (e) use of chlo-
rine or other chemicals to stabilize and disinfect sludge. Current
research shov/s preliminary promise in the use of high energy electrons
for disinfection of sludqe passing in a thin stream in a specially
adapted process. The feasibility of use of these and other means of
pathogen destruction should be continually considered for application
and use.
(2) The possible introduction of pathogens into surface waters
will be mitigated if sludge is not applied in the close vicinity of
lakes and other water bodies.
(3) Soil and water monitoring for pathogens should be regularly
conducted.
(4) Use of sludge on vegetable crops (such as in home gardens)
arid all foods eaten raw should be strictly banned. EPA guidlines sug-
gest a three-year waiting period prior to using sludge-treated land
for food crops to be eaten raw by humans.
(5) Use of sludge on parklands should be controlled to avoid
areas where humans could come in contact (e.g. grass areas) and lim-
ited to areas where control can be maintained (new sod, flower gar-
dens). Sludge applications should also be limited to times of the
year when chance of exposure is slight.
Exposure of Animals to Viable Pathogens
and Parasites
Mitigative measures such as those enumerated above, under Expos-
ure of Humans to Viable Pathogens and Parasites, are equally effec-
tive in protecting domestic animals and wildlife from adverse effects
of sludge pathogens and parasites.
Odor
Proper timing of sludge application will mitigate odor impacts.
Further mitigation measures applicable to odor are discussed above,
under Air Pollution from Particulate flatter of Sludge Origin.
Adverse Public Reactions
The promotion of a public education program to inform the public
of the benefits and potential effects of sludge application will al-
most certainly increase acceptability of the concept and its wide-
spread adoption in the farming community.
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Initial Toxicity of Liquid Sludge to
Seeds and Young Plants
Where liquid sludge is applied on irrigated or non-irrigated
farms, mitigation can consist of (1) delay of planting until one
month after application or (2) use of special sludge injectors,
applying the material in separate bands deep into the soil.
Ingestion of Sludge from
Foliage and Soil
(1) Spraying of sludge on growing crops and pastures should be
avoided;
(2) Cattle should not be pastured on land having received sludge
recently;
(3) Sludge should be incorporated into the soil as soon as pos-
sible;
(4) Use of deep liquid sludge injectors should be encouraged,
particularly on dryland farms and pastures.
EXISTING DISPOSAL OPERATIONS ("NO ACTION") AT LOWRY
BOMBING RANGE
Heavy Metals Accumulation in Soil, Plants,
Animals and the Food Chain
This impact is particularly severe in areas where livestock
grazing is conducted. It is somewhat mitigated by the limitation
of total application rates. However, the high time rate of applica-
tion causes uneven incorporation and high local concentrations, pos-
ing hazards to the food chain. For mitigation measures, refer to
page 133.
Possible Loss of Unique Vegetation
Type
The location of any relictual mixed-prairie units should be veri-
fied by a thorough site survey. Loss of any existing examples of
this type would be mitigated by the exclusion of these areas from
future sludge application sites.
Possible Destruction of Rare and Endangered
Plant Species
The occurrence of any rare and endangered plant species should
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be verified by a thorough site survey. Destruction of these plants
would be mitigated by avoiding areas where they may be found. Approp-
riate botanical authorities should be notified of the location of rare
or endangered plants.
Possible Loss of Black-Footed
Ferret Habitat
The location of any prairie-dog towns should be noted, and a
thorough site survey conducted to determine concurrent habitat assoc-
iation for the endangered black-footed ferret. If the black-footed
ferret is found on the site, its habitat should not be used for sludge
application.
Initial Toxicity of Liquid Sludge to
Seeds and Young Plants
The inhibition of seed germination can be mitigated by delaying
planting operations until one month after the application of liquid
sludge.
Application of liquid sludge in separate deep bands, with the
use of special injectors, can mitigate initial toxicity without a
need for delayed planting.
Air Pollution from Particulate Matter
of Sludge Origin
Mitigative measures are discussed above, under Sludge Recycling
Areas.
Reduction of Grazing Resource
The implementation of range management practices, such as weed
control and the exclusion of livestock from treated areas until a
forage crop is well established, will mitigate this impact.
LOWRY LANDFILL
Removal of Wildlife Habitat
A rigorous attempt at revegetation of the final cover over the
landfill area will help restore the habitat to some extent.
Groundwater Pollution
Unless the bottoms of new fill areas and the surfaces of old
areas are covered with impermeable materials such as liners or clay
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layers, groundwater will be polluted with nitrates, salts, carbon
dioxide gas and perhaps even heavy metals over long periods of time.
Explosive Gas Production
Use of venting systems, standard on sanitary landfills, can
prevent formation of explosive concentrations of combustible gases
generated in the sludge fill area. Such systems are not now in
place at the Lowry landfill.
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The long-term implications of the Metro
proposal and the continued use of the Lowry
system are reviewed in this Section. First,
those impacts of an adverse kind that cannot
be avoided—even with the use of mitigating
measures proposed in Section VI—are described.
Next, consideration is given to the irrever-
sible commitments of resource use that will
occur with this proposal or with the existing
system. Finally, an evaluation of overall
productivity in the long run is presented.
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SECTION VII
LONG-TERM CONSIDERATIONS
Major projects such as the large-scale reuse of sludge on the
land have long-term implications which are often different from (and
sometimes far more significant to environmental parameters than)
those initially envisaged.
The state of knowledge on precise impacts of sludge reuse on
land is in the state of infancy. Thus it is relatively difficult
to determine accurately the short-term effects (such as water pollu-
tion, public health hazards, air pollution, food chain disorders,
etc.). There is even less basis for quantifying long-term effects,
which may be far more pernicious and pervasive than short-term im-
pacts, as a whole. By the same token, the beneficial long-term ef-
fects that can now be described only generally and qualitatively
may in time prove to have been totally underestimated or grossly ex-
aggerated.
The very unknown nature of future cumulative impacts should be
ample warning to proceed with caution, to use sludge on lands where
known impacts are minimal (such as sod farms, mine spoil sites and
dry farms) and to avoid those where we now know the impacts can be
significant (such as home gardens and farms growing crops consumed
directly). The transitional state of knowledge about sludge reuse
impacts also makes it extremely important that the planned and neces-
sary additional monitoring activities on all environmental parameters
be implemented rigorously and diligently to provide early warnings
of hazardous conditions which may be developing.
ADVERSE IMPACTS THAT CANNOT BE AVOIDED
Sludge Drying and Distribution Site
Disturbance of 240 Hectares [600 Acres]
of Soil —
The destruction of soil profile to create the drying basins can-
not be mitigated. Once the natural soil strata are destroyed, they
cannot be reconstituted, nor can they be restored to those that were
formed under natural soil-forming conditions over geological time.
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Destruction of Wildlife Habitat—
Most of the 800-hectare [2000-acre] drying and distribution
site will be irretrievably lost as wildlife habitat.
Salt Movement Toward Groundwater Table--
Approximately 160 metric tons [180 tons] of salts will leach
each year from beneath the sludge drying basins under present de-
sign conditions.
Nitrate Pollution of the Groundwater
Reservoir—
Unless further research and possible procedural adaptations can
assure complete denitrification at the bottom of the drying basins,
pollution of the groundwater by nitrates leaching from the sludge
drying basins will be unavoidable under present design conditions.
Land Application Sites for Recycling Sludge
Salt Accumulation in the Region--
The soluble salts in the sludge constitute a cumulative, con-
servative (i.e. not subject to breakdown) pollution of the soils
and waters of the whole region. Their dispersal over a very large
area, as expected in the agricultural scheme, only delays the time
at which their increasing regional concentration will become per-
ceptible. The time frame for such accumulation will probably be a
few hundred years.
Exposure of Burrowing Animals to
Pathogens and Toxic Elements—
No effective long-term mitigation measures exist to prevent
burrowing animals from possible exposure to pathogens and trace ele-
ments by ingestion or direct contact.
Mismanagement and Consequent
Unmitigated Adverse Effects--
Under present plans, no firm controls on the ultimate users of
the sludge are envisioned. The possibility is very real that some
of the recipients will fail to include recommended mitigative measures
in their sludge use activities. This will cause all the negative
impacts enumerated in Section VI, under Land Application in Sludge
Recycling Areas, to be threats to the region.
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Lowry Bombing Range Sludge Disposal
Area (No Action)
Salt Accumulation in Soils--
No mitigation measures exist for the addition and accumulation
of inorganic salts in the soils under present applications rates
and conditions.
Nitrate Pollution of Groundwate'r—
At the current very high annual application rates, far more
nitrogen is introduced into the soil than can be utilized by the
plants. The balance is partly denitrified and partly leached—with
the occasional rainwaters—below the root zone and toward the ground-
water table. The impact upon groundwater quality will not be evi-
dent for many decades because of the very slow rates of unsaturated
flow of water. But eventually, perhaps in 50 to 100 years, impacts
will begin to appear. It will then take many more decades to re-
verse the trend.
Ingestion and Direct Contact with Sludge
by Burrowing Animals—
No effective long-term mitigation measures exist to protect
burrowing animals from the possible exposure and accumulation of
sludge constituents by ingestion or direct contact.
Exposure of Domestic Grazing Animals to
Heavy Metals Accumulation, Viable Pathogens
and Parasites--
Under present practices, domestic livestock graze the sludge-
amended fields without restriction, ingesting sludge along with soil
particles which comprise about ten percent of their regular diet.
To the extent that the "no-action" alternative implies continuation
of this and other existing practices, endangerment of animal health
and the subsequent food chain impact are unavoidable.
Waste of Nutrient Resources—
No mitigation measures exist for the loss of nutrient resources
under a high-annual-rate sludge application program, or when sludge
is landfilled under emergency circumstances.
IRREVERSIBLE AND IRRETRIEVABLE RESOURCE COMMITMENTS
Four main resource commitments are involved in the proposed
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project.
Destruction of Soil Profile
Destruction of the soil profile on 240 hectares [600 acres] of
land at the site of the proposed drying basins is irreversible.
These areas would be forever altered as agricultural areas with their
characteristic soils.
Energy Use
Commitment of fossil fuels to produce energy for treatment, pipe
transport, trucking and other sludge handling processes is necessary
and irretrievable. The total value of this commitment for the pro-
posed action has been estimated to be about eight million KWH per
year. However, it is estimated that total savings in energy use accom-
plished by implementing alternative 2 (compared with the "no-action"
alternative) amount to at least 28 million KWH per year.
Groundwater Use as Receiving Medium
Commitment of the groundwater reservoir as final repository of
soluble salts and nitrates leached from the applied sludge is im-
plicit under present design conditions for the sludge drying and dis-
tribution center. Over several centuries, salt accumulations in the
groundwaters will gradually become increasingly appreciable. It is
a slow but inevitable process that can only be corrected by nature
over a similar length of time after cessation of land application
operations.
Application Site Soil Commitment
Commitment of the soil root zone as a final repository of heavy
metals (and in some locations soluble salts) in the sludge is inevit-
able as long as sludges continue to contain these materials. This
allocation of the soil resource is irreversible in the sense that up-
on completion of the land application it will take many centuries of
continuous cropping to remove the heavy metals, through gradual up-
take, from the soil.
RELATIONSHIP BETWEEN SHORT-TERM USES OF THE HUMAN ENVIRONMENT AND
THE MAINTENANCE AND ENHANCEMENT OF LONG-TERM PRODUCTIVITY
Tne land recycling proposal by Metro will probably have a dura-
tion of 25 to 50 years. This is a rather long period of time, given
the rapidity of change in today's society. Nevertheless, it is a
fair and important question to ask what the implications of the proj-
ect may be for the next few hundred years—with regard to the soils,
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the water and other areas of human environmental concern.
Conservation of Non-Renewable
and Renewable Resources
Such an evaluation can begin with the baseline of how the pro-
posed system compares with the existing Metro sludge handling and
disposal system. At present, high doses of lime, ferric chloride
and polymers are necessary to obtain a dry enough sludge for truck
hauling. Furthermore, the dewatering and trucking operations are
fairly energy-intensive, requiring the use of electricity and fos-
sil fuels.
The Metro proposal represents a positive step in conserving
natural resources by eliminating the need for chemicals. Over a
50-year period, more than 200,000 metric tons [220,000 tons] of
ferric chloride and 450,000 metric tons [500,000 tons] of lime
could be conserved, along with a smaller tonnage of complex fossil-
based polymers. These are chemicals that have little or no value
to Denver area soils or in the landfills.
Overall, there is a net energy saving with the Metro proposal
of at least 8 million KWH per year. While this overall amount rep-
resents a small fraction of the total energy used in the Denver
metropolitan area, it nonetheless represents a significant step
toward an energy efficiency and conservation ethic in wastewater
management. The chief purpose of chemicals and energy in inputs
to the sludge handling process is stabilization and drying of the
sludge. In the proposed system, anaerobic digestion is used in
lieu of chemicals and energy to stabilize the material; the pro-
posed air-drying process represents a shift toward the use of solar
energy in the drying basins, replacing mechanical dewatering sys-
tems, which require much energy, derived from use of non-renewable
fossil fuels. Solar energy is an inexhaustible replacement for
these rapidly diminishing fossil fuels.
In the long term, the recycling of nutrients to the soil rep-
resents a forward-looking step for a society that will have to rec-
ognize the finite limitations of its natural resources. At present
the bulk of our commercial fertilizers is produced from fossil
fuels, particularly natural gas. While future sources of fertilz-
er (especially nitrogen fertilizers) will probably include coal,
this, too, is a fossil fuel which has its limits.^ If nitrogen
that has already been fixed (that is, made chemically reactive, as
is the case with amino acids, proteins, nitrates, ammonia, etc.
found in sludge) is reused, society will be able to make much fur-
ther use of the resources for which there are no substitutes.
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At present, the primary source of phosphorus fertilizer is de-
posits of phosphate that are extremely limited. Because phosphates
in wastewaters are concentrated in sludge as a result of the treat-
ment process, land recycling can be an important long-term mechanism
for reuse of this element, providing soils with one of the macronu-
trients essential for crop production.
A third long-term benefit of land application of sludge from
the Metro system is its effect on soil structure. Sludge contains
large amounts of organic matter; in semi-arid areas of the western
United States, where soils are poorly developed and are high in
clay content, the addition of organic matter to the soil mass im-
proves the friability of the soil and increases its water-retention
capability. Ultimately the soil becomes more porous and allows
greater root penetration. Agricultural experts usually warn against
depletion of the organic matter in soils through exclusive use of
commercial fertilizers. The Metro project could reverse this trend
by recycling carbonaceous matter to the soil.
Potential Cumulative Long-Term Environmental Damage
A long-term view of the Metro proposal must include potential
harmful effects. Because sludge contains elements that may be toxic
or that may occur in combinations that are harmful, the potential
exists for some long-term damage to the productivity of soils for
growing crops.
Many of the trace elements of concern (zinc, copper, iron, etc.)
are micronutrients when found within appropriate ranges of available
concentration in the soil. It is tneir availability in excessive
quantities that can produce toxic or inhibiting effects on plants.
Growing plants continually remove small quantities of these elements
from the soil as they are cropped, but this removal rate is far too
slow to be expected to remedy the effects of rapid additions of tne
elements through sludge application—until centuries after applica-
tion has ceased.
Another undesirable aspect of sludge application is the addi-
tion of salts to the soil profile. Over a long period of time,
salts can have an inhibitory effect on plant growth. This problem
is not confined to the Metro sludge operation but is common to all
irrigated agriculture. Increased salinity of soils has an extreme-
ly harmful effect on the food-producing capability of a region. It
is generally recognized in irrigated agriculture that proper long-
term maintenance of an irrigated soil includes a leaching require-
ment, for flushing these salts below the root zone. This is accom-
plished through application of additional irrigation water, which
cofTinonly is subsequently collected in subsurface drains. While
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potential soil salinity can be remedied by leaching and drainage
in irrigated agriculture, its occurrence on nonirrigated farms as
a result of sludge addition would be inevitable.
Salts can also become contaminants of the groundwater resource.
On any given sludge application area, the total annual salt load
from applied sludge will be fairly small. It is at the sludge dry-
ing and distribution center that the greatest potential for effects
on groundwater can occur, hence the need for lined basins and other
mitigative measures.
The chief measure for avoiding the detrimental long-term ef-
fects of soil salinization and heavy metal accumulation is limita-
tion of the amount of sludge applied to any one area to what is
considered safe for that type of soil and land use. Recommended
safe levels are still somewhat tentative; any long-term assessment
of tnis project must recognize that some effects may conceivably
occur in a manner different from that stated here. However, assum-
ing that no change in sludge heavy metal content will occur, there
is nothing at present to indicate that any completely irreversible
damaging effects on productivity of the soil, through the proposed
sludge application system, might occur.
What is most critically needed for the future is a research
program to find out what can and will happen on various soils with
applications of sludge. Maximum allowable heavy metal loading
rates (hence sludge application limits) may have to be adjusted
downward or upward as experience with actual sludge application be-
comes available. EPA feels that the limits so far recommended rep-
resent a conservative approach to protection of the soil.
The Long-Term Environmental Perspective
EPA feels that, viewed from an overall perspective, this proj-
ect can put into action the goals of the National Environmental Pol-
icy Act. Although that part of iNEPA requiring environmental impact
statements has received the greatest attention, it should be remem-
bered that the basic intent of NEPA is a national environmental pol-
icy integrating the actions of people with their environment. One
item in particular stands out in articulating this policy in the
Act which the proposed project can help achieve:
10(b)(6)...[to] enhance the quality of renewable resources
and approach the maximum attainable recycling of depletable
resources.
The extent to which the proposed project can increase use of
renewable resources (such as nutrients, organic matter and solar
energy) while decreasing dependence on nonrenewable chemicals and
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fossil fuels is considerable. If the additional measures recommended
to protect against untoward effects .(such as groundwater contamina-
tion and heavy metal accumulations) are included, EPA believes that
this project can become a valuable pioneering effort toward building
a society in which recycling and resource conservation are a way of
life.
te fatad
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h
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An important provision of the National En-
vironmental Policy Act is that during the EIS
process responsible public agencies and the pub-
lic must be provided ample opportunity to parti-
cipate and make contribution to the EIS. This
Section is a brief report of the extent and na-
ture of such involvement in the process of prep-
aration of the Draft EIS.
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SECTION VIII
COORDINATION WITH AGENCIES AND PUBLIC INVOLVEMENT
GOVERNMENTAL AGENCIES
During preparation of this Draft EIS, regular contact was main-
tained with the various public agencies charged with responsibili-
ties for the environment, waste management, public health, food safety,
water supplies, agricultural production, soil conservation and other
public concerns related to the project. Among the agencies whose re-
cent, current and planned activities were monitored in relation to
sludge management are:
Various internal EPA units
Metro Denver Sewage Disposal District No. 1
Denver Regional Council of Governments
Colorado Department of Health
Adams County Commissioners
USDA Soil Conservation Service
U.S. Food and Drug Administration
U.S. Bureau of Reclamation
The Preliminary Draft EIS, prepared by Engineering-Science, Inc.
in November, 1975 was reviewed by the EPA and local agencies dir-
ectly involved with the proposed project. The comments received from
their review have been of value in upgrading the present Draft EIS.
PUBLIC INVOLVEMENT
The proposed Metro Denver sludge management program has elicited
significant public reaction. Some of the reaction was solicited by
the District through public meetings and formation of a Citizens'
Advisory Committee, formed in 1972, consisting primarily of represen-
tatives of interested agencies. Interested groups and property owners
near the proposed site were also represented. The members of the com-
mittee were:
Beverly Fleming Keep Colorado Beautiful (Chairwoman)
Gary Eaton Adams County Engineering
Bob Fleming Adams County Planning
Alan Foster Denver Regional Council of Governments
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Jim Fowler Sierra Club, Enos Mills Group, Denver
William Gahr Colorado Department of Health, Engineer-
ing and Sanitation Division
Mike Gansecki U.S. Environmental Protection Agency
Jack Haines Adams County
Richard Heaton Denver Water Board
Bernard Korbitz Presbyterian Medical Center, Department
of Medicine
Glenn Kreag CSU Extension Service, Adams County
Fred Matter Colorado Department of Health, Water
Quality Control Division
Rodney Preator Soil Conservation Service
Elizabeth Richardson League of Women Voters
Steve Rohlf City of Commerce City
Robert Sandquist Adams County
Calvin Tupps Property owner in proposed project area
Way!and Walker City and County of Denver Planning Office
Bob Wardell CSU Extension Service, Adams County
Ann Ziegler Property owner in proposed project area
Bob Ziegler Property owner in proposed project area
While the reactions of environmentalists and public agencies
were generally favorable, the public meetings with citizens of ru-
ral Adams County showed a strong resistance to locating the site in
their vicinity. Earlier plans to locate District facilities in Weld
County had met with similar resistance. The 1972 meeting in Bennett--
a small town in eastern Adams County—drew about 80 persons. The
strongest opinions of those attending the Bennett meeting were the
following (Reference 8):
(1) The sludge application site should not be located in Adams
County.
(2) More experimentation should be conducted before committing
a large land area to sludge application.
(3) The consensus was that sludge application was not approp-
riate for dryland wheat farming.
(4) Subsurface injection of sludge would be preferred rather
than spraying or other means of spreading on top of the ground.
A petition was submitted at this meeting opposing location of
the sludge application in Adams County.
Following the Bennett meeting and a follow-up meeting at the
Adams County Fairgrounds, and on the advice of the Citizens' Advi-
sory Committee, the project was modified to overcome several of the
200
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most serious objections. The revised project was presented in the
March 1974 report "Agricultural Reuse Program" (Reference 5). Citi-
zens and Commissioners of Adams County, however, still expressed
opposition to locating the project in Adams County. At the four pub-
lic meetings in 1974, concerns were again expressed about possible
condemnation of the land required for the site, potential odor prob-
lems, the feasibility of marketing the sludge, land devaluation and
the visual aspects of the facilities. The major outcome of this
public involvement in the project was its influence on the site selec-
tion study. The relatively isolated site finally selected (site B-2
shown in Figure 2) was recommended in large part to minimize adverse
socio-economic impacts and public opposition.
In summary, public involvement in the project since 1972 has in-
cluded seven sessions of the citizens' Advisory Committee and seven
well-attended public meetings (with 75 participants). Persons at-
tending the public meetings were antagonistic towards having the pro-
posed project located near them in Adams County. The substantive
issues brought up (odors, public health hazards, water quality im-
pacts, etc.) are treated elsewhere in this report. Viewed simply
from the point of view of public opinion indices, the meetings dis-
play a negative view of public opinion toward the project. However,
these views may be unrepresentative since those believed to have ob-
jections to the project were contacted for the public meetings, and
the meetings were held near the areas of greatest opposition to the
project.
A meeting held with the Adams County Commissioners as part of
the EIS process (Reference 83) showed that the Commissioners gen-
erally reflected the views of their constituents at the public meet-
ings. While they were not opposed to the proposed project in prin-
ciple, they wished to be more fully assured that potential environ-
mental degradation had been adequately studied, that Metro Denver was
not going to exploit Adams County and that the citizens of Adams
County were not being treated in a high-handed or arbitrary manner.
Environmentalist groups have been in favor of the proposed pro-
ject, generally viewing it as a beneficial reuse of a resource. It
has also been favorably received by the general public (since except
in the case of a very few people, the project is located near some-
one else).
Recent contacts with concerned parties have shown that the gen-
eral attitudes described above are still prevalent at the time of
this study. The farmers of Adams County have on the whole remained
opposed to the proposed project (References 84, 70).
Some farmers within a 32-km [20-mile] radius of the drying sites
have expressed a desire to use the dried sludge (References 85, 86).
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Some have told the District that they are interested in using the
sludge but prefer anonymity because the project is so controversial
in this area. A sampling of some of the favorable responses from
more distant areas is given in Appendix F.
Public Reaction to Drying and Distribution Site
The future project implementation in the area of the drying and
distribution site will probably produce significantly adverse public
reactions. One part of this expected impact is due to the rural/urban
difference between the sludge-generating and sludge-receiving areas.
If the residents of Adams County feel powerless to prevent, and are
unwilling to accept, the project proposed by the more populous region
to the west, public resentment will be inevitable.
A second reason to expect adverse reactions is the history of
such reactions to Metro Denver in Adams County. Opposition appears
to have hardened after years of altercations. Much of this opposi-
tion is perhaps inevitable with projects of this sort: however, even
many sympathetic to the project have said that in the past Metro Denver
public relations programs have left much to be desired (Reference 39).
It will be difficult though not impossible to reverse this unfavor-
able image. The litigation between Metro Denver and Adams County con-
cerning jurisdiction over the proposed project will probably not im-
prove relations, regardless of its eventual outcome. Future litiga-
tion over condemnation of land and rights-of-way would be probable
(Reference 113).
Public Reaction to Land Application Sites
While a generally unfavorable reaction tov/ard the project can be
expected, at least initially, adverse reactions against particular
users of the dried sludge are not expected. A typical example of the
reasons for this can be seen in the case of a representative farm
studied east of Platteville (Reference 85) in Weld County. The farmer
involved is interested in using the dried sludge from Metro and does
not expect any problem with his neighbors. His farm is large—as are
most farms in this general area—and the relative remoteness from the
public makes nuisance conditions unlikely. This particular farmer
has had experience with similar uses of sludge in Denver on lawns
(about 30 years ago) and therefore sees no problem with using it now.
He thinks that odors are not a problem and that some neighboring
farmers are using smellier materials on their own land right now (e.g.,
heat-treated chicken manure from a nearby chicken farm). Such ma-
nure applications are considered an accepted part of farming opera-
tions. Finally, he has farmed his land for 30 years and is confident
that other fanners will generally respect his right to conduct his
operation as he judges best.
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w
h
•I
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References listed in this Section include
published material, unpublished reports and
articles, personal communications, (telephone,
visits, letters, etc.), meeting notes and other
sources of data.
-------
SECTION IX
REFERENCES
1. U.S. Environmental Protection Agency, "Grant Regulations and
Procedures - 30.420-6 Conservation and Efficient Use of Energy",
Federal Register, July 1975.
4
2. Colorado Department of Health, Water Quality Control Commission,
"Water Quality Standards and Stream Classification, Denver,
Colorado", June 19, 1974.
3. Martin, W. J. and J. D. Boyle, "Alternatives for Disposal for
the Metropolitan Denver Sewage Disposal District No. 1", pre-
sented at Second National Conference on Municipal Sludge Manage-
ment Disposal, W18-20, Anaheim, California, August 1975.
4. CH2M HILL, "Sewage Treatment Plant Expansion - Predesign Study",
for Metropolitan Denver Sewage Disposal District No. 1, April
1972
5. CH2M HILL, "Agricultural Reuse Program", for Metropolitan Denver
Sewage Disposal District No. 1, March 1973
6. CH2M HILL, "Metro Denver District Sludge Management, Volume II,
Alternative Systems", February 1975.
7. Brehany, John J., Project Manager for Ralph M. Parsons Co., Per-
sonal Communications, 19 September and 27 October 1975.
8. CH2M HILL, "Metro Denver District Sludge Management, Volume IV
Environmental Assessment", February 1975.
9. Black and Veatch, "Water Quality Management Program, Volumes I
through IV", for Denver Regional Council of Governments, May 1974.
10. U.S. Soil Conservation Service, "Soil Survey of Adams County,
Colorado", October 1974.
11. Officials of NOAA, U.S. Department of Commerce, Climates of the
States, Volume II, Water Information Center, Inc., Port Washington,
New York, 1974.
203
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12. U.S. Department of Commerce, "Decennial Census of United States
Climate - Climatic Summary of the U.S. - Supplement for 1951 -
1960, Climatography of the U.S., No. 86-5, Colorado", Washington,
D.C., 1964.
13. U.S. Department of Commerce, "Climatological Data for the U.S.:
Colorado", 1962-1975.
14. U.S.D.A., Soil Conservation Service, "Soil Survey of Arapahoe
County, Colorado", March 1971.
15. U.S. Geological Survey, "Generalized Surficial Geologic Map of
the Denver Area, Colorado", Miscellaneous Geologic Investiga-
tions, Map 1-731, 1972.
16. Smith, Rex 0., Paul A. Schneider, Jr., and Lester R. Petri,
"Ground Water Resources of the South Platte River Basin in West-
ern Adams and Southwest Weld Counties, Colorado", U.S. Geological
Survey-Water Supply Paper 1658, 1964.
17. Pearl, Richard Howard, "Geology of Ground Water Resources in
Colorado", Colorado Geological Survey, Department of Natural
Resources, Denver, 1974.
18. Schwochow, S. D., R. R. Shroba, and P. C. Wicklein, "Sand, Gravel
and Quarry Aggregate Resources, Colorado Front Range Counties",
Colorado Geological Survey, Department of Natural Resources, Den-
ver, 1974.
19. Adams, W. and Ed Mansfield, "Engineering Geology Case Histories
No. 8, Engineering Seismology: The Works of Man", Prepared for
the Division on Engineering Geology of the Geological Society
of America, Boulder, Colorado, 1970.
20. Price, Don and Ted Arnow, "Summary Appraisals of the Nation's
Ground-Water Resources - Upper Colorado Region", U.S. Geological
Survey Professional Paper 813-C, 1974.
21. McConaghy, J. A. et al., "Hydrogeologic Data of the Denver Basin,
Colorado", U.S. Geological Survey, Denver, 1964.
22. U.S.D.A., Soil Conservation Service, Greeley Office, "Official
soil series descriptions and interpretations for selected soils
in southern Weld County", 1971-1974.
23. U.S. Geological Survey, "Urban Corridor", 1975.
24. Cary, Merritt, "A Biological Survey of Colorado", U.S.D.A. Bureau
of Biological Survey - North American Fauna £33, 1911.
204
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25. U.S.D.A. Soil Conservation Service, "Natural Vegetation of
Colorado", Map and legend, October 1972.
26. Phillips Petroleum Company, Pasture and Range Plants. Bartles-
ville, Oklahoma, 1963.
27. U.S. Department of the Interior, Fish and Wildlife Service,
"United States List of Endangered Fauna", May 1974.
28. Neidrach, R. J., and R. B. Rockwell, Birds of Denver and Moun-
tain Parks, Denver Museum of Natural History Popular Series No.
5, 1959.
29. Peterson, Roger Tory, A Field Guide to Western Birds, Houghton
MiffTin Company, Boston, Mass., 1961.
30. Yocum, C., W. Weber, R. Beidleman and D. Malick, Wildlife and
Plants of the Southern Rocky Mountains, Naturegraph Publishers,
Healdsburg, California, 1969.
31. Beckman, W. C., Guide to the Fishes of Colorado, University of
Colorado Museum, Boulder, Colorado, 1963.
32. Rodeck, H. G., Guide to the Mammals of Colorado, University of
Colorado Museum, Boulder, Colorado, 1963.
33. Beidleman, R. G., Guide to the Winter Birds of Colorado,Univer-
sity of Colorado Museum, Boulder, Colorado, 1963.
