EPA-908/5-78-003
BOULDER
COLORADO
WASTEWATER
TREATMENT
FACILITIES
FINAL
ENVIRONMENTAL
IMPACT STATEMENT
NOVEMBER 1978
U.S. ENVIRONMENTAL
PROTECTION AGENCY
REGION VIII
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EPA-903/5- 78-003
BOULDER, COLORADO
WASTEWATER TREATMENT FACILITIES
FINAL
ENVIRONMENTAL IMPACT STATEMENT
Prepared by
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION VIII
DENVER, COLORADO 80203
NOVEMBER 1978
Prepared with the Assistance of
ENGINEERING-SCIENCE, INC.
600 Bancroft Way
Berkeley, California 94710
Approved by
Regional Administrator
Date November 30. 1978
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This report has been reviewed by the Region VIII
Office of the U.S. Environmental Protection Agency
and approved for publication. Mention of trade
names or commercial products does not constitute
endorsement or recommendations for use.
This document is available to the
public through the National Technical
Information Service, Springfield,
Virginia, 22161.
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Preface
This final Environmental Impact Statement (EIS) is documenta-
tion of an intensive review and analysis by EPA of alternative
means for the City of Boulder to improve its wastewater treatment
facilities. These improvements are needed in order for the City
to meet State, Federal, and its own goals for improving Boulder
Creek water quality to a much higher level than currently exists.
Eight different alternative means of treating Boulder's wastes
have been analyzed in this EIS. Because of various technical,
economic, environmental, and policy considerations only three of
these alternatives have been found to possess the requisites neces-
sary to rank them as contenders for final selection. These three
alternatives are infiltration/percolation basins; activated sludge
process following trickling filters; and an agricultural reuse system.
A fourth alternative, aeration-polishing ponds, which was suggested
as a possible candidate in the draft EIS, has since been found to be
incapable of consistently meeting required treatment levels and has
been eliminated for that reason.
The infiltration-percolation basin system, though promising a
high level of treatment, was not selected because of factors re-
lated to location of the necessary 200+ acre site. One site that
was evaluated (adjacent to 75th St.) would impact the White Rocks
Uatural Area and the Gunbarrel area developments to an unaccept-
able level. The other site (at the 95th St. - Boulder Creek area)
was eliminated because of potential for ground-water pollution,
transmission costs, and because it would lead to a partial dewater-
ing of a section of Boulder Creek.
The second alternative considered in the final selection process
was an agricultural reuse system. This type "land treatment" sys-
tem is one potentially offering significant energy and fertilizer
savings and is one that offers a very high level of treatment and
other advantages. In Boulder's situation, however, it was found that
problems associated with acquiring a long-term commitment of some
12,000 acres of land for this use, presence of truck farms, use of
irrigation ditch water by a municipality, and other problems preclude
implementation of this alternative.
The last alternative, activated sludge process following trickling
filters, is the one favored by the City of Boulder, Boulder County,
and most of those who responded to the draft EIS. This system is
capable of providing a very high level of treatment, it avoids the siting
problems associated with the other alternatives, and is one that can
actually be implemented because it avoids the "institutional" problems
associated with the other systems considered. Because of the problems
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discovered with the other alternatives, EPA agrees that this alterna-
tive best meets Boulder's particular needs and circumstances. It
should be pointed out that EPA will require Boulder to pursue energy
conservation measures on the design and operation of this system.
The reader should note that another part of the Boulder waste-
water improvements project, land injection of sludge, which was
analyzed in the draft EIS does not appear in this final. The sludge
disposal analysis has been deleted because of a City of Boulder and
EPA decision to look at an additional sludge injection site. This
decision was made late in the final EIS preparation process and to
include this analysis would have seriously delayed issuance of this
document and further progress of the project. Sludge injection will
now be analyzed in a separate Addendum to the final EIS which will be
issued at a later date.
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SUMMARY
DRAFT ENVIRONMENTAL IMPACT STATEMENT — WASTEWATER
TREATMENT IMPROVEMENTS FOR THE CITY OF BOULDER, COLORADO
Environmental Protection Agency
Region VIII
1860 Lincoln
Denver, Colorado
1. Type of Statement: Draft ( ) Final (x)
2. Type of Action: Administrative (x) Legislative ( )
3. Description of Action:
The objective of this project is to design and construct
additional wastewater treatment facilities for the City of
Boulder. These facilities have been proposed so that water
quality in Boulder Creek will meet the goals established by the
Water Pollution Control Act Amendments of 1972 (Public Law 92-500)
and the more restrictive State of Colorado water quality classi-
fications. This Environmental Impact Statement (EIS) identifies
alternatives for providing Boulder with improved wastewater
facilities designed to meet the needs of its residents and to
maintain and improve environmental quality. The projected
service area contains approximately 140 square miles and is
bounded by the foothills to the west, Davison Mesa to the south
and Gunbarrel Hill to the north. The City of Boulder's popu-
lation was estimated to be approximately 73,000 in 1976. The
1995 population for the city is projected to be 116,700; and
the planning area is projected to be 129,000.
Historically, treatment plant effluent discharges to the
Boulder Creek sub-basin have been a major source of stream
pollution. The city's two existing wastewater treatment plants
have experienced problems with both liquid- and solids-handling
processes. The long-term and cumulative effects of surface
water degradation caused by all of the sub-basin's pollution
sources include loss of sensitive fish and the development of
simple ecosystems with only a few pollution-tolerant species
in the streams.
The wastewater facilities planning process began in 1973
and is continuing at. the present with the preparation of this
EIS. This assessment is focused on modifications and additions
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to the treatment plant liquid flow processes, method of final
effluent disposal and final disposal of sludge.
4. Summary of Environmental Impacts and Adverse
Environmental Effects:
The type and magnitude of potential impacts vary according
to the alternative proposed. Alternatives A-G represent different
treatment concepts while Alternative H represents the no project
situation. The impacts have been divided into: short-term impacts
(construction), long-term direct impacts (operation), and long-term
indirect impacts (secondary effects).
(1) Short-term impacts associated with construction include
removal of groundcover, loss or transfer of soil resource,
localized soil erosion, disruption of wildlife patterns, aerial
pollutants, noise, visual impact, spoil disposal, traffic con-
gestion, utility service disruption, safety hazards and water quality
impairments. No short-term impacts Will be associated with
Alternative H.
(2) Long-term impacts associated with operation include:
a. Improvements of local water quality in Boulder
Creek;
b. Lowering of groundwater table and partial diversion
of flow in the vicinity of 75th Street at Boulder
Creek;
c. Effects on groundwater quality at certain sites;
d. Potential odor generation;
e. Fog or aerosol formation over large ponds;
f. Increased energy demand;
g. Effects on local land-use patterns and property
values;
h. Potential public health and safety problems;
i. Impacts on the visual and aesthetic environment; and
j. Effects on soil productivity.
(3) Long-term indirect impacts includes those changes from
population growth accommodated by provision of sewer services such
as future construction in the sub-basin leading to erosion and
subsequent stream pollution, loss of natural areas and wildlife
habitat, loss of scenic resources, energy, utilities and service
demands, and a long-term change in life style and quality of life.
5. Alternatives Considered:
Alternative^ - Land treatment by infiltration/percolation.
Capital cost: 75th Street site—$9,889,000; 95th Street site—
$11,171,000.
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Alternative B - Activated sludge process following trickling
filters. Capital cost - $10,272,000.
Alternative C - Aeration/polishing ponds. Capital cost -
$7,832,000.
Alternative D - Activated sludge process prior to trickling
filters. Capital cost - $11,544,000.
Alternative E - Multi-media filtration of effluent. Capital
cost - $6,926,000.
Alternative F - Chemical coagulation. Capital cost - $4,681,000.
Alternative G - High-rate irrigation of effluent. Capital cost -
$34,875,000.
Alternative H - No action. Capital cost - $0.
Alternative I - Agricultural reuse program. No estimate of capi-
tal cost was made.
All of the alternatives, except F, will incorporate beneficial
reuse of sludge to the maximum amount possible. Twenty-five percent
of the sludge will be made available for use in the community; the
remainder will be injected into a 170 acre field near the 75th Street
plant. Sludge from Alternative F would contain alum and be unsuitable
for agricultural use, thus, necessitating disposal to the county land-
fill. The description and analysis of the sludge-injection system
will be presented separately as an addendum to this final EIS.
6. Distribution:
The agencies and interested groups that have been requested to
comment on the draft EIS are listed on the following pages.
iii
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The Wilderness Society
Denver, Colorado
Mr. Robert Farley
Director, Denver Regional
Council of Governments
Denver, Colorado
Federal Highway Administration
Denver, Colorado
Regional Director
Bureau of Outdoor Recreation
Denver, Colorado
State Conservationist
U.S. Soil Conservation Service
Denver, Colorado
District Chief
U.S. Geological Survey
Denver, Colorado
Regional Director
National Park Service
Denver, Colorado
Regional Director
U.S. Bureau of Reclamation
Denver, Colorado
Regional Director
U.S..Fish and Wildlife Service
Denver, Colorado
Regional Director
U.S. Department of Health,
Education and Welfare
Denver, Colorado
State Clearinghouse
Office of State Planning
Denver, Colorado
Air Pollution Control Division
Colorado Department of Health
Denver, Colorado
Colorado State Water
Conservation Board
Denver, Colorado
State Historical Society
Denver, Colorado
Water Quality Control Division
Colorado Department of Health
Denver, Colorado
Colorado Division of Highways
Den ve r, C ol or ado
Colorado Department of Natural
Resources
Denver, Colorado
Colorado State Land Use
Commission
Denver, Colorado
Regional Administrator
U.S. Department of Housing
and Urban Development
Denver, Colorado
District Engineer
U.S. Army Engineer District
Albuquerque
Albuquerque, New Mexico
Director
Environmental Project Review
U.S. Department of the Interior
Washington, D.C.
Environmental.Review Officer
U.S. Department of the Interior
Denver, Colorado
Mr- Gary Broetzman
State 208 Coordinator
Denver, Colorado
Division of Planning
Boulder County
Boulder, Colorado
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Office of Federal Activities
Environmental Protection Agency
Washington, B.C.
Office of Public Affairs
Environmental Protection Agency
Washington, B.C.
Office of Legislation
Environmental Protection Agency
Washington, B.C.
State Archaeologist
State Historical Society
Denver, Colorado
Department of Local Affairs
Denver, Colorado
Colorado Open Space Council
Denver, Colorado
Rocky Mountain Center
on the Environment
Denver, Colorado
Thome Ecological Institute
Boulder, Colorado
Colorado Wildlife Federation
Denver, Colorado
National Wildlife Federation
Denver, Colorado
Environmental Action Committee
Denver, Colorado
Environmental Defense Fund
Denver, Colorado
Friends of the Earth
Denver, Colorado
Planning Director
City of Boulder
Boulder, Colorado
Planning Director
Boulder County
Boulder, Colorado
Mary Taylor
Boulder, Colorado
Vince Porreca
Boulder, Colorado
Colorado Mountain Club
Boulder, Colorado
Plan - Boulder County
Boulder, Colorado
John D. Musick
Boulder, Colorado
Richard Wepner
Boulder, Colorado
District 6 Water Users
Association
Longmont, Colorado
Representative Lee Jones
State Representative - District kj
Boulder, Colorado
Representative Bill Hilsmeier
State Representative - District h9
Longmont, Colorado
Representative Charles B. Howe
State Representative - District 53
Boulder, Colorado
Senator Ron Stewart
State Senator - District 2k
Longmont, Colorado
Senator Leslie R. Fowler
State Senator - District 23
Boulder, Colorado
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Representative Timothy Wirth
U.S. House of Representatives
Washington, B.C.
Senator Floyd Haskell
U.S. Senate
Washington, B.C.
Senator Gary Hart
U.S. Senate
Washington, D.C.