34. U.S. Department of the Interior, Fish and Wildlife Service,
"State Lists of Endangered and Threatened Species of the Con-
tinental United States", Federal Register, Vol. 40, No. 127,
July 1, 1975.
35. Colorado Legislature S. B. 142, "Nongame and Endangered Species
Conservation Act", 1973.
36. Tully, R. J., "Endangered Wildlife", in Colorado Outdoors,
Colorado Division of Wildlife, March-April 1973.
37. State of Colorado Department of Health, Air Pollution Control
Commission, "Regulation No. 2 in Odor Emission Regulations",
April 20, 1971.
38. Benci, John, Assistant Climatologist, Department of Atmospheric
Science, Colorado State University, personal communication on
September 3, 1975.
205
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39. Berve, Donn W., Chief of Environmental Health Services, Tri-
County District Health Department, personal communication on
September 4, 1975.
40. Park Superintendant II, Denver General Parks Department, per-
sonal communication on September 4, 1975 and October 9, 1975.
41. Brown, Larry, Environmental Control Engineer, Climax Molybdenum
Company, letter to William Martin of Metro Denver, July 25, 1975.
42. Works Project Administration in the State of Colorado, Colorado:
A Guide to the highest State, Hastings House, New York, 1941.
43. Community Resource Development Cooperative Extension Service,
"Adams County, Colorado: County Information Service", Colorado
State University, Fort Collins, March, 1974.
44. Nichol, Ron, Associate Planner, Department of Planning and De-
velopment, Commerce City, Colorado, written communication on
September 13, 1975.
45. Adams County Board of Commissioners, "Comprehensive Plan: Adams
County, Colorado", 1975.
46. Adams County Planning Commission, "Zoning Regulations: Adams
County, Colorado", 1975.
47. Metropolitan Denver Sewage Disposal District No. 1, "Long Range
Planning Study: 1974", May 31, 1974.
48. Amax Inc., "Comprehensive Plan for Land Reclamation and Stabili-
zation at the Urad Mine", 1975.
49. Denver Regional Council of Governments, "Population Change in
the Seventies",.published pamphlet, 1975
50. Henley, Jan, Economic Analyst, Metropolitan Denver Sewage Dis-
posal District No. 1, personal communication on October 3, 1975.
51. Thompson, Arthur, Statistician, State of Colorado, Office of
State Planning, personal communication on October 1, 1975.
52. Rail, Ellis, Communications Director, Denver Regional Council
of Governments, personal communication on October 1, 1975.
53. Johnston, William, Socio-Economic Analyst, Denver Regional
Council of Governments, personal communication on October 7, 1975.
206
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54. Denver Regional Council of Governments, "Appraisal of the DRCOG
Policy Population Forecast", August 1975.
55. CH2M HILL, "Metro Denver District Sludge Management, Vol.Ill
Agricultural Reuse System Predesign", January 1975.
56. Denver Regional Council of Governments, "Regional Simplified
Base Map", revised December 1971.
57. Colorado Department of Highways, Planning and Research Division
in cooperation with the U.S. Highway Administration, Bureau of
Public Roads, "General Highway Map, Adams County, Colorado",
revised November 20, 1968.
58. Kochevar, Robert, Traffic Engineer, Road and Bridge Department,
Adams County, Colorado, personal communication on August 29, 1975.
59. American Association of State Highway Officials, "A Policy of
Geometric Design of Rural Highways", revised 1973.
60. Colorado Department of Highways, "Colorful Colorado", 1974.
61. Colorado Legislature, "Solid Waste Disposal Sites and Facilities
Law", Chapter 36, Article 23, CRS 1963 as amended by Senate Bill
132, July 1, 1971.
62. Colorado, Colorado Revised Statutes, pertaining to Metropolitan
Sewage Disposal Districts, 1974.
63. Korbitz, William, Manager, Metropolitan Denver, meeting with
management and staff personnel, July 18, 1975.
64. United States Department of Commerce, Bureau of the Census, "1970
Census of Population and Housing, Denver Colorado SMSA", March
1972.
65. United States Department of Commerce, Bureau of the Census, "1970
Census of Population, Colorado General Social and Economic
Characteristics", February, 1972.
66. McDonald, F. M., Deputy Assessor, Adams County, Colorado, personal
communications on September 8, and 11, 1975-.
67. Flanagan, Linda, Research and Analysis Section, Colorado Depart-
ment of Employment, personal communication on October 24, 1973.
68. Adams County Sheriff's Department, Administrative Officer, Brigh-
ton, Colorado, personal communication on October 14, 1975.
207
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69. Mr. Fitch, Fire Chief, Brighton Fire Department, Unit 500,
Brighton, Colorado, personal communication on October 14, 1975.
70. Schwing, James E., CH2M-Hill, Denver, Colorado, personal
communication on October 2 and 17, 1975.
71. VanBeek, Marvin, U.S. Disposal Systems, Commerce City, Colorado,
personal communication on October 1, 1975.
72. Rugtles, Dorothy, Engineering Technicican, and Union Rugtles,
Engineering Technicican, Union Rural Electricity Company,
Brighton, Colorado, personal communication on October 2, 1975.
73. Metropolitan Denver Sewage Disposal District No. 1, "1976 Budget,
1975-1980 Program", August 19, 1975.
74. U.S. Department of Commerce, Bureau of the Census, "Statistical
Abstract of the United States", 1972
75. Ventura County Planning Department, "Ventura County Superregional
Transportation Study, 1974: Environmental Evaluation, part 1",
1974.
76. Mitts, David, Production Operations Manager, Bendini Fertilizer
Company, personal communication on October 6, 1975.
77. Martin, William, Metropolitan Denver Sewage Disposal District
No. 1, personal communication on October 1, 1975.
78. Colorado Legislature, "Solid Waste Disposal Sites and Facilities
Law", Chapter 36, Article 23, Section 5, CRS 1963 as amended by
Senate Bill 132, July 1, 1971.
79. U.S. Environmental Protection Agency, "Technical Bulletin-Muni-
cipal Sludge Management Environmental Facors", preliminary draft,
EPA 430/9-75XXX, July 1975.
80. Council on Environmental Quality in association with the Environ-
mental Protection Agency, "Evaluation of Municipal Sewage Treat-
ment Alternatives", February 1974.
81. Chaney, Rufus L, "Land Application of Sewage Sludge, Benefits
and Probe!ems", Proceedings of the 1973 Lime and Fertilizer Con-
ference, 5:15-23, 1973.
82. Dotson, G. K., "Constraints to Spreading Dewage Sludge on Crop-
land", from "News of Environmental Research in Cincinnati",
Environmental Protection Agency, May 31, 1973.
203
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83. Covy, James, Jerry Grant, John C. Campbell, Adams County Com-
missioners; Ralph Anderson, former Adams County Commissioner;
and Morris Lubow, Adams County Attorney, meeting on September
4, 1975.
84. Kreag, Glen, Adams County Cooperative Extension Service, per-
sonal communication on September 29, 1975.
85. Olin, Ray, Weld County Farmer, personal communication on October
9, 1975.
86. Sharp, William, Adams County farmer, personal communication on
July 30, 1975.
87. Romero, J. C. and E. R. Hampton, Colorado Division of Water Re-
sources and U.S.. Geological Survey, "Maps showing the approxi-
mate configuration and depth to the top of the Laramie-Fox Hills
Aquifer, Denver Basin, Colorado", 1974.
88. Baxter, John, Agricultural Research Specialist, Metropolitan
Denver Sewage Disposal District No. 1, personal communication on
October 1975.
89. U.S. Department of Transportation, "Transportation Noise and its
Control", DOT P5630.1, June 1972.
90. Sandy's Commercial Turf Farm, Brighton, Colorado, personal com-
munication on October 27, 1975.
91. Rambat, John, Reynolds Turf Farms, Brighton, Colorado, personal
communication on October 27, 1975.
92. New, Rex, Denver Turf Farm, Hudson, Colorado, personal communi-
cation on October 27, 1975.
93. Rich, Mel, Rich!awn Turf Farm, Parker, Colorado, personal com-
munication on October 27, 1975.
94. Matthews, William, Matthews Sod Farm, Brighton, Colorado, per-
sonal communication on October 27, 1975.
95. Colorado State Department of Agriculture, "Colorado Agricultural
Statistics, 1974 Preliminary, 1973 Final", Bulletin 1-75, July
1975.
96. Pratt, P. F., "Effects of Sewage Sludge or Effluent Application
to Soil on the Movement of Nitrogen, Phosphorus, Soluble Salts
and Heavy Metals to Groundwaters", presented at 2nd National
209
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Conference on Municipal Sludge Management and Disposal, Anaheim,
California, August 18-20, 1975.
97. Danford, Jack, President, Organic Earthworm Corporation, per-
sonal communication on August 7, 1975.
98. Maphis, S. W., Principal, Briscoe-Maphis, Inc. Deep-six division,
personal communication on August 7, 1975.
99. State of California Air Resources Board, "Emissions Forecasting
Methodologies", July 1974.
100. Trammah, Joseph, Supervising Engineer, Sewage Treatment Plant
Monitoring, Los Angeles Air Pollution Control District, personal
communication on October 3, 1975.
101. Gerardi, Albert, Colorado Air Quality Commission, personal com-
munication on October 3, 1975.
102. Ulwelling, William, "Smells in the Urban Environment", unpublished
research paper on file in the U.C. Berkeley School of Environ-
mental Design Library, 1972.
103. Meyer, Ron, Deputy Director of Public Works, Adams County Road
and Bridge Department, personal communication on October 15, 1975.
104. Spiegel, John, Engineering and Enforcement Officer, Air Pollution
Control Department, Denver, Colorado, personal communication on
October 15, 1975.
105. Straub, Richard, Engineer, Weld County Engineering Department,
Greeley, Colorado, personal communication on October 15, 1975.
106. Searne, Robert, Staff Coordinator, Mayor's Task Force for the
Platte River Development Committee, Denver Planning Department,
Denver, Colorado, personal communication on October 15, 1975.
107. Hornback, Kenneth E., Joel Guttman, et. al., "Studies in Environ-
ment: Quality of Life, Volume II", prepared for Office of Re-
search and Development, November 1973.
108. Roll, John L., Metropolitan Sanitary District of Greater Chicago,
personal communication on September 15, 1975.
109. Thomas, Harold J., Manager, Mountain Bell Telephone Company,
Aurora, Colorado, personal communication on October 6, 1975.
210
-------
110. McGauhey, P. H., and R. B. Krone, "Soil Mantle as a Wastewater
Treatment System", Sanitary Engineering Research Laboratory
Report 67-11, University of California Press, Berkeley, 1967.
111. Bernenson, Abram, ed., Control of Communicable Disease in Man,
American Public Health Association, Washington, D.C., llth
edition, 1970.
112. Feth, J. H., "The Urban Environment", U.S. Geological Survey,
Circular 601-1, 1973.
113. Deline, James, Mohaghan Farms Manager, personal communication
on October 2, 1975.
114. Cohen, David B., William J. Martin and John Baxter, "Agricul-
tural Reuse Program: Applied Research and Development Budget
(1975-76)", Metropolitan Denver Sewage Disposal District No. 1,
January 16, 1975.
115. U.S.D.A., "Diagnosis and Improvement of Saline and Alkali Soils,
Agriculture Handbook No. 60", February 1954.
116. Chaney, Rufus L, "Crop and Food Chain Effects of Toxic Elements
in Sludges and Effluents", In Proceedings of the Joint Confer-
ence on Recycling Municipal Sludges and Effluents on Land, U.S.
Environmental Protection Agency, U.S.D.A., and the National
Association of State Universities and Land Grant Colleges,
Champaign, Illinois, July 9-13, 1973.
117. Wood, Gene W., D. W. Simpson and R. L. Dressier, "Effects of
Spray Irrigation of Forests with Chlorinated Sewage Effluent
on Deer and Rabbits", In Recycling Treated Municipal Wastewater
and Sludge through Forest and Cropland, Edited by William E.
Sopper and Louis T. Kardos, Pennsylvania State University Press,
University Park, 1973.
118. CH2M HILL, "Metro Denver District Sludge Management, Volume I:
Summary Report", February 1975.
119. Mr. Frandsen, Construction Engineer, District 1, Colorado Divi-
sion of Highways, Denver, Colorado, personal communication on
October 15, 1975.
120. Kelly, George T., Supervising Architect/Planner, Metropolitan
Sanitary District of Greater Chicago, personal communication
on September 17, 1975.
121. Engineering-Science, Inc. /'Pipeline Transport of Digested Sludge
to Strip Mine Spoil Site for Spoil Reclamation", August 1975.
211
-------
122. King, L. D. and H. D. Morris, "Land Disposal of Liquid Sewage
Sludge: I. The Effect on Yield, in vivo Digestibility, and
Chemical Composition of Coastal Bermuda Grass", Journal of
Environmental Quality, Vol. 1, No. 3, 1972.
123. Sabey, B. R. and W. E. Hart, "Land Application of Sewage Sludge:
1. Effect on Growth and Chemical Composition of Plants", Jour-
nal of Environmental Quality. Vol. 4, No. 2, 1975.
124. Lagerwerff, J. V., "Heavy-Metal Contamination of Soils, in
Agriculture and the Quality of Our Environment", American
Association for the Advancement of Science, Washington, D. D.,
1967.
125. Westfall, D., Agronomist, Great Western Sugar, Longmont, Colorado,
personal communication on July 30, 1975.
126. Epstein, Eliot, "Effect of Sewage Sludge on Some Soil Proper-
ties", Journal of Environmental Quality, 4(1): 139-142, 1975.
127. Scott, M. L., "Trace Elements in Animal Nutrition", In Mi erg-
nutrients in Agriculture, Edited by J.J. Mortvedt, P. M.
Giordano and W. L. Lindsay, Soil Science Society of America, Inc.
Madison, Wisconsin, 1972.
128. Chaney, Rufus L., "Recommendations for Management of Potentially
Toxic Elements in Agricultural and Municipal Wastes", In Factors
Involved in Land Application of Agricultural and Municipal Waste,
USDA, ARS, Beltsville, Maryland, 1974.
129. Epstein, E. and G. B. Willson, "Composting Raw Sludge", in Pro-
ceedings of the 1976 National Conference on Municipal Sludge
Management and Disposal, Anaheim, California, August 1975.
212
-------
ENVIRONMENTAL TEAM
MICHAEL A. GANSECKI, B.S., M.S.
*BAHMAN SHEIKH-OL-ESLAMI, Ph.D.,
P.E.
JOHN A. DAVIS, M.S., M.I.C.E,
P.E.
*SAMUEL B. EARNSHAW, B.A., M.A.,
B.S.
*EMY CHAN, A.B.
TARAS A. BURSZTYNSKY, M.S.,
P.E.
PATRICIA SHOWALTER, A.B.
PHILIP N. STORRS, M.E., P.E.
MARY STAUDUHAR, B.A.
Project Officer; Legal and Ju-
risdictional Aspects, Alter-
natives Evaluation, Summary
Project Manager; Agriculture,
Soils, Water
Sanitary Engineering, Alterna-
tives Evaluation
Vegetation, Sludge Reuse
(Appendix D)
Fauna, Habitats, Graphic Arts,
Noise
Sanitary Engineering, Alterna-
tives Evaluation
Geology
Technical Direction
Editing, Typing Supervision
ALAN D. KOTIN, M.A.
GEORGE A. JOHNSON, M.B.A., M.S.
*WILLIAM P. ULWELLING, M.P.H.
*JANICE HARWELL, M.A.
SHLOMO BACHRACH, M.A.
Economics
Economics
Public Health, Socioeconomics
Socioeconomics
Socioeconomics, Coordination
Members of the Association of Environmental Professionals
213
-------
•llll
•
-------
This Appendix contains the cost, engineering
and environmental evaluations of basic process al-
ternatives for sludge handling and disposal by
EPA's consultant—Engineering-Science, Inc. (ES).
ES concludes that the "apparent best alternative"
is the system proposed by the Metro District. The
Appendix also contains a detailed description of
each alternative considered. Process flow diagrams,
with sludge quantities passing through the process
train, are presented. Pertinent assumptions in de-
sign and cost calculations are listed.
-------
APPENDIX A
EVALUATION OF ALTERNATIVE SLUDGE HANDLING
AND DISPOSAL SYSTEMS
INTRODUCTION
In the course of its efforts to improve its sewage sludge manage-
ment practices, Metropolitan Denver Sewage Disposal District No. 1 re-
tained an engineering consultant (CH2M Hill) to study alternative
sludge processing and disposal systems and to recommend the best alter-
native. The results of the consultant's work are contained in a four-
volume report, Volume II of which is entitled "Alternative Systems"
(Reference 6).
Part of the present study involves an independent evaluation of
the alternatives considered by the consultant, together with others,
prior to assessment of the environmental impacts associated with the
more promising alternatives. The material contained in this section
summarizes the results of this independent evaluation. A more de-
tailed description of the alternatives, with flow process diagrams,
and their associated costs is included at the end of this appendix.
SYNTHESIS OF ALTERNATIVES
In order to compare alternatives in an equitable manner, the basic
principle that each system must be complete in itself was adhered to.
Thus, the complete system must take as its starting point the raw and
digested sludges at the Central Plant, and as its end a disposal mode
that is truly final; that is, a disposal mode requiring no further ac-
tion to process or transport the sludge.
ALTERNATIVE SYSTEMS
Sixteen alternative systems were considered, eight of them similar
to those evaluated and reported by CH2M-Hill. For convenience, the
numbering system used in the consultant's report has been retained.
Thus, Alternatives 1A through 8 are those evaluated by CH2M-Hill.
Alternative 1A Existing system, waste-activated and other
sludges trucked to Lowry Bombing Range for
landspreading
A-l
-------
Alternative IB
Alternative 2
Alternative 3
Alternative 4
Alternative 5
Alternative 6
Alternative 7
Alternative 8
Alternative 9
Alternative 10
Alternative 11
Alternative 12
Alternative 13
Alternative 14
Alternative 15
Alternative 16
Existing system with anaerobic digestion
Anaerobic digestion, pipeline transport,
air drying and beneficial reuse (prod-
uct: 100 percent air-dried sludge)
Filter presses, incineration, landfill
of ash
Heat treatment, vacuum filtration, land-
fill
Heat treatment, air drying, landfill
Heat treatment, vacuum filtration, in-
cineration, landfill of ash
Anaerobic digestion, filter presses,
compost (product: 100 percent nutrient-
enriched composted sludge)
Filter presses, compost (product: 100
percent nutrient-enriched composted
sludge)
Anaerobic digestion, centrifugation, com-
post (product: 100 percent nutrient-
enriched composted sludge)
Anaerobic digestion, pipeline transport,
air drying, compost (product: 50 per-
cent air-dried sludge; 50 percent
nutrient-enriched composted sludge)
Anaerobic digestion, centrifugation,
landfill
Anaerobic digestion, pipeline transport,
air drying, landfill, compost (product:
33 percent air-dried sludge; 33 percent
nutrient-enriched composted sludge; re-
mainder to landfill)
Anaerobic digestion, vacuum filtration,
compost (product: 100 percent nutrient-
enriched composted sludge)
Vacuum filtration, compost (product: 100
percent nutrient-enriched composted
sludge)
Anaerobic digestion, vacuum filtration,
pipeline transport to solid waste re-
cycling plant
Vacuum filtration, pipeline transport to
solid waste recycling plant
A-2
-------
Reviewing the alternatives briefly, alternatives 1A and IB are
variations of the existing system of processing at the Central Plant,
with truck-haul to Lowry Bombing Range for incorporation into the soil.
Alternative 2 is the sytem recommended by CH2M HILL, slightly modified.
As evaluated by CH2M-H111, the final product of this system was a
stored stockpile of air-dried sludge, the presumption being that users
of the sludge would haul the product from the stockpile to the final
reuse sites. As evaluated here, the truck-haul to the use site is in-
cluded as part of the total system. Alternatives 3, 4, 5, 6 and 11
are options for processing prior to landfill. Alternatives 7, 8, 9,
13 and 14 are options for processing prior to composting and sale.
Alternatives 10 and 12 are variations on Alternative 2, but with a dif-
ferent product mix.
Alternatives 15 and 16 are options for processing prior to trans-
port to a regional solid waste processing plant. The feasibility of
these alternatives is currently being studied by Ralph M. Parson, Inc.
for the Denver Regional Council of Governments. The alternatives con-
sidered here are based on the assumption that the solid waste process-
ing plant would be located 5 km [3 miles] distant from the District's
plant and that digested sludge, at 25 percent solids content, would be
accepted at the processing plant at no charge to the District (Refer-
ence 7).
COST OF ALTERNATIVE SYSTEMS
Economic evaluation of alternative sytems which incur future
costs and accrue future benefits, always difficult, has become increas-
ingly so in a time of severe price inflation and doubt concerning fu-
ture resource costs and availability. In view of these difficulties,
it is not surprising that differences of opinion exist in the engineer-
ing profession vis-a-vis the costs of certain processing and disposal
activities.
The approach adopted in reevaluating the alternatives was to ac-
cept previous cost assumptions unless it appeared that an error of judg-
ment had been made which might have a significant effect on the compar-
ative costs of alternatives. After thorough review, the earlier assump-
tions were found to be generally acceptable, an exception being the
omission of salvage values from the cost calculations. This omission
has been rectified in order to conform with EPA cost-effectiveness
guidelines. A more detailed discussion of cost assumptions is included
elsewhere in this appendix.
The presentation of system costs is prefaced by a brief discussion
of several factors that influence the economic evaluation.
A-3
-------
Revenue
All systems considered that involve beneficial reuse have a poten-
tial for revenue generation. However, the market for sewage-sludge-
derived products is somewhat uncertain; demand is low and competitive
products are still relatively cheap and abundant. The potential reve-
nues from beneficial reuse to be accrued in the Denver area have been
estimated conservatively on the basis of experiences in other locations.
Because of the doubts about the marketability of the products, the cost
of each alternative assuming no revenue is presented in the cost tabu-
lation together with a cost adjusted for revenue.
Inflation
Cost-effectiveness analysis guidelines published by the U.S. Envi-
ronmental Protection Agency dictate that the effect of inflation should
be neglected in cost comparisons of alternatives. The basis for this
is the belief that, although future costs will escalate, the ability
of the users to pay these costs will also escalate at the same rate.
In addition, the discount rate used in the present-worth calculations
is intended to take account of the declining value of money, the cost of
borrowed funds and the opportunity cost of money. Because the alterna-
tive sludge management systems range from those with a high initial capi-
tal cost and low operating expenses to those with low initial capital
costs and high operating expenses, the role of inflation in the cost com-
parison is crucial. For this reason, comparative costs are presented
first without an inflationary factor and a second time with an inflation-
ary factor of 8 percent.
Sunk Costs
A further difficulty was encountered in establishing a basis for
equitably comparing the alternatives. Recently, the District began
implementation of a plan to construct new anaerobic digesters. How-
ever, some of the alternatives being considered do not include anaero-
ic digestion as a necessary step in the total system. The question
arises whether the cost of the digesters should be regarded as a sunk
cost, to be ignored in the evaluation, or (since the funds are com-
itted and construction is about to begin) be included in all alterna-
ives, irrespective of the need for this system component. Adopting
either of these approaches penalizes alterantives that do not include
anaerobic digestion. Because of this problem, the cost comparison was
made in two ways: first, and most logically, the total costs of each
system were compared, including a cost for digestion only where tech-
nically necessary; second, recognizing the realities of the situation,
a comparison was made treating the digestion cost as a sunk cost.
A-4
-------
Comparative Cost of Alternatives
Table 1 shows the present-worth cost of ten years of operation of
each of the alternative systems. Similar information is presented in
Table 2, but in this case the capital cost of the new anaerobic diges-
tion system is treated as a sunk cost. A notable feature of the cost
comparisons is the apparent economic attractiveness of alternatives 15
and 16, those that involve delivery of sludge to a regional solid waste
processing facility. It should be remembered that at this stage these
alternatives are poorly defined; the corresponding cost estimates are
inevitably lacking in precision. Of course, the viability of these
alternatives is predicated upon the existence of a facility of this
type in the future. Because of the uncertainty, these alternatives are
not strictly comparable with the other alternatives considered and are
neglected in the following discussion. However, alternatives 15 and
16 are worthy of serious evaluation; further remarks on this subject
are contained in the discussion that concludes this section.
A review of Table A-l indicates that if inflation and revenue-
generation potential are ignored then Alternative 2, the recommended
plan, is one of a group of less costly alternatives, although by no
means the least costly. If selection were to be based on this cri-
terion alone, then Alternative 2 offers no notable economic advantages.
Considering the uninflated cost with revenue taken as a credit,
Alternative 2 is again one of a group of less costly alternatives, but
again not the cheapest. However, it should be noted that those alter-
natives that become significantly less expensive than Alternative 2
rely heavily upon revenue generated from sales; and, of course, doubts
exist regarding the saleability of the product.
Turning to the cost comparison adjusted for an 8 percent inflation
rate, the advantages offered by Alternative 2 become more apparent.
Even if no revenue is accrued, Alternative 2 is the least expensive.
If in fact sludge users collect dried sludge from the processing as
assumed in the original evaluation, then the total cost of Alternative
2 will be reduced still further.
Table A-2 shows the cost of alternative systems treating the capital
cost of anaerobic digestion as a sunk cost. As noted previously, this
reduces the apparent cost of all alternatives that include anaerobic
digestion. Thus the economic advantages of Alternative 2 are empha-
sized in the cost comparison.
ENVIRONMENTAL IMPACT OF ALTERNATIVE SYSTEMS
The environmental effects of the alternative systems fall into
two general categories: the on-site effects—that is, the effects re-
A-5
-------
Table A-l. COST OF ALTERNATIVE SYSTEMS
(million dollars)
i
en
Present-worth cost of
Unadjusted
Alternative
1A
IB
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
without revenue
24.1
24.7
24.0
24.2
22.5
33.3
23.6
30.3
34.0
33.8
28.8
26.4
28.9
28.4
27.0
16.8
10.1
with revenue
24.1
24.7
19.3
24.2
22.5
33.3
23.7
19.6
17.0
25.9
20.5
26.4
20.7
20.5
14.5
16.8
10.1
ten years of operation
Adjusted for 8% inflation
without revenue
34.3
30.1
17.7
26.8
25.9
30.2
23.6
35.1
45.1
40.1
24.4
30.8
24.5
33.8
36.4
17.8
13.3
with revenue
34.3
30.1
10.8
26.8
25.9
30.2
23.6
19.3
20.1
28.5
12.3
30.8
12.4
22.2
18.0
17.8
13.3
-------
i
--J
Table A-2. COST OF ALTERNATIVE SYSTEMS TREATING THE CAPITAL COST
OF ANAEROBIC DIGESTION AS A SUNK COST
(million dollars)
Present-worth cost of
Unadjusted
Alternative
1A
IB
2
3
A
5
6
7
8
9
10
11
12
13
14
15
16
without revenue
24.1
18.6
17.8
24.2
22.5
33.3
23.7
24.2
33.9
27.6
22.7
20.2
22.8
22.2
30.0
10.6
10.1
with revenue
24.1
18.6
13.1
24.2
22.4
33.3
23.7
13.5
17.0
19.8
14.4
20.1
14.5
14.4
14.5
10.6
10.1
ten years of operation
Adjusted for 8% inflation
without revenue
34.3
26.4
14.0
26.8
26.0
30.2
23.6
31.4
45.1
36.3
20.7
27.1
20.9
30.1
36.4
14.1
13.3
with revenue
34.3
26.4
7.1
26.8
26.0
30.2
23.6
15.6
20.1
24.8
8.6
27.1
8.7
18.5
18.0
14.1
13.3
-------
suiting directly from and at the site of the project components; and
off-site effects. Off-site effects are the effects of the ultimate
sludge disposal method used on the receiving environment.
Volume IV of the Sludge Management report to the District (Refer-
ence 8 in Section IV of the main text) is an environmental assessment
of the alternative systems. The analysis emphasizes on-site impacts and
concludes that Alternative 2 is the best option from an environmental
standpoint. Off-site impacts are the subject of detailed analysis in
subsequent sections of this report.
An independent review of the earlier assessment of on-site impacts
led to general concurrence with the major conclusions presented. The
more significant points emerging from the review are discussed below.
Process Options
Many of the alternatives are different only in that they employ
different methods for stabilizing and dewatering sludge. The direct
environmental implications of these different processing options are
relatively insignificant when compared to the environmental consequences
of different transportation and ultimate disposal methods. One excep-
ion to this is the relative resource economy of the processing options.
All alternatives that include vacuum filters, filter presses, incinera-
tors or heat treatment systems require chemicals and fuel for success-
ful operation. Alternative 2, which employs anaerobic digestion, re-
quires neither. In a time of doubt concerning future energy and mater-
ials costs and availability, the processing element of Alternative 2
offers a significant advantage.
Transportation
Alternatives 2, 10 and 12 involve pipeline transport of digested
sludge to a remote location, while the remaining alternatives involve
trucking of dewatered sludge or ash to an ultimate disposal site.
Pipeline transport is superior because it consumes less energy, does
not involve vehicular air-pollutant emissions and does not involve
long-term impacts upon the community arising from traffic and noise.
PERFORMANCE OF ALTERNATIVE SYSTEMS
In this context, the performance of a sludge management system is
used as an index of its effectiveness as a method of residual solids
disposal. A number of elements contribute to system performance; they
include process reliability, susceptibility to random physical and cul-
tural disruption (due to earthquakes, labor disputes, etc.), suscepti-
bility to resource shortages, and permanence.
A-8
-------
Process Reliability
Some of the process components of the alternatives are inherently
more reliable than others in making the required changes in sludge
quality. Anaerobic digestion and air drying, the processes employed
in Alternative 2, are well understood and widely applied. Properly de-
signed and operated, they are proven to be reliable. Vacuum filtra-
tion (employed in alternatives 1A, IB, 4, 6, 13 and 14) is probably the
most reliable of the mechanical dewatering methods, followed by centrif-
ugation (employed in alternatives 9 and 11) and filter presses (used in
alternatives 3, 7 and 8). Incineration is a reliable process but is
inherently more hazardous than are the mechanical processes. Heat
treatment systems are not widely applied and have incurred some problems
in continuous operation.
Susceptibility to Disruption
All alternatives involve processing activities at the main plant
which would be disrupted during a labor dispute; the more complex pro-
cessing options are more vulnerable, however, due to the need for con-
tinuous operation by skilled personnel. Pipeline transport would be
less likely to be subject to disruption during a labor dispute than
would trucking because it is not a labor-intensive operation. With
respect to disruption of ultimate disposal operations, Alternative 2
would be less vulnerable than would other alternatives by virtue of its
considerable storage capacity.
Alternatives involving pipeline transport are more vulnerable to
disruption due to physical phenomena such as earthquakes and accidental
damage during other, unrelated human activities. However, the Denver
region is not particularly earthquake-prone, as discussed in the section
on environmental setting.
Susceptibility to Resource Shortages
An alternative's susceptibility to resource shortages is directly
related to its requirements for energy and chemicals. All alternatives
that employ truck haul are relatively high energy consumers. All alter-
natives that involve mechanical dewatering are relatively high chemical
consumers. By virtue of its processing method (anaerobic digestion),
its transportation method (pipeline transport) and its use of free solar
energy for dewatering, Alternative 2 emerges clearly as the best option
with respect to this evaluation factor.
Permanence
Assuming that no unforeseen regulatory or physical constraints
emerge, all alternatives considered can represent permanent solutions
A-9
-------
to the sewage sludge disposal problem. Permanent, in this context,
means having a life in excess of 100 years.
THE APPARENT BEST ALTERNATIVE
An independent evaluation of the alternative sludge management
systems led to a general concurrence with the results of the earlier
evaluation, indicating that Alternative 2, anaerobic digestion, pipe-
line transport, air drying and beneficial reuse, is the apparent best
alternative. This conclusion is drawn on the basis of the following:
1. It is economically attractive, particularly when inflation
is taken into account.
2. Its economic appeal does not depend heavily upon revenue
from sales that may not, in fact, occur.
3. It is flexible: the product mix can be adapted to the
needs of the ultimate user; even under the worst circum-
stances, air-dried sludge in excess of need could be
landfilled without seriously increasing costs.
4. It is conservative of energy and materials.
5. Its on-site environmental impacts are generally less
serious than those resulting from the other alternatives.
Disadvantages of Alternative 2 are some doubt regarding long-term
off-site effects (discussed in detail in a later section) and high ini-
tial cost. A cost-benefit analysis of Alternative 2 is included as
Appendix G.
Because of the present funding arrangements for water pollution
control facilities, projects with a high capital cost and low operating
cost attract a larger proportion of Federal and State funds than do
projects with low capital cost and high operating cost. Thus it is in
the interest of local agencies responsible for sewerage service to
select capital-intensive projects in order to maximize financing by
outside agencies and minimize local user charges. On the other hand,
it may be in the interest of the outside funding agencies to adopt an
opposite approach in order to maximize the local share and distribute
the available grant funds to a larger number of individual projects.
Basically, high initial capital cost can be regarded as a disad-
vantage only if its investment does not bring a return in terms of
significantly reduced total costs. In the case of this project, and
accepting that inflation should be accounted for in the cost calcula-
tions, it appears that the initial capital investment does in fact
result in significantly reduced costs.
The cost estimates for alternatives 15 and 16 (processing and
A-10
-------
transport to a regional solid waste processing plant), admittedly some-
what lacking in precision at this stage, do indicate tnat economically
these options and Alternative 2 are equally attractive. This is par-
ticularly true if sludge can be delivered to the plant undigested in
order to retain a higher heat value. Although Alternative 2 is pres-
ently the apparent best alternative, it is recommended that a detailed
environmental analysis of alternatives 15 and 16 be undertaken if there
is a decision to implement a regional solid waste processing facility.
DETAILED DESCRIPTION OF ALTERNATIVES AND
PROCESS FLOW DESIGNS
Alternative 1A
Alternative 1A will involve the continuation of existing modes of
sewage sludge disposal. The Denver Northside Plant will, in 1985, de-
liver 20 metric tons [approximately 20 short tons] of dry sewage sludge
to the Central Plant to be put into storage tanks. From the storage or
holding facilities, sludge would be withdrawn and receive polymer con-
ditioning, here estimated at 4 kg/inetric ton [10 pounds per short ton]
of sludge solids. The conditioned sludge would be dewatered on coil
vacuum filters and trucked to the Lowry Bombing range, where smaller
appropriate vehicles would apply the sludge to the land.
It is envisioned that the present vacuum filter capacity would
need expansion to accommodate future flows, and chemical conditioning
facilities would be added with the new coil vacuum filters. Expanded
dewatered sludge hauling needs would necessitate the use of additional
trucks. Existing coil filters would need repairs and renovation, as
will the filtration building.
It is believed that the existing waste-activated sludge thickener
can be used to thicken future design flows.
Alternative IB
This alternative, similar to Alternative 1A, represents continua-
tion of the existing system but with anaerobic digestion as an early
processing step. This results in a marked reduction in dry solids to
be handled in subsequent processing and disposal steps.
Alternative 2
Alternative 2 embodies the basic concept of beneficial sludge
reuse through soil conditioning. All waste sludges would be anaerobi-
cally digested and then pumped, unthickened, to a drying and distribu-
tion center. The drying and distribution center, which is discussed in
detail in Metro Denver District Sludge Management, Volume III, Agricul-
tural Reuse Predesign, would air dry the sludge and stockpile it for
A-ll
-------
1
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CENTRAL 88 W.A.S
W.A.S (97) THICKENING
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UNITS ARE METRIC TONS (EC
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O COIL
5kg/metric ton V VACUUM LOWRY BOMBING
QK rnFN>iirAi / Q^ FILfEKS TRiirkiwr RANGE (INCORPORATION
1 95 CHEMICAL / 95 TRUCKING IMTO TUC QHII i
iirKTwiwr; • ,. ..1,1 1 I,.HIM/' / •»' — \ INTO THF son )
IICKLNING- •» CONUI ! lUNIIMt, / (|nc,,y \
(iaj) W/POLYMER^4 (I05V , ) DL -, ,
V / qi ^^ /*^\ rH
(10 IbAhort ton ) v 1 J 3I to> 1— •» 1 — r- ^V-1.!
^ w vium/.nori ion, ^i^ (|00) TY")" O yT\ J 0
DECANT FILTRATE
TO TREATMENT TO TREATMENT
JGLISH SHORT TONS IN PARENTHESES) OF DRY SOLIDS PROCESSED DAILY.
O
c
m
-------
CENTRAL 88 W.A.S
W.A.S (97) ^ THICKENING
CENTRAL 45 fc
PRIMARY (49) "
NORTH SIDE IB
DIGESTED (20)
CENTRAL 86 fc W.A.S.
W.A.S. (97) THICKENING
CENTRAL 45 m
PRIMARY (49) ""
NORTH SIDE l8 ^
ALTERNATIVE 2
STORAGE AND
133 ANAEROBIC 79 DISTRIBUTION
/I/KM more-Tinm IO7\ PUMPING DRYING BEDS ....
(146) DIGESTION 187) q7 ^ f /$>&
97 / J tiny) ^7 i \c\7\ >5?9?R^i
(I07) V_/ 95(105) '
ALTERNATIVE 3
FILTER PRESS INCINERATION TRUCKING LANDFILL
P,.—
n J L
T \ \ x" ^*~~~V
,m CHEMICAL / IQ7 , > 1 , IQK 1 1 70 — i
151 J CONDITIONING <5/ | ^ ^C=l-=3 196 ^ | 76 „ | pL, ^ |
(166) W/LIMEAND ° ^l/» 1 , > (**>> \ IB«» • OO ^ X
FERRIC CHLORIDE L- xi y/////////////S/ r///^^^^^//'
(620 Ib/short ton) l~" (ftj 'V/Zffffi//
FILTRATE
PRIMARY (20) TO TREATMENT
DIGESTED
UNITS ARE METRIC TONS (ENGLISH SHORT TONS IN PARENTHESES) OF DRY SOLIDS PROCESSED DAILY.
o
c
ZJ
m
-------
E»
_J
pi
rn
Z
en
z
m
m
3)
Z
O
1
CO
0
m
z
o
m
z
o
CENTRAL 88 W.A.S.
W.A.S. (97) THICKENING
CENTRAL 45
PRIMARY (49)
NORTH SIDE l8 B
PRIMARY (20)
DIGESTED
CENTRAL 88 „ W.A.S.
W.A.S. 197) THICKENING
fFMTPJAI 45 ^.
PRIMARY (49)
NORTH SIOF l8 fc
ALTERNATIVE 4
1 HEAT COOL AND
TREATMENT DECANT
CLOTH
•^ r VACUUM
151 151 FILTER
(166) "~ (166) 1 TRUCKING LANDFILL
WWW ' 35
/\ >88888£ , . ,„, — ^^ ^\
/ \ »»•»»»• (149) / \
•^ ui P \ 1 / 133
•" ^~\ (147)
* Z 1 riMW...
* (2) '///x^///
r- 0}
DECANT a FILTRATE
TO TREATMENT
ALTERNATIVE 5
a
_J V
g-' \
'"//' '^'%>*$i$>$$§$!:/$$/^/f'
HEAT COOL PUMPING DRYING BEDS TRUCKING LANDFILL
TREATMENT
•^ f" "| r ^ 151 133-142
51 '5 1^. '5'^ ^(166)^ p= / (146 156)^
^ — v
f ~\r ^ F "V ^
(166) (166) (\66)\^ 2? ?/////////>//, WfatfSBSSBtf'''
\ 1 oiiQ
V()j LEACHATE
TO TREATMENT
'///////////
PRIMARY (20) ~~
DIGESTED
UNITS ARE METRIC TONS (ENGLISH SHORT TONS IN PARENTHESES) OF DRY SOLIDS PROCESSED DAILY.
-n
o
c
3]
m
>
i
rT
0
;-»
-------
CENTRAL 88 W.A.S. _^
W.A.S (97) THICKENING ~~^
CENTRAL 45 l51
PRIMARY (49) •" (I66
NORTH SIDE '8
PRIMARY (20)
DIGESTED
CENTRAL 88 W.A.S.
W.A.S. 7q?) THICKENING "^
'33 ANAEROB
(,46)DIGESTIO
CENTRAL 45
PRIMARY (49)
NORTH SIDE IB
ALTERNATIVE (
i%
HEAT COOL AND
TREATMENT DECANT
CLOTH
•\ r VACUUM
151
) (166)" |
/-i $$8$8$ */
in r-
2
-IF
N (J>
i '^~*
DECANT a FILTRAT
TO TREATMENT
ALTERNATIVE
C 79 0
N (HrT ^l(^ kg /metric ton J*
' f
97 T 95 CHEMICAL / |
007) |tl05lw/LIMEAND^ (1
1 FERRIC CHLORIDE
"1^ (620 Ib/short ton)
DECANT
PRIMARY (20) " 1U '"tM"vlt"'
DIGESTED
UNITS ARE METRIC TONS ( ENGLISH SHORT TONS IN PARENTHESES ) OF D
FILTER INCINERATION TRUCKING LANDFILL
r" x r-i
J>"J 1«. *! .
(147) 1 (44) nn p ^
I ^ /////Y/////S/S '//fy,sG$$$&s0/'/''
E
7
^BULK
^SALE
FILTER PRESS TRUCKING COMPOSTING
25^ ' ' 1 124^ °j-] ^$&. ^ /^A
^«) i —1(1^7) on p ,^^8^, A / f /
1 Y////////////, 'TV//////, T [ \j/
r-- BAGGING
FILTRATE NUTRIENT
TO TREATMENT ADDITION
RY SOLIDS PROCESSED DAILY.
0
C
;o
m
>
rT
o
-------
ALTERNATIVE
8
ENTRAL
W.AS
CENTRAL 45
PRIMARY (49)
NORTH SIDE l8
PRIMARY (20)
DIGESTED
FILTER PRESS
TRUCKING
COMPOSTING
310 kg/metric ton
151
(166)
CHEMICAL /
CONDITIONING*^
W/LIME AND
FERRIC CHLORIDE
197
196
(217)
(216)
b
CJ
BULK
SALE
(620 Ib/short ton)
BAGGING
FILTRATE
TO TREATMENT
NUTRIENT
ADDITION
ALTERNATIVE
9
W.A.S
CENTRAL 45
PRIMARY (49)
NORTH SIDE
PRIMARY
DIGESTED
5 kg/metric ton
CHEMICAL
CONDITIONING
W/POLYMER
(10 Ib/short ton)
CENTRIFUGATION
CENTRATE
'(5) TO TREATMENT
DECANT
TO TREATMENT
(20)
BULK
'SALE
TRUCKING
BAGGING
NUTRIENT
ADDITION
UNITS ARE METRIC TONS (ENGLISH SHORT TONS IN PARENTHESES) OF DRY SOLIDS PROCESSED DAILY.
3!
o
c
33
m
o
o
-------
CENTRAL 88 W.A.S.
~~w:A.s"~l^r THICKENING ~+\ |33_ ANAEROBIC 79^
(146) DIGESTION (87)
CENTRAL 45 fc
PRIMARY (49) ^
NORTH SIDE 18 _
PRIMARY (go)
DIGESTED
fTMTDAI flfl W A *•} , .... •.
W.A.S. (97) m THICKENING 133 ANAEROBIC 79
'"- - (KeT DIGESTION (87*
CENTRAL 45
PRIMARY (49)
NORTH SIDE '8 fc
ALTERNATIVE 10
PUMPING DRYING BEDS STORAGE
^ 1 97 fcv 95(105) , /ggi
9/ / t-J MH71 V / ^^-^^^ /vVyxx mil i/
(I07)V_/ i^^Vx SALE
%^^K f *"( ( /
COMPOSTING 1 BAGGING
NUTRIENT
ADDITION
ALTERNATIVE II
/=) CENTRIFUGATION
5 kg/metric ton ^/
/
-^. THICKENING ' ^^ CONDIT^ING ^/ -^/ V* CENTRATE
(107) (105) w/POLYMER (105)^ 7 (5) TO TREATMENT
(10 Ib/short ton) °
OJ OJ OT §
* 1 '
I 1
51
Tn THFATMPNT OO O *
'/////////////A //t>*gd§8®&7/'
PRIMARY (20) '///////////
DIGESTED
TRUCKING LANDFILL
UNITS ARE METRIC TONS ( ENGLISH SHORT TONS IN PARENTHESES) OF DRY SOLIDS PROCESSED DAILY.
~r\
0
C
3)
m
>
i
cT
o
-------
ALTERNATIVE 12
CENTRAL 88
W.A.S.
PUMPING
CENTRAL 45
PRIMARY (49)
NORTH SIDE l8
PRIMARY
DIGESTED
9?
DRYING BEDS
95 (105)
-
(20)
ALTERNATIVE 13
:ENTRAL_£8
W.A.S.
CENTRAL,45
PRIMARY
5 kg/metric ton
(87)
NORTH SIDE, Ig
PRIMARY
DIGESTED
(107)
THICKENING
~1 95_
I
CHEMICAL /
CONDITIONING /
W/POLYMER*^3
(10 Ib/short ton)
DECANT
TO TREATMENT
FILTRATE
TO TREATMENT
TRUCKING
LANDFILL
STORAGE
BULK
Y////7////y,
\
BAGGING
NUTRIENT
ADDITION
BULK
BAGGING
NUTRIENT
ADDITION
(20)
UNITS ARE METRIC TONS (ENGLISH SHORT TONS IN PARENTHESES) OF DRY SOLIDS PROCESSED DAILY.
~n
o
c
33
m
-------
ALTERNATIVE
14
CENTRAL
W.A.S.
CENTRAL 45
PRIMARY (49)
NORTH SIDE
PRIMARY
DIGESTED
18
5 kg/metric ton
CLOTH
VACUUM
FILTER
TRUCKING
COMPOSTING
(166)
CHEMICAL /
CONDITIONING <5/
W/POLYMER
(10 Ib/short ton)
(20)
SALE
BAGGING
FILTRATE
TO TREATMENT
NUTRIENT
ADDITION
ALTERNATIVE
\5
CENTRAL
W.A.S.
CENTRAL 45
PRIMARY (49)
NORTH SIDE
PRIMARY (20)
DIGESTED
PUMP TO
PYROLYSIS SITE
5 kg/metric ton (
CHEMICAL 7
CONDITIONING /
W/POLYMER^
(10 Ib/short ton)
CLOTH
VACUUM
FILTER
SOLID
WASTE
PYROLYSIS
DECANT
TO TREATMENT
(100)
FILTRATE RETURN
TO TREATMENT
UNITS ARE METRIC TONS (ENGLISH SHORT TONS IN PARENTHESES) OF DRY SOLIDS PROCESSED DAILY.
3!
CD
c
30
m
>
i
con
-------
m
z
o
z
m
m
33
ALTERNATIVE 16
CENTRAL
WA.S.
(97)
45
CENTRAL
PRIMARY (49)
NORTH SIDE
PRIMARY
DIGESTED
l8
PUMP TO
PYROLYSIS SITE
SI 1 C.
(151
(166) ~"
CHEMICAL /
CONDITIONING ^
W/POLYMER
152 to
(167) Y
CLOTH
VACUUM
FILTER
SOLID
WASTE
PYROLYSIS
(10 Ib/short ton)
(20)
144
(159)
FILTRATE RETURN
TO TREATMENT
I
-------
distribution. The center would include demonstration facilities showing
the benefits of applying sludges to farmlands and would also have some
subsurface disposal capacity to be used as an interim measure until a
market for dried sludge develops. The subsurface storage would be ac-
complished by injecting liquid sludge several feet into the eoil.
New anaerobic digesters, some of which are under construction,
would be needed for the Central Plant sludge as would a new pumping
and pipeline system. The drying and distribution center location, ap-
proximately 40 km [25 miles] east of Denver, has not been finalized and
is one of three under consideration.
Alternative 3
In this alternative plan, raw sludge from the Central Plant and
digested sludge from the Denver Northside Plant would be conditioned
with lime and ferric chloride, estimated at 230 kg [500 pounds] of lime
and 54 kg [120 pounds] of ferric chloride per ton of sludge solids.
This conditioning would permit a filter press to dewater the sludge to
35 percent solids content. This level of dryness is desirable for the
subsequent step of sludge incineration. It has been assumed that a
multiple-hearth furnace would oxidize the sludge to carbon dioxide and
water, leaving 35 percent of the original solids as ash. The ash would
be trucked to a sanitary landfill or land application site within 40 km
[25 miles] of Metropolitan Denver.
New chemical feed systems would be needed along with a completely
new sludge filtration system. It has been assumed that all alterna-
tives involving filtration would need an expansion of the present
building and improvements to the ventilating systems. Trucking system
improvements would include three new trucks for hauling incinerator ash
to the disposal site. A multiple-hearth incinerator was chosen in
preference to a fluidized-bed incinerator because we feel that the lat-
ter has lower reliability due to feed mechanism difficulties and to
high corrosion and erosion from sludge and bed material, particularly
upon the subsequent air pollution control equipment.
Alternative 4
Concern with the increasing costs of conditioning chemicals re-
quired prior to any sludge dewatering operation led to this alternative
using heat treatment of sludge to break down the gel structure of the
sludge particles and make them more amenable to settling and filtration.
Raw Central and digested Northside sludges would be heated in a Zimpro
Heat Treatment Unit and then cooled and decanted in a gravity separator.
The thickened sludge, of approximately nine percent solids content,
would be vacuum filtered through a cloth fabric on a belt or drum fil-
ter. The thickened sludge, of approximately 25 percent solids content,
would be trucked to a sanitary landfill or a land disposal site.
A-21
-------
The decant from the thickener would contain almost 10 percent of
the original sludge solids and pollutants. This material would need
treatment and represents a sizeable load upon any wastewater treatment
facility. Published results of the Porteous heat treatment unit opera-
tion at Colorado Springs indicate that the decant liquor has contained
8,470 mg/1 of COD and 3,800 mg/1 of BOD.
New facilities needed for implementation of this alternative in-
clude a heat treatment unit, thickeners, expanded and renovated cloth
filters and expanded trucking facilities. Additional treatment capaci-
ty may need to be added for the heat-treated decant liquor.
Alternative 5
Alternative 5 is similar to Alternative 4 in the treatment and dis-
posal of sewage sludge except that the dewatering by vacuum filtration
would be replaced by dex«7atering on drying basins with an underdrain re-
turn system. Since the drying beds would be removed from the Central
Plant location and it would be difficult to pump sludges of 9 to 10 per-
cent solids content, the heat-treated sludge would not be thickened,
only cooled after dewatering. It is felt that pumping is to be pre-
ferred over the daily trucking of large quantities of thickened but
watery sludge. It would be necessary to treat the leachate from the
drying beds either at the Central Plant or at a new facility near the
drying beds. Dewatered sludge would be trucked to a landfill or land
disposal site.
New components needed for this alternative include a heat treat-
ment unit, cooling tank, pumping and piping facilities, drying beds
with under drains, leachate collection and treatment and a new truck-
ing system.
Alternative 6
Alternative 6 is similar to alternative 4 in that raw Central
Plant sludge and digested Denver Northside Plant sludge would be heat
treated, cooled and decanted, and then filtered through a cloth, belt
or drum, vacuum filter. However, instead of directly trucking the
sludge to a landfill, in Alternative 6 an incinerator would be employed
to reduce the sludge solids by 70 percent and the sludge water by 100
percent to lessen the trucking and land disposal costs.
The following new items of process equipment would be needed to
implement this alternative: a heat-treatment unit, assumed to be manu-
factured by Zimpro; cooling and decant tanks, fabric media vacuum fil-
ters, along with conversion of existing coil filters to fabric filters;
a multiple-hearth incinerator; and trucking facilities.
A-22
-------
The decant and filtrate from heat-treated sludges contain substan-
tial loads of pollutants that must be properly treated. This can re-
quire expansion of existing wastewater treatment units to accommodate
the new load.
Alternative 7
Composting of sludge for beneficial reuse is the principal feature
of Alternative 7. Central Plant sludges would be anaerobically digested,
combined with Denver Northside Plant sludges and thickened in a gravity
thickener. The thickened sludge, of approximately 5 to 7 percent solids,
would be conditioned with lime and ferric chloride prior to dewatering
in a filter press. Dewatered sludge would be trucked to a 200-hectare
[500-acre] composting and storage area. Approximately 70 percent of the
composted sludge would be sold in bulk, and 30 percent would receive nu-
trient enrichment to a fertilizer level of 6-6-6 and be bagged for urban
sale.
New facilities necessary for implementation of this alternative
include anaerobic digester, gravity thickeners, chemical conditioning
systems, filter presses and trucking. A new composting facility would
also be developed.
It is felt that the addition of lime to the sludge on the order of
25 percent by weight makes the sludge generally unacceptable as compost.
For this reason Alternative 13 was developed to allow for a different
conditioning system.
Alternative 8
Alternative 8 is very similar to Alternative 7 except that no
digesters would be constructed at the Central Plant, and most of the
sludges undergoing composting would be previously unstabilized. Again,
the addition of lime to the sludge makes it a poor choice for general
use as compost material, and Alternative 14 was developed to overcome
this difficulty.
Alternative 9
Alternative 9 would also produce composted sludge as a final prod-
uct with a variation in the sludge treatment system. Anaerobically di-
gested sludges from both plants would be thickened and then chemically
conditioned with polymers on the order of 4 kg [10 pounds] of polymer
per ton of sludge solids. The conditioned sludges would be cer.trifuged
to remove water and it is estimated that a sludge cake with 80 percent
moisture could be achieved. The dewatered sludge would be trucked to
a new 200-hectare [500-acre] composting and storage facility. From
there, 70 percent of the composted sludge would be sold in bulk, and
30 percent would be nutrient enriched and sold as a bagged fertilizer.
A-23
-------
New facilities required for this alternative include anaerobic
digesters, gravity thickeners, chemical conditioning systems, centri-
fuges, trucking and composting. The use of polymers for sludge condi-
tioning would make the sludge perfectly acceptable as compost,
Alternative 10
Alternative 10 is almost identical to Alternative 2 in that the
sludge treatment processes and the final drying and distribution center
would be the same. However, it is felt that the complete disposal sys-
tem of distribution to farmers of bulk dried, stabilized sludge may not
necessarily be sufficiently encompassing of beneficial uses. In particu-
lar, a substantial market need may exist for composted and enriched
sludge for urban homeowners and landscapers. Alternative 10 adds to the
process train of Alternative 2 the provision for composting, enriching
and bagging a portion of the drying sludge. At this time it is diffi-
cult to specify the size of the market for composted and enriched sludge,
and this disposal system could be reserved as a contingency measure for
excess sludge disposal. An estimate of tonnage demand for costing pur-
poses could be made after a market analysis for composted sludge. In
the interim, the additional composting facilities are not reflected in
any costs of alternatives.
Alternative 11
Alternative 11 is similar to Alternative 4 because it would provide
a dewatered sludge for land disposal. Alternative 11 adds anaerobic
digestion for Central Plant sludges in order to stabilize them and make
them less noxious. The best treatment system, and attendant strong de-
cant liquor, of Alternative 4 would be replaced by polymer treatment of
the digested sludge, followed by centrifuge dewatering to produce a
sludge cake containing 20 percent dry solids. This material would then
be trucked to a sanitary landfill or other land disposal site.
New facilities needed for this alternative include anaerobic diges-
ters, gravity thickeners, polymer feed systems, centrifuges and expanded
trucking capability.
Alternative 12
Alternative 12 is basically identical to Alternatives 2 and 10 in
producing anaerobically digested sludges for drying and distribution
for beneficial reuse. This alternative includes a contingency plan to
produce some composted and nutrient-enriched sludge for the urban mar-
ket. Additionally, if due to unforeseen circumstances a market for
dried or composted sludges is not adequately developed or is delayed in
expansion, provisions would be made for trucking the dried sludges to a
landfill site.
A-24
-------
New components of Alternative 12 which would be in addition to
those of Alternative 2 include composting pads, nutrient storage and
addition facilities, a bagging machine and trucks for hauling sludge to
a landfill. These additional facilities have not been included in the
costs of Alternative 12 because the proportion of the sludge production
duction likely to go to each disposal system has not been determined.
Alternative 13
Alternative 13 was developed to alleviate the concerns about lime
content of composted sludge in Alternative 7. In Alternative 13, di-
gested sludges would be thickened and treated with polymers. The condi-
tioned sludge would be dex^atered to approximately 25 to 30 percent dry
solids content on a cloth vacuum drum or belt filter. Trucks would
transport the dewatered sludges to a 200-hectare [500-acre] composting
facility, from where it is estimated approximately 70 percent would be
sold in bulk as compost. Approximately 30 percent of the compost would
be enriched with nutrients to a 6-6-6 fertilizer level and sold to urban
users. The fertilizer value of the compost could be adjusted to the
specifications of large-quantity purchasers.
New facilities necessary for the implementation of this Alternative
include anaerobic digesters, polymer mixing systems, trucking and a com-
posting facility. It was calculated that the existing coil vacuum fil-
ters, if converted to fabric media with a loading rate of 17 kg/m2/hour
[3.5 lb/(ft2)(hr)], could readily handle the expected load of digested
sludge due to the solids reduction that occurs in an anaerobic digester.
Alternative 14
Alternative 14 is intended to provide a replacement for Alternative
8, which employs lime and ferric chloride conditioning of undigested
sludges prior to dewatering in a filter press and composting. In Alter-
native 14, the sludges would be conditioned with a harmless and accept-
able polymer and then dewatered on cloth vacuum filters. The use of
filter presses can give drier sludge cakes, but with polymer condition-
ing could result in poor performance with rapid filter blending. The
dewatered sludges would be trucked to a composting and distribution fa-
cility.
Alternative 15
Alternative 15 involves anaerobic digestion and thickening, followed
by pipeline transport to a regional soliu waste processing center assumed
to be located 5 km [3 miles] from the District's Central Plant. At the
processing center site, the sludge will be chemically conditioned and
vacuum filtered to approximately 25 percent solids content. This prod-
uct material will be accepted by the operators of the solid waste pro-
cessing center at no charge.
A-25
-------
Alternative 16
This alternative is similar to Alternative 15 except that anaerobic
digestion is omitted in order to retain higher heat values in the final
product material delivered to the solid waste processing center.
Assumptions Used in Costing Alternatives
1. Process cost curves and other costing assumptions used by CH2M-
Hill were used in the cost analysis after review and verification.
Changes in basic assumptions were made only where it was determined that
the assumptions were clearly in error or were unacceptable for some
other reason.
2. Sources for cost and performance data were as follows.
a. "Metro Denver District Sludge Management Report, Volume II,"
by CH2M-Hill, 1975, together with back-up calculations supplied by CH2M-
Hill.
b. "An Analysis of the Sewage Sludge Disposal Problem in
Southern California," by Engineering-Science, Inc. and J. B. Gilbert and
Associates for EPA, 1974.
c. Composting cost and performance data were based upon esti-
mates prepared by Dr. Gar Forsht of the Economic Research Service, USDA
and supplied by CH2M-H111.
d. Estimates of revenue from sale of composted sludge were
based on information supplied by Mr. 'Kellogg of Kellogg Sales Company,
Carson, California, the distributor of Los Angeles County's composted
sludge.
e. Engineering-Science, Inc. in-house files on sludge process-
ing performance and chemical dose rates.
3. All costs are related to an Engineering News-Record construc-
tion cost index of 2128, applicable to the Denver area in December 1974.
4. Alternative facilities are sized for 1985 sludge production
projections.
5. Annual operation and maintenance costs derived for 1985 design
flows were assumed to apply uniformly to the period 1975 through 1985.
6. Alternatives 1A and IB involve continued use of existing coil
filters and addition of new and similar filters to handle the increased
quantities of sludge. Needed capacity of new filters (at a solids load-
ing rate of 17 kg/m2/hr [3.5 Ib/ft2/hr]) was calculated on the basis of
the demonstrated capacity of the old filters at 14.6 to 17 kg/m2/hr [3
to 3.5 Ib/ft2/hr]. The earlier estimates were in error on this point;
A-26
-------
the existing filter capacity was calculated too low by a factor of five.
Alternative IB would result in substantially lower tonnage of sludge
solids fed to the filters because of reductions in the digestion process
and would need only a renovation of existing filters.
7. Vacuum filters were assumed to be belt or drum type. Perform-
ance and chemical dosage rates were assumed to be similar to those pub-
lished by Los Angeles County Sanitation District.
8. Composting costs were recalculated on the basis of information
contained in Dr. Gar Forsht's paper entitled "Estimated Processing Cost
for Composting Sludge." The earlier estimates were in error in that a
purchase of 400 hectares [1,000 acres] of land for composting was treated
as an annual expenditure rather than a one-time-only initial cost.
9. It was assumed that for composting alternatives 30 percent of
the sludge would be nutrient-enriched to a 6-6-6 fertilizer value.
Estimated Costs
Cost breakdowns for each alternative are shown in Tables A-3 and
A-4. All costs are expressed in 1974 dollars. Salvage values were de-
termined by straight-line depreciation on the basis of the estimated
useful life of system components.
A-27
-------
Table A-3. COST SUMMARIES USING 10 PERCENT DISCOUNT - NO INFLATION
(thousands of dollars)
r\3
co
Alter-
native
1A
IB
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
I
capital
2,186
9,893
25,759
14,236
12,636
29,060
20,636
15,503
8,538
15,675
26,616
12,913
26,746
12,705
5,830
10,813
2,763
t salvage
value (P.W.)
193
2,390
7,913
3,045
1,664
7,437
3,720
3,309
1,249
3,358
7,913
2,782
7,913
2,893
846
2,714
485
Differ-
ence
1,993
7,503
17,846
11,191
10,972
21,623
16,916
12,194
7,289
12,317
18,703
10,131
18,833
9,812
4,984
8,099
2,278
10 year
0 and M
(P.W.)
22,102
17,229
6,157
13,014
11,484
11,693
7,484
18,175
26,655
21,481
10,108
16,228
10,108
18,557
21.97C
8,744
7,841
With digesters .