Chairman, Biology Department
University of Colorado
Boulder, Colorado
Chairman, Geography Department
University of Colorado
Boulder, Colorado
Mr. Jim Thomas
Environmental Center
University of Colorado
Boulder, Colorado
Ms. Claire Lindgren
Chairman, Boulder Planning Board
Boulder, Colorado
Dr. Edwin Bennett
Civil Engineering Department
University of Colorado
Boulder, Colorado
Dr. Ernest Flack
Civil Engineering Department
University of Colorado
Boulder, Colorado
Dr. Gilbert White
Institute of Behavioral Science
University of Colorado
Boulder, Colorado
Dr. Charles Howe
Chairman, Department of Economics
University of Colorado
Boulder, Colorado
Mr. Floyd Mann
Environmental Council
University of Colorado
Boulder, Colorado
Gunbarrel Homeowners Association
Boulder, Colorado
Mr- Dan Bowers
Sierra Club
Indian Peaks Chapter
Boulder, Colorado
Mr. Richard Ekrem
Chairman, Boulder County
Planning Commission
Boulder, Colorado
Mr. Howard Klemme
Vice-Chairman, Boulder
County Planning Commission
Boulder, Colorado
Mr. Henry Stovall
Boulder County Long-Range
Planning Commission
Broomfield, Colorado
Parks and Open Space
Advisory Committee
Boulder, Colorado
St. Vrain and Left Hand Water
Conservancy District
Longmont, Colorado
Colorado Water Pollution
Control Commission
Denver, Colorado
Mr. Ed McDowell
Flatiron Companies
Boulder, Colorado
Mr. Phil Stern
Boulder County District
Attorney's Office
Boulder, Colorado
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City Manager
City of Longmont
Longmont, Colorado
City Manager
City of Lafayette
Lafayette, Colorado
City Manager
City of Louisville
Louisville, Colorado
League of Women Voters
Boulder, Colorado
Northern Colorado Water
Conservancy District
Loveland, Colorado
Heatherwood Homeowners Association
Boulder, Colorado
Martha Weiser
Boulder, Colorado
Scott Weiser
Boulder, Colorado
Board of County Commissioners
Boulder, Colorado
Boulder Chapter Audubon Society
Boulder, Colorado
Mr. Jack Hibbert
208 Project Director
DRCOG
Denver, Colorado
Mr- George Codding
Trout Unlimited
Boulder, Colorado
Mr. Doug Smith
City of Boulder
Boulder, Colorado
Mr. Ken Wright
Boulder, Colorado
Mr. Lee Rice
Leonard Rice Consulting
Water Engineers
Denver, Colorado
Board of Realtors
Boulder, Colorado
Audubon Society
Boulder, Colorado
Boulder Chamber of Commerce
Boulder, Colorado
Mr. Erving Nelson
President, Boulder Valley Soil
Conservation District
Bo-flilder, Colorado
Ms. Tess McNulty
County Health Board
Boulder, Colorado
Ms. Ann Raisch
County Attorney's Office
Boulder, Colorado
Ms. Hester Holz
Boulder Garden Club
Boulder, Colorado
Ms. Marge Burns
Gardens Tomorrow
Boulder, Colorado
Mr- Bob McGregor
Chairman, Water Quality Workshop
Colorado Open Space Council
Denver, Colorado
Mr- Bob Weaver
Trout Unlimited
Denver, Colorado
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Mr. Sain Hobbs
Director of Public Works
Boulder, Colorado
Dr. John Donnelly
Director, Boulder City and
County Health Department
Boulder, Colorado
Mr. Anthony J. Madonna
Boulder, Colorado
Boulder Audubon Wildlife Society
Boulder, Colorado
Mary Ann Firby
Boulder, Colorado
Wendell A. Niswonger
Boulder, Colorado
J. Horstman
Boulder, Colorado
Mr. Jim Smith
Boulder, Colorado
Ms. Jeanne Morris
Boulder, Colorado
Pat Vogel
Boulder, Colorado
Loyd Farver
Boulder, Colorado
Keith Paxten
Boulder, Colorado
viii
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TABLE OF CONTENTS
Section
I INTRODUCTION AND SUMMARY 1
Introduction 1
Background 2
Project Development 4
Summary 5
Alternative Plans 6
Environmental Impacts 9
Project Costs 14
II ENVIRONMENTAL SETTING 17
Physical Environment 17
Climate 17
Air Quality 18
Geology 19
Soils 23
Water 26
Biological Environment 43
Ecology of Boulder Creek 43
Biotic Communities 45
Sensitive Ecological Areas 48
Treatment Plant and Proposed
Land Application Sites 50
Social and Economic Environment 52
Visual and Aesthetic Environment 52
Recreation Areas 52
Noise 54
Odor 54
History 55
Archaeological Resources 56
Population 56
Demography 59
Land Use 60
Tax Base - Assessed Values 61
Land and Property Values 61
Bonded Indebtedness and Subsidies 61
Utility Services 62
Transportation 64
III PROPOSED ALTERNATIVES 65
Changes to the Facilities Plan 65
Design Flows and Pollutant Loadings 66
Alternatives 68
Common Features 68
Alternative A 73
IX
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Section Page
III PROPOSED ALTERNATIVES (continued)
Alternative B 75
Alternative C 75
Alternative D 77
Alternative E 77
Alternative F 77
Alternative G 79
Alternative H 79
Engineering Evaluation of Alternatives 81
Common Features 81
Alternatives 82
Project Costs 86
Capital Costs 86
Operation and Maintenance (0 & M) 87
Cost Comparison of Alternatives 87
Interaction with Other Plans 90
Regional Plans 90
County Goals 91
Local Water Quality Goals and
Objectives 92
Screening of Alternatives 92
IV ENVIRONMENTAL IMPACTS AND MITIGATION MEASURES 95
Short-term Impacts 95
Long-term Direct Impacts 100
Physical Environment 100
Biological Environment 107
Social and Economic Environment 114
Long-term Indirect Impacts 130
Soils 130
Water 131
Biotic Communities 131
Air Quality 133
Resources 134
Socio-Economic 134
V UNAVOIDABLE ADVERSE IMPACTS 137
Alternative Plans 137
Alternative A 137
Alternative B and D 139
Alternative C 139
Alternative G 139
VI IRREVERSIBLE AND IRRETRIEVABLE RESOURCE COMMITMENTS 141
Irretrievable Loss of Wildlife Habitat 141
Irreversible Destruction of Soil Profile 142
Irreversible and Irretrievable Energy and
Economic Resource Commitment 142
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Section Page
VII RELATIONSHIP BETWEEN SHORT-TERM USES OF THE HUMAN
ENVIRONMENT AND THE MAINTENANCE AND ENHANCEMENT
OF LONG-TERM PRODUCTIVITY 143
Enhancement of Soil Productivity 143
Potential Cumulative Long-Term
Environmental Damage 144
The Long-Term Environmental Perspective 144
VIII COMMENTS ON THE DRAFT ENVIRONMENTAL IMPACT STATEMENT
AND RESPONSES 147
Public Hearing 147
Letters of Comment 149
IX REFERENCES 207
Appendices
A Soil Characteristics of the Proposed Project Area A-l
B Biological Environment B-l
C The Aesthetics of a Landscape as a Resource
Commodity C-l
D Evaluation of Infiltration/Percolation Basins at the
95th Street Site and an Agricultural Reuse Program D-l
E Short-Term Environmental Impacts E-l
F Colorado Water Quality Control Commission June 6, 1978
Guidelines for Wastewater Discharge Enforcement
Policies F-l
G Environmental Team G-l
LIST OF TABLES
Table
1 Project Costs - All Alternatives 15
2 Point Source Pollution Loadings 34
3 Future Effluent Limitations, Boulder 75th Street
Treatment Plant 39
4 Colorado State Water Quality Standards Summary 41
5 Local Effluent Limitations 42
6 Alternative Site, Approximate Biotic Community
Composition 51
7 Four Population Estimates for Boulder City and Boulder
County for 1990 57
XI
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Table page
8 Population Projections for Boulder City and
Wastewater Service Area 58
9 Existing and Projected Wastewater Flows 67
10 Estimated Future Wasteloads 68
11 Preliminary Estimates of Treatment Effectiveness 83
12 Total Project Costs—All Alternatives 88
13 City of Boulder Project Costs—All Alternatives 89
14 Short-term Impacts and Mitigation Measures 96
15 Existing and Expected Plant Species at Alternative
Site A 108
16 Marginal Energy Consumption 118
17 Potential Losses in Assessed Valuation and Tax
Revenues to Affected Jurisdictions 123
18 Environmental Summary of Unavoidable Adverse
Impacts of Project Alternatives 138
19 Comments Received, Boulder Wastewater Facilities
Plan—Draft EIS 150
LIST OF FIGURES
Figure Page
1 Wastewater Facilities Planning Area 3
2 Boulder Creek Project Area 7
3 Generalized Surficial Geology 21
4 Surface and Bedrock Elevation—Cross-Section ' 22
5 Soil Series, Boulder Creek Project Area 25
6 Limitations for Septic Tank Use 27
7 Water Table Contours and Flow Direction 29
8 Depth to Groundwater, Proposed Project Area 30
9 Watercourses, Flood Prone Areas and Point Source
Discharges 32
10 BOD, Ammonia and Temperature in Boulder Creek 36
11 Biotic Communities and Sensitive Ecological Areas 46
12 Unit Processes, Alternative Systems 69
13 Proposed Alternative A with Sludge Injection 76
14 Proposed Alternative C with Sludge Injection 78
15 Potential Area for High-Rate Irrigation 80
xii
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SECTION I
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SECTION I
INTRODUCTION AND SUMMARY
INTRODUCTION
The National Environmental Policy Act of 1969 (NEPA) requires
that all agencies of the federal government prepare a detailed En-
vironmental Impact Statement (EIS) on proposals for projects that may
significantly affect the quality of the human environment. NEPA re-
quires that agencies—in this case the Environmental Protection Agency
(EPA)—include in their decision-making process local and regional
environmental considerations, the environmental impact of the proposed
project and its alternatives, and a discussion of ways to avoid or
minimize adverse effects.
The action being considered by EPA is the approval of federal
funding for the design and construction of additional wastewater
treatment facilities for the City of Boulder, Colorado. These faci-
lities have been proposed so that water quality in Boulder Creek will
meet the goals established by the Water Pollution Control Act Amend-
ments of 1972 (Public Law 92-500). One of the key goals of this law
is to have water quality good enough to support fish and allow re-
creation on and in the water by 1983. Usually, secondary wastewater
treatment will meet these goals. In the case of Boulder Creek, more
restrictive state and regional water quality classifications require
that treatment processes beyond the secondary treatment level may be
needed.
To assist municipalities in meeting the stated water qulaity
goals through treatment facility modifications, Congress set aside $18
billion in a Construction Grant Program to pay 75 percent of the eli-
gible costs of publicaly-owned waste treatment works. For "innovative"
treatment technology, such as land treatment, federal funding may
cover up to 85 percent of the eligible costs. Facilities planning and
implementation under the Constrution Grant Program provides for a
three-step approach for the planning, design and construction of muni-
cipal treatment works, the majority being paid for by federal money.
Step I involves the development of a "facilities plan" that evaluates
treatment needs, systems capacities and alternatives, and develops a
preliminary design for the project. EPA is charged with review and
approval of such Step I plans before design (Step II) and construction
(Step III) funds can be obtained.
EPA has determined that the proposed modifications and additions
to the Boulder Wastewater treatment facilities could have significant
environmental effects and has required the full-scale analysis of an
Environmental Impact Statement (EIS). The EIS is to be a "full
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disclosure" document and must follow specific regulations of the EPA
as contained in 40 CFR, Part 6, as published in the Federal Register,
Vol. 40, No. 72, April 14, 1975.
Data for this EIS was compiled from various existing studies
within the Boulder area, field reconnaisance and numerous personal
contacts with interested individuals and groups. A complete
listing of references appears in the final section of the report.
The project staff that prepared this EIS is listed in Appendix G.
BACKGROUND
The planning area of the Boulder wastewater facilities plan is
outlined in Figure 1. The planning area contains 140 square miles
and is bounded geographically by the foothills to the west, Davidson
Mesa to the south and Gun Barrel Hill to the north. The planning
area is essentially the area projected to be served by the proposed
wastewater treatment facilities. This includes many areas in
Boulder County which are presently unsewered and where utility
provision may be an issue.
The population of Colorado has been growing at a rate greater
than that of the nation as a whole. The City of Boulder has at-
tracted a substantial portion of this new development and growth
is expected to continue. On the basis of local estimates, the
City of Boulder population was approximately 73,000 in 1976.
Population projections for the City of Boulder and the Boulder
planning area were made by the Boulder Area Growth Study Commission,
and recent refinements have been made by the City and County
planning departments and the Denver Regional Council of Governments
(DRCOG). The projected 1995 populations for the City of Boulder and
for the Boulder planning area are 116,700 and 129,000 respectively.
These population estimates were used in the facilities planning
study.
The City of Boulder is served by two wastewater treatment plants,
located on Boulder Creek as shown in Figure 1. The East Pearl Street
Treatment Plant is a small primary treatment facility handling 4.3
million gallons per day (mgd). Wastewater effluent was discharged
directly to Boulder Creek above 55th Street until 1 May 1975, when the
effluent was diverted to the main facility for secondary treatment.