Revenue
0
0
4,710
0
0
0
0
10,748
16,947
7,846
8,238
0
8,238
7,846
12,474
0
0
Sub-total
w/o revenue
24,095
24,732
24,003
24,205
22,456
33,316
23,680
30,369
33,944
33,798
28,811
26,359
28,941
:3,369
26,963
16,843
10,119
Total with
revenue
24,095
24,732
19,292
24,205
22,456
33,316
23,680
19,621
16,997
25,952
20,573
26,359
20,703
20,523
14,489
16,843
10,119
Without digesters
Sub-total
w/o revenue
24,095
18,568
17,839
24,205
22,456
33,316
23,680
24,205
33,944
27,634
22,692
20,195
22,822
22,205
26,963
10,679
10,119
Total with
revenue*
24,095
18,568
13,129
24,205
22,456
33,316
23,680
13,457
16,997
19,788
14,409
20,195
14,539
14,359
14,489
10,679
10,119
*0ver a ten-year period.
-------
Table A-4. COST SUMMARIES
1=
ro
USING 10 PERCENT DISCOUNT AND 8 PERCENT INFLATION
(thousands of dollars)
Alter-
native
1A
IB
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
I
capital
2,186
9,893
25,759
14,236
12,636
29,060
20,636
15,503
8,538
15,675
26,616
12,913
26,746
12,705
5,830
10,813
2,763
£ salvage
value (P.W.)
416
5,160
17,084
6,573
3,592
16,054
8,031
7,144
2,696
7,248
17,084
6,005
17,084
6,245
1,826
5,859
1,046
Differ-
ence
1,770
4,733
8,675
7,663
9,044
13,006
12,605
8,359
5,842
8,427
9,532
6,908
9,662
6,460
4,004
4,954
1,717
10 year
0 and M
(P.W.)
32,562
25,383
9,071
19,173
16,919
17,227
11,026
26,777
39,270
31,647
14,891
23,908
14,891
27,339
32,38'.
12,881
11,551
With digesters
Revenue
0
0
6,939
0
0
0
0
15,835
24,967
11,559
12,137
0
12,137
11,559
18,377
0
0
Sub-total
w/o revenue
34,332
30,116
17,746
26,836
25,963
30,233
23,631
35,136
45,112
40,074
24,423
30,816
24,553
33,799
36,385
17,835
13,268
Total with
revenue
34,332
30,116
10,807
26,836
25,963
30,233
23,631
19,301
20,145
28,515
12,286
30,816
12,416
22,240
18,008
17,835
13,268
Without digesters
Sub-total
u/o revenue
34,332
26,424
14,054
26,836
25,963
30,233
23,631
31,444
45,112
36,382
20,731
27,124
20,861
30,107
36,385
14,143
13,268
Total with
revenue*
34,332
26,424
7,115
26,836
25,963
30,233
23,631
15,609
20,145
24,823
8,594
27,124
8,724
18,548
18,008
14,143
13,268
"over a ten-year period.
-------
-------
This Appendix contains descriptions of soils,
by county, within areas which may receive sludge
under the proposed recycling scheme.
-------
Table B-l. SOIL ASSOCIATIONS IN THE VICINITY OF DENVER
Soil association
Description
Map code*
ADAMS COUNTY
Weld-Adena-Colby
Samsil-Shingle
Ascalon-Vona-Truckton
Nunn-Satanta
Alluvial land
Terry-Renohill-Tassel
Blakeland-Valent-Terry
Arvada-Heldt-Nunn
Platner-Ulm-Renohill
Nearly level to steep, well-drained, loamy soils formed 27
in wind-laid deposits; on uplands
Sloping to steep, excessively drained, clayey and loamy 72
soils formed in materials from soft shale and sandstone;
on uplands
Nearly level to strongly sloping, well-drained and some- 71
what excessively drained, loamy and sandy soils formed
in wind-laid deposits; on uplands
Nearly level, well-drained, loamy soils formed in alluvial 23
materials that are underlain by gravel in some places; on
terraces and fans
Nearly level, poorly drained to well-drained, loamy and 30
sandy soils formed in stream and river deposits; on flood
plains
Gently sloping to steep, well-drained and somewhat ex- 6
cessively drained, loamy soils formed in materials from
soft sandstone and shale; on uplands
Undulating to hilly, somewhat excessively drained, 5
dominantly sandy soils; on uplands
Nearly level, well-drained, loamy and clayey soils 8
formed in alluvium; on terraces and fans
Nearly level to strongly sloping, well-drained, loamy 73
soils formed in old alluvium on interbedded shale and
sandstone; on uplands
en
O
'Tl
^
w
!Z
O
M
X
ta
-------
Table B-l (continued). SOIL ASSOCIATIONS IN THE VICINITY OF DENVER
Soil association
Description
Map code*
bd
I
ho
ARAPAHOE COUNTY
Alluvial Land-Nunn
Weld-Adena-Colby
Renohill-Buick-Litle
Nunn-Bresser-Ascalon
Truckton-Bresser
Stapleton-Bresser
Fondis-Weld
OTHER AREAS
Fluvaquents-Fluvents
Valent-Vona
Deep, nearly level, mainly loamy and sandy soils; on
flood plains and terraces
Deep, nearly level to sloping, loamy soils that have a
clayey to loamy subsoil; formed in silty, wind-deposited
material; on high-lying divides between creeks
Sloping to steep, loamy soils that have a loamy to clayey
subsoil; moderately deep and deep over shale or sand-
stone; on uplands
Deep, nearly level and undulating, loamy soils that have a
clayey to loamy subsoil; developed in outwash; on uplands
and terraces
Deep, rolling, loamy and sandy soils that have a loamy
subsoil; on uplands
Moderately steep soils that are loamy throughout;
moderately deep and deep over arkosic sandstone; on
foothills
Deep, nearly level and gently sloping, loamy soils that
have a clayey layer in the subsoil; formed mainly in
silty, wind-deposited material; on foothills
Deep, somewhat poorly drained, nearly level, coarse-
textured soils; on flood plains and low terraces; commonly
flooded
Deep, excessively drained to well-drained gently sloping
to moderately steep sandy soils; on uplands
23
3
42
24
43
27
18
148
-------
Table B-l (continued). SOIL ASSOCIATIONS IN THE VICINITY OF DENVER
Soil association
Description
Map code*
OTHER AREAS (continued)
Ascalon-Olney-Vona
Nunn-Dacono-Altvan
Deep, well-drained, nearly level loamy soils; on
terraces with high water table
Deep, well-drained, nearly level soils; on terraces and
flood plains
173
174
Map code numbers refer to Figure 7 in Section III
Source: Denver Region Water Quality Management Program
td
Co
-------
-------
This Appendix contains tabular listings
of plant species observed during the field re-
connaissance phase of the EIS process, at the
Lowry Bombing Range and at the sludge applica-
tion portion of the Range. It also contains
lists of common plants, birds and mammals in
the Denver region.
-------
APPENDIX C
BIOLOGY
Table C-l. LIST OF PLANT SPECIES OBSERVED DURING FIELD RECONNAISSANCE,
AUGUST 7, 1975
Common name Scientific name £P
P*-> *H
J-i ,i"*
s e
0 0
iJ M
rt
QJ
ao
C
s
(U
co
-a
d
^
CD
?*,
§
o
c
o
•H
4J
u
•Hw
rH
p,
&
Q
cd
0)
03
Tree
Plains cottonwood
Shrub
Broom snakeweed
Rabbitbrush
Willow
Herbs
Alfalfa
Aster
Buffalobur
Bull thistle
Cocklebur
Common burdock
Common sunflower
Coneflower
Dandelion
Fanweed
Fetid marigold
Golden aster
Goosefoot
Gumweed
Mikvetch
Narrow-leaved
umbrella-wort
Plantain
Prickly lettuce
Prickly pear
Prickly poppy
Prostrate knotweed
Prostrate pigweed
Redroot pigweed
Rocky Mountain beeplant
Russian thistle
Sand verbena
Scarlet falsemallow
Sedge
Skeleton weed
Populus sargent!i x
Gutierrizia sarothrae x
Chrysothamnus nauseosus x
Salix sp. x
Medicago sativa x
Aster sp. x
Solanum rostratum
Cirsium vulgare x
Xanthium i tali cum x
Arctium minus x
Helianthus annuus x
Ratibida columnifera x
Taraxacum officinalis x
Thlaspi arvense x
Dyssodia papposa x
Chrysopsis sp. x
Chenopodium leptophyllum x
Grindelia sguarrosa x
^stragraJus sp. x
Oxybaphus linearis
Plantago spinulosa x
Lactuca scariola x
Opuntia polyacantha x
Argemone polyanthemos x
Polygonum aviculare x
Amaranthus graecizans - - x
Amaranthus retroflexus
Cleome serrulata x
Salsola kali var. tenuifolia x
Abronia fragrans x
Sphaeralcea coccinea x
Carex sp. x
Lygodesmia juncea
x
X
X
C-l
-------
Table C-l (continued). LIST OF SPECIES OBSERVED DURING FIELD RECON-
NAISSANCE, AUGUST 7, 1975
Common name
Snow-on- the-mountain
Stinging nettle
Scientific name
Euphorbia marginata
Urtica dioica ssp. gr,
00
Crt
>> -H OJ
M J2 CO
3 ^ c
o o nj
nJ PQ 03
X
acilis x
Q)
00 C
-a o
3 -rl
rH 4-*
03 <3
O
t^T-tn
U H id
3 O. 0)
O D. >-i
_i ca ca
Summer cypress
Tansy mustard
Tumble pigweed
Umbrella plant
Vervain
Yucca
Grass
Beardless wheatgrass
Blue grama
Buffalo grass
Cheat grass
Downy brome
Fescue
Junegrass
Little bluestem
Milo
Needle-and-thread
Oat
Red three-awn
Saltgrass
Sand dropseed
Sorghum sudangrass
Squirreltail
Sudan
Three-awn
Western wheatgrass
Wheat
Kochla scoparia
Descurainia pinnata
Amaranthus albus
Eriogonum effusum
Verbena bracteata
Yucca glauca
Agropyron inerme
Bouteloua gracilis
Buchloe dactyloides
Bromus japonicus
Bromus tectorum
Festuca sp.
Koeleria gracilis
Andropogon scoparius
Sorghum vulgare
Stipa comata
Avena sativa
Aristida longiseta
Distichlis stricta
Sporobolus cryptandrus
Sorghum bicolor X
S. sudanense
Sitanion hystrix
Sorghum sudanense
Aristida sp.
Agropyron smithii
Triticum sativa
x
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Portion of Site A not amended with sludge, shown in Figure 12.
Sludge-amended portion of Site A, shown in Figure 12.
Q
Planted by Metro Denver Sewage Disposal District No. 1.
C-2
-------
Table C-2. COMMONLY OCCURRING RANGE SPECIES IN THE DENVER AREA
Common name
Scientific name
Native, climax grass species
Big bluestern
Blue grama
Buffalograss
Indiangrass
Junegrass
Kentucky bluegrass
Little bluestem
Mountain muhly
Needle-and-thread
Needlegrass
Prairie dropseed
Red three-awn
Sideoats grama
Sloughgrass
Squirreltail
Switchgrass
Western wheatgrass
Associated woody plants, forbs
and legumes - noxious weeds
Canada thistle
Field bindweed
Halogeton
Horsenettle, Caroline
Horsenettle, white
Povertyweed, silver-leaf
Povertyweed, woolly-leaf
Russian knapweed
Saint Johnswort
Sorghum almum
Sowthistle, perennial
Spurge, leafy
Toadflax, Dalmation
yellow
common
Toadflax,
Whitetop,
Whitetop, hairy
Whitetop, tall
Associated woody plants, forbs
and legumes - poisonous to
livestock
Arrowgrass
Brake fern
Chokecherry
Andropogon gerardi
Bouteloua gracilis
Buchlbe dactyloides
Sorghastrum nutans
Koeleria cristata
Poa pratensis
Andropogon scoparius
Muhlenbergia montana
Stipa comata
Stipa spartea
Sporobolus heterolepis
Aristida longiseta
Bouteloua curtipendula
Spartina pectinata
Sitanion hystrix
Panicum virgatum
Agropyron smithii
Cirsium arvense
Convolvulus arvensis
Halogeton glomeratus
Solanum carolinense
Solanum elaeagnifolium
Franseria discolor
Franseria tomentosa
Centaurea repens
Hypericum perforatum
Sorghum almum
Sonchus arvensis
Euphorbia esula
Linaria dalmatica
Linaria vulgaris
Cardaria draba
Cardaria pubescens
Lepidium latifolium
Triglochin spp.
Pteridium aquilinum
Prunus virginiana
C-3
-------
Table C-2 (continued). COMMONLY OCCURRING RANGE SPECIES IN THE
DENVER AREA
Common name Scientific name
Deathcamas Zygadenus spp.
Larkspur Delphinium spp.
Locoweed Oxytropis spp.
Water hemlock Cicuta occidentalis
Associated woody plants, forbs
and legumes - others
Black-eyed Susan Rudbeckia hirta
Elderberry Sambucus racemosa
Goldenrod, stiff Solidago altissima
Horseweed Erigeron canadensis
Prickly pear Opuntia rafinesquii
Rose Rosa acicularis
Russian thistle Salsola kali var. tenuifolia
Sunflower Helianthus spp.
Yucca yucca grlauca
Source: Denver Regional Council of Governments Water Quality Management
Plan.
C-4
-------
Table C-3. NATIVE TREES AND ASSOCIATED SHRUBS IN THE DENVER AREA
Common name
Scientific name
Overstory and climax trees
Alder
American elma
Box elder
Douglas fir
Hackberry
Narrow leaf cottonwood
Pinyon pine
Plains cottonwood
Ponderosa pine
Rocky Mountain juniper
Russian olive
Siberian elma
White fir
Willow
Associated shrubs
American plum
Bitterbrush
Buffaloberry
Chokecherry
Creeping mahonia
Gambel oak
Hawthorn
Indigobush
Leadplant
Mountain mahogany
Ninebark
Rabbitbrush
Redosier dogwood
Sagebrush
Sandcherry
Serviceberry
Skunkbrush
Smooth sumac
Snowberry
Alnus tenuifolia
Ulmus americana
Acer negundo
Pseudotsuga menziesii
Celtis accidental is
Populus angustifolia
Pinus edulis
Populus sargentii
Pinus ponderosa
Juniperus scopulorum
Elaegnus angustifolia
Ulmus pumila
.Abies concolor
Salix spp.
Prunus americana
Purshia tridentata
Shepherdia argentea
Prunus virginiana
Mahonia repens
Quercus gambeli
Crataegus spp.
Amorpha fruticosa
Amorpha canescens
Cercocarpus montanus
Physocarpus monogynus
Chrysothamnus spp.
Cornus stolonifera
Artemisia spp.
Prunus besseyi
Amelanchier spp.
PJius trilobata
Rhus glabra
Symphoricarpos spp.
Species is not native but has volunteered from established plantings.
Source: Denver Regional Council of Governments Water Quality Manage-
ment Plan.
C-5
-------
Table C-4. COMMON BIRDS OF THE DENVER REGION
Common name
Scientific name
Aquatic birds
Canada goose
Whistling swan
Lesser snow goose
Mallard
Gadwall
American widgeon
Pintail
Green-winged teal
Blue-winged teal
Cinnamon teal
Shoveler
Redhead
Canvasback
Ring-necked duck
Lesser scaup
Common goldeneye
Barrow's goldeneye
Bufflehead
Common merganser
Ruddy duck
Red-breasted merganser
Hooded merganser
Greater scaup
Wood duck
Pied-billed grebe
Eared grebe
Western grebe
Hawks and falcons
Turkey vulture
Sharp-shinned hawk
Marsh hawk
Rough-legged hawk
Ferruginous hawk
Red-tailed hawk
Swainson's hawk
Golden eagle
Bald eagle
Prairie falcon
Sparrow hawk
Grouse, quail and pheasant
Sharp-tailed grouse
Bobwhite quail
Ring-necked pheasant
Branta canadensis
Cygnus columbianus
Chen hyperboea
Anas platyrhynchos
Anas stepera
Marceca americana
Anas acuta
Anas carolinensis
Anas discors
Anas cyanoptera
Spatula clypeata
Aythya americana
Aytha valisineria
Aytha collaris
Aytha affinis
Bucephala clangula
Bucephala islandica
Bucephala albeola
Mergus merganser
Oxyura jamaicensis
Mergus serrator
Lophodytes cucullatus
Aytha marila
Aix sponsa
Podilymbus podiceps
Podiceps caspicus
Aechmophorus occidentalis
Cathartes aura
Accipiter velox velox
Circus hudsonius
Buteo lagopus
Buteo regalis
Buteo borealis
Buteo swainsoni
Aguila chrysaetos canadensis
Haliaeetus leucocephalus
Falco mexicanus
Faico sparverius
Pedioecetes phasianellus
Colinus virgianus
Phasianus colchicus
C-6
-------
Table C-4 (continued). COMMON BIRDS OF THE DENVER REGION
Common name
Scientific name
Shorebirds
Great blue heron
Black-crowned night heron
American bittern
Sandhill cranes
Virginia rail
Sora rail
American coot
American avocet
Killdeer
Spotted sandpiper
Willet
Lesser yellowlegs
Long-billed dowitcher
Wilson's phalarope
Common snipe
Franklin's gull
Black tern
Pigeons and cuckoos
Band-tailed pigeon
Rock dove
Yellow-billed cuckoo
Owls and goatsuckers
Screech owl
Great-horned owl
Short-eared owl
Barn owl
Burrowing owl
Poor-will
Common nighthawk
Terrestrial birds
Ruby-throated hummingbird
Belted kingfisher
Red-shafted flicker
Common redpoll
Red-headed woodpecker
Hairy woodpecker
Downy woodpecker
Eastern kingbird
Western kingbird
Say's phoebe
Ardea herodias
Nycticorax nycticorax
Botaurus lentiginosus
Grus canadensis tabida
Rallus limicola limicola
Porzana Carolina
Fulica americana americana
Recurvirostra americana
Charadrius vociferus
Actitis macularia
Catoptrophorus semipalmatus
Totanus flavipes
Limnodromus griseus scolopaceus
Steganopus tricolor
Capella delicata
Larus pipixcan
Chlidonias nigra surinamensis
Columba fasciata
Columba livia
Coccyzus americanus
Otus asio
Bubo virginianus
Asio flairsmeus flammeus
Tyto alba pratincola
Speotyto cunicularia
Phalaenoptilus nuttalli
Chordeiles minor
Archilochus coluoris
Megaceryle alcyon
Colaptes cafer
Acanthis linaria linaria
Melanerpes erythrocephalus
Dryobates villosus
Dryobates pubescens
Tyrannus tyrannus
Tyrannus verticalis
Sayornis saya
C-7
-------
Table C-4 (continued). COMMON BIRDS OF THE DENVER REGION
Common name
Scientific name
Traill's flycatcher
Horned lark
Barn swallow
Cliff swallow
Bank swallow
Black-billed magpie
Common crow
Black-capped chickadee
Common bushtit
Dipper
Red-breasted nuthatch
House wren
Mockingbird
Catbird
Brown thrasher
Robin
Hermit thrush
Veery
Golden-crowned kinglet
Ruby-crowned kinglet
Water pipit
Bohemian waxwing
Cedar waxwing
Loggerhead shrike
Starling
Warbling vireo
Orange-crowned warbler
Yellow warbler
Ovenbird
Yellowthroat
Yellow-breasted chat
American redstart
House sparrow
Western meadowlark
Yellow-headed blackbird
Red-wing blackbird
Brewer's blackbird
Common grackle
Brown-headed cowbird
Bullock's oriole
Lazuli bunting
House finch
American goldfinch
Dickcissel
Emphidonax traillii
Otocoris alpestris
Hirundo erythrogaster
Petrochelidon albifrons
Riparia riparia riparia
Pica Pica hudsonia
Corvus brachyrhynchos
Penthestes atricapillus
Psaltriparus minimus
Cinclus mexicanus unicolor
Sitta canadensis
Troglodytes aedon
Mimus polyglottos
Dumetella carolinensis
Toxostoma rufum
Turdus migratorius
Hylocichla guttata
Hylocichla fuscencens fuscescens
Regulus satrapa
Corthylio calendula
Anthus spinoletta
Bombycilla garrula pallidiceps
Bombycilla cedrorum
Lanius ludovicianus
Sturnus vulgaris vulgaris
Vireo gilvus
Vermivora celata celata
Dendroica petechia
Seiurus aurocapillus
Geothlypis trichas
Icteria virens
Setophaga ruticilla
Passer domesticus domesticus
Sturnella neglecta
Xanthocephalus xanthocephalus
Agelaius phoeniceus
Euphagus cyanocephalus
Quiscaleus guiscula
Molothrus ater
Icterus bullocki
Passerina amoena
Carpodacus mexicanus frontalis
Spinus tristis
Spiza americana
C-8
-------
Table C-4 (continued). COMMON BIRDS OF THE DENVER REGION
Common name
Scientific name
Rufous-sided towhee
Grasshopper sparrow
Lark bunting
Vesper sparrow
Lark sparrow
Tree sparrow
Chipping sparrow
Field sparrow
Lincoln's sparrow
Song sparrow
McCown's longspur
Chestnut-collared longspur
Townsend's solitaire
Pipilo erythrophthalmus
Armodramus savannarum australis
Calamospiza melanocorys
Pooecetes gramineus confinis
Chondestes granwacus strigatus
Spizella arborea ochracea
Spizella passerina arizonae
Spizella pusilla arenacea
Melospiza lincolni lincolni
Melospiza melodia
Rhynchophanes mccownii
Calcarius o mat us
Myadestes townsendi
C-9
-------
Table C-5. COMMON MAMMALS OF THE DENVER REGION
Common name
Scientific name
Big game
Antelope
Mule deer
Small game
Blacktail jackrabbit
Whitetail jackrabbit
Fox squirrel
Desert cottontail
Eastern cottontail rabbit
Furbearers
Coyote
Opossum
River Otter3
Bobcat
Striped skunk
Shortail weasel
Longtail weasel
Black-footed ferret
Raccoon
Spotted skunk
Gray fox
Red fox
Swift fox
Rodents, shrews, and bats
Spotted ground squirrel
Thirteen-lined ground
squirrel
Whitetail prairie dog
Blacktail prairie dog
Ord kangaroo rat
Big brown bat
Rodents
Porcupine
Least chipmunk
Colorado chipmunk
Plains pocket gopher
Silver-haired bat
Red bat
Hoary bat
Prairie vole
Antilocapra americana
Odocoileus hemionus
Lepus californicus
Lepus townsendi
Sciurus niger
Sylvilagus audubonii
Sylvilagus floridanus
Canis latrans
Didelphis marsupialis
Lutra canadensis
Lynx rufus
Mephitis mephitis
Mustela erminea
Mustela frenata
Mustela nigripes
Procyon lotor
Spilogale putorius
Urocyon cinereoargenteus
Vulpes fulva
Vulpes velox
Citellus spilosoma
Citellus tridecemlineatus
Cynomys gunnisoni
Cynomys ludovicianus
Dipodomys ordi
Eptesicus fuscus
Erethizon dorsatum
Eutamias minimus
Eutamias quadrivittatus
Geomys bursarius
Lasionycteris noctivagans
Lasiurus borealis
Lesiurus borealis
Microtus ochrogaster
C-10
-------
Table C-5 (continued). COMMON MAMMALS OF THE DENVER REGION
Common name
Scientific name
Meadow vole
California myotis bat
Long-eared myotis bat
Brown myotis bat
Small-footed myotis bat
Fringed myotis bat
Long-legged myotis bat
Eastern woodrat
Northern grasshopper mouse
Plains pocket mouse
Silky pocket mouse
Hispid pocket mouse
Deer mouse
Western big-eared bat
Western harvest mouse
Plains harvest mouse
Masked shrew
Merriam shrew
Dusky shrew
Mexican freetail bat
Big freetail bat
Northern pocket gopher
Meadow jumping mouse
Western jumping mouse
Microtus pennsyIvanicus
Myotis californicus
Myotis evotis
Myotis lucifugus
Myotis subulatus
Myotis thysanodes
Myotis volans
Neotoma floridana
Onychomys leucogaster
Perognathus flavescens
Perognathus flavus
Perognathus hispidus
Peromyscus maniculatus
Plecotus townsendi
Reithrodontomys megalotis
Reithrodontomys montanus
Sorex cinereus
Sorex merriam
Sorex obscurus
Tadarida braziliensis
Tadarida molossa
Thomomys talpoides
Zapus hudsonius
Zapus princeps
Classed rare to near extinct due to constriction of habitat.
Source: Reference
C-ll
-------
Table C-6. COMMON AMPHIBIANS AND REPTILES OF THE DENVER REGION
Common name
Scientific name
Salamanders
Barred tiger
Toads
Great plains
Woodhouse's
Plains spadefoot
Frogs
Boreal chorous
Bull
Leopard
Turtles
Snapping
Painted
Yellow western box
Western spiny softshell
Lizards
Lesser earless
Eastern short-horned
Northern sagebrush
Skinks
Six-lined racerunner
Snakes
Eastern yellow-bellied racer
Prairie rattlesnake
Plains hognose
Central Plains milk
Smooth green
Bullsnake
Plains black-headed
Wandering garter
Plains garter
Red-sided garter
Ambystoma tigrinum mavortium
Bufo cognatus
Bufo woodhousei woodhousei
Scaphiopus bombifrons
Pseudacris triseriata maculata
Rana catesbeiana
Rana pipiens
Chelydra serpentina
Chrysemys pi eta
Terrapene ornata luteola
Trionyx spiniferus hartwegi
Holbrookia maculata
Phrynosoma douglassi brevirostre
Sceloporus graciosus graciosus
Cnemidophorus sexlineatus
Coluber constrictor flaviventris
Crotalus viridis viridis
Diadophis punctatus nasicus
Lampropeltis triangulum gentilis
Opheodrys vernalis
Pituophis melanoleucus sayi
Tantilla nigriceps
Thamnophis elegans vagrans
Thamnophis radix
Thamnophis sirtalis parietalis
Source: Reference
C-12
-------
Table C-7. COMMON FISHES IN STREAMS AND LAKES OF THE DENVER REGION
Common name
Scientific name
Brown trout
Carp
Tench
Creek chub
Fathead minnow
Red shiner
Carp sucker
White sucker
Channel catfish
Black bullhead
Killifish
White bass
Largemouth bass
Smallmouth bass
White crappie
Black crappie
Green sunfish
Blue gill
Pumpkinseed
Yellow perch
Log perch
Darters
Salmo trutta
Cyprinus carpio
Tinea tinea
Semotilus atromaculatus
Pimephales promelas
Notropis lutrensis
Carpiodes carpio
Catostomus commersonnii
Ictalurus lacustris
Ictalurus melaf
Fundulas sp.
Lepibema chrysops
Micropterus salmoides
Micropterus dolomieu
Pomoxis annularis
Pomoxis nigromaculatis
Lepomis cyanellus
Leponiis macrochirus
Lepomis gibbosus
Pesca flaves cans
Percina caprodes
Percidae sp.
Source: Reference
C-13
-------
-------
This Appendix presents an overall discussion
of the feasibility of applying municipal sludge
to land, as evaluated by Engineering-Science, Inc.
-------
APPENDIX D
SLUDGE APPLICATION TO LAND
TABLE OF CONTENTS
INTRODUCTION D-l
PLANT NUTRIENT REQUIREMENTS D-3
SOILS AS SLUDGE ASSIMILATORS D-4
Soil Suitability for Sludge Application D~4
Allowable Sludge Application Rates D-4
Chemical Reactions in Soil B-5
Physical Effects of Sludge Addition to Soils D-5
ENVIRONMENTAL CONSIDERATIONS AND CONSTRAINTS D-6
Surface Runoff D-6
Groundwater D-6
Aesthetics D-7
Odor D-7
Food Chain D-7
Nitrogen D-9
Heavy Metals D-ll
Pathogens D-12
Salts D-14
AGRICULTURAL CONSIDERATIONS D-15
Fertilizer Value D-15
Fertilizer Market D-15
Crop Selection D-16
Germination D-l8
Weeds D-21
Application Rates D-21
General Conclusions D-22
CHEMICAL PROPERTIES OF METRO DENVER SLUDGE - D-24
LAND USE OPTIONS FOR SLUDGE APPLICATION D-24
City Parks D-24
Sod Farms D-28
Irrigation and Dryland Farms D-28
REFERENCES D-30
D-l
-------
APPENDIX D
SLUDGE APPLICATION TO LAND
INTRODUCTION
The agricultural reuse of materials generated in the processing of
municipal wastes is a contemporary issue that has as its philosophical
base the belief that sewage wastes should be considered not as refuse
but as useful resources. Past practices of sewage disposal have placed
a burden on the environment in the form of air and water pollution and
have essentially involved the elimination of a significant amount of
nutrient resources from the ecosystems. Many communities in America are
involved in programs of recycling municipal sludges and effluents on the
land; many universities and public agencies are conducting long-term
research projects on the effects of waste recycling on the environment.
Preliminary results are appearing in increasing numbers in scientific
and technical journals and other publications.
The intent of this appendix to the Metro Sludge EIS is to provide
general information concerning the land application of sludge, with
specific consideration to the chemical composition of Metro Denver sludge
as it relates to agricultural reuse. Sources for more detailed or more
situation specific information are given in the reference section.
The Metropolitan Denver Sewage Disposal District No. 1 proposes the
transfer of anaerobically digested liquid sludge from the central plant
to a drying and distribution site, where the sludge would be air dried
and stockpiled for distribution for agricultural reuse purposes. The
land application of sludge can be grouped into three general categories
according to application rates; these are presented below and summarized
in Table D-l.
"The reuse of waste sludges for fertilization as shown in
Table D-l utilizes low loading rates (less than 45 tons
per hectare per year [20 tons/acre/year]), depending on
sludge characteristics, soil, and the crop grown. The
objective is the maximization of crop production by full
use of the nutrients present. Almost any soil suitable
for high rate agricultural production is suitable for this
type of operation. The key feature of this system is that
a balance between the nutrients added and the nutrients
removed with the crops should be maintained. Only the
amount of organic material required to maximize crop
production is applied.
The 'high rate fertilizer' system uses higher loading rates
(up to 170 metric tons per hectare per year [75 tons per
acre per year]). The objective is to maximize the amount
D-2
-------
Table D-l. THREE MAIN CATEGORIES FOR WASTE ORGANICS APPLICATION TO LAND
i
UJ
Method
Fertilization
High rate
fertilizer
Loading rates,
Annual
<2 to 45
depending
on waste
organica
character-
istic, soil
and crop
grown.
<11 to >168
, metric ton.s/haa
Maximum
accumulation
224 to 2240 to
prevent excess
accumulation of
heavy metals or
other pollutants
in soil.
900 to 2240 to
prevent toxic
accumulations
of pollutants
in the soil.