The 75th Street treatmentplant is a secondary level treatment facility
with a nominal capacity of 15.6 mgd. Wastewater effluent from the
main treatment plant is discharged directly to Boulder Creek, above
75th Street. Based on a future flow projection of 120 gallons per
capita per day (g/c.d), the 75th Street plant could presently handle
the average daily flow equivalent to a population of approximately
130,000. However, the treatment plant needs to be upgraded to meet
local effluent limitations and state stream water quality criteria for
Boulder Creek.
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FIGURE
PLANNING AREA
BOUNDARY
BOULDER
CREEK
PROJECT
AREA
WASTEWATER FACILITIES
PLANNING AREA
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The existing wastewater treatment plants are experiencing
problems with both liquid- and solids-handling processes. Up-
grading of the liquid flow processes is under consideration in order
to serve regional growth and expansion and to establish and maintain
a high-quality fishery downstream of the treated effluent discharge
point near 75th Street on Boulder Creek. Treatment plant effluent
has historically been the major source of stream pollution within the
upper Boulder Creek subbasih. High levels of organic material and
dissolved nutrients from treatment plant effluents, sediment loads
from agricultural return flows and industrial discharges have led to
a degradation of the stream environment. Long-term effects include
loss of sensitive fishes and other aquatic organisms, silt deposits,
nuisance algal growths, and the development of unstable ecosystems
with only a few pollution-tolerant species (Reference 1 ).
PROJECT DEVELOPMENT
Improvement of the water quality and stream environment of
Boulder Creek is necessary to restore and maintain the scenic and
recreational resources of the Boulder Creek corridor, and conform to
the goals of the Boulder Valley Comprehensive Plan. The Boulder City
Council committed the city to upgrade and improve the quality of
Boulder Creek to allow primary water-contact recreation and the develop-
ment of a sport fishery in a resolution on June 17, 1975. The primary
targets were the closure of the East Pearl Street treatment plant and
outfall, and the modification of the 75th Street treatment plant to a
higher level of treatment.
The wastewater facilities planning process in Boulder began in
November 1973, when the city contracted with two engineering firms to
prepare independent reports comparing land treatment of wastewater
effluent with conventional or advanced wastewater treatment methods.
Three levels of treatment were evaluated; zero discharge of pollutants
advanced wastewater treatment, and secondary treatment including am-
monia-removal. The two parallel reports were completed in July 1974
(References 2 and 3).
The city staff evaluated the reports with the aid of a Citizen's
Advisory Committee and made recommendations to the city council for
future action. These recommendations became "The Clean Water Package",
defining water quality goals and included a suggested plan for the
realization of these goals. An additional study, to concentrate on
a specific set of water quality standards and funding restrictions, was
requested and was formally approved by the city council in November
1974.
The city staff then proceeded with an application for an EPA Step
I Grant for facilities planning. This grant application was approved
in April 1975, and the resulting facilities plan (Reference 1) was
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published in October 1975. On the basis of recommendations from the
facilities plan, the city has applied to EPA for a two-phase Step II
grant for improvements and expansion of existing wastewater facilities.
Phase I is concerned only with sludge digestion processes and related
facilities for control of odor problems at the 75th Street treatment
plant. These additions and changes to the physical plant are not
expected to create significant environmental impacts and are
therefore covered separately in a negative declaration issued by EPA
on 10 November 1976. (Reference 4.) Phase II, the subject of this
environmental evaluation, consists of modifications and additions to
the treatment plant liquid flow processes, and the method of effluent
disposal. Final disposal of sludge will be analyzed in a separate
addendum to this EIS to be issued at a later date. On 15 December
1976, the Regional Administrator of EPA sent a "Notice of Intent to
Prepare an Environmental Impact Statement for Approval of the Boulder,
Colorado Wastewater Facilities Plan" to government agencies, public
groups and citizens. On 29 September 1976, EPA contracted with
Engineering-Science, Inc., to undertake the studies ana analysis nec-
essary for the preparation and completion of an EIS for the proposed
project under the NEPA process.
In August 1977, EPA distributed the draft EIS to federal, state,
and local agencies as well as to interested groups and individuals for
review and comment. Attention was focused on three specific alterna-
tives as the most cost-effective treatment systems. After numerous
public meetings, local agency meetings, and a public hearing, the
majority of Boulder City and County residents favored a conventional
method of wastewater treatment (activated sludge) but were undecided
as to the method of sludge disposal. The conventional treatment sys-
tem represented a compromise agreement; for although it would be more
costly and energy-intensive, it did not have the controversial en-
vironmental impacts associated with land-based treatment systems.
In February 1978, EPA decided that further work was needed before
an alternative could be recommended for design and construction under
federal funding. In August 1978, additional evaluations were perform-
ed for two land-based treatment systems and sludge disposal. The
treatment systems are included as Appendix D of this EIS. Sludge
disposal will be described in an addendum to this EIS to be issued at
a later date.
SUMMARY
The facilities plan identified seven alternative plans for the
development of wastewater treatment facilities in the planning area.
These alternative plans are: A—land treatment of effluent with
infiltration/percolation ponds; B—installation of an activated
sludge process to follow the existing trickling filter process; C—
effluent treatment in aeration and polishing ponds; D—installation
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of an activated sludge process before the existing trickling filters;
E—multimedia filtration of effluent; F—chemical coagulation; G—high-
rate irrigation of effluent and I—an agricultural reuse program. All
alternatives except Alternative F incorporate sludge digestion and
stabilization with approximately 75 percent applied to a local field
by subsurface injection and the remainder to be dried and stockpiled
for reuse. Sludge digestion and stabilization are incorporated under
Phase I described in the section on project development and are not
discussed in this EIS. Sludge produced from system F is not suitable
for agricultural reuse practices and therefore would have to be dis-
posed of in a landfill. An additional Alternative H, was considered
in this EIS and was defined as the no-project course of action.
Alternative Plans
Based on the estimated treatment effectiveness and engineering
evaluation of alternatives in Section III of this EIS, two of the
alternative systems proposed in the facilities plan would not be able
to meet state and local water quality goals. These alternative sys-
tems are: E—multimedia filtration and F— chemical coagulation.
Modification of Alternatives E and F to bring treatment quality up to
the required standards would have produced systems essentially the
same as other alternatives proposed. In the same manner, Alternative
H would not be able to meet state and local water quality standards
and goals. Therefore, in the detailed analysis of this EIS, only
those systems which had a potential to meet the desired standards and
goals were considered. This narrowed range includes five alternatives:
A—infiltration/percolation ponds; B—activated sludge process fol-
lowing trickling filters; C—aeration and polishing ponds; D—activat-
ed sludge before the trickling filters; and G—high- rate irrigation
of effluent. Alternative I, an agricultural reuse program was evaluat-
ed in August 1978 and is included in this summary. Alternative H—no
project, is included in the summary below for purposes of comparison.
The proposed project area with the main alternative sites in the vici-
nity of the 75th Street treatment plant is shown in Figure 2.
Alternative A - Land Treatment by Infiltration-Percolation—
This process would use the high infiltration and permeability
capabilities of the sands and gravels bordering Boulder Creek. Two
sites were evaluated in the vicinity of 75th Street and 95th Street.
The system would be operated all year around. A drain tile system
would be installed to depress the groundwater profile and collect
the filtered effluent for return to the creek. Approximately
225 acres of land would be needed for infiltration/percolation
basins and a buffer zone. Wastewater would be treated by the
existing 75th Street treatment plant prior to application to the
basins.
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HEATHERWOOO RESTATES
STREE
lREAIMENT _PLA_NT
AUTERNATIVE C
\ AERATED AND
ING PONDS
SITE
r-
Og cALTERji|ALiyES_A_-G
Oo8 °TDI
'Qoo 0 TREATMENT PLANT
WALDEN PONDS
SITE
" o
•a
WILDLIFE f ------ L ___ °_
HABITAT
ALTERNATIVE A
iflFILTRATION/PERCOLATldk
BASINS SlTEv ^ ' !
J \
\ '
FIGURE 2
BOULDER CREEK PROJECT
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Alternative B - Activated Sludge Process following Trickling Filters—
This alternative would employ a complete-mix activated sludge
process following existing plant treatment processes, and the addi-
tion of final clarifiers. The activated sludge basins would have
a short aeration time (2 hrs ) and would oxidize any organics escaping
the trickling filter process. No additional land would be required,
because the facilities could be constructed on the existing plant
site. This alternative also includes ammonia removal.
Alternative C - Aerated and Polishing Ponds—
Treated effluent from the existing 75th Street plant would be
pumped to aerated ponds with a 2-day detention time. Most of the
remaining organics would be oxidized in the ponds with the effluent
from the ponds overflowing into succeeding polishing ponds where
suspended solids would settle out. The first polishing pond would
probably have algae growths with their associated maintenance
problems, while the last pond could probably support a warm water
sport fishery. All of the ponds would be constructed in gravel pits
that will be excavated from the site in the future. Total additional
land needed, including buffer area, would be approximately 145 acres.
It is questionable whether this alternative can provide adequate treat-
ment for: (1) NH N in winter; (2) TSS in summer; and (3) BOD in
summer.
Alternative D - Activated Sludge Process prior to Trickling Filters—
A pure oxygen, complete mix, activated sludge process would be
constructed ahead of the existing trickling filters to treat all the
effluent entering the 75th Street plant. This process would oxidize
approixmately 90 percent of the organic content before the effluent is
applied to the trickling filters. The filters would then receive a
wastewater low in BOD, which would permit nitrification of the waste-
water. No additional land area would be required for implementing
this system.
Alternative G - High Rate Irrigation of Effluent—
This system would principally be employed for wastewater treat-
ment while utilizing the residual nutrients in the effluent for crop
production. This system would include a 350-acre lagoon with an 8,800
acre-foot capacity to store the effluent for five months during the
nongrowing season. Irrigation with the effluent from the lagoon would
be at a rate of 10 feet/year. Fescue or smooth brome grass would be
planted and harvested as hay for livestock feed. The total area of
land needed would be 3,360 acres, which includes irrigation fields,
buffer space and a 350 acre storage lagoon approximately 30-feet deep.
Under this alternative, the city would actually own, or in some like
manner, control the land involved.
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Alternative H - No Action—
The existing wastewater treatment facilities at the East Pearl
Street and 75th Street plants would continue operation. Phase I of
the facilities plans, as discussed in the Project Development Section
has already been approved by EPA and is currently undergoing engi-
neering design. Thus, the new sludge digester and stabilization sys-
tem would become part of the existing facilities and would alleviate
most of the present odor problems associated with the treatment plant.
The present trickling filter system is adequate for a secondary treat-
ment level. However, discharge of this effluent to Boulder Creek will
not comply with the local and state goals of primary water-contact
recreation and development of a sport fishery in that creek. Organic
material, dissolved nutrients, ammonia and coliform bacteria from
treatment plant effluents would exceed the new upgraded stream stan-
dards. These pollutants have historically altered the ecology of
Boulder Creek and would hinder restoration efforts for the Boulder
Creek corridor.
Alternative I - Agricultural Reuse Program—
This program is a land-based treatment system which would involve
exchanges of effluent water rights with irrigation water rights held
by local ditch companies. Secondary effluent would be conveyed to
privately-owned ditches and applied to private farmland during the
growing season. The nutrients in the effluent would be used by crops,
while the wastewater would be renovated through the soil column.
Approximately 10,000-12,000 acres of farmland would be required. In
winter, effluent would be conveyed to a 10,000 acre-foot reservoir for
storage and release for the spring irrigation demand.
This system relies on a private irrigation and farm system and
thus would require a long-term contract between the city and each
ditch company. In addition, the city must either acquire the develop-
ment rights to the irrigation sites in order to ensure a fixed land
area for effluent application or in some other manner be able to assure
that this land will remain available for irrigation use for the design
life of the project (approximately 20 years).
Sludge Disposal—
All alternatives, except F, will incorporate beneficial reuse of
sludge to the maximum amount possible. Not addressed in this EIS are
alterations and additions to the existing facility which will include
sludge thickening, anaerobic digestion, and dewatering of 25 percent
of the sludge by vacuum filtration and sand drying beds. Phase II,
which will be addressed in a later addendum to this EIS, includes the
construction of force mains to a proposed field near the treatment
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plant or to another site near 95th Street currently being evaluated.
The remaining 75 percent of liquid sludge from the plant will be
pumped to these fields and injected below the ground surface with
special equipment for beneficial reuse to crops. A potential field
site of 170 acres near the 75th Street plant has been proposed for
Alternatives A through G. As stated, another site of approximately
the same size, is being investigated near 95th Street. Sludge pro-
duced from Alternative System F will contain large volumes of alum and
will be unsuitable for crop reuse, necessitating disposal to a land-
fill.
Environmental Impacts
In the engineering evaluation performed in Section III and in the
Appendix D, only alternatives A, B, C, D, G and I had the potential to
meet regional water quality goals. The major beneficial and adverse
environmental impacts of these alternatives along with feasible miti-
gation measures considered are summarized below. A sludge-injection
site has not been finally selected and will be presented separately as
an addendum to the final EIS.
Impacts on the 75th Street site are evaluated in Section IV of
the EIS. Impacts associated with the 95th Street site were evaluated
in August 1978 and are included in Appendix D. For most situations,
impacts at the two sites were similar and are summarized below. Dif-
ferences at individual sites are noted below also.
Construction of additional treatment processes will commit the
nominal treatment plant capacity to 17.6 mgd. The ability to handle
this volume of flow effectively allows the city to handle sewerage
flows for 129,000 persons during the design period.
Alternative A - Infiltration/Percolation Ponds—
1. Construction activities will cause short-term erosion, down-
stream sedimentation, dust emissions and noise. These effects can be
reduced by specific construction practices.
2. Removal of ground cover and pasture habitat with eventual
replacement by plant and animal species that can tolerate an inter-
mittent wet and dry cycle will occur. Water-associated bird and ani-
mal species will be encouraged.
3. Pond operations will cause a lowering of the groundwater
table below and immediately adjacent to the pond sites. Groundwater
flow through that area will be disrupted with diminished volumes im-
mediately east of the site. This effect could be mitigated with a
recharge system along the eastern site boundary if the effects on sub-
irrigation are severe.
10
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4. Minor groundwater contamination from percolates immediately
east of the site when fields are saturated after heavy rain or irri-
gation.
5. A potential public health hazard may occur from aerosols
arising from the effluent in the infiltration basins during windy
periods. Certain bacteria and viruses may be transmitted through
contact with the aerosols. In the event that the site becomes flood-
ed, overflow of effluent to adjacent public and private property may
expose persons in the area to bacterial and viral contamination from
surface waters. This impact could be effectively mitigated by disin-
fection of wastewaters.
6. The infiltration/percolation ponds can produce a high qual-
ity effluent that will greatly enhance the water quality and aquatic
productivity in Boulder Creek. Nitrate levels, however, are not re-
duced by this system and are higher than the recommended regional
goals, as reviewed on pages 40 and 41 of Section II.
7. The warm effluent in the ponds may have a potential to gene-
rate steam fog during extremely cold winter days. Fog may drift over
adjacent roadways and inconvenience travellers and adjacent residences.
8. Under adverse operation conditions, such as soil clogging,
localized odor generation may occur and drift to downwind areas. At
the 75th Street site, this may affect local housing subdivisions. At
the 95th Street site, a few local residences may be affected. Plans
for subdividing areas near the 95th Street site may conflict with this
treatment location.
9. Construction activities at the 95th Street site may disrupt a
heron rookery immediately east of the site through dust, noise, vi-
brations and destruction of some feeding habitat. This effect can be
eliminated by scheduling construction during the fall and winter when
the birds have migrated south and are absent from the rookery.
10. The 95th Street site lies within a probable recharge area
which connects the shallow aquifer with the Pierre Shale Transition
Zone. Effluent infiltration at the site may potentially enter the
deep aquifer and contaminate it. This effect is difficult to mitigate
as the exact location and character of the fault need to be confirmed
by further study.
11. Diversion of effluent discharge from above 75th Street to
the vicinity of 95th Street would reduce groundwater recharge by Boul-
der Creek and subsequent pasture sub-irrigation as well as remove the
water supply from the headgates of Leggett and Lower Boulder Ditch.
These effects can be mitigated by pumping the renovated wastewater
back upstream to the vicinity of 75th Street or at least to headgates
of Leggett and Lower Boulder Ditches.
11
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Alternatives B and D - Activated Sludge Systems—
1. Construction activities will cause short-term erosion, dust
emissions, noise and increased traffic. These effects can be reduced
by specific construction practices.
2. There will be a commitment of only a small land area to the
facilities construction, thereby causing a negligible impact upon
vegetation and wildlife habitats.
3. There will be a production of a good quality effluent that
will greatly enhance the water quality and aquatic productivity of
Boulder Creek. Organic and nitrate levels, however, would be higher
than the recommended regional goals, as presented on pages 40 and 41
of Section II.
4. Comparatively large expenditures of energy will be required
to run an activated-sludge system, particularly the oxygen-generation
unit. System D will consume 2-5 times more energy than Alternatives A
or C.
5. Systems B and D have the greatest potential for energy gene-
ration. Methane gas produced from the anerobic digestor would help
reduce the total amount of energy required for the system. This may
account for up to one-third of the energy requirements in Alternative
B and one-fifth of the requirement in Alternative D.
Alternative C - Aeration/Polishing Ponds—
1. Construction activities will cause short-term erosion, dust
emissions, noise and increased traffic. These effects can be reduced
by specific construction practices.
2. Creation of a continuous chain of ponds covering approximate-
ly 140 acres will increase aquatic habitat in the area. This may be
attractive to waterfowl, shorebirds and other animals associated with
water bodies.
3. This alternative could adequately meet the local BOD and
suspended solids limitations, however, the level of assurance would be
lower than Alternatives A, B, D or G. Periodically high ammonia and
suspended solids levels would continue to be a problem in the creek.
4. Odors may be produced during particular periods in the spring
when anaerobic waters and decaying materials are brought to the pond
surface or in the summer following algal blooms and subsequent decay.
The odor-causing conditions and odor situations can possibly be miti-
gated by a monitoring and control program to control and/or harvest
excess algal growth.
12
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5. Creation of a picnic area and bicycle path along Boulder
Creek and around the final polishing ponds could increase the re-
creational resource of the area. The final polishing ponds could also
be stocked with warmwater fish species. Public acceptability would
depend upon the ability to control odors.
6. The conversion of existing and future gravel pits into well-
designed ponds west of the 75th Street plant would reclaim the area
into a pond and waterfowl area. This would increase the diversity of
the area. However, implementation of this alternative may be counter
to Boulder County reclamation plans for the Walden Ponds Wildlife
Habitat area. Prior to project approval, interagency cooperation and
agreement would be required.
7. Steam fog could be generated over the ponds on extremely
cold winter mornings. The probability of a dense fog affecting roads
would be low. Fog generation cannot be mitigated effectively.
Alternative G - High-Rate Irrigation—
1. Construction activities will cause short-term erosion, dust
emissions, noise and increased traffic. These effects can be miti-
gated with specific construction techniques.
2. 350 acres will be irreversibly committed to the construction
of a permanent storage lagoon. Permanent destruction of soil profile
at the lagoon site and irretrievable loss of 17 million cubic yards of
soil resource at the lagoon site will occur. Soil loss at the site
cannot be mitigated; however, the soil resource can be transferred to
other areas for use.
3. Crop production will utilize nitrates in the effluent, how-
ever, some quantity of nitrates and other constituents may enter the
groundwater or surface runoff on the irrigation sites.
4. The existing communities at the proposed irrigation areas
will be altered from mixed pastureland/agricultural to a monoculture
of grass species tolerant to high-rate irrigation. Changes in wild-
life numbers and composition will also occur.
5. Odors may be produced during the following conditions: a)
the storage lagoon becomes anaerobic in winter and spring thaws bring
the odorous material to the surface; b) large algal blooms in the
summer with subsequent die-off decay; c) suspended algae in irrigation
waters may dry and decompose on fields after irrigation; and, d) sum-
mer drawdown of the lagoon may bring settled decaying algae to the
surface. Odor effects may be mitigated by control algae in the la-
goon; however, complete odor control would be difficult to achieve.
13
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6. Nutrient resources in wastewater effluents are conserved by
recycling them to agricultural lands.
7. High-rate irrigation, under some conditions, can damage
vegetation by excess hydraulic loadings or cause salt accumulations in
soils. Under a properly managed system, hydraulic overloading can be
controlled and salt accumulations reduced to a low level.
8. A comparatively large expenditure of energy will be required
to pump the treated effluent to the storage reservoir and operate
irrigation equipment. Energy commitment for this system is approxi-
mately twice the amount required for system B.
9. Pumping of the treated effluent to a regional storage lagoon
and a provision of high-rate irrigation system makes this alternative
compatible for a future agricultural reuse program for Boulder County.
In the future, control of irrigation rates, crop selection and exten-
sion to formerly non-irrigated areas could optimize use of treated
effluent in a reuse program.
Alternative I - Agricultural Reuse Program—
This alternative was evaluated in summer 1978 and the impacts
discussion is presented in Appendix D.
1. Construction activities will cause short-term erosion, dust
emissions, noise and increased traffic. These effects can be miti-
gated with specific construction techniques. Significant construction
impact may occur with the construction of a new storage reservoir or
the dredging of an existing reservoir to increase the storage capa-
city.
2. Provision of a high level of water treatment by purification
through the soil column. However, high evapotranspiration associated
with irrigated cropland may increase water salinity.
3. Beneficial reuse of the wastewater nutrients by crops.
4. Domestic use of the ditch company water would have to be
limited. At present, the town of Frederick in Weld County draws do-
mestic water from the Lower Boulder Ditch.
5. Nuisance odors and algal growth may occur in the storage
lagoon similar to those mentioned under Item 5 of Alternative G.
6. A long-term contract for water exchange would be required
between the city and each ditch company. This would severly limit
options for individual water use for contracted farms within the ditch
14
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company. An alternative may be for the city to purchase individual
water rights and lease them back to the fanners. This method would be
costly and require a complex administration.
7. A long-term agricultural commitment of land areas is re-
quired for effluent application. The city would probably have to
institute a program such as acquiring development rights for the pro-
posed sites to ensure that they will not be developed during the pro-
ject life. Commitment of these areas to agricultural use within Boul-
der County would conform with the "greenbelt" concept of the Boulder
Valley Comprehensive Plan. However, the majority of the land irri-
gated by the ditches that were evaluated in Appendix D are in Weld
County and the "greenbelt" concept would not apply.
8. The city would be required to provide restitution for addi-
tional ditch and farm operation costs. To meet public health con-
cerns, only crops not grown for direct human consumption could be
grown with effluent, and the city may have to compensate growers for
higher value crops that might have been grown with regular irrigation
water or provide another water supply for these areas.
9. A comparatively large expenditure of energy will be required
to pump the treated effluent to the fields and storage reservoir as
well as operate irrigation equipment. Energy commitment for this
system would be twice the amount required for system B.
10. Administration of an agricultural reuse program would be
relatively complex in the event that: 1) more than one ditch company
is involved; 2) if the ditch companies have junior water rights and
the decreed flow is small; or 3) multiple agreements must be made
between ditch companies and individual farmers. The greater the num-
ber of entities involved the less control the city will have over the
final disposition of the effluent and the resultant water quality.
11. As of August 1978, several local ditch companies have been
approached to determine their receptiveness to an agricultural reuse
program. Major problems were anticipated with negotiating the pur-
chase of development rights, water rights, system reliability and
other considerations. As a whole, the ditch companies were reluctant
to enter into any long-term agreements.
Project Costs
The present worth of all costs for each alternative in January
1977 dollars is shown on Table 1. Costs were not estimated for Alter-
native I (Agricultural Reuse Program) as no workable water exchange
system was developed. The present worth is a combination of total
capital costs less salvage values and the cumulative operation and
15
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operation and maintenance (O&M) costs during the design period. A
detailed explanation is given in Section III. Alternative A is sep-
arated into two series denoting costs associated with two different
sites. Alternative C is the lowest with a present worth value of
$10.1 million. Alternative A, B and D are intermediate at $11.9-14.7
million and Alternative G is highest at over $44 million.
Alternative H (no action) would have no associated capital costs.
Annual O&M Costs would remain similar to present levels at the treat-
ment plant. Alternative I, the agricultural reuse program, was not
developed in sufficient detail to be costed. The reuse program en-
countered a number of institutional problems and was not considered
workable by EPA at the present time. No estimate could be made with-
out additional information regarding costs for purchasing water and
development rights.
Capital Costs—
Under the facilities plan and supplement (References 1 and 5),
each alternative was costed out for two construction phases occuring
in 1978-1980 and 1988-1989. Salvage values were projected in the year
2000.