Impact on quality
Objective
Maximize crop
production by
use of ferti-
lizer to sup-
ply part or
all of pri-
mary anu/or
micro nutri-
ents.
Apply organics
to cropped
soil. Main-
tain crop while
maximizing or-
ganics appli-
cations .
Suitable soils
Any soil which
is suitable for
high agricultural
production.
Generally fine
textured soils
with a high capa-
city to adsojrb or
precipitate
large quantities
of heavy metals
or other pollu-
tants.
Soil
Improves soil
fertility and
organics improve
soil structure.
No detrimental
effects.
May reduce soil
usefulness for
some crops or uses.
Soil would prob-
ably be improved
at lighter load-
ings. Accumula-
tion of pollutants
in soil must be
monitored.
Water
With a well managed
system there would
be no harmful effect
on groundwater or
surface water.
Possibly would result
in excess nitrogen
which could be
leached to ground-
water. Proper man-
agement of surface
runoff would protect
surface waters.
Disposal
(landfill)
11 to
several
hundred
Several hun-
dred to 2240
or more
To dispose of
organics by in-
corporation in
soil. A crop
may or may not
be grown be-
tween applica-
tions.
Generally fine
textured soils
with a high capa-
city to adsorb or
precipitate
large quantities
of heavy metals
or other pollu-
tants.
Soil usefulness
will likely be
greatly reduced.
Accumulation of
pollutants in
soil should be
monitored.
Excess nitrogen could
be leached to ground-
water. Proper man-
agement would mini-
mize potential for
pollution from other
materials.
al metric ton/hectare - 0.446 English tons/acre
Source: Agricultural Reuse Program (Reference D-l).
-------
of sludge applied, with crop production secondary in
importance. Solids suitable for this type of operation
should be fine textured with a high capacity to absorb
or precipitate large quantities of heavy metals. Even-
tually, continued unbalanced applications of waste
organic materials may reduce the soil's usefulness to
grow certain crops because of accumulations of heavy
metals or salts. The application of the nitrogen con-
tained in the waste organic materials would not be
balanced by crop removal or natural denitrification,
and accumulation of nitrogen in the soil would probably
occur. Nitrogen compounds could eventually reach the
ground water or surface system if proper precautions
were not taken.
The third general method of operation involves 'dis-
posal' at very high loading rates (up to several hun-
dred tons of waste sludge applied per hectare per year).
The objective is to dispose of as much sludge as possible
by incorporation into the soil with little or no emphasis
on crop production. Fine textured soils will precipitate
large quantities of heavy metals or other pollutants and
are suitable for this type of operation. The end result
of continued operation using the 'disposal' method is the
potential impairment of the soil due to accumulation of
salts, heavy metals, and nitrates in the soil. Leaching
of nitrates, salts, and heavy metals from the soil into
the ground water or carrying of these materials into the
surface water regime is a potential hazard that must be
considered in design." (Reference D-l)
The method characterized as "fertilization" is the one proposed by
Metro Denver and is the one that will be focussed upon in this appendix
as well as in the body of the environmental impact statement.
PLANT NUTRIENT REQUIREMENTS
Sixteen elements are known to be essential for plants to be able to
complete their life cycle. Ten of these elements are required in rela-
tively large amounts for plant growth. These macronutrients are: carbon,
oxygen, hydrogen, nitrogen, phosphorus, potassium, sulfur, calcium, mag-
nesium and iron. The remaining six micronutrients which are essential
in trace amounts are: manganese, zinc, copper, boron, molybdenum and
chlorine. Certain plants may not require one or more of the sixteen
elements. Certain others require still other elements, or they must be
able to substitute to a degree some elements for others. Some of the
elements required by specific plants are sodium, selenium, cobalt and
silicon. All of these nutrients with the exception of carbon are drawn
by land plants mainly from the soil. Municipal sludge contains all of
D-4
-------
the essential plant nutrients in varying amounts.
SOILS AS SLUDGE ASSIMILATORS
Soil is primarily made up of mineral matter, organic matter, micro-
organisms, solutions and air. The assimilative potential of a soil depends
upon its ability to filter, buffer, adsorb and absorb sludge constituents.
Soils chemically and biologically transform sludge component and support
plants which utilize the nutrients in them (Reference D-2).
Soil Suitability for Sludge Application
Physical properties that affect a soil's ability to assimilate sludge
include: porosity, structure, texture (grain-size distribution) and
mineralogy. Soil filterability is a property that determines how
efficiently a soil can act as a physical filter of suspended particles
and pathogenic organisms. Permeable soils of intermediate texture with
enough colloidal content to trap particulates are generally the best
filters. Soils that are least suitable for land application include
those that are: 1) extremely fine-textures; 2) extremely coarse-textured,
such as sands and gravels; 3) very shallow; 4) wet or undrained; 5) frozen;
and 6) solonetz and others that are sodium saturated (Reference D-3).
Aspects of soil chemistry that are of importance to sludge assimilation
include: 1) ion exchange capacity, 2) chemical alteration, and 3) soil
pH and calcium reserve.
Ion exchange capacity refers to the total amount of cations and
anions that are sorbable per unit of soil weight (expressed as milli-
equivalents per 100 grains of soil) . Most soils have moderate to large
cation-exchange capacities but only limited anion exchange capacities.
Allowable Sludge Application Rates
The cation exchange capacity is the sum of both the capacities of
organic and inorganic soil components. The ability of a soil to retain
heavy metals from sludge applications - and to keep them out of the
ground and surface water and unavailable to plant tissues - is largely
a function of its cation exchange capacity (Reference D-3). Equation D-l
shows the maximum permissible sludge loading rate as determined by the
cation exchange capacity of a soil and the heavy metals content of the
sludge, where CEC equals the cation exchange capacity of the unsludged
soil in meq/100 g. and ppm equals mg/kg dry weight of sludge (Reference
D-4). The constant-200 adjusts for the addition to the soil of some ex-
change capacity in the sludge (Reference D-5).
Total Sludge (dry wt. metric tons/hectare)=
73,000 (CEC)
ppm Zn + 2(ppin Cu) + 4(ppni Ni) -200
D-5
-------
This equation limits the heavy metal additions calculated as zinc
equivalent to 10 percent of the cation exchange capacity. The zinc
equivalent takes into account the greater plant toxicities of copper and
nickel. This equation applies only to soil that can be adjusted and
held at a pH of 6.5 or greater for a period of at least two years after
sludge application (Reference D-10).
Chemical Reactions in Soil
The soil may chemically alter many of the materials which have been
introduced into the profile through the addition of sludge. These alter-
ations may lessen or increase the environmental impact of sludge applica-
tion. For example, through the conversion of organic nitrogen to nitrate,
a potential threat to groundwater quality and public health (Reference D-6)
is introduced.
Soil pH and calcium reserve are very important properties that de-
termine to what degree a soil can inhibit the solubility of heavy metals
compounds. Contrasting properties of alkaline (calcareous) and acid
soils are given below (Reference D-7) :
Alkaline (Calcareous) Soils Acid Soils
High in calcium Low in calcium
High in pH and carbonate Low in pH; no carbonate
Rich in nutrients Poor in nutrients
Low solubility of heavy metal High solubility of heavy metal
ions ions
High activity of nitrogen fixing Low activity of nitrogen fixing
and nitrifying bacteria and nitrifying bacteria
Physical Effects of Sludge Addition to Soils
Sludge can act as a soil conditioner by the provision of those
organic compounds that eventually become valuable humus in the soil.
Sludge humus performs all the beneficial functions in the soil that any
other kind of humus does: it holds large quantities of water, it improves
soil structure and water absorption capacity (Reference D-8). It also
improves root penetration and proliferation in the soil.
Sludge as a soil conditioner promotes desirable physical properties
in soils such as friability (loose and crumbly rather than hard and
cemented) and improved drainage (Reference D-9). Sludge residue decreases
the bulk density of the soil (Reference D-10). In clay soil, sludge
alleviates unfavorable characteristics by providing large pore spaces
among soil aggregates. In sandy soil, it creates chemical reaction sites
for nutrient exchanges, improves soil aggregation, and makes a good
D-6
-------
binder to hold the sand from blowing away (Reference D-ll). It reduces
the erodibility of all soils through enhancement of more resistant soil
structure.
Adding sewage sludge initially increases the hydraulic conductivity
of a soil, but the conductivity later decreases. Organic matter, through
the activity of microorganisms, increases soil aggregation thereby
increasing permeability. The subsequent decrease in hydraulic conductiv-
ity appears to be due to clogging of soil pores by microbial decompo-
sition products.
Incorporation of sludge markedly influences the soil atmosphere. The
low oxygen and high carbon dioxide contents initially result from high
rates of liquid sludge application which can reduce root growth, nutrient
uptake and plant growth. Other gas products of decomposition, such as
methane and ethylene, can be detrimental to plants under high sludge
application rates (Reference D-12). However, anaerobically digested
air-dried sludge is stable enough so that decomposition reactions take
place over a rather extended period of time and do not deplete soil
oxygen (Reference D-32).
ENVIRONMENTAL CONSIDERATIONS AND CONSTRAINTS
The application of sewage sludge to the land can have effects on
many functional components of the ecosystem. These effects, along with
the major constraints to sludge application, are discussed in this
section.
Surface Runoff
The area east of the Metropolitan Denver area is subject to heavy
runoff during the spring thaw and during the summer when relatively
short duration, high intensity thunderstorm activity occurs. Application
of sludge during the spring and summer months could, if not handled
correctly, contaminate surface runoff with elevated levels of nitrate,
salts and suspended organic materials. Heavy tnetals contained in the
organic materials are bound physically and chemically in the soil (when
sludge is incorporated into the soil), and as long as the soil stays in
place, little movement of heavy metals is expected. Special attention
should be given to methods of containing surface runoff in order to pre-
vent contamination of surrounding surface water supplies (Reference D-l) .
Groundwater
If the application of sludge on irrigated farmlands is implemented
by the private farms in the area, certain precautions concerning nitrogen
loading must be observed so that a balance between the amount of nitrogen
applied and the amount removed by the crops can be obtained. This should
prevent excess nitrates from percolating into the groundwater table.
D-7
-------
For dry land farm applications, the percolation problem is much less
severe. Downward leaching of nitrates into the groundwater table would
occur rather slowly, estimated by Pratt (Reference D-30) to average about
0.15 to 0.75 m/yr (0.5 to 2.5 ft/yr) through unsaturated strata in an
area with characteristics similar to those of Adams County. The possi-
bility of groundwater contamination from excess nitrates under excess
sludge application regimes cannot be overemphasized.
Aesthetics
Land application of sludge can be managed so that no more of an
aesthetic impact would result than with general agricultural field
practices. Certain precautions can reduce any major aesthetic problems.
Surface application of dry or liquid sludge should be followed shortly
by incorporation into the soil either by discing or plowing. The time
of the year when this is done should be controlled to prevent dust con-
ditions from occurring. Farm practices in the Denver area are fairly
well defined and a great deal of experience on the part of the farmers
has been accumulated to prevent dust problems. Sludge should be applied
only during the times of the year when proper dust prevention techniques
can be observed (Reference D-l) .
Odor
Since the Metro Denver sludge would be anaerobically stabilized, the
odor potential would be quite low. The odor conditions are closely re-
lated to anaerobic bacterial action on volatile organic matter in both
the liquid and solid portions of the sludge. Either a high degree of
reduction of volatile matter, or chemical treatment to inhibit bacterial
action, is necessary to prevent nuisance odors. The degree of volatile
reduction achieved by anaerobic digestion is generally not less than 40
percent to achieve a stabilized sludge (Reference D-4).
The application of organic materials to the soil, followed by plowing
in shortly thereafter, should be no more objectionable than the use of
barnyard manure. With proper attention to application techniques, odors
should not be detectable outside of the immediate vicinity of application.
Those odors which are detectable when standing within the application
area can best be characterized as faint tarry odors with a slight trace
of ammonia. These odors will dissipate rapidly after application to
the land.
Food Chain
The application of sludge to agricultural land on which crops enter-
ing the human food chain are grown is a matter of some concern, although
there are no documented cases of disease resulting from the use of sludge,
EPA guidelines require that the application of sludge to lands on which
crops entering the human food chain will or may be grown must be examined
closely in terms of hazards to human health and future land productivity.
(Reference D-4)
D-8
-------
The principle of food chain concentration (biological magnifi-
cation) involves the accumulation and concentration of some sub-
stances as energy is passed in the form of food along the food chain.
Thus, a substance which is contained in minute amounts in individual
plants can become highly concentrated in certain organs in an animal
which eats a large number of those plants.
Heavy Metals in Sludge—
Elements in sludge that are potential hazards to plants or higher
species in the food chain are: boron, cadmium, cobalt, chromium cop-
per, mercury, nickel, lead and zinc. The elements that are a signifi-
cant potential hazard to the food chain through plant accumulation
are cadmium, copper and zinc. Molybdenum has on rare occasions caused
animal toxicities when they have pastured on soils naturally rich in
this element. Sludge from Metro Denver District is not expected to
contain toxic levels of molybdenum. Toxic metals added to soils are
not a hazard to the food chain until they have entered an edible part
of a plant, such as the leaf, grain, fruit, or edible root or tuber.
Copper will cause severe plant injury before the content is high enough
to be toxic to most animals. Cadmium and zinc, when added to the soil
in sludge, can lead to increased food chain cadmium and zinc (Refer-
ence D-13).
Cadmium and Zinc—The Food and Drug Administration expects to
specify the permissible level of cadmium in foods in the marketplace,
possibly to be established at the current natural background levels
(Reference D-13). Cadmium accumulates in the kidney and liver over
many years. Kidney damage and hypertension have been related to in-
creased cadmium levels in these organs. "Itai-Itai" disease was caused
in Japan by increased dietary cadmium; cadmium suppressed calcium
absorption and led to weak bones in older persons (Reference D-5).
The only apparent way proposed so far to ensure that the cadmium
level in a food crop grown on a sludge-treated soil will not be a
food-chain hazard, is to reduce the cadmium content of sludges to 0.5
percent of the zinc content, and as near as possible to 0.1 percent
of the zinc content. In this way, zinc excess (at about 500 ppm Zn
in leaves) would injure the crop before the zinc or cadmium content
of the crop became a health hazard. Zinc appears to compete with
cadmium at the sites of uptake and injury in animals, and the high
zinc in crops grown on sludge-treated soil should serve to reduce
cadmium uptake and accumulation. Grain, fruit, and edible roots have
a lower zinc content than the leaves of the same plants. Cadmium is
excluded even more strongly, so that the cadmium/zinc ratio of grain,
fruit, and edible roots are one-half to one-tenth that of leaves. The
choice of these types of crops in preference to leaf crops would mini-
mize cadmium movement into the food chain. Further research is needed
D-9
-------
to determine what levels of cadmium and zinc are safe for the human
food chain (Reference D-13).
Copper, Mercury and Lead—Copper, mercury, lead and some of the
other elements in amounts normally found in sludges will not cause
appreciable plant and food chain injury unless they are sorbed onto
vegetative material by direct contamination and then ingested by
animals in large amounts (Reference D-14).
Direct Ingestion of Sludge by Pasturing Domestic Animals—
Animals, notably cattle, are known to eat considerable quantities
of soil as part of their daily diet. Sludge-applied soils, eaten by
domestic animals, would short-circuit the capacity of the soil in
screening contaminants from the food chain. Metro Denver District is
now engaged in a research project aimed at determining accumulations
of heavy metal elements in various tissues of animals fed controlled
quantities of sludge.
Nitrogen
Nitrogen contained in digested sludge is the most immediate limit-
ing factor to annual rates of application on a given tract of land.
This is due to the fact that addition of excess nitrogen to the soil
involves the risk of polluting the groundwater with nitrates. The
threat of methemoglobinemia, caused by nitrates and nitrites in water
supplies, are discussed under public health impacts. The processes
which affect the form of nitrogen in soils (mineralization, nitrifi-
cation, denitrification, immobilization, fixation, adsorption by cation
exchange, volatilization, convection, dispersion, and plant uptake) may
take place concurrently. The reates of these processes are determined
largely by soil type and climate. The nitrogen content of the anaer-
obically digested liquid sludge at Metro Denver will consist of approxi-
mately 40 percent ammonia nitrogen and 60 percent organic nitrogen
(Reference D-l). During drying, most of the ammonia and about half
of the organic nitrogen are lost tn volatilization.
Nitrogen is available to plants mainly as nitrates and ammonium.
The ammonium form is rapidly converted by soil nitrifying bacteria
to the nitrate form. Organic nitrogen is also mineralized to the nit-
rate form abailable to plants. Excess nitrates not taken up by plants
can be leached into the groundwater reservoirs. Nitrogen is lost
through denitrification and volatilization of ammonia and nitrogen gas
to the atmosphere. Volatilization can account for at least a 25 per-
cent loss of ammonia nitrogen, with this percentage increasing the
longer the sludge is subject to air-drying. Approximately 30 percent
of the remaining nitrogen in applied sludge becomes available for plant
uptake in the first year, 15 percent in the second year, 10 percent in
D-10
-------
the third year and 5 percent in the fourth and succeeding years.
Nitrogen pollution problems can be controlled with correct management
which involves the formulation of a nitrogen balance for the sludge
application program that prevents excessive nitrate leaching. The com-
ponents of a nitrogen balance which must be known or estimated include:
1) Total nitrogen concentration of the applied sludge as percent
of solids (N);
2) The amount of sludge applied in metric tons per hectare (R):
3) The amount of residual available nitrogen in the soil in metric
tons per hectare (p);
4) The percent of nitrogen which is mineralized in a given year (c );
5) Nitrogen losses through denitrification and volatilization;
6) Potential annual uptake of nitrogen by each crop in Kg/ha/yr (U);
7) Proportion of the nitrogen in the crop removed from the land at
harvest (c^);
8) The amount of leaching to be allowed;
9) A timing pattern to retain the balance sufficiently close to an
equilibrium.
The major elements of this balance are expressed in Equation D-2:
C]_ U
R = 1,000 c2 N ~ P (Equation D-2)
The variable p is assumed to be zero for the first year, and for success-
ive years is calculated according to the decay of residual available
nitrogen (30 percent in the first year, etc.)
Nitrogen losses through denitrification and volatilization during
air-drying should be estimated and subtracted from the total before N
is computed. The amount of leaching allowed is determined by the initial
groundwater quality, the size and rate of flow in the groundwater
reservoir, and the size of the sludge application site. A certain amount
of leaching is required in order to restrict the buildup of soluble salts
in the soil root zone below tolerable limits. This leaching water will
inevitably carry available nitrate forms to the groundwater. As a
rule of thumb, sludge application rates should be such that no more than
one half of the nitrogen in the applied sludge can be carried by the
leaching fraction of irrigation water. Timing of sludge application
depends on the site and the specific situation. It depends on 1) the
rate of nitrification and, 2) assuming that nitrate ion movement occurs
only with percolate movement, the moisture content properties of the
soil, and 3) the amount of water added to the area. If sludge nitrogen
is nitrified and moves below the root zone before it is absorbed by
plants, it will percolate on to the groundwater. If leachate nitrate
concentration is low during most of the year, high levels for a short
period of time are more tolerable. Monitoring of the leachate must be
included with the management program to compensate for unknown factors
D-ll
-------
(Reference D-15).
Heavy Metals
Heavy metals are found in digested sludge and usually occur in the
soils as well. Toxic conditions are not caused merely by a high metal
content in soil or sludge, but rather by the presence of heavy metals
in soluble form. Heavy metals are adsorbed on the cation exchange sites
of soil clays. Metals may also be precipitated, chelated, or complexed
with organic matter in a form that is unavailable to plants (Reference
D-16). The major heavy metals that are potentially hazardous to plants
because of their amounts in sludge, availability in soils, and toxicities
to plants or animals are zinc, copper, nickel and cadmium (Reference
D-15). Successful treatment of sludge heavy metals by the soil occurs
when they are adsorbed or otherwise held by the soil matrix so that
they cannot be taken up by plants or leached into the groundwater.
The availability of heavy metals in sludge to crops is largely a
function of soil pH and cation exchange capacity, phosphorus, calcium,
organic matter, and crop variety, species, organ and age. The following
summary presents methods of minimizing metal uptake by crops (Reference
D-14):
Factors for Reducing Availability of
Sludge Trace Elements and Their Uptake by Plants
Sludge: Low concentration of trace elements
Low Cd to Zn ratio
High Phosphorus
High organic matter
High lime
Soil: Neutral to high pH
High cation exchange capacity
High organic matter
Calcareous soils
Crop: Trace element tolerant variety and species
Fruit and seeds compared with vegetative tissue
Younger compared with older vegetative tissue
Plants vary greatly in tolerance to heavy metal toxicity and the relative
tolerance of some plants is shown below (Reference D-14):
D-12
-------
Relative Tolerance to Metal Toxicity
Very Beet crops (chard, sugarbeet, redbeet), kale, mustard,
Sensitive: turnip, tomato
Sensitive: Beans, cabbage, collards, other vegetable crops
Moderately Many farm crops, i.e., corn, small grains, soybeans
Tolerant:
Tolerant: Most grasses, i.e., fescue, lovegrass, Bermudagrass,
perennial ryegrass
Very Ecotypes of grasses
Tolerant:
EPA guidelines for sludge application rates are based on the soil
cation exchange capacity and the concentrations of zinc, copper and
nickel, as shown above in Equation 1. The limits imposed by this
equation are designed to keep down the level of heavy metals being
absorbed by plants and to protect the fertility of agricultural lands
(Reference D-4) .
Pathogens
The control of pathogens is of importance because of possible direct
exposure to sludge in the handling and application steps and in the
food chain. Although anaerobic digestion reduces the pathogen content
of sludge, a significant number of pathogens may survive the process
(Reference D-2). There is no documented evidence of disease caused by
the use of digested sludge on agricultural land, yet some pathogenic
organisms have been reported to survive in soils for long periods of
time.
Four major groups of pathogenic organisms that are found in munici-
pal wastewater are: 1) Salmonella, Shigella and Mycobacterium bacteria;
2) the protozoa, Entamoeba hystolytica and Naegleria; 3) Helminth
parasites, As caris, Ancyclostoma, Necator, Taenia, and Tricahuris; and
4) viruses. Of the 150 viruses isolated from sewage, only two, the
causative agents for poliomyelitis and infectious hepatitis, have been
found to be epidemiologically significant (Reference D-15). The sur-
vival and movement of viruses through the soil is the subject of much
research (Reference D-16). Fecal and total coliform bacteria, although
not pathogenic, are used for pathogen determinations because of their
large numbers and the ease of measurement as an indication of the
presence of other enteric bacteria and pathogens (Reference D-15).
D-13
-------
Additional pathogen reduction beyond that attained by stabilization
can be achieved by the following methods:
1) Pasteurization for 30 minutes at 70°C (158°F);
2) High pH treatment, typically with lime, at a pH greater than 12
for 3 hours;
3) Long-term storage of liquid digested sludge for 60 days at 20°C
(68°F) or 120 days at 4°C (40°F);
4) Complete composting at temperatures above 55°C (131°F) for at
least 30 days;
5) Use of chlorine or other chemicals to stabilize and disinfect
sludge (Reference D-4, D-2).
Current research shows preliminary promise in the use of high energy
electrons for disinfection of sludge passing in a thin stream in a
specifically adapted process (Reference D-31).
The viability of pathogens is extremely variable and may be from a
few hours to several months. Among the factors influencing the survival
of pathogens in the soil and on vegetation are:
1) Type of organism;
2) Temperature - lower temperature increases viability;
3) Moisture - longevity is greater in moist soils than in dry soils;
4) Type of soil - neutral, high moisture holding soils favor sur-
vival; and
5) Organic matter - the type and amount of organic matter present
may serve as a food or energy source to sustain the microorgan-
isms (Reference D-2).
The potential for groundwater contamination by pathogens is depend-
ent on the ability of pathogens to survive and move through the soil
system. Fine clay solids are more effective than sandy soils for the
removal of pathogens. A soil system is generally efficient in removing
pathogens unless rapid movement of sludge (or later, irrigation water)
occurs through large cracks in the soil profile. Generally, surface
water contamination constitutes a greater hazard through surface
erosion or surface water runoff during periods of snowtnelt or thunder-
storm precipitation (Reference D-2).
EPA guidelines state that sludge-treated land should not be used
for human food crops to be eaten raw until three years after sludge
application. Sludge applied to crops which are cooked or processed be
before consumption, to pastures, or to crops used for forage, should
test negative for pathogens by normally applied analytical procedures.
EPA suggests the use of Salmonella and Ascaris as pathogens of choice
for a monitoring program (Reference D-4).
D-14
-------
Salts
The soluble ions calcium, magnesium, sodium, potassium, chlorine
and carbonate are the principle inorganic ions added to soil in sludge
and mineralized from sludge organic materials in large concentrations.
These highly soluble salts are involved in exchange reactions in the
soil and, depending upon the composition of the adsorbed phase, will
be temporarily retained and slowed in their passage through the soil.
In the Denver area, normally there is sufficient excess irrigation or
rain water available to flush these ions through the soil and into the
groundwater table. In arid and semi-arid parts of the country, water
is relatively expensive and thus scantily used, and rainfall is infre-
quent, resulting in an accumulation of salts in the upper soil layers.
This accumulation can, in time, prove deleterious to crops. Frequently,
in the case of high sodium concentrations, soil permeability is drasti-
cally decreased before sodium directly affects plant growth. This
occurs with too high a percentage of sodium ions on the exchange sites
when sodium replaces calcium and magnesium ions on clay particles, dis-
persing the soil particles and decreasing soil permeability.
The salt content of soils is determined by the electrical conductiv-
ity (millimhos per cm) or percent of the soil mass in more severe con-
ditions. Generally, when the conductivity rises to above 4.0 minhos/cm,
the salt content is considered high and.will affect yields of all except
salt-tolerant plants (Reference D-19).
Crops commonly grown in the Denver region will suffer 50 percent
reduction in yield at a soil salt concentration of 0.25 percent (with
50 percent water saturation). Assuming a 1.2 m [4 ft]- root zone and
a background salt level of 0.05 percent, 200 metric tons [200 tons] of
dry solids would add the maximum limit of 0.20 percent more salt to the
root zone (Reference D-l).
Low-rate application of sludge probably will not cause salt accumu-
lation in amounts that would affect plant growth. For irrigated land,
the leaching provided by the irrigation water should prevent a harmful
buildup of salts. Crop yield would be reduced on dry land farms by
lower salt concentrations that were not flushed by leaching. At load-
ing rates of less than 1 m ton per year [1 ton/yr], over 100 years would
be required to reach potentially harmful salt concentrations of 0.15 per-
cent in the soil (Reference D-l). Salt accumulation in soils is easily
monitored and can be controlled with proper management.
Boron is a potentially hazardous element, commonly viewed with
alarm in irrigation waters. The most boron-sensitive crops are adverse-
ly affected at levels above 0.3 mg/1 in the irrigation water. No
limits have been established on the tolerable levels of boron in
sludges; however, it is possible to compare boron loadings resulting
from typical irrigation applications with equivalent applications of
D-15
-------
sludge. About 100 mg/kg of boron concentration in sludge, applied with
recommended limits, can be considered a safe limit. Historical data on
the boron concentration of sewage sludges in Denver do not exist. A
recent grab sample analysis of the three Denver sludges produced the fol-
lowing boron concentrations:
Denver Central Plant Primary Sludge: 60 mg/kg
Denver Central Plant Waste Activated Sludge: 62 mg/kg
Denver North Side Digested Primary Sludge: 31 mg/kg
AGRICULTURAL CONSIDERATIONS
Fertilizer Value
Anaerobically digested sludge contains all of the essential plant
nutrients and has valuable soil conditioning properties. The literature
contains many references to increased plant growth resulting from the
application of sludge. The major fertilizing elements, nitrogen, phos-
phorus and potassium, are present in varying proportions depending upon
the nature of the sludge and other factors such as the length of time
which the sludge has been dried or stored. Essentially, the solids
portion of the sludge contains most of the nitrogen and phosphorus,
while the liquid portion contains most of the potassium (Reference D-20).
In calcareous soils, such as those found in the Denver area, potassium
is more available to plants than in non-calcareous soils, and thus the
low potassium content of dried sludge would probably not need to be
supplemented by commercial fertilizer.
Total nitrogen content of air-dried sludge is approximately 6 to 8
percent of the dry weight, with about one-half of that present as
ammonium nitrogen. It is assumed that approximately 30 percent of the
total nitrogen in applied sludge is made available for plant use in
the first year, 15 percent in the second year, 10 percent in the third
year, and 5 percent in the fourth and succeeding years. Since nitrogen
is usually considered to be the limiting factor in annual sludge
application rates, sludge as a commercial fertilizer substitute can
supply the needed amount of nitrogen for a particular site and crop.
Other nutrients, such as potassium, may be deficient and require supple-
mental fertilization. Phosphorus (at 3 percent of the dry solids) is
abundantly supplied in an application which is computed to balance
nitrogen with uptake by plants. The possibility of applying excess
phosphorus exists in non-calcareous soils.
Fertilizer Market
In 1972, 36,000 metric tons [40,000 tons] of fertilizer were sold
in the Denver area, a large part of which was used for urban lawns,
gardens and other non-farm purposes (Reference D-l). The 1970 farm
fertilizer use percentage by crop and the total land area are shown
D-16
-------
in Table D-2. The main source of organic fertilizer in Colorado is
livestock manure (88 percent), with about 10 percent of organic fertiliz-
er sales consisting of sewage sludge (Reference D-l). Commercial
sales of natural organic fertilizers have dropped off considerably in
Colorado, but the amount of manure that is used for fertilizer far
exceeds the amount which is sold commercially (Reference D-l).
The overall commercial fertilizer market adds perspective to the
use of sludge in place of chemical fertilizers. Increased demands are
being made on the fertilizer industry as a result of various factors,
including the energy crisis, the need for heavier applications in old
farming areas, and increases in newly added farming areas. Domestic
supplies are predicted to fall short of the demand, and the increasing
prices of commercial fertilizer may induce more farmers to view the use
of sludge favorably.
The ability of sludge to compete with fertilizers in the marketplace
is an issue that will certainly emerge in the near future. For example,
at a trucking cost of $0.08 per cubic meter-kilometer [$0.10/cu yd-mile], a
distance of about 100 km [60 mi] would represent the limit at which the
transportation cost of air-dried sludge (with 5 percent nitrogen on a
dry weight basis and 50 percent solids) equals the current price of
equivalent commercial chemical fertilizer nitrogen ($0.55 per kilogram
[$0.25/lb]) alone. A general formula for computing the break-even
distance for trucking sludge is given simply by:
D = F NYWS (Equation D-3)
where D is distance from the distribution center to the ultimate appli-
cation area, F is unit commercial fertilizer cost, N is fraction of
nitrogen in the dry solids, W is the fraction of solids in the slude, S
is specific weight of sludge and Y is cost of trucking a unit volume of
sludge (including Water) over a unit distance, all parameters being in com-
patible (metric or English) units. Application cost is assumed equal for
sludge and chemical fertilizer.