Total capital costs for both phases of construction range from a
low of $7,832,000 for Alternative C (Infiltration/Percolation) to a
high of $34,875,0.00 for Alternative G (high-rate irrigation). Assum-
ing 75 percent federal participation in capital funding, corresponding
costs to the City of Boulder would range from a low of $1,958,000
(Alternative C) to a high of $8,178,000 (Alternative G). Table 1
lists the capital costs, for the total project and the Boulder portion
of each alternative system. The salvage value of facilities and land
conversely is lowest for Alternative C ($579,000) and highest for
Alternative G ($4,053,000) due to the large amount of land involved.
Annual O&M Costs—
The average annual equivalent post to be borne by Boulder for
each alternative is shown in Table 1. The annual equivalent costs for
each construction phase with a 6-3/8 percent discount factor over 30
years. The annual equivalent costs are lowest under Alternative C
($613,000) and highest under Alternative G ($2,849,000).
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Table 1. PROJECT COSTS — ALL ALTERNATIVES
(In Thousands of Dollars)
Alternative
Aj A^ B C D G
Capital Costs
Total project costs 9,889 11,171
Boulder's share of total
project costsa 2,473 2,793
Average annual equivalent cost 707 754
Salvage value of facilities and
land 853 946
Net present worth0 11,911 13,130
10,272 7,832 11,544 34,875
2,568 1,958 2,886 8,718
904 608 904 2,824
853 579 940 4,053
13,799 10,133 14,706 44,685
Assuaes federal participation of 75 percent of total project costs.
Represents annual 0&>! charges plus capital recovery costs to Boulder for each phase. For detailed
explanation of costs, see Section IV, Alternatives-Project Costs.
present worth of all costs less salvage value of facilities and land. For detailed explanation,
see Section IV.
A -costs associated with infiltration/percolation basins at 75th Street site.
A^-cost associated with infiltration/percolation basins at 95th Street site.
17
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SECTION II
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SECTION II
ENVIRONMENTAL SETTING
PHYSICAL ENVIRONMENT
The planning area is situated at the base of the eastern slope
of the southern Rocky Mountains, commonly referred to as the Front
Range. The mountains rise dramatically more than 2,000 ft in a
distance of two miles and overshadow the relatively flat plains
area of Boulder.
Climate
Climate has a direct bearing on wastewater treatment facility
operations in relation to equipment performance during weather ex-
tremes. Low temperatures can limit the reliability of biological
treatment systems; winds carry odors; freezing conditions and
evapotranspiration rates affect land application of effluents; and
rainfall affects receiving stream and wastewater flows.
In general, the Boulder area has a continental, semi-arid cli-
mate which is greatly influenced by the Rocky Mountain system lo-
cated immediately to the west. The Front Range and the prevailing
westerly winds modify the plains climate with generally lower day-
time temperatures; narrower temperature range; warm-to-cool summer
days; higher relative humidity; greater, more evenly distributed
precipitation; and very strong winds in the higher, exposed areas
(Reference 6).
Temperature—
The annual normal temperature is 51.8°F. The range of monthly
average mean temperatures is 33.1°F (January) to 73.9°F (July).
The range of record temperature extremes is -33°F (January 1930)
to 104°F (June/July 1951). The average frost-free season is 152
days between 9 May and 8 October. The average number of days hav-
ing temperatures above 32°F during the frost season is 83 (Refer-
ences 4, 7). In the context of sewage treatment plant operations,
low temperatures can be significant if they limit the reliability
of biological sewage treatment systems. Low temperatures can sig-
nificantly retard percolation rates for percolation pond treatment
systems. Freezing temperatures can halt pond operations and shut
down irrigation systems. High temperatures, on the other hand,
can be significant if they stimulate the growth of algae which sub-
sequently decay, causing odors.
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Precipitation and Evaporation—
The wet season in Boulder generally falls between April and
September, with the peak period occurring during April through
June. The mean annual precipitation is 18.42 in., with an annual
maximum of 27.52 in. and an annual minimum of 10.91 in. The area
is relatively arid, and the rate of evaporation is high during the
summer months, as indicated in general by evaporation data at Fort
Collins, 40 miles to the north. The low relative humidity of the
area, rather than the summer temperature, is the major factor
causing this high rate of evaporation. The Boulder area receives
approximately 81.0 in. of snow annually, with most snow falling be-
tween October and May. In the context of wastewater treatment
systems, precipitation and evaporation rates are important working
factors in relation to reliability and efficiency of wastewater
pond systems.
Winds—
During the winter and early spring, Boulder is subject to strong
down-canyon winds off the eastern mountain slopes called Chinooks.
As these winds descend through Boulder Canyon, their speed and tem-
perature increases greatly. When the Chinooks enter the cooler
plains area, they can cause sharp temperature increases in several
hours. In addition to Chinooks, Boulder is subject to severe wind-
storms at least once a year during the winter. The windstorms are
characterized by overall speeds in excess of 50 mph, gusts up to 90
mph, rapid and frequent fluctuation in speed and extremely low rel-
ative humidity (References 8, 9). Chinook episodes and windstorms
could be of significance at construction sites and in areas with
bare, exposed surfaces, such as earth berms and drying beds, where
potential for blowing dust and soil is high.
In the vicinity of the 75th Street treatment plant, prevailing
winds are from the southwest through west. Winds also blow occa-
sionally from northeast and east. Generally, winds tend to parallel
Boulder Creek. At night in very cold weather, southwesterly drainage
winds down the valley are likely. Ambient wind conditions are impor-
tant in estimating dispersal of potential odors or steam fogs gener-
ated from the alternative treatment systems.
Air Quality
Boulder forms the northwest portion of the Metropolitan Denver
Air Quality Control Region (AQCR) as defined by the Colorado State
Air Pollution Control Commission (Reference 10). Within this
region, air pollution control priorities have been established for
carbon monoxide, particulates and reactive hydrocarbons. Pollutants
18
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in the Boulder area are generated to some degree by light industry
(manufacturing); however, the majority of emissions are derived
from automobile traffic. Air pollution effects are often compounded
by winter temperature inversions which trap pollutants in the
Boulder Valley (Reference 11).
In a recent report by the Boulder City/County Health Depart-
ment (Reference 12), air quality in the Boulder area was determined
to be greatly influenced by traffic in the central area of the
city. On days with stable atmospheric conditions and little dis-
persion, air pollution levels may routinely exceed National Ambient
Air Quality Standards (NAAQS). Carbon monoxide concentrations are
due almost entirely to vehicular traffic and exceed state and federal
standards periodically in heavily travelled areas. Relief of areas
with traffic congestion greatly reduces carbon monoxide levels.
Federal primary and secondary standards for particulates have
often been exceeded in Boulder. Particulates can be derived from
industrial activity as well as from automobile exhaust. Ozone
levels measured at the National Oceanic and Atmospheric Administra-
tion building in Boulder show that the 1976 federal photochemical
oxidant standard of 0.080 ppm was exceeded during-23 of the 34
months of data available from 1973 to 1976 (Reference 12). High
ozone levels are expected to continue as long as the source pollu-
tants (reactive hydrocarbons) are emitted into the air. As federal
emission controls work towards reducing vehicle emissions, ozone
levels may decrease. However, there are sufficient naturally oc-
curring emissions of reactive hydrocarbons that the ozone standards
may be exceeded in the future (Reference 12).
Throughout the remainder of the planning area, traffic is re-
latively freeflowing, resulting in less congestion, fewer emissions
and better air quality. As winds pick up or other climatic ac-
tivity along the Front Range takes place, temperature inversions
are broken up, and pollutant levels throughout the planning area
are reduced below significant levels.
Geology
Local Bedrock Geology—
Knowledge of general permeability characteristics of the bed-
rock formations is important in examining the potential for ground-
water pollution by land-disposed effluent.
With the formation of the mountains and hogbacks to the west
and the retreat of an ancient sea covering the region, Boulder
County was exposed to such forces as running water, glaciation and
19
-------
wind. The wearing and reshaping effects of these forces on the ex-
posed land surface have resulted in the formation of vast quanti-
ties of new (Quaternary age, less than two-million-years-old) al-
luvial (river-transported), colluvial (landslide-transported),
eolial (wind-transported), and various glacial sediments and mate-
rials which cover much of the area. These unconsolidated surfi-
cial deposits, which are shown in Figure 3, include loose sand,
silt, gravel and clay. The coarse material is quite permeable
and may be more than 30 ft thick in the eastern part of the study
area.
Underlying and in some places breaking through the surface of
these young sediments and related materials are older, more ero-
sion-resistant Upper Cretaceous (80-million-year-old) sedimentary
rock formations known as Pierre Shale, Fox Hills Sandstone and
Laramie. Pierre Shale is the most widespread formation in the
study area. It is 5,000 to 8,000 ft thick and consists of gray to
black clay and sandy shale. The formation is highly impermeable
and generally prevents recharge of water to lower rock units.
Most of the City of Boulder and both wastewater treatment plants
are situated above the Pierre Shale Formation. Bedrock and surface
elevation contours for the proposed project area are shown in Fig-
ure 4. The bedrock consists of gray clay and shale of the Pierre
Shale Formation and buff to brown to olive silty clay derived from
the Pierre Shale or the lower Fox Hills Formation.
Bedrock elevations generally rise from east to west along with
the gradual rise in topography. In the vicinity of the 75th Street
treatment plant, bedrock generally lies 15-20 ft below the ground
surface. East of 75th Street, the bedrock layer generally lies
10-15 ft below the ground surface. The bedrock layer strongly de-
fines the movement of the overlying groundwater aquifer. The depth
to bedrock is also an important consideration in designing pond
sizes and building foundations.
Unique Geologic Features—
One of the most visible areas in Boulder County where the Fox
Hills and Laramie formations outcrop at the surface is the "White
Rocks." These sandstone bluffs rise over 100 ft above the flood-
plain and are limited to a two-mile segment along Boulder Creek.
The geological uniqueness of the White Rocks is due to joints in
the rock which intersect to form polygons that differ from those
typically found in sandstone. Two basic polygonal patterns occur.
The first is characterized by right-angle intersections and bears
close similarity to mud cracks and ice-wedge polygons. The second,
occurring within the first, is composed of hexagonal and pent-
agonal figures that resemble columnar jointing in horizontal per-
spective. The resultant hummocky, "turtleback" topography
20
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TREATMENT
PLANT
GENERALIZ
SURFICIAL
GEOLOGY
BEDROCK WITH
THIS RESlSL'iL S'jRflC14L COVER
'••'.'-'^ UND1FFERENTIATED OLCES ALLUVIUM
t : W'N08LC*N "EOL'AS" DEPOSITS
-------
UJ
>
UJ
UJ
(O
UJ
O
CD
UJ
UJ
U-
§
UJ
5140
(C) WEST
(C') EAST
NORTH 75 TH ST
ALLUVIUM - SAND 8 GRAVEL
WATER TABLE
MAY 182, 1975
BOULDER
CREEK
SILTY, SANDY CLAY
(PIERRE SHALE AND FOX HILLS
FORMATION, UNDIFFERENTIATED)
8000
7000
6000
5000 4000 3000
DISTANCE FROM BOULDER CREEK IN
2000
1000
FEET
FIGURE 4
SURFACE AND BEDROCK ELEVATION - CROSS - SECTION
PROPOSED PROJECT AREA
-------
gives a unique appearance to the surface relief and in-
fluences the distribution of a variety of common and unique local
flora and fauna (Reference 13). Further discussion of the biotic
and aesthetic importance of the White Rocks is given in sections
to follow.
WHITE ROCKS GEOLOGIC FORMATION
Soils
Knowledge of local and on-site soil characteristics is impor-
tant to project planning to avoid or minimize construction or opera-
tion problems. Also, where soils are to be an integral factor in
project operations, such as sludge injection, it is important to
know which are the most suitable types. Lastly, knowledge of the
soils' agriculture and other productivity potential is important
in assessing the long-term resource losses that may result from a
given project.
The characteristics of the soils identified for the project
sites are discussed in this section and in Appendix A, and a gene-
ral soil map of the 75th Street proposed project areas is shown on
Figure 5. This information is general in nature and should be
augmented with additional field investigations by soils scientists,
agronomists and/or soils engineers at the project design stage.
23
-------
Niwot—Loveland-Calkins Association-—
Both of Boulder's wastewater treatment plants are situated on
soils of the Niwot-Loveland-Calkins association. The soils of
this association, formed from loamy alluvium, occupy narrow, nearly
level areas adjacent to major streams in eastern Boulder County.
About 35 percent of the association is Niwot soils, and 15 percent
is Loveland soils. All of the major soils of this association are
mottled and have a water table that is within plant root zones at
sometime during the year. Mottled soils generally indicate poor
aeration and lack of drainage. The majority of soils in this as-
sociation have severe limitations for septic tank use and sewage
lagoon operation because of high water tables and flooding hazards.