Crop Selection
Selection of crops suitable for growth on sludge-enriched soils
should be done in consultation with the local extension service of the
U. S. Department of Agriculture. Plants vary widely in their reactions
to sludge application, and these reactions are site-dependent. Under
most conditions, some crop species take up and accumulate certain trace
elements, reducing crop yield and inhibiting use in the food chain. The
major factors governing crop response on sludge amended soils are soil
type, pH, moisture content, climate, and crop species. Soils that
have a neutral or higher pH, a high cation exchange capacity and a
high amount of organic matter reduce the availability of trace elements
and their uptake by plants.
Crops that are grown for their seeds or fruits rather than vegetative
D-17
-------
Table D-2. ON-FARM FERTILIZER USED IN DENVER AREA, 1970
i
M
00
Crop
Corn
Wheat
Sugar beets
Potatoes
Barley
Oats
Dry beans
Sorghum
Alfalfa
Total tons sold
and surface
area
Percentage of
N
51
7
23
1
10
2
0
1
5
100
4,003, metric
[A, 413, short]
total element
P
12
1
50
3
19
2
I
I
11
100
1,187, metric
[1,308, short]
applied
K
__ .
-
28
16
-
-
7
11
38
100
110,
[121,
Hectares
planted
32,684
123,525
8,829
830
33,453
14,418
4,617
3,657
37,058a
metric 259,070
short ]
Acres
planted
80,700
305,000
21,800
2,050
82,600
35,600
11,400
9,030
91,500a
639,680
Harvested.
Source: Agricultural Reuse Program (Reference D-l).
-------
tissue and crops whose younger rather than older vegetative tissue is
utilized are more desirable in terms of trace element accumulation.
Some crop species and varieties are more tolerant to trace elements
than others. Field crops such as corn, small grains, and soybeans are
moderately tolerant. Most grasses (fescue, lovegrass, Bermudagrass,
orchard grass, perennial ryegrass) are tolerant to high amounts of
metals. Unusually metal-tolerant ecotypes of the grasses are found on
ore outcrops containing extremely high amounts of metals (Reference
D-5). The leafy vegetables such as beets, mint, vine, lettuce, swiss
chard, tend to accumulate cadmium and other heavy metals in their
le aves.
The nutrient uptake potential of different crops is essential
information for determining nitrogen loading rates, as discussed above
under Nitrogen. Table D-3 presents nitrogen uptake by certain forage,
field and forest crops. The varying capacities of different crop
species to use water through evapotranspiration relate to the water
regime of the area and possible salt accumulations in the soil. Daily
consumptive water use of three crops, grown near Denver is shown in
Figure D-l.
The selection of vegetative cover can also influence the potential
for contamination of surface waters, since certain plants stabilize the
soils and control erosion and runoff more efficiently than others. For
example, most grasses would be superior to crops such as soybeans or
corn in the control of runoff (Reference D-20).
Germination
The inhibition of germination following the application of liquid
digested sludge on soils has been occasionally reported. The results
of two research efforts in this field are briefly presented below.
Molina, Braids, Hinesly and Cropper conducted experiments with corn
and soybeans (Reference D-22). Seeds did not germinate in the liquid
phase of fresh digested sludge. This inhibition was not due to ammon-
ium nor solely due to a salt effect, an oxygen deficiency, or a low
oxidation-reduction potential of the medium, they concluded. Seeds
did germinate in digested sludge which had been aged in contact with
the air for one week.
Sabey and Hart worked with sorghum sudangrass, millet and wheat,
using Metro Denver sewage sludge (Reference D-19). They found that
increasing amounts of sewage sludge caused increased inhibition of
germination and emergence of sorghum sudangrass and millet when planted
shortly after the sludge was incorporated into the soil. Wheat was
planted five months later and did not show any inhibitory effects, even
with high rates of application. A later greenhouse study (the results
of which have not been completely analysed) shows that with low applica-
tion rates (22 to 45 metric tons/hectare [10 to 20 tons/acre]), two
D-19
-------
Table D-3. REPORTED NUTRIENT REMOVAL BY CROPS
Crop
Forage
Coastal Bermuda grass
Reed canary grass
Fescue
Alfalfa
Sweet clover
Red clover
Lespedeza hay
Field
Corn
Soy beans
Irish potatoes
Cotton
Milo maize
Wheat
Sweet potatoes
Sugar beets
Barley
Oats
Forest
Young deciduous (up to 5 years)
Young evergreen (up to 5 years)
Medium and mature deciduous
Medium and mature evergreen
Nitrogen
(kg/ha/yr)
538-672
253-402
308
174-246
177
86-141
146
174
105-127
121
74-112
91
56-85
84
82
71
59
112
67
34-56
22-34
uptake
(Ibs/ac/yr)
480-600
226-359
275
155-220a
158a
77-1263
130
155
94-1133
108
66-100
81
50-76
75
73
63
53
ioob
60b
30-50b
20-3 Ob
legumes obtain a substantial part of their nitrogen requirements
from the air.
tv •
Estimated.
Source: Design Seminar for Land Treatment of Municipal Waste-
water Effluents (Reference D-21).
D-20
-------
<
I5
I
UJ
CO
I-
OL
CO
z
o
o
< 2
Q
i0.30
LEGEND
ALFALFA
CORN (GRAIN)
WINTER WHEAT
0.25
I
I
10.20
UJ
O)
UJ
O.I5 >
I-
Q.
CO
•z.
o
10.10 °
\
0.05
MAR. APRIL MAY JUNE JULY AUG. SEPT. OCT. NOV.
MONTH
SOURCE : AGRICULTURAL REUSE PROGRAM ( REFERENCE D-l )
FIGURE D-l
DAILY CONSUMPTIVE WATER USE OF CROPS
GROWN NEAR DENVER,COLORADO
0-21
-------
weeks to one month is sufficient to eliminate the inhibitive effects
on wheat. The time period increases with higher rates of application.
The germination of corn and sorghum sudangrass hybrid was somewhat more
affected by the sewage sludge than the wheat, although this result was
thought to be adversely affected by greenhouse conditions.
Sabey and Hart conducted a preliminary study to determine whether
inorganic salts or organic compounds caused the germination inhibition
(Reference D-19). The authors concluded that the salt content of the
sludge did not cause the inhibition, and that the inhibitive factor is
associated x^ith the organic compounds since destroying or volatilizing
the organic compounds eliminates the inhibition.
Weeds
Weed control may be a major problem when sludge is applied to agri-
cultural land, although the literature contains few references to this
problem. A cause of weeds associated with sludge applications is the
viability of seeds of many food crops through the human digestive
system and the wastewater and sludge treatment processes. Application
of sludge may necessitate the use of herbicides for effective weed
control. The concentration of herbicides in runoff and drainage water
should be monitored.
Application Rates
Application rates depend on sludge composition, soil characteris-
tics, climate, vegetation, and cropping practices. Applying cludge at
an annual rate to support the nitrogen needs of a crop avoids problems
associated with pollution of water supplies. Almost all ill-effects a-
rise from too heavy or too frequent applications of sludge (Reference D-3).
Total sludge application limitation is imposed by heavy metals content
of the sludge and is defined by Equation D-l on page D-5. Annual applica-
tion rate, on the other hand, is constrained by the available nitrogen
content of the sludge and is expressed in Equation D-2 on page D-ll above.
General Conclusions
The application of liquid digested sludge has been shown by research
and by practical experience to have beneficial effects on agricultural
lands if proper rates of application (as determined by the properties of
the sludge, the nature of the site and the characteristics of the crops
grown) are adhered to. These beneficial effects are generally the re-
sult of the enhancement of soil properties and the addition of plant
nutrients that lead to increased crop yields. There are many references
that document increases in plant growth as a direct result of the applica-
tion of sludge. Some studies even show that yields are higher on sludge
enriched soils than on soils which have received commercial fertilizer.
(Reference D-23).
-------
Although the application of sludge to a given area is extremely
site dependent, some general conclusions which may be of use are pre-
sented below (Reference D-10, D-15, D-19):
1) Salt buildup in the soil can create a short term hazard to
plant growth, but will not cause long-term problems if proper
irrigation and drainage practices are followed.
2) Pathogenic dangers, as indicated by fecal coliforms, will not
extend more than 120 to 150 cm (50 to 60 in.) into the soil
profile, nor last more than 2.5 months near the soil surface.
3) Heavy metal contamination of the groundwater is not a problem
even at high sludge loadings because of the soil's ability to
adsorb and retain them. Cadmium may be the first metal to
present such a problem (Reference D-15).
4) Heavy metal uptake by plants grown on sludge amended soil is
not expected to be excessive and should cause no plant toxicity
or human dangers as long as the ultimate application rate limit
is not exceeded.
5) Nitrate leaching to the groundwater can be substantial, increas-
ing directly with sludge application rates, and will be the
first limiting factor for sludge application on a yearly basis.
6) Nitrate leaching can be controlled with management techniques
involving balancing nitrogen applications with crop uptake.
7) Potential hazards to the groundwater can be more accurately
monitored by measuring leachate quality and quantity than
through direct groundwater sampling.
8) Direct ingestion of sludge-applied soil by domestic animals
can be a potential danger to the human food chain through direct
accumulation of heavy metals in edible tissues.
9) Seed germination can be inhibited if sludge is added just prior
to planting. If planting is conducted two weeks to one month
after sludge application, seed germination is uninhibited.
10) Properly digested sludge will produce no offensive odors after
application and incorporation into the soil.
11) A sound agronomic and environmental principle is to apply the
least amount of sludge that will supply sufficient nutrients
for plant growth.
D-23
-------
12) Monitoring is necessary for sludge application programs to
ensure against creating environmental hazards.
CHEMICAL PROPERTIES OF METRO DENVER SLUDGE
The organic material generated by the Metro Denver Sewage Disposal
District No. 1 will be anaerobically digested, and will contain organic
and inorganic nutrients, humus, and residual levels of various metallic
compounds. The digested sludge will contain 6 to 8 percent total
nitrogen (expressed as a percentage of the dry weight of the organic
materials), of which 3 to 4 percent (of the total dry solids) will be
ammonia nitrogen. The sludge will contain approximately 3 percent
total phosphorus.
The most recent heavy metals concentrations of primary and waste-
activated sludges from the Northside and Central treatment plants are
presented in Table D-4. A flow-weighted average concentration is also
computed and presented for the mixture that would result from blending
these sludges. A comparison of the quality of this mixture with that
of a "good" sludge is presented in Table D-5.
It can be seen that nickel and copper exceed the suggested limits.
Excessive levels of these two heavy metals can adversely affect plant
growth. The cadmium/zinc ratio, which is perhaps the most important
indicator of heavy metal toxicity, is higher than the suggested limits.
However, with the conservative application rate recommendations and the
calcareous nature of soils in the study area, it probably will not
cause a significant problem.
Metro Denver sludge contains all of the essential plant nutrients
and possesses soil conditioning properties. The nitrogen content is
satisfactory for fertilization purposes. The longer sludge is dried,
the more ammonium nitrogen is lost through volatilization.
LAND USE OPTIONS FOR SLUDGE APPLICATION
Four specific land use areas are being considered by Metro Denver
for the application of sludge. These are: 1) city parks, 2) mine
spoil sites, 3) sod farms, and 4) irrigation and dryland farms. In
this section, specific parameters will be discussed as they relate to
each land use.
City Parks
The literature contains general references to the application of
sludge on city parks, lawns and golf courses, but no definitive studies
have been reported. In New York City, sludge has been used as a soil
conditioner to produce artificial topsoil on proposed park sites (Ref-
D-24
-------
Table D-4. SLUDGE HEAVY METALS CONTENT COMPUTED FROM SAMPLES OBTAINED
AND ANALYZED OVER A PERIOD OF FOUR MONTHS IN EARLY 1975
Parameter
Zinc
Copper
Nickel
Chromium
Lead
Cadmium
,. d
Manganese
Mercury6
Cd/Zn ratio
Pri-
mary
sludgesa
927
587
268
301
275
9
131
17.8
0.0065
Heavy metals content ,
ing/kg dry sludge
Concentrated
waste-activated
sludges'3
1,252
916
289
545
383
24
97.5
4.2
0.019
Flow-
weighted
average0
1,145
808
282
465
347
19
109
8.7
0.017
Arithmetic averages computed for 18 samples except for manganese and
mercury (see footnotes d and e, below).
Arithmetic averages computed for 17 samples except for manganese and
mercury (see footnotes d and e, below).
Q
It was assumed that the mixture contains 33 percent primary and 67
percent concentrated waste-activated sludge.
Arithmetic averages computed for two samples.
g
Arithmetic averages computed for three samples.
Source: Raw data obtained from Metropolitan Denver Sewage Disposal
District No. 1.
D-25
-------
Table D-5. COMPARISON OF METRO DENVER SLUDGE HEAVY METAL CONTENT
WITH SUGGESTED LIMITS
(mg/kg dry solids)
Element
Zinc
Copper
Nickel
Chromium
Lead
Cadmium
Manganese
Mercury
Boron
Existing
concentrations
1,145
808
282
465
347
19
109
8.7
51a
Suggested
(Reference D-24)
1,500
750
150
500
500
50
-
-
-
limits
(Reference
2,000
800
100
-
1,000
< 0.5 % of
-
15
100
D-13)
zinc
Cadmium/zinc
ratio
0.017
0.001 - 0.005b
0.005
Obtained by computing a sludge solids flow-weighted average of grab
samples described on page D-15. Grab samples were collected on 30
October 1975.
Reference D-13.
D-26
-------
erence D-ll). Composted sludge and leaf mold are being used to
renovate the soil at the newly created Constitution Gardens in Washing-
ton, D.C. (Reference D-25). Liquid and possibly dewatered sludge can
be applied to the surface of turf grass, but odor might be a problem
and time would be required before traffic could be allowed to return
(Reference D-14). The timing of sludge application could control the
odor problem. If sludge is applied in the winter, the snow and moisture
will carry the nitrogen value to the root zone, will eliminate any
perceptive odor, and will accelerate lawn growth in the spring (Reference
D-26).
In general, grass is a good crop for sludge fertilization because
it is tolerant of heavy metals, has a high rate of nitrogen uptake,
and minimizes problems from runoff. Furthermore, with each cutting
appreciable quantities of salts and nutrients are removed from the
land, if only to be placed in landfills.
Mine Spoil Sites
The literature contains many references to the use of sewage sludge
for revegetation programs on mine spoil sites. Most of these sites
have been coal mine spoils, although the extreme environmental conditions
associated with coal mine spoil sites are generelly similar to those of
other large scale mining operations. In general, problems result from
extremely acid soil conditions, high rates of erosion and runoff, acidic
runoff, toxic levels of certain metals in the soil, low soil fertility,
low soil moisture content, and high summer surface temperatures. Be-
cause of the nature of mining operations, spoil sites necessarily do
not possess a substrate favorable to plant growth. Most soils evolve
over long periods of time as a result of x^eathering of parent material
and the accumulation of organic matter.
Experiments with revegetation of spoil sites have confirmed the
difficulty of establishing vegetative cover on such harsh conditions.
There is frequently 100 percent mortality of plants on spoil sites with
no amendment. On sites treated with sludge, plants germinate and
survive.
The potential toxicity of a mine spoils site is best characterized
by the pH, Although there is a difference in plant tolerance to acidity,
a spoil material with pH below 4.0 is toxic to most plants. The pH of
most spoil sites is between 2.0 and 3.0. At these values the high
solubility of certain metals such as iron, aluminum and manganese
severely inhibits plant growth. Evans and Sopper report that on an
experimental plot, the untreated control boxes had complete mortality
of trees, grasses and legumes. They also had the lowest average values
for phosphorus and nitrate-nitrogen and the highest values of iron,
manganese and aluminum. Plots treated with effluent and sludge, had
the highest values for phosphorus and nitrate-nitrogen and the lowest
for iron, manganese and aluminum. Since benign spoil materials are also
D-27
-------
low in soluble phosphorus and nitrate-nitrogen, they concluded that
iron, manganese and aluminum are more directly related to revegetation
failures. The higher concentrations of these and other heavy metals
appear to be the results of solubilization of the native rock by the
high acidity. Irrigation with effluent and sludge leached and diluted
the native salts (Reference D-27). The addition of sludge also
increased both phosphorus and potassium levels in the treated spoil
(Reference D-28) .
The establishment of a complete ground cover of vegetation is highly
desirable since it can result in (1) earlier stabilization and reduction
of erosion; (2) earlier mitigation of acid drainage by diminishing net
recharge through increased evapotranspiration losses; (3) the
acceleration of accumulation of organic residues which will chelate
and otherwise make unavailable the soluble iron, manganese and
aluminum (Reference D-27). Organic residues also provide the necessary
seed bed for plant germination.
The major effects of the application of digested sludge to mine
the spoil sites include the improvement of spoil pH, increased
infiltration of precipitation, the germination and establishment of
vegetation, and the reduction of acidity and concentrations of some of
the chemicals in the runoff issuing from the site (Reference D-29).
Sod Farms
The use of digested sludge on sod farms has been proposed by
Metro Denver and some of the sod growers in the Denver Area. Sludge
contains all of the essential plant nutrients and enhances soil
properties through the addition of organic residues. Sod farming
involves the periodic removal of the topmost plant and soil layers,
thus the importance of the ability of sludge to provide continuing
soil-building material becomes apparent. Site conditions regulate the
application rate of sludge, depending on specific soil and crop
characteristics. Grass is a good crop for sludge fertilization because
it is tolerant of heavy metals, is not used as feed or food, has a
high rate of nitrogen uptake, and minimizes problems from runoff and
erosion. If sludge is applied in the winter, the snow and moisture
will carry nitrogen to the roots, will eliminate any perceptive odor,
and will accelerate vegetative growth in the spring (Reference D-26).
Irrigation and Dryland Farms
Digested sludge has been used widely in agriculture throughout the
United States and in other parts of the world. Most of the material
discussed in this appendix relates to the agricultural use of sludge
and need not be repeated. In general, dry farmland will sustain a
lower application rate of sludge because the rate of nitrogen uptake
of dryland crops is much lower than that of irrigated crops. Most
irrigated and non-irrigated crops grown in the study area are either
D-28
-------
not consumed by humans or are processed to such a degree that sludge
contaminations are removed.
Irrigated crops include many plants intended for direct human
consumption with minimal processing. Even though it is not recommended
to apply sludge on fields growing such crops, proximity of the various
fields, rotation patterns and loss of records may lead to inadvertent
sludge contact with these plants. Therefore, a greater degree of im-
portance should be attached to control and management recommendations
to mitigate adverse impacts on the food chain.
D-29
-------
REFERENCES FOR APPENDIX D
D-l. CH2M HILL, Agricultural Reuse Program, Denver, Colorado,
March 1973.
D-2. U.S. Environmental Protection Agency, Process Design Manual for
Sludge Treatment and Disposal, EPA 625/1-74-006, October 1974.
D-3. Evans, James 0., "Soils as Sludge Assimilators," Compost Science,
Vol. 14, No. 6 (Nov.-Dec. 1973).
D-4. U.S. Environmental Protection Agency, Municipal Sludge Manage-
ment: Environmental Factors, Technical Bulletin, EPA 430/9-75-
XXX, Preliminary Draft.
D-5. Chaney, Rufus L. "Recommendations for Management of Potentially
Toxic Elements in Agricultural and Municipal Wastes," in "Fac-
tors Involved in Land Application of Agricultural and Municipal
Waste," USDA, ARS, Beltsville, Maryland, 1974.
D-6. Ellis, Boyd G., "The Soil as a Chemical Filter," in Recycling
Treated Municipal Wastewater and Sludge Through Forest and Crop-
land, Edited by William E. Sopper and Louis T. Kardos, The Penn-
sylvania State University Press, University Park, 1973.
D-7. Epstein, Emanuel, Mineral Nutrition of Plants: Principles and
Perspectives, John Wiley and Sons, New York, 1972.
D-8. Anonymous, "Waste Water Expert Answers Indignant Old Lady,"
Compost Science, Autumn, 1969.
D-9. Lisk, Donald J. "Trace Metals in Soils, Plants, and Animals,"
Advances in Agronomy, Vol. 24, 1972.
D-10. Hinesly, T. D., 0. C. Braids, and J. E. Molina, Agricultural
Benefits and Environmental Changes Resulting from the Use of
Digested Sewage Sludge on Field Crops, U. S. Environmental Pro-
tection Agency, SW-30d, 1971.
D-ll. Kirkharn, M. B., "Disposal of Sludge on Land: Effect on Soils,
Plants, and Ground Water," Compost Science, Vol. 15, No. 2
(March-April 1974).
D-30
-------
D-12. Epstein, Eliot, "The Physical Processes in the Soil as Related to
Sewage Sludge Application," in Proceedings of the Joint Confer-
ence on Recycling Municipal Sludges and Effluents on Land, U.S.
Environmental Protection Agency, U.S. Dept. of Agriculture, and
the National Association of State Universities and Land Grant
Colleges, Champaign, Illinois, July 9-13, 1973.
D-13. Chaney, Rufus L. "Crop and Food Chain Effects of Toxic Elements
in Sludges and Effluents," in Proceedings of the Joint Confer-
ence on Recycling Municipal Sludges and Effluents on Land, U.S.
Environmental Protection Agency, U.S. Dept. of Agriculture, and
the National Association of State Universities and Land Grant
Colleges, Champaign, Illinois, July 9-13, 1973.
D-14. Walker, John M., "Sewage Sludges — Management Aspects for Land
Application," Compost Science, Vol. 16, No. 2 (March-April 1975).
D-15. Trout, T. J., J. L. Smith and D. B. McWhorter, Environmental
Effects of Land Application of Digested Municipal Sewage Sludge,
Interim Report, Department of Agricultural Engineering, Colorado
State University, Fort Collins, Colorado, 1975.
D-16. Office of Research and Monitoring, Task Force Report on Sludge
Disposal, U.S. Environmental Protection Agency, April 1972.
D-17. Malina, Joseph F., Jr., and Bernard P. Sagik, Eds., Virus Sur-
vival in Water and Wastewater Systems, Water Resources Symposium
No. 7, Center for Research in Water Resources, the University of
Texas at Austin, 1974.
D-18. Kellogg, Clay, "The Business of Processing and Marketing Wastes
as Fertilizer and Soil Conditioner," Compost Science, Vol. 16,
No. 3 (May-June 1975).
D-19. Sabey, B. R. and W. E. Hart, Land Application of Metro Denver
Municipal Sewage Sludge, Final Report, Colorado State University,
Agricultural Experiment Station, 1972.
D-20. Carroll, Thomas E., David L. Maase, Joseph M. Genco, and Chris-
topher N. Ifeadi, Review of Landspreading of Liquid Municipal
Sewage Sludge, National Environmental Research_Center, Office of
Research and Development, U.S. Environmental Protection Agency,
EPA 670/2-75-049, June 1975.
D-21. Powell, G. Morgan, Design Seminar for Land Treatment of Munici-
pal Wastewater Effluents, prepared for U.S. Environmental Pro-
tection Agency, Technology Transfer Program, CH2M HILL, Denver,
Colorado, May 1975.
D-31
-------
D-22. Molina, J. A. E., 0. C. Braids, T. D. Hinesly, and J. B. Cropper,
"Aeration-Induced Changes in Liquid Digested Sewage Sludge,"
Soil Science Society of America Proceedings, 35: 60-63, 1971.
D-23. Struble, Robert G., "Sewage Sludge Aids Farm Crops in West Ches-
ter, Pennsylvania," Compost Science, Vol. 15, No. 2 (March-April,
1974).
D-24. Shipp, Raymond F. and Dale E. Baker, "Pennsylvania's Sewage
Sludge Research and Extension Program," Compost Science, Vol. 16,
No. 2 (March-April 1975).
D-25. Patterson, James C., "Enrichment of Urban Soil with Composted
Sludge and Leaf Mold — Constitution Gardens," Compost Science,
Vol. 16, No. 3 (May-June 1975).
D-26. Olds, Jerome, "How Cities Distribute Sludge as a Soil Condition-
er," Compost Science, Autumn, 1960.
D-27. Evans, James 0. and William E. Sopper, "Forest Areas for Dis-
posal of Municipal, Agricultural, and Industrial Wastes," Paper
presented at the Seventh World Forestry Congress, Buenos Aires,
Argentina, October 4-18, 1972.
D-28. Sutton, P. and J. P. Vimmerstedt, "Treat Stripmine Spoils with
Sewage Sludge," Compost Science, Vol. 15, No. 1, (January-Feb-
ruary 1974).
D-29. Lejcher, Terrence R. and Samuel H. Kunkle, "Restoration of Acid
Spoil Banks with Treated Sewage Sludge," in Recycling Treated
Municipal Wastewater and Sludge through Forest and Cropland,
edited by William E. Sopper and Louis T. Kardos, The Pennsyl-
vania State University Press, University Park, 1973.
D-30. Pratt, 0. F. "Effects of Sewage Sludge or Effluent Application
to Soil on the Movement of Nitrogen, Phosphorus, Soluble Salts
and Heavy Metals to Groundwaters," presented at 2nd National
Conference on Municipal Sludge Management and Disposal, Anaheim,
California, August 18-20, 1975.
D-31. Farrell, Joseph, "High Energy Radiation in Sludge Treatments —
Status and Prospects," presented at 2nd National Conference on
Municipal Sludge Management and Disposal, Anaheim, California,
August 18-20, 1975.
D-32. Miller, R. H., "Factors Affecting Decomposition of an Anaerobi-
cally Digested Sewage Sludge in Soil," Journal of Environmental
Quality, Vol. 3, No. 4, 1974.
D-32
-------
-------
The discussion of environmental setting,
presented in Section III is supplemented in this
Appendix with a detailed study of site-specific
environmental characteristics. The sites dis-
cussed here include the drying and distribution
site, the representative sludge reuse sites
(city parks, sod farms, mine spoil sites, irri-
gated farms and dryland farms), and the site of
the existing operations at the Lowry Bombing
Range.
-------
APPENDIX E
ENVIRONMENTAL SETTINGS OF DRYING AND DISTRIBUTION SITE AND
SPECIFIC LAND APPLICATION SITES FOR METRO DENVER SLUDGE
DRYING AND DISTRIBUTION SITE
The proposed drying and distribution center, Site B-2, is located
about 32 km [20 miles] east of the District's Central Plant. As shown
on Figure 2, it is 18 km [11 miles] southeast, of Barr Lake and is bordered
on the south by Irondale Road. The site is rectangular, extending about
2.4 km [1.5 miles] in an east-west direction and 3.2 km [2 miles] in a
north-south direction. The description of the environmental setting of
the drying and distribution site is taken from "Metro Denver Sludge Man-
agement, Volume IV, Environmental Assessment," by CH2M-H111 (February
1975).
Topography
The topography of the project area is slight to moderately rolling
slopes. Elevation of the terrain ranges from approximately 1,570 m to
16,40 m [5,150 ft to 5,390 ft] above sea level. There is a slight ridge
running north-south through the center of the site. The view to the
north from Irondale Road is generally unobstructed by topographic fea-
tures up to the ridge in the midpoint of the site. A pronounced drain-
ageway occupies the southeastern corner of the site.
Soils
The soils at the site are in general a tight, silty clay material
and have a low permeability rate compared to many soils in the area.
Soil depths have not been determined in the area of the site. These
soils have sufficient organic materials, with satisfactory nutrient lev-
els, for most crop production. Low crop yields in the area can generally
be attributed to low rainfall.
Surface Water
The project site has no perennial streams or other water bodies.
The site is on high ground and receives runoff only from within the site.
A natural drainage area in the southeastern corner of the site subjects
a small off-site area to surface inflow and possible flooding.
E-l
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Part of the site is subject to severe water erosion problems as a
result of high-intensity, sudden thundershowers and snowmelt on unpro-
tected soils. The runoff is high in sediment and suspended solids.
Groundwater and Geology
The project area is underlain by the Denver-Arapahoe-Dawson forma-
tion and the Laramie-Fox Hills formation. Each of these formations
yields a small to moderate supply of water to wells for domestic and
livestock uses. The uppermost bedrock is the Denver or Arapahoe forma-
tion. Both formations are composed of layers of shale, sandstone
with some clay, and silt stone. The aquifers in these formations are
more or less confined, and vertical permeability between water-bearing
zones does not occur readily. The Laramie-Fox Hills formation under-
lies the site at an estimated depth of 270 to 400 m [900 to 1,300 ft]
and is considered the boundary between fresh water and brackish water.
Available resource information indicates that the water above the Laranie
formation is of good quality.
The depth to groundwater on the site is typically 15 m [50 ft] or
more, with upland wells having a water depth of 30 m [100 ft] or more.
No groundwater was encountered in the top 3 to 4 m [10 to 12 ft] during
exploratory investigations with a backhoe. The exact size and yield of
aquifers underlying the site is not known.
Biology
Vegetation—
Wheat crops are rotated on the project site, leaving 50 percent of
the crop area fallow each year. Within the southeastern corner, the site
has a 1.6-hectare [4-acre] area of overgrazed prairie. The site has no
trees or shrubs. Vegetation consists of short grasses (blue grama, west-
ern wheat and buffalo), yucca, Russian thistle, wild lettuce, sunflower
and prickly pear cactus. No rare or unique species of vegetation consid-
ered essential to the ecology of the region are present on the site.
Wildlife--
Wildlife studies did not identify any wildlife habitats essential
to the site's ecology. In the general vicinity of the site, there are
varying species of rabbit, mouse, owl, hawk and coyote. Except for the
coyotes, which are territorial animals, these species do well in dis-
turbed areas. There is sufficient area surrounding the site to provide
new habitats for animals displaced by construction.
Air Quality
Air quality in the vicinity of the project area is relatively good.
E-2
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The site is sufficiently removed from the Metropolitan Denver area to be
unaffected by the urban pollution problem. The only significant deterio-
ration of air quality in the area occurs during dust storms. The sever-
ity of these depends on conditions of wind, precipitation and soil dis-
turbance such as plowing. Even at its worst, however, wind-blown dust
does not constitute a major problem in the area.
CITY PARKS
The City of Denver has developed an elaborate park system. More
than 100 named parks, and many interconnecting landscaped parkways,
cover more than 1,100 hectares [2,800 acres] within the city limits.
The topography of Denver is relatively flat, with an elevation ranging
from about 1,570 to 1,670 m [5,150 to 5,480 ft]. Two perennial water-
courses, the South Platte River and Cherry Creek, flow through the city.
Many lakes have been created, most of which are included within the
City park system and are utilized for recreation. The lakes are dis-
cussed under General Environmental Setting, above. They are signifi-
cant with respect to runoff hazards from sludge applied to park areas
surrounding them.
Soils
The soils in the City and County of Denver have not been surveyed
for agronomic purposes because of the predominantly nonagricultural
land use in the metropolitan area. Therefore, detailed information
about these soils is unavailable. The information presented is thus
surmised from the general surface geology and soil conditions of the
surrounding counties, augmented with limited site observations.