In places, soils of this association are flooded by runoff from
adjacent areas. Soils of this association are not easily eroded;
however, bank-cutting near channels can be a problem for the Niwot
series. About half of the total acreage of this association is
used for growing irrigated crops. The rest is used for irrigated
pasture. Because of the high water tables, drainage practices
help increase crop yields. Many areas adjacent to watercourses
have been mined for their gravel resources (Reference 14).
4_
5_
16
\7_
]8
??
27
22
23
27
28
29
30
RO
FIGURE 5. SOIL SERIES
BOULDER CREEK PROJECT AREA
LEGEND
Ascolon sandy loam Slope
Ascalon Otero complex
Hargreave tini sandy loam
Manter sandy loam
Longmont clay *
Loveland soils *
Niwot soils
Nunn cloy loam
Samsil clay
Calkins sandy loam
Colby silty cloy loam
Colby- Gaynor association
Valmont clay loam
Valmont clobby clay loam
Weld Line sandy loam
Samsil Shingle complex E=5-25%
Rock Outcrop
Source: Soil Conservation Service
test site data from CH2M Hill
0-1%
I -3%
3-5%
5-9%
9-20%
Predominant soils
of proposed
project areas
24
-------
01
I9B
BOULDER
FEEDER
a I? 8 | °
c, * !° D; °
JAY "ROAD D
)27B|
v3E
iREATMENT PLANT
^"08
6 16
e 14 A
WAI DEN PO
WILDLIFE /
HABITAT 1
AREA
rx
— — n
i
NDS j
•-^ --)
HEATHERWOOD-
23
I9B
29B
3D
Rt*
WHITE
3C
e 7
18
06
i, ( i ^ r
(? A
FIGURE 5
SOIL SERIES
BOULDER CREEK PROJECT AREA
-------
Ascalan-Nunn-Manter Association—
All of the area of the proposed sludge injection site and a
small portion of the proposed infiltration-percolation basin site
is situated on soils of this association. These soils are on nearly
level terraces and on gently sloping to moderately steep valley
sides and uplands in the southeastern part of Boulder County. The
soils in this association were formed in mixed alluvial and eolial
materials. About 60 percent of the association is Ascalan soils,
about 15 percent Nunn soils and about 10 percent Manter soils
(Reference 14).
Most areas of this association are cultivated. About two-
thirds of the area is used for irrigated crops. Where these soils
are irrigated, good water management helps control erosion; use of
crop residue helps control soil blowing on both irrigated and dry-
farmed areas.
Soils Limitations for Septic Tank Use in the Boulder Area—
An important consideration in the analysis of programs for
improvement of wastewater facilities is the determination of which
areas have the most immediate need for service. The Boulder City/
County Health Department, in conjunction with the U.S. Geological
Survey, has mapped residential areas of various densities which are
dependent on septic tanks for liquid waste disposal. (Reference 15).
Based upon information from the County Health Department and the
U.S. Soil Conservation Service, Figure 6 displays gross areas of
septic tank use and limitation. Although the areas of septic tank
limitation shown on the map are likely to receive a higher degree of
attention in sewer system expansion planning, it must be kept in
mind that there are pockets within areas suitable for septic tank
use that will also require sewer service because of site-specific
soil limitations (References 14 and 15).
Water
Groundwater—
Knowledge of local groundwater conditions is important when-
ever excavations are planned so that construction problems may be
avoided. More specifically, when effluent treatment ponds are
planned, knowledge of groundwater conditions is necessary to as-
sure that the improvements do not inadvertently lead to a contami-
nation of local groundwater resources. Also, land disposal of
26
-------
PRESENT
SEPTIC TANKS
AREA WITH
POTENTIAL
FOR SEPTIC
TANK
MALFUNCTION
AREAS EXPERIENCING SEPTIC TANK
MALFUNCTIONS DUE TO HIGH WATER/TABLE
MODERATE-TO-SEVERE
LIMITATIONS
SLIGHT-TO-
MODERATE
LIMITATIONS
BOUNDARY OF
SOIL SURVEY
AREA
FIGURE 6
LIMITATIONS FOR SEPTIC TANK USE
IN THE BOULDER AREA
27
-------
sludge can contribute to the total dissolved salts (IDS) of local
groundwaters, In this ca^e, it is conceivable that highly saline
groundwater could affect surface water quality.
In the vicinity of the 75th Street treatment plant, ground-
water occurs in unconsolidated alluvial deposits of materials rang-
ing in size from clay to gravel which overlie a bedrock of clay and
shale. The deposits underlying the valley bottom and low terraces
along Boulder Creek are approximately one-mile wide and trend east
and west. While the overall thickness of the deposits range from
0 to 20 ft, the average thickness of deposits in the immediate
vicinity of the site is approximately 10 ft.
Groundwater levels in the deposits fluctuate with water table
conditions and are hydraulically connected to streamflow in Boulder
Creek. Figure 7, based on water level measurements at 68 observa-
tion wells in May 1975, shows the configuration of the water table
in the vicinity of the site, The ridge of groundwater under Boulder
Creek indicates that the alluvial aquifer is receiving recharge from
streamflow. The stream and aquifer are in equilibrium in the vi-
cinity of the gravel pit east of the site. Groundwater is also
moving toward the valley bottom from the terraces to the south, The
general direction of flow in the aquifer is northeastward, toward
and along Boulder Creek,
Figure 8 shows the depth to the water table in the area of the
site. Over most of the area, groundwater is near the land surface
and intersects it at many points. The depth to groundwater ranges
from 0 to 7.7 ft in the bottomlands along Boulder Creek and in-
creases to approximately 18 ft below the terraces south of the
stream. Groundwater levels vary in the site area throughout the
year.
During the spring, when water levels are lowest, Boulder Creek
is a losing stream in the vicinity of the site, which means that
water is lost to the groundwater table. Below the 75th Street
bridge, stream water directly recharges the groundwater aquifer
through the porous alluvium. The irrigation season, which begins
in late spring, increases water levels in the aquifer. As the
stream level of Boulder Creek falls after peak snowmelt runoff
during July, the stream begins to receive discharged groundwater.
The aquifer continues to drain to Boulder Creek during the fall,
winter and early spring. The aquifer again receives recharge from
Boulder Creek during the late spring, when the level of the stream
is rising as a result of snowmelt.
28
-------
FEEDER 1
DITCH T
v^
ro
HEATHERWOQD RESTATES
WOUND WATER ^.EVEL ELEVATION
UiRMTION OF GROUND WATER MOVEMENT
ARROW* «fJDICHT
>£
FIGURE 7
WATER TABLE CONTOURS
FLOW DIRECTION
-------
9 OBSERVATION SHELLS AND Ttt'feE NUMBER
* 1° "" o
JAY n RO AD
FIGURE 8
DEPTH TO GROUNDWATER
PROPOSED PROJECT AREA
-------
Surface Water—
General Conditions. The Boulder Creek Basin forms a part of
the South Platte River system. The basin extends from the Conti-
nental Divide to 22 miles east of Boulder, where it enters St.
Vrain Creek. The major streams in the basin which are affected
by the proposed project are Boulder Creek, draining approximately
440 sq mi, and South Boulder Creek, draining approximately 125 sq
mi. These two creeks run parallel courses in the mountains. Their
drainage course through the service area is shown on Figure 9, The
average annual flows from the creeks are 65,000 ac ft for Boulder
Creek and 55,000 ac ft for South Boulder Creek, for a combined
average annual flow of 120,000 ac ft. The range of combined an-
nual average flows is from a low of 50,000 ac ft in a dry year to
a high of 175,000 ac ft in a wet year. LOXJ flows usually occur in
February, and high flows, which result from mountain snowmelt and
spring rains, occur from April to July.
Many reservoirs have been constructed throughout the planning
area to store water from Boulder Creek diversions and from the Colo-
rado-Big Thompson Water Project to the west. The Boulder Valley
area has been allotted 19,000 ac ft of Colorado-Big Thompson Project
water. The City of Boulder has contract rights to 14,000 ac ft of
this amount. About 7,000 ac ft of the City's portion is sold to
farmers for irrigation, Municipal, industrial and agricultural
users consume approximately 115,000 ac ft of water per year.
Effects of Water Diversions in the Boulder Creek Basin on
Surface Flows. The basin is laced by large numbers of irrigation
canals and ditches that fill lakes and reservoirs used for irrigation,
domestic, industrial and recreational water supplies (Reference 16),
Extensive user demands on the available water resource combined with
the modest seasonal availability of water in this semir-arid area
are responsible for the creation of a water management system that
has substantially altered the natural flow cycle of the Boulder Creek
Basin. During the winter months, natural streamflows in Boulder
Creek are very low. Flows occurring between October and April are
due primarily to releases from mountain reservoirs. The released
water is diverted to Baseline, Six Mile, Marshall and Panama #1
Reservoirs situated in Boulder Valley, downstream from the City of
Boulder, The diverted flows refill approximately 4,000 to 6,000
ac ft of the 11,000 to 15,000 ac ft needed for the annual first re-
fill requirements of the valley reservoirs. This represents an
average diversion rate of 11 to 17 cfs, which is a significant por-
tion of the creek flow from fall through early spring. These winter
diversions leave but a trickle of water in Boulder and South Boulder
Creeks to flow through the City of Boulder.
31
-------
SIX MILE
SAN
TRAILER PARK
'/5th STREET
TREATMENT
PLANT
GRAVEL
PITS
FLOOD PRON
TRAIL
PARK
MILES
POINT SOURCE DISCHARGES
FIGURE 9
COURSES, FLOOD PRONE AREAS
POINT SOURCE DISCHARGES
32
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Winter flows in Boulder Creek are also affected by periodic
discharges from the Orodell hydroelectric power plant, operated
by the Public Service Company. The plant provides supplemental
service to the area during the peak morning and evening power de-
mand periods. When it is operating, the plant discharges water
at a rate of up to 150 cfs, creating extreme fluctuations in
Boulder Creek's streamflow.
During the spring, when snows are melting and rainfall is high,
the mountain reservoirs hold back runoff and regulate flows at rates
reflecting downstream water demands for ditch diversions and the
filling of storage reservoirs. Direct irrigation ditch diversions
begin in early May and continue through September, depending on the
availability of water and the seniority of diversion rights in indi-
vidual ditches.
When late summer deficiencies occur, the 15,000 ac ft of water
stored in the valley reservoirs is used along with the Colorado-
Big Thompson water to augment supplies. During the late summer,
Boulder Creek has a very low flow through the city. In the vici-
nity of the 75th Street Wastewater Treatment Plant, stream flows
are increased by water from the Colorado-Big Thompson feeder ditch,
by agricultural return flows, and by treatment plant effluent. Water
is drawn by other users from downstream segments of the creek.
The low streamflow conditions described above are significant
in understanding the need to maintain water quality downstream
from the wastewater treatment plant. Without adequate streamflow
for dilution of the treatment plant's wastewater discharge, body-
contact and other water-oriented recreation activities are limited.
Flooding. A definite flood hazard exists at Boulder and in-
cludes central portions of the city, residential and commercial
areas on Arapahoe Road, and the 75th Street treatment plant in the
Boulder Creek floodplain, which are shown in Figure 9. The maxi-
mum flood that may occur in a 100-year period for Boulder Creek
at Boulder is 18,000 cfs (Reference 17). Major floods have oc-
curred on Boulder Creek in 1864, 1876, 1894, 1914, 1923, 1938 and
1969 (Reference 18).
The 75th Street plant and its various on-site facilities were
constructed within the limits of the floodplain. To protect the
facility, permanent structures have been flood-proofed by design-
ing all openings with elevations two feet above the highwater line
of the 100-year flood. Some temporary structures, such as that for
lime treatment, have not been flood-proofed; however, the pro-
posed improvements to the 75th Street plant will obviate the need
for them, and the long-term potential for damage to these struc-
tures is thus insignificant (Reference 19).
33
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Water Quality—
Boulder Creek and its main tributary, South Boulder Creek,
are high quality streams before entering the City of Boulder. The
main point sources, i.e. readily identifiable pollution discharge
points, of stream pollution for the past 40 years in Boulder have
been the East Pearl Street and 75th Street treatment plants. With
the cessation of discharges from the East Pearl Street plant in
May 1975, the 75th Street plant became the only major point source,
Other, relatively minor, point sources have been the Sansui and
San Lazaro mobile home parks package sewage treatment systems and
the gravel extraction and processing operations of C and M Gravel
and Flatiron Sand and Gravel, downstream of 53rd Street. Figure
9 shows the locations of the discharge points. The mobile home
parks package systems discharge effluents of low concentration,
and the gravel operations discharge inorganic silts and other mate-
rials which contribute to stream turbidity and sedimentation.
Table 2 shows the flows, concentrations and wasteloads of these
sources as estimated in the facilities plan.
Table 2. POINT SOURCE POLLUTION LOADINGS
Discharge Point
Sansui Trailer Park
San Lazaro Trailer Park
Gravel Pits
75th St. Treatment Plant
Total
Flow, Concentration,3 Wasteload,3
gpd mg/1 Ib/day
18
135
50
10,310
10,513
,000
,000
,000
.000
.000
10
15
25
30
-
1.5
16.5
10.43
2,578
2,606
a
BODcj and/or suspended solids.
Nonpoint sources, i.e. an activity distributed over a wide
area that is a source of pollution, degrade the stream as it flows
through and beyond the city. The area's nonpoint sources are
typical of its urban/rural land uses. Boulder is also subject to
seasonally high irrigation rates and contributions of process water
from mining sites. Because of the area's semi-arid climate, ir-
rigation is necessary to sustain crops and landscaping. With ex*-
cessive irrigation, salts and nutrients are leached from soils and
enter the groundwater and streams. An overabundance of salts and
34
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nutrients generally degrades the local water quality. Mining ac-
tivities for coal and ores in the mountains west of Boulder may
contribute nonpoint pollutants through storm water to Boulder Creek.
Results of water quality sam-
pling in Boulder Creek indicate
two distinct stream segments.
Selected parameters from 1975 sam-
pling programs are shown in Figure
10. Biochemical oxygen demand
(BOD) and ammonia are low and rel-
atively stable in the upstream por
tions of Boulder Creek. Dissolved
oxygen levels remain within the
range 8 to 10 mg/1. Water temper-
atures are generally cool (13°C)
but rise several degrees after
55th Street, due probably to the
influence of agricultural return
flows. At the 75th Street treat-
ment plant discharge point, tem-
perature, BOD and ammonia increase
significantly. At this point,
Boulder Creek is classified as a
warmwater system. Ammonia levels
can exceed stream standards. It
has been shown that un-ionized
ammonia is toxic to game fish at
levels of 0.021 mg/1 in the stream
The strength of total ammonia-
nitrogen toxic to aquatic life is
approximately 1.5 mg/1. This
value was computed by EPA and
based on ambient stream tempera-
tures of 20°C and a pH of 7.5. Dilution from streamflows, agricul-
tural return flows and water diversions reduces these concentrations
the majority of the time. However, ammonia toxicity still remains a
significant hazard during low streamflow periods.
Water Rights—
Boulder Creek water rights are complex in nature. A study of
Boulder's water rights priorities, its problems and the potential
effects from land treatment of effluent was conducted in 1974 by
Blatchley Associates (Reference 21). Portions of this study are
incorporated into the material that follows, to present a brief
characterization of the water rights situation in Boulder.
TREATED EFFLUENT DISCHARGE CHANNEL
FROM 75TH STREET TREATMENT PLANT
35
-------
DO
O
DO —
CO
ON
nzo
Tsa
m
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73
H
C
73
g
CO
^
z
o
r- >
m i-
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o
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m
m
D.O..BOD AND AMMONIA-NITROGEN (mg/l)
ro
o
at
O
1. UK UDELL —
ro
bo
O
3. rULSOM BRIDGE ^
~
•X3
,1
CD
4. COTTONWOOO GROVE-
6. BELOW E. PEARL az~
PLANT £
ro
7. BELOW S. BOULDER CR.
CONFLUENCE
5
8. JUST ABOVE 73th ST.
PLANT 0.5
10. JUST BELOW 73th ST
PLANT
w
CO
1
1
1
1
M
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P
^=u=
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—•3
\
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/
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1
75th S
EFFLU1
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O
TEMPERATURE (°C)
-------
The City of Boulder collects its domestic water supply through
a system of surface water rights and storage rights in Boulder Creek
basin. This supply is supplemented by water imported from the Colo-
rado-Big Thompson (CBT) Project of the Northern Colorado Water Con-
servancy District (NCWCD). Boulder continues to buy water rights
and to apply for permission to change the place and nature of use
of these rights in order that the water can be used in their muni-
cipal water system. Boulder is also included in a subdistrict of
the NCWCD which is planning to develop additional Colorado River
water for diversion through the CBT Project system. This project
is known as the Windy Gap Water Supply Project and also is often
referred to as the Six Cities Project.
After one use of the above water rights, Boulder collects the
sewage effluent, treats and releases it back into Boulder Creek be-
low the 75th Street treatment plant. Downstream are ditches that
are dependent on this sewage effluent as a part of the water supply
for their vested water rights.
Colorado's water rights laws are based on' the concept "first in
time, first in right." Generally, waters may be used as long as other
users are not injured. Injury may be caused by a "senior" water
rights holder transferring a right so as to cut off supply to
"junior" water rights holders. In the Boulder Creek drainage,
under certain circumstances, only junior rights are dependent
upon the sewage return flows from the City; while under other
water supply conditions, the senior rights are dependent, in
part, on the Boulder return flows. The degree of potential injury
to other Boulder Creek water users will be unpredictable for any
plan to modify the disposal of Boulder's treated sewage effluent.
Any change in use that a disposal plan may impose on Boulder
Creek must take into account the fact that since the inception of
Boulder's sanitary system many junior water rights have been en-
riched by the uses, especially when storage waters are used in
the low flow season. Boulder cannot, on the other hand, assume
that when all junior rights are out of priority they are then free
to change the regimen of the creek. On the contrary, with the
Lower Boulder Ditch's 1 October 1859 decree for 25.00 cfs below
both sewage plant discharge points, it will be necessary to main-
tain flows to insure that the Lower Boulder Ditch does not call
out the City of Boulder's direct flow decrees at time of greatest
need. This threat should not affect in any way the use of Boulder's
reservoir or CBT water use. However, it may be proper to file on the
return flow rights on waters over and above the normal historic re-
turn flows in Boulder Creek.
37
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Water Quality Management and Regulations—
Water quality management involves the protection of water
quality and existing and potential water uses from the adverse ef-
fects of wastewater and nonpoint discharges. All changes that
may result from the proposed project are of concern to EPA in its
facilities planning and review process. Direct land use changes in-
clude sewer line and treatment plant construction. Indirect changes,
such as provision of sewer service could encourage land development
in a particular area resulting in sediment and nutrients entering
stream courses.
The federal, state and regional regulatory agency involvement,
together with the local agency interpretations and goals, are sum-
marized below.
Federal. The EPA administers the 1972 Water Pollution Control
Act Amendments, which are aimed at achieving certain national
water quality standards according to a given timetable. All surface
discharges are regulated and require permits under the National
Pollutant Discharge Elimination System (NPDES). This permit system
is now being administered by the State of Colorado. Boulder's two
treatment plants were issued permits in 1974. The effluent limita-
tions for the 75th Street plant are shown in Table 3. A minimum
streamflow of 45 cfs was assumed upstream from the discharge point,
and a total discharge of 10.7 mgd in 1978 was projected. These li-
mitations were assessed prior to the cessation of the East Pearl
Street treatment plant discharge and may be modified in the future.
The schedule for treatment plant modifications authorized in
the 1972 Water Pollution Control Act and promulgated by EPA is as
follows:
1. Secondary treatment for all municipal discharges by 1
July 1977. As defined by EPA, secondary treatment is the
removal of pollutants to the extent that the effluent
does not exceed 30 mg/1 BOD and suspended solids.
2. Best Practicable Waste Treatment Technology (BPWTT) to be
implemented by 1 July 1983. This goal will ensure water
quality capable of supporting fish and allowing recrea-
tion. As defined by EPA, this limitation implies secon-
dary treatment plus whatever measures are necessary to
meet state standards that may be more restrictive. For
Boulder, the existing discharge permit requires that BPWTT
be implemented by July 1977.
38
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Table 3. FUTURE EFFLUENT LIMITATIONS, BOULDER 75TH STREET TREATMENT PLANT
(NPDES Permit No: CO-0024147)
Parameter
BOD5, mg/la
Total suspended solids, mg/la
Fecal coliform, org./lOO ml
Ammonia (as N) , mg/1
pH, units
Total residual chlorine, mg/1
30 consecutive
day period
30
30
200
-
-
-
7 consecutive
day period
45
45
400
4.3
-
0.04
Daily Instantaneous
-
-
-
6.5 0
6.0 - 9.0
0.5
Oil and grease, mg/1
10
In addition to the above limitations, the arithmetic mean of the values for biochemical oxygen
demand and total suspended solids for effluent samples collected in a period of 30 consecutive
days Shall not exceed 15 percent of the arithmetic mean of the values for effluent samples
collected at approximately the same times during the same period (85 percent removal).
5In addition to the specified limitations, the discharge shall contain no visible oil and
grease.
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State. Water quality objectives for the State of Colorado are
primarily defined by the Colorado Department of Health. State waters
include both surface and groundwater supplies. The Water Quality
Control Commission, appointed by the Governor, determines the four
basic water quality categories for the state as shown in Table 4.
Through 1976, the western segment of Boulder Creek was classified as
Bl, while the lower segment, below the East Pearl Street treatment
plant, was classified as B2. In January 1977, the Commission approved
a change in classification for Boulder Creek on the basis of a peti-
tion by the City of Boulder. From the creek's source down to the
75th Street treatment plant, the creek has been upgraded to Al. Fur-
ther, from the treatment plant down to the confluence with Coal Creek,
the water quality category has been upgraded to A2.
Another major function of the Commission is the determination
of priorities for projects receiving federal grants and the event-
ual allocation of the State's portion of this federal money. Cri-
teria for awarding priority points is given in the Department of
Health Guidelines (Reference 22). The highest priority points are
given to those municipalities with the most severe water quality
problems. In Fiscal Year 1976, Boulder ranked 25th in priority
points out of 223 grant projects. Problem areas noted were the
need to remove excess BOD;, in relation to upgrading Boulder Creek
to an Al classification, population factors and stream category
factors. The Commission also took into consideration the validity
of treatment requirements beyond secondary, recognizing that in
some cases it may be more cost-effective to apply advanced waste-
water treatment now rather than add it at a later date.
Regional. The designated regional planning agency for Boulder
is the Denver Regional Council of Governments (DRCOG). This agency
is presently implementing Section 208 of the 1972 Act and has re-
cently completed a basinwide water quality management plan (Reference
70). The Section 208 study was performed independently of the
Boulder Facilities Plan. However, the Regional Water Quality Manage-
ment Plan of 1973 as adopted by DRCOG in August 1974 served as the
regional plan upon which the Boulder Facilities Plan was based
(Reference 23). The regional plan recommends the following effluent
limitations for the upper Boulder Creek Subbasin:
1) Nitrification of ammonia in effluent to prevent fish
toxicity which occurs at a threshold level of 1 me/1
NH3-N.
2) Maximum effluent concentrations of 5 mg/1 8005, 1 mg/1
nitrate-nitrogen and 8 mg/1 phosphate.
40
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Table 4. COLORADO STATE WATER QUALITY STANDARDS SUMMARY
Standard
Parameter
Settleable solids
Floating solids
Taste, odor, color
Toxic materials
Oil and grease
Radioactive material
Fecal coliform bac-
teria
Turbidity
Dissolved oxygen
PH
Temperature
Fecal streptococcus
Class Al
Free from
Free from
Free from
Free from
Cause a film or other
discoloration
Drinking Water Stan-
dards
Geometric mean of
< 200/100 ml from five
samples in 30-day
period
No increase of more
than 10 JTU
6 mg/1 minimum
6.5 - 8.5
Maximum 68 °F
Maximum change 2°F
Monthly average of
< 20/100 ml from five
samples in 30-day
period
Class A2
Free from
Free from
Free from
Free from
Cause a film or other
discoloration
Drinking Water Stan-
dards
Geometric mean of
< 200/100 ml from five
samples in 30-day
period
No increase of more
than 10 JTU
5 mg/1 minimum
6.5 - 8.5
Maximum 90°F
Maximum change:
Streams: 5°F
Lakes: 3"F
Monthly average of
< 200/100 ml from five
samples in 30-day
period
Class Bl
Free from
Free from
Free from
Free from
Cause a film or other
discoloration
Drinking Water Standards
Geometric mean of
< 1,000/100 ml from five
samples in 30-day period
No increase of more than
10 JTU
6 mg/1 minimum
6.0 - 9.0
Maximum 68 °F
Maximum change 2°F
_
Class
Free from
Free from
Free from
Free from
B2
Cause a film or other
discoloration
Drinking Water
Geometric mean
< 1,000/100 ml
Standards
of
from five
samples in 30-day period
No increase of
10 JTU
5 mg/1 minimum
6.0 - 9.0
Maximum 90°F
Maximum change
Streams: 5"F
Lakes: 3°F
-
more than
:
Legend:
Al: Waters suitable for primary contact recreation and a cold water fishery.