It is assumed that soils in the City parks are generally low in
clay content (loams, silt loams, sandy loams and possibly some dry
loams), with correspondingly low cation exchange capacity. Most of the
soils are probably calcareous, beginning at some depth below the sur-
face, if not found throughout the profile. Because of the necessary
grading and leveling activities, most of the profiles are probably sub-
stantially altered, and most of the topsoil has been moved from one
place to another. Of the more than 100 established parks in Denver,
most are on subsoils of heavy clay "plated" with a thin layer (7.5 to
10 cm [3 to 4 in.]) of imported topsoil. Some 15 to 20 parks are
planted on old landfills with a fine cover of topsoil.
Biology
Vegetation—
The vegetacion of the City parks can be characterized generally
as urban landscaping and has been described above, under Urban/Residen-
tial Unit. With the exception of the two stream courses traversing the
E-3
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cicy, the site of Denver was originally part of the mixed prairie, but
a variety of nonnative trees has been planted along the streets and in
the parks. Chief among these trees are soft maple, elta, weeping willow,
Carolina poplar, Lombardy poplar, ash, sycamore, Norway pine, Russian
olive and several varieties of fruit trees. The City park system is
entirely artificial, with extensive lawns, gardens, shrubs and trees
having been planted on graded, leveled and filled areas. Many of the
parks include golf courses with extensive areas of grass.
Some nearby urban communities with extensive park sites, such as
Northglenn, Commerce City and Aurora, have expressed interest in apply-
ing sludge to their City parks, also.
Wildlife--
The urban and residential environs of the Denver Metropolitan area
represent a unique, though unnatural, environment. The introduction of
nonnative shrubs, herbs, grasses and trees has incidentally selected
and attracted many animal species that normally would not occur in this
area.
Chief examples of such introductions are the red-eyed vireo,
bronzed grackle, robin and house sparrow. Some species are typically
introduced with urbanization and become established as pests which de-
stroy food and property or endanger public health. These "undesirables"
include the starling, house mouse, Norway rat and, in some cases, the
pocket gopher.
A woodland—type atmosphere has been created by planted groves of
trees within many of the City parks. Native species which can adapt to
human presence include the black-capped chickadee, house finch and
chipping sparrow. Occasionally several bat species may also be found
within the trees. The large expanses of grass within the City park
system and golf courses particularly attracts robins and starlings.
Noise
The Denver Metropolitan area has many noise sources and attendant
noise pollution similar to that found in all large cities. In the resi-
dential areas, transportation systems are the most noticeable sources of
noise. Generally, the extensive City parks are bounded and traversed by
multi-laned streets and expressways. Steady automobile traffic produces
ambient noise levels of 60 to 95 decibels. Particularly abrasive noises
greater than 85 decibels are generated by trailer trucks, motorcycles and
sports cars (Reference 89).
Within the urban and residential areas, noise sources are regulated
by speed limits and designation of traffic corridors. Thus, residences
E-4
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and community facilities are somewhat screened from extreme noises.
Trees and shrubs in the residential areas, particularly in the patchwork
City park system of Denver, reduce sound levels to some degree. The
presence of decorative plantings, although they do not significantly
reduce noise levels, often have the effect of reducing the incidence of
complaint about noise (Reference 89).
Odor
At the present time, odors in City parks are determined by particu-
lar local neighborhood activities (industrial emissions in certain parts,
poorly controlled exhaust from stationary and mobile sources in other
parts and temporary odors caused by applications of chemicals to lawns
and trees, etc.). City park and public works crexra attend to the
cleanliness and maintenance of the park areas. Overall, under most con-
ditions, there are no noticeable disturbing odors present at City parks
where large numbers of people spend a great deal of time walking, sit-
ting, lying on the grass, eating lunch and engaging in sports activi-
ties.
SOD FARMS
Sod farms represent a special type of irrigated farm. Many hec-
tares in Adams and Weld counties, as well as in other areas south of
Denver, are used for this grass culture. Sod farms yield one of the
major nonconsumptive crops in the area. The sod is used solely for
landscaping and decorative plantings. Sod farms typically require warm,
sunny weather, frequent irrigation and heavy fertilization.
A representative sod farm was examined in Adams County and is
shown in Figure E-l. The farm is located near Brighton, east of Barr
Lake. It is owned by Bill Mathews and includes areas in Sections 25
and 26, T.l.S, R.65W. Elevations vary gradually.
Soils
The soil in the Mathews sod farm is nearly uniformly Trackton
loamy sand, on nearly level to moderately sloping land, as shown on Fig-
ure E-2. The soil texture is rather uniform to a depth greater than
150 cm [60 in.]. It is a noncalcareous soil with neutral pH and rather
low cation exchange capacity. The soil absorbs water rapidly and does
not allow runoff except at very high precipitation rates; thus, water
erosion hazard is very low. However, the soil is subject to severe
x^ind erosion if it is not stabilized with vegetation.
Water
Groundwater is the only source of water for irrigation of the sod
farm studied. Groundwater table is at a depth of about 20 m [60 ft].
E-5
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FIGURE E-l
BOOT LAKE RES. 3km (2miles)
E 8km (5mil
!JRRIGATED\
39km (24miles]
SOD FARM
AND
DRYLAND WHEAT FARM
E-6
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NC
f\/\
NOTE : FOR A DESCRIPTION OF SOILS AND
CORRELATION OF MAP SYMBOLS SEE
TABLE
SOILS ON THE SOD FARM AND
ADJOINING DRYLAND FARMS IN
ADAMS COUNTY
-------
However, deep reservoirs are pretreated for irrigation water supply.
The Laramie-Fox Hills aquifer, at this point, is at a depth of approxi-
mately 370 m [1,200 ft] from the land surface and is well protected by
a great thickness of intervening aquitards, as described under Geology,
above.
Surface drainage is provided by Box Elder Creek, which traverses
the Mathews farm in a north-south direction. The streambed is dry
nearly year-round and is used for a cow pasture. (The owner of the
farm proposes to apply sludge to this part of his farmland as well as
to the sod farm and adjacent dryland wheat fields.) Frequency of oc-
currence of flow in Box Elder Creek, by the estimate of the owner, is
once every five years.
Biology
Vegetation—
Kentucky bluegrass is the basic crop of the sod farm. Thick sod
mats formed by this grass constitute a stable community, effectively
excluding other competitive plant species. The crop period varies from
nine to 18 months and follows the procedure described below:
1. Seed bed preparation—The fields are plowed and graded where
necessary. Chemical fertilizers with a nitrogen-phosphorus-potassium
(N-P-K) percentage of 16-16-8 or 18-46-0 are applied to the prepared
surface at up to 110 kg/ha [100 Ib/acre].
2. Seeding—Several varieties of Kentucky bluegrass may be used.
Particular strains may be chosen for their hardiness, ability to with-
stand cold and adaptability to local conditions. Common blends include
raerion, Windsor, pennstar, fylking, baron, nugget and newport.
3. Cultivation and maintenance—The newly planted beds are irri-
gated frequently for the first three to four weeks until the plants are
set and a sod layer begins to form. At this stage, the crop undergoes
a. regimen of spray irrigation as often as once per day, weekly mowing
and monthly fertilization. Chemical fertilizers most commonly used
have an N-P-K percentage of 20-20-10 or 16-16-8, such as ammonium sul-
fate, and are applied typically at 335 kg/ha [300 Ib/acre]. Compara-
tive fertilizer usage is shown in Table E-l.
4. Crop harvest—Prior to harvesting, the sod may be treated with
a high-nitrogen fertilizer such as 46-0-0 and irrigated every one to
two days to prepare it for transporting. The upper sod layer is har-
vested with special machines, which cut an approximately 5-cm [2-in.]
thick sod and soil mat of 45-cm [18-in.] width. The sod strips are
rolled up into large rounds and immediately shipped to the customer.
E-8
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Table E-l. COMPARATIVE FERTILIZER USAGE AT SELECTED SOD FARMS IN THE DENVER REGION
I
to
Farm
A
B
C
Dd
Ee
Fertilizer
type,a
N-P-K
20-20-10
16-16-8
46-0-0
18-46-0
33-0-0
5-3-3
5-3-3
32-0-0
20-20-10
Application
rate,
kg/hac
225
335
450
110
225
1,900
1,455
450
335
Application
frequency,
times per year
7 to 8
7 to 8
1 to 2
1
4
1
7 to 8
1
4
Maximum nitrogen Crop
application rate,° cycle,
kg/ha months
335 12
705 9 to 12
315 18
450
t0 14
840 ^
270 18
fertilizer composition expressed as percentage of nitrogen, phosphorus and potassium (N-P-K) in
the total mixture.
Nitrogen is calculated as N, assuming maximum amount and number of applications per year.
Cl kg/ha = 0.893 Ib/acre.
Farm D utilizes dried poultry wastes as primary fertilizer.
eMathews farm used as representative sod farm.
Source: References 90,91,92,93,94,
-------
As the cue sod does not store well, it is usually cut the day prior to
shipping. The harvest period varies from 9 to 18 months. Vegetative
growth is most active during the spring and summer and slows consider-
ably as the weather becomes colder. During the winter months, the
grass enters a period of dormancy requiring little irrigation or fer-
tilization. This resting period is necessary for future grass growth.
The type of grass species and length of winter dormancy determine, to
a great degree, the cropping period. Sod crops can also be regrown
from the trimmed sod. When the demand is low, the sod crop—unlike
consumptive products—can remain on the ground to be harvested at a
later date without deterioration of quality.
Wildlife—
A sod farm represents a greatly simplified ecosystem of short
grass and sod. Wildlife is generally dominated by a few species, which
are seasonal in occurrence. In the planting stage, seed-eating birds
such as Brewer's blackbird and the western vesper sparrow are common.
As the crop growth progresses, earthworms, grasshoppers and their preda-
tor, the western meadowlark, proliferate. Small grass-eating and burrow-
ing animals are less common in a sod farm compared to other cultivated
fields. This is due to the constant mowing and maintenance, which dis-
turb the animal habitat. Mammal species which may be found in the vi-
cinity of sod farms are the pocket gopher, meadow vole and jackrabbit.
Noise
The countryside is generally noted for its quietude. The vastness
of the plains area and generally open conditions allow for rapid noise
dispersal. The main sources of noise pollution are trucks and automo-
biles travelling on the roadways crossing the plains region as well as
farm equipment and machinery. Farm equipment is generally heavy duty
and can generate noise levels equivalent to a truck-trailer. However,
the relatively low density of farms and their remoteness make this
noise source insignificant in the overall context.
Odor
There are usually no noticeable odors on a sod farm except imme-
diately after mowings. These are pleasant and temporary smells con-
fined to the immediate area of the mowed fields.
MINE SPOIL SITES
The Climax molybdenum mine, used as an example of mine reclamation,
is situated in the Colorado Front Range approximately 80 km [50 miles]
west of Denver. The location of the mine and tailings pond is shown in
Figure E-3. The mine site is reached via U.S. Highway 40 and is approxi-
mately 6 km [3.7 miles] southwest of Berthoud Pass and 3.4 km [1.9 miles]
E-10
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south of the Continental Divide. The terrain is rugged and mountainous
and is transected by deep canyons. The Urad mine and spoils site is
located in the narrow canyon of Woods Creek, which is a tributary to
Clear Creek. The Henderson mine and spoils site is located in the upper
section of the west fork of Clear Creek. Elevation at the site is ap-
proximately 3,100 m [10,400 ft] above sea level.
The mining operations are conducted by Climax Molybdenum. The
molybdenum-rich ore is mined from 900 m [3,000 ft] below the surface.
The ore is crushed and washed in an acid solution to extract the metal,
which is further refined. The residual rock material is finally depos-
ited in the large tailings near the foot of Woods Creek Canyon and
Upper Clear Creek Canyon. Leachates from the tailings are further col-
lected downstream in a settling pond before entering Clear Creek.
The mine spoils areas are wedge shaped and cover approximately 60
ha [140 acres] to a depth of 75 m [250 ft]. The rock material on the
site is coarse monzonite, only 16 percent of which passes through a 2 mm
sieve. The final surface of the spoils site has been leveled to pre-
pare for reclamation with sludge and wood chips and for plantings. At
the present time, 6 ha [15 acres] have undergone initial reclamation
and another 50 ha [125 acres] await reclamation.
Climax Molybdenum anticipates reaching full capacity at the Woods
Creek Canyon spoils site by 1980. At that time, a new site will be
used for tailings, and the old site will be available for full reclama-
tion. By the year 2030, the ore at this particular site will probably
be depleted, and the operations will be transferred to a site near
Leadville, 190 km [120 miles] from Denver.
Climate
Located near the crest of the Continental Divide, the mine site
experiences some extremes in climate, as shown in Table E-2. The mean
annual temperature is less than 0°C [32°F], and mean temperatures are
below freezing for six months per year. The growing season is relative-
ly short, extending from one to two months in duration. Precipitation
is heavy. A great deal of the precipitation occurs as snowfall. Snow-
fall amounts to more than one meter [3.3 ft] for at least six months per
year, with the period from June to September being the most clement.
Geology
The mine spoil site is located on landslide deposits from the pre-
Cambrian Silver Plume Granite and the Tertiary Porphyritic Rhyolite.
Samples from the spoil site show that the tailings themselves are from
the Silver Plume Granite. Most of the tailings are composed of porphyri-
tic quartz monzonite veined with molybdenite and pyrite. Some pegmatite
with large grains of molybdenite also make up part of the tailings.
E-ll
-------
FIGURE E-3
BERTHOUfr PASS 5 km (3_mi
^
fVi.ir • .
\ \'"o \ ' , ^BM. '• ^
^-^
•^DENVER 80 k^m (50 miles)
REPRESENTATIVE
MINE
SPOIL SITE
E-12
-------
Table E-2. TEMPERATURE, PRECIPITATION, SNOW AND FREEZE DATA, BERTHOUD PASS
^emperaturjB
•c
[«F]
Precipitation.
mm
[in.]
Snowfall
cm
[in.]
-11.4 -11.4
11.5 11.4
72.9 73.2
2.87 2.88
110.2 112.5
43.4 44.3
-8.4 -4.4
16.8 24.1
91.7 108.5
3.61 4.27
134.6 144.5
53.0 56.9
Freeze threshold temperature
i
°C
0
-2.2
-4.4
-6.7
-8.9
[ °P 1
32
28
24
20
16
1.6 5.
34.8 42.
84.6 73.
3.33 2.
80.8 41.
31.8 16.
Mean
spring
7 10.4 9.1
3 50.8 48.3
4 72.9 63.0
89 2.87 2.48
7 0 0.8
4 0 0.3
Nov Dec
5.3 0.6 -6.2 -9.1
41.6 33.0 20.8 15.6
58.2 55.1 73.7 94.5
2.29 2.17 2.90 3.72
23.9 65.0 112.3 125.5
9.4 25.6 44.2 49.4
Annual
-1.5
29.3
921.5
36.28
951.7
374.7
number of days between date of last
occurrence and first fall occurrence
41
64
90
118
137
Source: Decennial Census of United States Climate; Climatological Data for the U.S.: Colorado.
-------
Both molybdenite (MoS2) and pyrite (FeS2) are sulfides whose oxida-
tion leads to acidic mine drainage. Without alterations and amendments,
these rocks can be expected to provide an inhospitable substratum for
plant growth.
Soils
There are no soils in the mine spoil site under study; nor
would there be any developed soils at any other such sites destined for
reclamation. The material involved in reclamation is processed rock,
extracted from great depths, largely unaffected by soil-forming factors.
At the Urad and Henderson mine sites, the spoil materials are very
coarse (from gravel to boulder-size primary particles), are angular and
are incapable of supporting plant life. Due to the acid treatment for
extraction of molybdenum, these rocks can be expected to retain an aci-
dic reaction for several years. Any reclamation scheme would necessari-
ly require a change in the texture of the surface material in addition
to introduction of organic matter and fertilizer elements.
Water
Tributaries to Clear Creek, i.e., Woods Creek and the upper sec-
tion of the west fork of Clear Creek, flow along the mine spoil sites
studied. Because of the exposed bedrock and occurrences of very thick
consolidated rocks in the area, groundwater is of minor significance.
Large holding basins in the mining areas are used to settle the fine
particles suspended during processing of the rocks. Effluent from the
ponds is discharged directly to the streams draining into Clear Creek.
Biology
Vegetation—
The vegetation on the mine spoil site is quite sparse, mainly be-
cause of the lack of soil. A thin layer of sludge mixed with wood chips
and bark has been applied, and systematic planting of spruce, pine, juni-
per and aspen seedlings has been conducted. Some grass has also been
seeded, and a few other native plants, such as yarrow, big sagebrush,
bear berry and buffalo berry, have established themselves with the germi-
nation and growth of a few individuals. All of the vegetation on this
site is growing very slowly, and some of it, such as the buffalo berry,
appears stunted. Some of the tree seedlings have died.
Wildlife—
The mine spoils site is a severely disturbed area with very sparse
plant growth, as described above. The exposed strata of rock and gravel
provide a relatively sterile environment with no resident animal species.
Visitants from the neighboring lodgepole pine forests may include mule
E-14
-------
deer, coyote, striped skunk, mountain vole and snowshoe hare. Probable
bird species passing over the area are Cooper's hawk, turkey vulture,
gray jay and gray-headed junco.
Noise
The nine spoils site is rural and fairly isolated. Traffic along
Highway 40, which is 1.6 km [1 mile] away from the site, represents a
small fraction of ambient noise. The main source of noise is from the
processing of the ore. The rock-crushing and washing apparatus prob-
ably generate the most noise, while the small but steady truck traffic
to and from the site augments the background noise levels. The rela-
tive isolation, heavy growth of trees adjacent to the site and steep
valleys effectively confine the noise from the mining operations.
Odor
The molybdenum mine has few associated odors. On the limited
tailing areas where reclamation has begun, some odors uncommon to the
area are generated. The weathering of wood chips and sludge into the
upper rock material exudes a faint decomposition odor at close range.
However, the material deodorizes rapidly, and no odors are perceptible
30 m [100 ft] from the site.
IRRIGATED FARMS
There were almost 17,000 hectares [42,000 acres] of irrigated
farms in Adams County in 1973 (Reference 95), about five percent of
the whole county. By contrast, only about 900 hectares [2,200 acres]
are irrigated in Arapahoe County (Reference 14), less than one percent
of the county. Areas of irrigated crops and value of all crops grown
in Weld, Adams and Arapahoe counties are presented in Table E-3. The
proportion of irrigated land increases from south to north due to in-
creased availability of surface and groundwater supplies. In Adams
County, most of the irrigated farms are along the South Platte River
and its tributary creeks. Water is directed from these watercourses,
and pumped from the groundwater reservoir, as well as from various
sources on the western slopes of the Rockies.
The principal irrigated farm used for detailed study is located
in the southern part of Weld County, east of Platteville, as shown on
Figure E-4. It is a 223-hectare [550-acre] field owned by Ray Olin of
Platteville and is, in part, in Sections 16 and 17, "T.3N., R.66W. The
land has gentle, uniform slopes of about two percent draining into the
Platte Valley Canal. It is, at its closest boundary, about one km
[0.6 mile] from the eastern edge of the town of Platteville. U.S.
Highway 85 and the Union Pacific Railroad tracks are located about one
km [0.6 mile] to the west of the irrigated farms. Road 32 connects the
farm to the town and to the major thoroughfares.
E-15
-------
Table E-3. VALUE AND AREA OF CROPS HARVESTED IN WELD, ADAMS AND ARAPAHOE COUNTIES IN 1973
Crop
Winter wheat
Spring wheat
Grain corn
Silage corn
Barley
Grain sorghum
— i Dry beans
cr>
Sugar beets
Oats
All hay
Potatoes
Other crops
All crops
Value,
1,000
dollars
15,644
18
15,284
35,789
3,138
35
7,396
20,033
388
14,700
2,285
4,529
119,239
Weld County
Irri- Non-
gated irrigated
(hectares)"1
1,900 70,100
40 40
24,100 200
48,000b
9,500 4,200
40 200
7,400 80
14,300b
2,100 500
49,200b
1,400
.... ....
157,980° 75,320°
Adams County
Value,
1,000
dollars
14,073
179
1,442
1,560
921
86
122
474
54
2,644
...
2,624
24,179
Irri- Non-
gated irrigated
(hectares)3
1,600 53,000
400 500
2,200 100
2,500b
1,400 5,100
100 300
200
400b
300 300
7,900b
....
17,000° 59,300C
Arapahoe County
Value,
1,000
dollars
5,378
13
125
320
304
24
• • •
...
4
711
...
358
7,237
Irri"
gated
Non-
irrigated
(hectares)3
200
...
100
700b
40
80
• • *
...
...
3,200b
...
...
4,320C
23,000
100
200
....
2,600
100
• • * •
....
80
....
....
26,100C
Original source data are in acre:,: 1 hectare « 2.471 aTes.
Total area (irrigated and nonirrigated, if any).
°Total areas of harvested crops do not include "other crops" and vary considerably from year to year. Irrigated areas may include
minor amounts of nonirrigated areas.
Source: Colorado Department of Agriculture, 1973-1974 Colorado Agricultural Statistics
-------
FIGURE E-4
PLATTEVILL
— _ I
IRRIGATED
ROAD 32
,
HIGHWAY 85
REPRESENTATIVE
AGRICULTURAL
REUSE AREAS
-------
The crops that have been grown on this irrigated farm in recent
years include alfalfa, corn, wheat and some sugar beets. Groundwater
is used as the principal source of irrigation water supply. Depth to
groundwater table is, at places, only one meter [3 to 4 ft] from the
surface. Intensive agronomic management practices, typical of high-
yield irrigated agriculture, are followed using modern equipment and
the recomendations of agricultural extension services. Thus, a high
degree of control over application of amendments to the soils can be
expected in this and most other irrigated farms. Commercial fertilizer
application rates commonly used in the irrigated farms in the area are
87 kg/ha [78 Ib/acre] nitrogen (as N) and 100 kg/ha [90 Ib/acre] phos-
phorus (as P) on pinto beans and sugar beets. Barnyard manure is used
on sugar beets in the early growing stages. Corn receives from 112 to
225 kg/ha [100 to 200 Ib/acre] of nitrogen in anhydrous ammonia form,
injected into the irrigation water.
Soils
The most widespread soils which are found in the irrigated farms
in southern Weld County and northern Adams County (nearest to the sludge
distribution center) are presented in Table E-4. The pertinent charac-
teristics of each soil are tabulated from data furnished by the U.S.
Soil Conservation Service. The suitability and limitations of each
soil are also presented, on the basis of the characteristics of the soil.
These subjective ratings do not include the properties and implications
of the crops grown upon these soils. Crop implications are covered under
the discussion of impacts upon the food chain and in Appendix D.
It appears that most of the soils under irrigation in the study
area possess the properties which would potentially make them suitable
for sludge application. There are, however, a few soils (such as Loup-
Boel, Valent and Tassel) which may be patently unsuitable for reuse of
sludge.
Biology
Vegetation—
Large areas of Weld County and smaller sections of Adams and
Arapahoe counties are irrigated farmland. Primary crops are corn for
silage and grain, sugar beets, winter wheat and hay. Crops of lesser
importance in the study area are barley, dry beans, sorghum, oats, po-
tatoes, fruits and vegetables.
Crops are generally cultivated on a rotational basis that varies
with the soil, terrain and available water. Spring-planted crops are
seeded in the relatively dry, open-weather months, from early March
through June. The ambient temperatures and type of crop determine the
E-18
-------
Table E-4. PERTINENT CHARACTERISTICS OF SELECTED SOILS UNDER IRRIGATION IN WELD COUNTY
Soil tt.p
series, sym-
type" bol
Vona, 51,
fine 51B,
sandy 11B
loam
Dacono, 17M
clay
loam
Olney, 21B
loamy
sand
Altvan, 23
loam
Thedalund, 43
clay
loam
Loup-Boel, -9
sandy
loam
Otero, 53,
sandy 54
loam
Renohiil, 66B
clay
loam
Valent, 72
fine
sand
Depth Clay
to con-
rock, Slope, tent,
cmc * %
>150 0
to
12
>150 0
to
6
>150 1
to
10
>150 0
to
15
50 0
to to
100 15
(unavailable at
>150 0
to
10
>150 2
to
15
>150 0
to
25
low
35
to
50
18
to
35
17
to
35
18
to
35
the present
5
to
18
35
to
50
very
low
Cation
exchange
capacity,
meq per
100 g soil
very
low
60
to
80
12
to
20
„_
—
time)
—
70
to
100
very
low
6.6 to 7.3
7.4 to 8.4
6.6 to 7.8
7.4 to 8.4
6.6 to 7.8
7.9 to 8.4
6.1 to 7.3
7.4 to 9.0
7.9 to 8.4
7.4 to 8.4
6.6 to 7.8
7.9 to 9.0
6.6 to 7.8
Permea-
bility,
cma/hr
5
to
15
0.5
to
1.5
0.5
to
15
0.05
to
5
1.5
to
5
15
to
50
0.05
to
1.5
15
to
50
Sludge application/reuse
Suita- Limt- Management
bility tation needed
moderate low CEC liming,
and pH low rates
high low pH liming
moderate low pH liming
moderate surface
texture
high
low flooding
moderate low CEC, —
clay
content
high
low low clay liming
content,
low pH
-------
Table E-4 (Continued). PERTINENT CHARACTERISTICS OF SELECTED SOILS UNDER IRRIGATION IN WELD COUNTY
I
rv>
o
Soil
aeries,
typcb
Tassel,
fine
sandy
loam
Shingle,
clay
loam
M»p
sym-
bol
84
87B
Depth
to
rock,
cmc
25
to
50
>150
Slope,
%
3
to
25
0
to
25
Clay
con-
tent,
%
low
18
to
35
Cation
exchange
capacity,
meq per
100 g soil
very
low
low
Permea-
bility,
pHd cms/hr
7.4 to 8.4 5
to
50
7.4 to 9.0 1.5
to
5
Sludge
Suita-
bility
low
moderate
application/reuse
Limi-
tation
low clay
content,
depth to
bedrock,
high per-
meability
low clay
content
Management
needed
__
—
aBaaic soil characteristics were obtained from soil survey descriptions and interpretations provided by the USSCS.
Soil type refers to the texture of the airface of the typifying pedon.
cl cm - 0.3937 in.
The first values refer to soil characteristic in the upper layers (top 15 to 50 cm) and the second values refer to deeper layers.
-------
irrigation water need. Spring and summer rainfall is generally inade-
quate for most crop production. Harvest of spring grains begins in
August and is completed by mid-September. Cutting of dry beans occurs
in early September, while corn and sorghum are harvested from late
September to mid-October. Sugar beets are harvested from early October
to mid-November.
Wildlife—
Wildlife on cultivated lands is generally seasonal and often re-
flects the type of crop grown in an area. On irrigated farmlands that
produce crops such as alfalfa, corn, vegetables and some grains, insec-
tivorous birds predominate. Easily visible spring and summer birds in-
clude the western meadowlark, Brewer's blackbird, robin, lark sparrow
and grasshopper sparrow. Seed-eating and often crop-eating birds,
which are most abundant after planting and at harvest times, include
several species of blackbirds, sparrows, migratory waterfowl and, in
some areas, the introduced ring-necked pheasant.
Small rodents, generally viewed as agricultural pests, are an im-
portant part of the food chain. Burrowing and nest-making animals in-
clude pocket gophers, ground squirrels, jackrabbits, harvest nice and
meadow voles. Predators which control the small animal populations are
the red-tailed hawk, Swainson's hawk, ferruginous hawk and, rarely, the
golden-eagle.
The cultivation of former prairie lands has not only changed the
overall habitat but has also added a few ecological "niches." Agricul-
tural remnants and surplus areas, such as streambanks, road edges,
fencerows, corners and woodland patches are important wildlife shelter
and wintering areas. Unharvested strips, stubble and fallow areas pro-
vide a valuable food supply during the winter.
Noise
Noise levels of an irrigated farm are similar to those discussed
in the section on noise under the heading Sod Farms, above.
Odor
Background odors on irrigated farms are often pleasant and natural:
the scents of the freshly turned soil and cut hay and the subtle aroinas
of growing crops. To some, even the animal manure odors on farms are
not particularly unpleasant because of their association with the seren-
ity of rural living. Where chemicals are used (fertilizers, pesticides,
herbicides, etc.), temporary odors from their vapors, dusts and other
aerosol components spread to surrounding areas, downwind of application
areas.
E-21
-------
DRYLAND FARMS
In Adams County there are 146,000 ha [360,000 acres] of nonirri-
gated farms, and in Arapahoe County nearly all farms are nonirrigated
(Reference 95), Areas of various crops under nonirrigated culture are
shown in Table 22 for Weld, Adams and Arapahoe counties.
An estimated 97,000 ha [240,000 acres] in Adams County is unsuit-
able for cultivation or is in native grasses used for grazing (Refer-
ence 10). These areas are also potential recipients of sludge for
improved production of fodder and are treated collectively under the
heading Dryland Farms both in the discussion of general environmental
characteristics in the present section and in the section on impacts,
below.
Wheat and barley are the principal crops grown under dry farming.
Generally, dryland farming involves a lower degree of management control
than does irrigated farming because of the low relative value of crops
produced per unit area of land. Occasional droughts (sometimes lasting
for two consecutive years) bring production down to nearly zero. Dry-
land farming is typically characterized by very extensive land holdings
requiring highly mechanized harvesting procedures and equipment. Soil
conservation practices, such as rotation fallowing, and water conserva-
tion practices, such as scarring the soil surface for better penetration
of rainfall and improved water storage, are generally practiced.
In dry-farming areas, sources of water supply are generally at
considerable distances from the farms and thus are not threatened by
pollution from runoff from those farms. However, in certain other areas
(where dry farms are adjacent to irrigated areas or dry river bottoms
are used for pasture), the groundwater table may be close to the surface,
and intermittent stream courses may be affected by the operations.
Two example sites used for detailed study are (1) east of the sod
farm described earlier and (2) near the irrigated farm described above.
These sites are shown on Figures E-2 and E-4, respectively.
Topography
Dry farms are generally located on gently sloping, rolling topogra-
phy with slopes up to about 15 percent. The noncultivated pasture areas,
such as dry strearabeds, flood plains, hillsides and rocky areas, have
less regular topography and have steeper slopes. None of the dry-farmed
areas are graded.
Soils
Soils in the dryland farm areas in Adams County are shown in Fig-
ure E-4. Some of their characteristics pertinent to sludge application
E-22
-------
are presented in Table E-5. These soils are deep, almost uniformly non-
calcareous in the surface "plow" layer and highly calcareous below (with
the exception of Truckton, which is noncalcareous throughout). This
pattern leads to low pH in the top layers and alkaline condition in the
lower strata. Clay content and cation exchange capacity are generally
very low, and the soils are subject to erosion by blowing wind and over-
land flow of water.
Biology
Vegetation—
Crops are generally cultivated on an annual cycle beginning in
the fall. After the first fall rains, winter wheat and winter barley
are seeded in September and October. In some cases, erosion and crust-
ing of soils may necessitate a second seeding. Favorable climatic con-
ditions during November and December enable the crops to grow to a
strong stand before entering dormancy during January and February.
The wheat plants begin greening up by March but are subject to dry,
windy conditions during April and May. The amount of spring and summer
rain determines the success of the wheat and barley crops. Under favor-
able conditions, the crops can be harvested during the summer. The
higher elevations are often harvested late into the summer. With the
fall rains, the dry-farming cycle begins again. Water conservation re-
quires fallowing and scarification of the land surface in the fall.
Wildlife—
Dryland farm areas are generally less intensively cultivated com-
pared to irrigated farm areas. This seasonal monoculture of grain
crops leads to somewhat lower diversity of animals than is found in
the irrigated farm. Easily visible spring and summer birds include
the western meadowlark, Brewer's blackbird, robin, lark sparrow and
grasshopper sparrow. Seed-eating and often crop-eating birds, which
are most abundant after planting and at harvest times, include several
species of blackbird, sparrow, migratory waterfowl and, in some areas,
the introduced ring-necked pheasant.
Small rodents, generally viewed as agricultural pests, are an im-
portant part of the food chain. Burrowing and nest-making animals in-
clude pocket gophers, ground squirrels, jackrabbits, harvest mice and
meadow voles. Predators which control the small animal populations
are the red-tailed hawk, Swainson's hawk, ferruginous hawk and, rarely,
the golden-eagle.
Dryland farming is generally practiced over large areas, with
minimal supervision. The unharvested strips, stubble and fallow from
these grainfields are an important winter food source for wildlife.
E-23
-------
Table E-5. PERTINENT CHARACTERISTICS OF SELECTED SOILS IN DRYLAND FARMING IN ADAMS COUNTY
~ " ~~" ~ " " • " • "-• - - - - - - - - ----.-r-, .--i_. ,___!. _-L J J ^— __-,-•-, I --L -~«JJ._— ^_ -.- .._..-
Depth
Soil Map to
series, sym- rock,
typeb bol cmc
Ascalon, As >150
sandy
loam
Platner, PI >150
loam
Stoneham, St >150
loam
Truckton, Tt >150
sandy
loam
Vona, V:. >150
loamy
sand
Slope,
3
to
5
0
to
3
3
to
9
1
to
3
3
to
9
Clay
con-
tent,
very
low
mod-
erate
low
very
low
very
low
Cation
exchange
capacity,
meq per
100 g soil
very
low
low
low
very
low
very
low
Permea- Sludge application/reuse
6.6
7.9
6.6
7.9
7.4
7.9
6.6
6.6
pHd
to 7.8
to 9.0
to 7.3
to 8.0
to 7.8
to 8.4
to 7.8
to 8.4
bility, Suita- Limi-
cms/hr bility tation
1.6 moderate low CEC
to
16
0.15 moderate low CEC
to
5.0
1.6 low low CEC
to
16
0.13 low low pH
to
0.3
16 moderate low CEC
to
>20
Management
needed
runoff
control
runoff
control
liming
runoff
control
aBasic soil characteristics were obtained from soil survey descriptions and interpretations provided by the USSCS •
Soil type refers to the texture of the surface of the typifying pedon.
cl cm - 0.3937 in.
dThe first values refer to soil characteristic in the upper layers (top 15 to 50 cm) and the second values refer to deeper layers.
-------
Noise
Noise levels of dryland farming are similar to those discussed
in the section on noise under the heading Sod Farms, above.
Odor
No particular odors are generally associated with dryland farms.
Only during the harvest is the subtle scent of crushed chaff barely
noticeable.
LOWRY BOMBING RANGE SLUDGE DISPOSAL
AREAS AND LANDFILL
The Lowry Bombing Range is located 24 km [15 miles] east of Denver
in Arapahoe County. The Metropolitan Denver Sewage Disposal District
No. 1 and the City and County of Denver are currently engaging in three
separate, although related, disposal operations on 810 hectares [2,000
acres] of the old bombing range, which is just to the west of the pres-
ent bombing range. The site is bounded on the west by State Highway
30 and on the south by Airline Road, and falls within Sections 31 and
32, T.4S., R.65W. and Sections 4 and 6, T.5S., R.65W. The locations
of the three operations are shown in Figure E-5. Approximately 527 hec-
tares [1,300 acres] are currently being used for the land appliction
of dewatered sludge. The City and County of Denver is utilizing 69
hectares [170 acres] in the western part of Section 6 as a solid waste
disposal dump. In the eastern part of Section 4, approximately 145
hectares [360 acres] are being used for landfill operations during the
winter. These areas will be referred to as Sites A, B and C, respec-
tively.
Site C is the winter disposal area where sludge is dumped when
the soil is frozen. It is referred to as a deep incorporation area
because trenches are excavated and the sludge is dumped and then cov-
ered up. Upon completion of the operation, the site will be revege-
tated with native grasses. The groundwater supply is being monitored
to detect groundwater pollution.
Site D, located south of Site C in the northeast part of Section 9,
T.4S., R.65W., is a completed winter landfill area that is being revege-
tated with native grasses.
Topography
The elevation of this area ranges from 1,720 m to 1,785 m [5,650
ft to 5,850 ft]. The relief is subdued, consisting of gently rolling
hills and shallow valleys. Murphy Creek and several of its tributaries
run from south to north through the western part of Site A. Senac
Creek also runs from south to north, lying to the west of Site C and
E-25
-------
FIGURE E-5
DENVER 24km(l5miles
STATE HIGHWAY 3O
ITE C
SITE A - LAND APPLICATION
SITE B - CITY AND COUNTY DUMP
SITE C - LANDFILL
SITE D - COMPLETED LANDFILL
LOWRY
BOMBING RANGE
DISPOSAL AREA
E-26
-------
to the east of Site A, and joins Coal Creek to the north of the prop-
erty. Both creeks are dry most of the year, flowing only during per-
iods of stream runoff. Associated with these watercourses are flat,
wide floodplains.
Soils
Soil characteristics for this area are summarized in Table E-6,
and occurrence of the soils is shown on Figure E-6. The particular
occurrence of lime layering in the soil profile is the most notable
property of these soils. A layer of noncalcareous (acidic) surface
soil to a depth of from 30 to 60 cm [12 to 23 in.] overlies deeper,
highly calcareous (alkaline) materials. This relatively uniform se-
quence has important implications for sludge application because of
the differential solubility of heavy metal compounds at various soil
reactions.
Surface layers (to a depth of about 15 to 25 cm [6 to 10 in.] are
also coarser (i.e., contain less clay) than are the deeper layers of
most soils in the area. This usually gives rise to a corresponding
stratification in the cation exchange capacity of the soils. Wind and
water erosion hazards are generally severe on the Bombing Range, with
great dust clouds generated by trucks and automobiles, even in slow
winds.
The Fondis and the Renohill soil series are the most extensive
soils in the study area, occurring on approximately 80 percent of the
total area, as shown in Figure 13. The Fondis series, which includes
the Fondis silt loam and the Fondis-Colby silt loam soil types, occu-
pies approximately 50 percent of Site A. These are deep, well-drained
soils with a high water-holding capacity. The surface layer of soil is
15 to 17 cm [6 to 7 in.] thick and rests abruptly on the subsoil, which
consists of dense clay 46 to 51 cm [18 to 20 in.] thick. The Fondis
soils are high in natural fertility but are moderately susceptible to
water and wind erosion. These soils are suited to native grasses and
cultivated crops. Smaller units occur on Sites B and C.
The Renohill series, which includes the Renohill-Buick loams and
the Renohill-Litle-Thedalund complex, occurs on approximately 30 percent
of Sites A and B, and on the majority of Site C. These are moderately
deep, well-drained, gently sloping to steep soils that have moderately
slow to slow permeability and moderate water-holding capacity. The
Renohill soils are moderate in natural fertility, but are susceptible
to water and wind erosion. These soils support native grass and are
unsuited to cultivation because of the shallowness of the rooting zone
and the severe hazard of erosion.
E-27
-------
Table E-6. PERTINENT CHARACTERISTICS3 OF SOILS IN LOWRY BOMBING RANGE SLUDGE DISPOSAL SITES
Soil Map
series, s;tn-
typc bol
Buick, Bx
loam
Fondis, Fd
silt
loam
Fondis- Fo
Colby,
silc
loam
i 1 1
i
ro Renohill- Rh
00 Buick,
loam
Renohill- Rt
Litle-
Thedalund,
complex
Nunn, :!1
loam
Terry- Te
Olney-
Thedalund,
sandy
loams
Weld- Wr
Deertrail,
silt
1 nnm
Depth
to
rock,
cmc
120
to
180
>150
>150
50
to
100
50
to
100
>150
60
to
150
>150
Clay
con-
Slope, tent,
% %
3 low
to
9
1 low
to high
5
3 low
to high
5
3 moderate
to
9
9 moderate
to
30
0 moderate
to
3
5 very
to low
20
0 low
to
3
Cation
exchange
capacity,
meq per
100 g soil
low
low
moderate
high
low
moderate-
high
moderate
moderate
moderate
very
low
low
Permea-
bility,
pHd cms/hr
6.8 to 8.0 1.6
8.0 to 9.0 to
16
6.4 to 7.5 <1.6
7.5 to 9.0
6.4 to 7.5 <1.6
7.5 to 9.0
7.5 to 8.5 <1.6
7.5 to 8.5 <1.6
6.5 to 7.0 <1.6
7.5 to 8.5 1.6
to
16
6.8 to 7.5 1.6
to
16
6.5 to 9.0 <1.6
8.0 to 9.0 1.6
to
16
Sludge application/disposal
Suita- Limi- Management
bility tation needed
moderate low CEC runoff
control
high — aubsoiling
high — aubsoiling
moderate shallowness erosion
control
moderate ahallowness erosion
control
high — erosion
control
moderate — erosion
control
moderate low CEC erosion
control
-------
I
ro
Table E-6 (continued). PERTINENT CHARACTERISTICS* OF SOILS
IN LOWRY BOMBING RANGE SLUDGE DISPOSAL SITES
Basic soil characteristics were obtained from soil survey descriptions and Interpretations provided by the USSCS.
Soil type refers to the texture of the surface of the typifying pedon.
Cl ca - 0.3937 In.
The first values refer to soil characteristic In the upper layers (top 15 to 50 on) and the second values refer to deeper layers.
-------
SOILS OF THE
LOWRY BOMBING RANGE
SLUDGE DISPOSAL AREAS
SOURCE-U.S. SOIL CONSERVATION SERVICE
-------
Water
Coal Creek, Senac Creek and Murphy Creek are ephemeral water
courses traversing the 850 ha [2,100 acre] disposal area at the Lowry
Bombing Range toward the north and northwest. Groundwater occurs both
in the alluvial material and in the underlying bedrock, moving in a
northwest direction, similarly to the surface waters. Shallow ground-
water, lying at a depth of about 18 to 30 m [60 to 90 ft] is of ade-
quate extent and yield to be used for some irrigation and/or domestic
purposes. Deeper groundwater levels of the Laramie-Fox Hills aquifer
lie at about 520 m [1,700 ft] from the ground surface (Reference 87).
This is an important regional aquifer, used principally in the upstream
areas in eastern Arapahoe and Adams counties. There are a number of
wells downstream, in Denver, tapping this aquifer. In the immediate
vicinity of the Lowry Bombing Range disposal area, some 15 domestic
wells equipped with electrical or windmill-powered pumps are in active
use. About 30 other observation and monitoring wells have been estab-
lished by the U.S. Geological Survey in cooperation with the Metropoli-
tan Denver Sewage Disposal District No. 1 to study impacts upon ground-
water quality. Furthermore, the District maintains surveillance on
runoff and surface water quality by sampling and analysis of waters in
six catch basins, two springs, two creek stations and two wells.
Biology
Vegetation—
The vegetation of the bombing range can be described as being
characteristic of the Uplands Vegetation type. It is primarily pasture
and range land that has been subject to grazing for many years. While
the original vegetation was probably a short-grass prairie, heavy graz-
ing has changed it to a weedy grass type that contains annual grasses
and annual and perennial weeds along with the original perennial bunch-
grasses. Good range management practices are needed to prevent over-
grazing and to control erosion, particularly on the Renohill soils.
Site A has been subject to the land application of thousands of
tons of dewatered sludge since 1969. The sludge is applied in alter-
nating strips of varying widths along 1-m [3-ft] elevation contours,
plowed under and planted with wheat and/or grasses, and subsequently
used for the grazing of 300 to 500 beef cattle. This site will be used
by the City and County of Denver for solid waste disposal as soon as
current operations are completed on Site B.
Most of the vegetation that has appeared on Site A can be charac-
terized as weedy species that are fast-growing colonizers of bare soil.
E-31
-------
Common stint lower, Russian thistle, summer cypress and tumble pigweed
are almost ubiquitous, covering the belts of application with a swathe
of greenery that provides little food value to livestock. The practice
of livestock grazing on this site has resulted in the almost total de-
-truction of the planted crops (milo, oats, wheat and sudan) since
cattle eat the succulent young shoots as soon as they reach a height
of 10 to 20 cm [4 to 8 in.]. Some grasses can be expected to appear
over time, although heavy grazing makes it difficult for them to be-
come established.
Wildlife—
Wildlife within the Lowry Bombing Range is characteristic of the
Uplands Vegetation unit. The large expanses of rolling plains with low
vegetative cover favor small mammal species such as the prairie vole,
Ord kangaroo rat, pocket mouse, ground squirrel and jackrabbit. These
rodents occupy varying ecological niches and occur sporadically through-
out the range area. The openness of the plains area and relatively low
animal density contribute to several wide-ranging predator species such
as the red-tailed hawk, Swainson's hawk and coyote. The thin stands of
cottonwood trees along the seasonal creek drainages in the area are
prime roosting areas for the predatory birds and for occasional golden
eagles. Several reptiles may be found throughout this arid region, in-
cluding the bullsnake, prairie rattlesnake and central plains milksnake,
which prey primarily upon rodents. Other reptiles, feeding upon in-
sects, are the horned lizard and sagebrush lizard. Infrequent bluffs
and cliffs over river bottoms and eroded areas provide a specialized
habitat for the bank swallow and kingfisher, which utilize overhangs
ind vertical walls for nesting and feeding.
Noise
The countryside is generally noted for its vastness and quietude.
The main sources of noise pollution at the Lowry Bombing Range are the
roadways traversing the plains, farm equipment, solid waste processing
equipment at the landfill, sludge handling and transport vehicles and
aircraft. Heavy equipment for solid waste and sludge handling probably
generates the greatest daily noise. Military vehicles and aircraft also
cause disturbances, although infrequently. However, the relatively low
density of the military reservation and its remoteness make all these
noise sources insignificant in the overall context.
Odor
There are currently no significant odors originating at any of the
sites on the Lowry Bombing Range (Reference 88). There have been no
complaints since 1972, when the contractor had piled quantities of
sludge without plowing it under. After public hearings in June 1972,
E-32
-------
the Metropolitan Denver Sewage Disposal District No. 1 revised methods
of land application, and current practices do not generate significant
odors. Freshly applied sludge can be smelled only at very short dis-
tances.
E-33
-------
Him
l
llll
-------
This Appendix contains examples of letters
of support for the Metro sludge recycling pro-
posal. The letters were solicited by the Metro
District in order to obtain a semi-quantitative
estimate of the potential market for the sludge.
Many of the writers indicate a desire to have
the sludge available for their own uses. This
Appendix is not intended to present representa-
tive samplings of opinion vis-a-vis the sludge
reuse concept. An assessment of the public re-
actions to this concept is presented in Section
VIII.
-------
APPENDIX F
XAMKES OF APPROVAL FOR OR INTEREST IN THE PROPOSED PROJECT
•«>o.o«..u.« cm_nr^3/\Tr r-nni •vr=inr=r^B irrs COMPANY
A DIVISION OP INC.
HENDERSON MINE
Box 68
Empire, Colorado 80438
(303) 569-3221
July 25, 1975
Mr. William J. Martin
Director of Resource Recovery and Reuse
Metropolitan Denver Sew.-ge Disposal District No. 1
3100 East 60th Avenue
Commerce City, Colorado 80022
Dear Bill:
This letter is basically to inform you that this year's
planting has gone very well. The 300 dry-weight tons of
sewage you supplied for mine reclamation revegetation at the
Urad mine has been spread on the 15 acres slated for seeding
this year, and the grass and trees are beginning to look pretty
good. The test plots planted last year are looking very good
also, even with 18 consecutive dry days in late June and parly
July.
Although the whole process is still somewhat in the ex-
perimental stage, I can see no reason why-things shouldn't go
pretty well as planned in tl2 future. The tentative schedule
for the future sewage needs is as follows:
Spring 1975 300 tons
Fall 1975 300 tons
Spring 1976 300 tons
Fall 1976 650 tons
Fall 1977 750 tons
Fall 1978 750 tons
Fall 1979 450 tons
Fall 1980 350 tons
TOTAL 3,850 tons
F-l
-------
WJM July 25, 1975
It Is the sewage that is making the difference. The sewage
is pretty well the key to the whole operation of revegetating
the fragmented rock covering the mine tailing. We appreciate
everything you are doing to help us in this endeavor.
Larry F.V Brown, Ph.D.
Environmental Control Engineer
LFB:mb
F-2
-------
Michael Dulacki
656 i.ilvauke- St.
Denvsr, Colorado 80205
Metro Denver Sev/age Disposal Dist. £1
3100 2. &0th Avenue
Commerce City, Colorado S0022
Dear Sirs:
I am v/riting this letter to you to tell you that I endorse
the recycling of r.uncipal vastes in general and that I endorse
your particular plan of recycling Denver sev;age sludge as a
fertiliser and soil conditioner. The possibilities of this plan
are many; for one, the Denver Parks jepartnent could use this
fertiliser for the city parks. -mother example is the uso of
the fertilizer by • private citizens for their ovrn lav.ns and gardens,
I hope you are successful in your efforts to implement this plan.
Sincerely yours,
f-3
-------
5
o
TLANlA
ORT SMfTH
ORT WORTH
ITTLE ROCK
CW ORLEANS
HILADELPHIA
AVANNAH
AMPA
AMBURG. WEST GERMANY
AN JOSE. COSTA RICA
INCOPPORATED
IMPORTERS-EXPORTERS
ORGANIC AND CHEMICAL FERTILIZER MATERIALS
ANIMAL FEEDING SUPPLEMENTS
OILS, FATS AND MEALS
36O LEXINGTON AVENUE
INETVTYCXRK., JSIEW YORK 1O017
July 29, 1975
1ILIPHONC
2I2-867-O2OO
CAVLC ADDWCS9
'BAKER8RO'
TCLCX t-2487
42O944
223482
Metropolitan Denver Sewage Disposal
District No. 1
Commerce City/ Colorado
Gentlemen:
We noticed in the July 28th issue of the publication Air/Water
Pollution Report, that you have been granted $76,029 to study
the effect of feeding to cattle, crops grown on sludge amended
soils. From our letterhead, you will see that we are in the
fertilizer and feeding materials business, and for many, many,
years, we have actively sold heat dried activated sewage sludge
to the fertilizer industrye Some of this sludge finds its way
on to pasture lands as part of a complete mixed fertilxzer0
Consequently, we will be keenly interested in knowing the outcome
of your study, if this information could be made available to us.
As a matter of fact, we would like to know whether you are recovering
and heat drying your sludge and whether you would be in a position
to offer us tonnage. We are currently selling, nationally, the
entire output of the Metropolitan Sanitary District of Chicago for
the people who have the contract with them and can handle additional
supply.
We look forward to the pleasure of hearing from you.
Very truly yours,
H
JWR/nw
Wi Reisack
President
F-4
BAKERBPO CCNTROAMERICANA S.A . COSTA RICA • NUTRITION PRODUCTS DIVISIONS. NEW ORLEANS. PHILA-
DELPHIA . THE KAINIT DIVISION. SAVANNAH • POULTRY DY.PRODUCTS. INC.. HANCEVILLE. ALAOAMA . THE
PRO-PAK CORPORATION. FERNANDINA DCACH, FLORIDA . H. J. DAKER & DRO. (CANADA) LTD. MONTREAL
-------
lie
CITY of
10959 IRMA DRIVE
NORTHGLENN, COLORADO 80233 (303) 452-1941
Bill Martin
C/0 Metro Denver Sewer
3100 E. 60th Avenue
Commerce City, CO 80022
We are extremely interested in obtaining anarobically
digested stabilized sludge for use on our parks and green-
ways. We understand that this caterial will be made avail-
able in the near future and would like to be contacted so
ve can use this valuable resource. We can use approximately
200 to 500 tons annually.
Could you please send me the Chenical analysis c-f the
material also, what method will be used in transporting to
Northglenn.
Thank you,
DeBell
'Superintendent of Public Works
City of Northglenn
JDB/cw
F-5
'• of the director of community works
-------
City of Commerce City
4407 East 60lh Avenue
Commerce City, Colorado 80022
TELEPHONE (303) 287-3485 COMMUNITY
DEVELOPMENT
August 11, 1975
Mr. William J. Martin, Director
Resource Recovery & Reuse
Metropolitan Denver Sewage Disposal District #1
3100 East 60th Avenue
Commerce City, CO 80022
Dear Mr. Martin:
I am writing this letter pursuant to our conversation of Thursday,
August 7, 1975.
The City of Commerce City has been strongly considering and hopes
at some future date using "sludge" as a fertilizer for both new park
development and park maintenance. The City has approximately 40-
acres of developed park and open space which we are fertilizing
(commercial) a minimum of three times a year. As well, we are
planning to construct between 10 and 15 additional acres each year
for the next four years in which we have been applying manure for
topsoil development.
We would like to substitute your sludge in both these instances.
Since-fely,
Dale W. Gilbert
Director of Community Development
th
F-6
-------
August, 1971*
TOi 1KB METROPOLITAN DENVER SEWAGE DISPOSAL DISWICP NO. 1
We, the undersigned, in the interests of minimizing environ-
mental pollution and conserving cur resources, wish to affirm our
support for the recycling of municipal wastes. In particular, we
strongly support efforts which would r.ake nuniciple wastes avail-
able to the public for use as an organic fertilizer.
HAMS ADDRESS ZIP
This petition was signed by 461 persons, primarily in the Metropolitan
Denver area.
F-7
-------
COLORRDO ORGRN1C GROUERS'fiNO fi3Ri£TER5'fl55QClffl]ON
DEN»tR, COLORRDO £D2il
477-6Z9!
)the Metropolitan Denver Sewage Disposal District #1.
V/e the undersigned individuals, residents of Metropolitan Denver com-
itted to the usage of natural fertilizers only and convinced that, as
i^payers, v;e are entitled to stabilized,dry or semi-dried activated sludge
id concentrated anaerobic-produced sludge, semi-dry or dried.
Name
Address
land area 1/4 ton 1/2 ton 1 ton (+]
This petition was signed by 15 persons who requested a total of 37 1/2
tons of sludge.
F-8
-------
mm
-------
This Appendix comprises a reproduction of the
tabulation of the environmental evaluation ma-
trix used by the facilities planner (CH2M—HH1)
in selecting site B-2 from the three finalists
for a sludge drying and distribution site. Even
though site B-2 has been selected by the plan-
ners as the most favorable location, nagging
problems remain with respect to neighborhood
acceptance and potential market proximity. For
more information on the environmental, engineer-
ing and cost factors weighed in the process of
site selection refer to Reference 8 in Section IX
of the main body of the EIS.
-------
CONSIDERATION CRITERIA
Overall land reciuireinents Are 2000 acres available?
On sue Duffer
Current lana u
tt>e region wiin posted speeds of 55 MPH. witn speeds of 55 MPH.
SOIL AND GEOLOGY Soil Characteristics Soil Series T.uckum Lu;
-------
CONSIDERATION
CLIMATIC CONDITIONS
I
ro
Same as Site A.
Same as Site A.
Same as Siie A.
Same as Site A.
Same as Site A.
-------
CONSIDERATION
RELIABILITY
cn
eened?
$ J 1,948,000 Based on 197.
tie approximately $675,000.
$11,695.000 baieO on 1974 cc
approximately $688,000.
$12,899,000 baieU on 197.
Same ai Site A.
-------
APPENDIX H
DISTRIBUTION LIST
-------
DISTRIBUTION LIST
Federal Agencies
Council on Environmental Quality
Environmental Protection Agency
Office of Federal Activities
Office of Solid Waste Management Programs
Office of Water Programs
Office of Public Affairs
Office of Legislation
Dr. Joseph Parrel!, NERC Cincinnati
G. Kenneth Dotson, NERC Cincinnati
Environmental Impact Coordinators, Regions I-X
U.S. Department of Agriculture
Dr. Rufus Chaney, Agricultural Research Service
Dr. Elliot Epstein, Agricultural Research Service
Forest Service, Region II
Forest Service, James Evans, WO
State Conservationist, Soil Conservation Service
Food and Drug Administration, Dr. George Braude
Department of Interior
Department of Health, Education & Welfare, Regional Director
Energy Research & Development Administration, Herb Pennington
Army Corps of Engineers, Omaha District
National Commission on Water Quality, Dr. Harold Allen
National Technical Information Service
Department of Transportation
Federal Highway Administration
Department of Housing & Urban Development, Regional Director
Department of Defense
Commander, Rocky Mountain Arsenal
Commander, Lowry Air Force Base
Farmers Home Administration, State Director
William Armstrong, U.S. House of Representatives
Pat Schroeder, U.S. House of Representatives
Floyd Haskell, U.S. Senator
Gary Hart, U.S. Senator
Jim Johnson, U.S. House of Representatives
Dr. Richard Hayes, Public Health Service, Ft. Collins
State Government
State Clearing House, Office of Planning
Executive Secretary, Colorado Water Pollution
Control Commission
Colorado Department of Health
Colorado Water Pollution Control Division
Colorado Air Pollution Control Division
Colorado Solid Waste Division
H-l
-------
Colorado Department of Natural Resources
Colorado State Land Use Commission
Colorado State Department of Highways
Colorado Wildlife Division
Colorado State Water Conservation Board
Colorado State Soil Conservation Board
Office of the Governor
State Historical Society
Regional , County and Local Government
Denver Regional Council of Governments
Adams County Commissioners
Adams County Planning Department
Boulder County Planning Department
City of Boulder, Publics Works Department
Arapahoe County Planning Department
Jefferson County Planning Department
Tri-County Health Department, Don Turk
Larimer-Weld Planning Department
City & County of Denver
Planning Department
Health Department
Adams County Agricultural Extension Service
Denver Water Board
City of Westminister
City of Golden
City of Commerce City, Attn: Mr. Dale Gilbert
City of Bennett
City of Brighton, Attn: Mr. Bill Sharp
City of Englewood
City of Littleton
City of Lakewood-
City of Prospect Valley
Denver City Parks Department, Ron Maketric
City of Aurora, Attn: Mr. Charles Wemlinger
City of Arvada
City of Thornton
City of Northglen, Attn: Mr. Jack Debill
Sanitation Districts
Metropolitan Denver Sewage Disposal District #1
City and County of Denver Wastewater Control Division
Applewood Water & Sanitation District
Berkeley Water & Sanitation District
Crestview Water & Sanitation District
North Pecos Water & Sanitation District
North Table Mountain Water & Sanitation District
North Washington Street Water & Sanitation District
H-2
-------
Northwest Lakev/ood Sanitation District
Pleasant View Water & Sanitation District
Westridge Sanitation District
Wheatridge Sanitation District
Alameda Water & Sanitation District
Bancroft Water & Sanitation District
Fruitdale Sanitation District
Highland Park Sanitation District
Other Associations & Individuals
Colorado Open Space Council
Rocky Mountain Center on Environment (ROMCOE)
ECO-Center, Environmental Clearinghouse
Colorado Clean Water Action Project
Sierra Club, Enos Mills Chapter, Jim Fowler
Keep Colorado Beautiful, Beverly Fleming
Environmental Action, Maury Wolfson
League of Women Voters
National Wildlife Federation
Thorne Ecological Institute
The Denver Post
The Rocky Mountain News
Straight Creek Journal
Denver Public Library
Adams County Regional Library
University of Colorado Library
Colorado State University Library
Burlington Ditch Company
Dr. Edward Bryan, Program Manager
National Science Foundation
Mr. Martin Sorensen
Sierra Club Wilderness Coordinate
Golden, Colorado
Miss Katherine O'Keefe, Attorney at Law
Berkeley, California
Larry Brown
Environmental Control Division
Climax Molybdenum Company
4704 Harlan
Denver, CO
Dr. Parviz Soltanpour
Department of Soils/Laboratory
Colorado State University
Fort Collins, Colorado
H-3
-------
John J. Brehaney
RMP Company
100 West Walnut Street
Pasadena, California 91124
Dr. Richard G. Burau
Associate Professor of Soil Chemistry
Department of Land, Air and
Water Resources
University of California
Davis, California 95616
Mr. Eugene L. Begg
Soil Scientist
Department of Land, Air
and Water Resources
University of California
Davis, California 95616
Mr. Ronald W. Crites
Metcalf and Eddy, Inc., Engineers
1029 Corporation Way
Palo Alto, California 94303
Jack Danford
1450 South Havana Street, Suite 340
Aurora, Colorado 80012
Dr. Wilfred G. Iltis, Entomologist
Department of Biology
California State University
San Jose, California
Mr. Bill Mathews
229 Pierce
Lakewood, Colorado
Mr. Ray 01 in
No. 13487 Road 32
Platteville, Colorado
Dr. E. W. McCord
Northern Colorado Research Station
Greeley, Colorado
Dr. John Pourbaugh, Entomologist
California State Health Department
2151 Berkeley Way
Berkeley, California 94704
H-4
-------
Dr. Parker F. Pratt
Professor of Soil Science
University of California
Riverside, California
Mr. S. W. Maphis
Briscoe-Maphis, Inc.
Deep Six Division
2336 Pearl Street
Boulder, Colorado
Dr. Berne R. Sabey
Department of Soils
Colorado State University
Fort Collins, Colorado
Dr. James Smith
Department of Civil Engineering
Colorado State University
Fort Collins, Colorado
Reynolds Turf Farms
Post Office Box 595
Brighton, Colorado 80601
Dr. Duane Westphal
Great Western Sugar Company
Longmont, Colorado
Mr. Calvin Tupps, Adams County
Bob Ziegler, Adams County
Dr. Bernard Korbitz
Department of Medicine
Presbyterian Medical Center
Denver, Colorado
Jack Haines, Adams County
Robert Sandquist, Adams County
Dr. Edwin Bennett
Department of Environmental Engineering
University of Colorado
Environmental Assessment Project
Environmental Defense Fund
John Schwing, Jerry Boyle
Cornell, Hayes, Howl and & Merryfield-Hill (CH2M-Hill)
Engineering Science, Inc.
Berkeley, California
H-5
-------
Benedetti, Opperman & Martinez
1 Park Central
Donald Warner, Bennett, CO
Catherine & Leroy Mundell, Bennett, CO
F.W. & Blanche Meyer, Bennett, CO
Clarence Smith, Commerce City, CO
Edith Marlott, Byers, CO
Brighton Adams County Standard
The Brighton-Blade
Brighton Market-place
TIC «U.S Government Printing Office: 1976-678-352
------- |