A2: Waters suitable for primary contact recreation and a warm water fishery.
Bl: Waters suitable for noncontact recreation and a cold water fishery.
B2: Waters suitable for noncontact recreation and a warm water fishery.
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3) Disinfection of treated secondary effluent by chlorination.
4) Effluent aeration prior to discharge to ensure adequate
dissolved oxygen levels in the creek.
County. Boulder County has no articulated water quality ob-
jectives at the present time. The major involvement by the county
agencies in the Boulder Facilities Plan is concern with odors and
the ultimate disposal of wastewater residues. Sludge is currently
disposed of in the county landfill. In 1972, the County Commissioners
passed a resolution to eventually phase out disposal of raw or un-
digested sludge to the county landfill. Possible land disposal or
reuse of wastewater sludge would be reviewed through the Special
Use Review process of the County Planning Board.
Local Objectives. The City of Boulder is strongly committed
to a program to upgrade and preserve Boulder Creek. Improvement of
the local stream quality is integral to the long-term restoration
and preservation of the Boulder Creek Corridor under the Boulder
Valley Comprehensive Plan. On the basis of recommendations from the
Citizens' Advisory Committee, the Boulder City Council passed a
resolution on 17 June 1975 solidly committing the City to upgrade the
quality of Boulder Creek to a sport fishery.
To achieve the community goals stated by the City Council, the
resultant effluent limitations were developed, as shown in Table 5.
Table 5. LOCAL EFFLUENT LIMITATIONS
Pollution Parameter
Monthly
Average
Weekly
Average
Suspended solids, mg/1
BOD5, mg/1
Ammonia (as N), mg/1
Fecal coliform, no./lOO ml
Effluent dissolved oxygen
Total oil and grease, mg/1
Residual chlorine, mg/1
Color, CPU
Turbidity, JTU
pH, units
20 20
20 20
4.3 4.3
1,000 2,000
90 percent of saturation
10 10
< 20
< 20
6.0 - 9.0
< 20
< 20
6.0 - 9.0
Source: Facilities Plan
42
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BIOLOGICAL ENVIRONMENT
The topography within the study area consists primarily of
level and gently rolling plains, piedmont areas--where the plains
meet the foothills—and the foothills themselves. Floodplains
and terraces wind through the uplands, forming flat riparian cor-
ridors. The plains, while relatively flat, are on a gentle
slope from west to east that decreases continuously in elevation
at an average of approximately two ft/mile. Local elevation
ranges from approximately 5,100 ft at the eastern edge of the
study area to 5,600 ft along the western edge of the Boulder
city limits.
The project area occurs within the plains grassland life
zone which includes Boulder Valley and extends up to 5,600 ft
(Reference 24). The plains typically experience a growing sea-
son of five to six months, and climatic conditions are relatively
dry.
Natural vegetation in presettlement days was primarily sod-
forming short grasses, such as blue grama and buffalo grass, and
associations of mixed to tall grasses, such as wheatgrass, needle-
grass, sand reed and bluestem (References 25, 26). Riparian cor-
ridors throughout the plains often supported gallery forests
which consisted of well-developed stands of cottonwoods. Since
settlement, the lower parts of the grasslands have been under
cultivation, and the higher parts have been used for grazing.
Boulder Creek flows through the heart of the planning area,
linking the Lower Montane Forest region and the Plains Grassland
region. The creek passes through the city and then traverses resi-
dential, farm and pasture area before emptying into St. Vrain Creek
approximately 15 miles northeast of Boulder. Since the proposed
project location is within the vicinity of Boulder Creek, the
detailed environmental setting will focus on Boulder Creek and the
biotic communities in its immediate environs.
Ecology of Boulder Creek
Boulder Creek and its tributaries represent one of the major
hydrologic systems in Boulder County and are important for economic,
cultural and ecological values. Two miles west of Boulder, the
water flow is harnessed in Boulder Canyon for power generation.
Upon reaching the plains area, ditches and canals divert much of
the streamflow for irrigation. Farther east, the creek serves
as a repository for urban runoff, agricultural return flows,
43
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limited industrial flows and treated effluent from the city's
sewage treatment plant. Recreational use of Boulder Creek is
primarily focused on the upper portions, in Boulder Canyon;
however, the natural areas of the creek within the plains are
also appreciated for their aesthetic and educational value. The
development of a major park along the length of Boulder Creek
has been under consideration by the city and the state for many
years (References 27, 28). The Boulder Creek floodplain, pre-
viously discussed under the physical environment, also has many
implications for planning and environmental analysis. Flood-
plain features such as marshes and meandering channels are
important aspects of the local ecology.
Within the study area, portions of Boulder Creek can be
categorized as undisturbed (close to a natural state) and others
as disturbed (altered by human activity).
Undisturbed Areas—
The areas along Boulder Creek with the least amount of phy-
sical modification are mountain areas and selected locations with-
in the floodplain. Stream segments within Boulder Canyon are
characterized by clear, turbulent waters passing through steep
grades and capable of supporting a cold-water fishery. As Boulder
Creek enters the plains area, it becomes slow and meandering, and
the 'watercourse is bordered by native cottonwood trees, shrubs
and herbaceous vegetation, much of which consists of introduced
weeds. The typical meandering of the stream maintains pools and
undercut banks with trees, shrubs and other bank vegetation, pre-
venting excessive erosion. In other areas, the well-developed
meander system has caused the formation of oxbow ponds, marsh
areas and meander loops, all of which provide productive and im-
portant wildlife habitats.
One mile east of town, before 55th Street, is one of the
largest remaining cottonwood groves along Boulder Creek. The
broad- and narrow- leaved cottonwood trees grow to a large
size rapidly and are ecologically important for their moderating
influences. The trees shade the water surfaces, facilitate a
shrubby understory in places and provide a habitat for bird
and animal species that otherwise could not tolerate the warm
climate of the plains. The aquatic ecosystem of the natural
areas is complex and typically contains species requiring "clean
water " such as mayflies, stoneflies and caddisflies, and cold-
water fish such as trout.
44
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Disturbed Areas—
The lower portion of Boulder Creek, from the Boulder City
limits to the confluence with St. Vrain Creek, shows varying de-
grees of disturbance from human activity. Gravel mining, channeli-
zation, tree cutting, livestock grazing and wastewater disposal
have produced profound effects on the creek. The gravel banks of
the straightened and newly-formed streambeds induce a generally
harsh environment colonized mainly by weeds. The loss of stream-
side vegetation and the trampling of banks and creekbed by live-
stock inhibit the formation of undercut banks, destroy aquatic
habitat and increase siltation. Disposal of wastewater to Boulder
Creek is important to the maintenance of stream flow; however, the
addition of nutrients—particularly nitrogen and phosphorus—en-
courages excessive algal and bacterial growth, which degrades the
aquatic environment. Effluent constituents, such as nitrites,
chlorine and ammonia in high seasonal concentrations, can also be
toxic to fish and other aquatic organisms.
In Boulder Creek, the aquatic environment historically has
deteriorated sharply at the junction with the East Pearl Street
sewage outfall. With the discontinuation of this outfall in May
1975, the creek has shown a gradual and positive improvement in
types of aquatic life and numbers. Stream ecology is a dynamic
process and capable of some amount of self-purification and restora-
tion if the system is not severely damaged. Boulder Creek has
achieved some degree of recovery in the vicinity of White Rocks.
Livestock access is restricted in places, and as a result, undercut
banks and overhanging vegetation for fish habitat have reappeared.
Small dams and weirs along the stream create pools of sufficient depth
to shelter fish populations during low water. However, few fish, if
any, are found in these latter stream sections because of pollution
levels (Reference 20). The physical improvement of the stream environ-
ment has led to the reappearance of several groups of aquatic inverte-
brates such as freshwater shrimp, mayflies, aquatic sowbugs and leeches
in the vicinity of 95th Street.
The partially recovering and semi-natural areas of Boulder Creek
retain some ecological value as wildlife habitats. With proper manage-
ment, these areas could be improved in their capability for supporting
a diverse and interesting flora and fauna.
Biotic Communities
Within the projected area, biotic communities can be categorized
into six units: (1) pasture/agricultural, (2) riparian, (3) ponds
and marshes, (4) White Rocks, (5) residential/urban and (6) gravel
mining area. The general occurrence of the six biotic communities
within the project area is shown in Figure 11. These units are
45
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LLLULLL
ULl-Ui-LL
ULLLLLLULUL
l_Ll_l-L_Ll_LLLUl_LL
LLLLLLLLULLLLLLLI-L.
UU_I_UUI_L<-LI_LI-LI-L
LLLLLLLLUL
BOUIDER
FEEDER
DITCH
l_LLLULLLLL_LLl_l_l_Ll-
•>pOOOOQqtaCOOOQOOOO^«
jSooooo3aoooooocoo?«
^?423SS82S29SS2S2e
7?th STREE
R.EAIM.ENT
PASTURE/AGRICULTURE
RIPARIAN
POND AND MARSHES
oooc WHITE ROCKS
RESIDENTIAL/URBAN
GRAVEL MINING AREAS
SENSITIVE ECOLOGICAL AREAS
FIGURE I
BIOTIC COMMUNITIES AND
SENSITIVE ECOLOGICAL AREAS
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characterized by various vegetation and wildlife associations and
in some cases may have overlapping features, The composition and
extent of these units are a function of many environmental factors,
of which the prime elements in the project area are: climate,
soils, geology, land formations,;watercourses and land use.
BOULDER CREEK NORTH OF THE 75TH STREET TREATMENT PLANT
The pasture/agriculture unit is spatially the most dominant
in the vicinity of the 75th Street; treatment plant and proposed pro-
ject site. The riparian and ponds and marshes units supply impor-
tant water-associated habitats that provide diversity within the
pasture/agriculture unit, Many plant and animal species within
the area occur mainly in these units, and some are entirely depen-
dent upon it. The White Rocks area also provides diversity with
steep cliffs and rock faces overlooking the flat plains area. The
rocky substrate also furnished plant and wildlife habitats unique to
the project area. Several rare arid endangered plant species have
been recognized in the White Rocks,. The residential/urban units are
primarily composed of structures. Most notable is the Heatherwood Es-
tates on 75th Street which has gradually changed the face and ecology
of the pasture/agriculture unit. The gravel mining area unit represents
47
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the only industrial activity within the project area. Mining ac-
tivities have in the past greatly affected the surrounding pasture/
agriculture, riparian and to some extent White Rocks units. Some
abandoned gravel pits, on the other hand, have created new pond and
marsh habitat areas and added to the local diversity. A detail dis-
cussion of the characteristic vegetation and wildlife within each
community is presented in Appendix B. Lists of wildlife species and
probable occurrences within the biotic communities are also given in
Appendix B.
State and federal listings were examined for the status of rare
or endangered species (References 29,30). No rare or endangered
plant species are known to occur in those parts of the Boulder Creek
floodplain and pasture/agriculture units that would be affected by
the proposed project (Reference 29).
The following eight rare and endangered plant and animal species
are found on the White Rocks (References 29,31):
1. Asplenium andrewseii, an endangered fern species of which
the only other occurrence in the Western Hemisphere is in
Chihuahua, Mexico (Reference 32).
2. Forktip three awn (Aristida basiramea), a grass that is
found in two counties in Colorado.
3. American potato bean (Apios americana), a legume that occurs
in two counties in Colorado.
4. Aphaenogaster fulva (ant species).
5. Aphaenogaster huachucana (ant species).
6. Formica criniventris (ant species).
1- Lasius occidentalis (ant species)
8. Perdita opuntiae, a mining bee, unique to the area, which
drills burrows into sandstone cliffs.
Sensitive Ecological Areas
Human settlement of the plains areas has greatly changed the
local ecology of the Boulder area through the introduction of non-
native vegetation and animals and changes in land use by humans.
Despite these changes, several areas along Boulder Creek still re-
tain much of their natural condition. Other areas, modified by
human land use, have replaced some lost habitat and increased the
diversity of the local environment. These special habitat areas
48
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are important to plant and wildlife ecology and do not tolerate
great changes. Along the Boulder Creek project area, three such
sensitive ecological areas have been identified as meriting con-
sideration in future planning activities in order to preserve a
diverse and interesting flora and fauna. Figure 11 indicates the
approximate location of these areas.
White Rocks Natural Area—
The area that is known locally as the White Rocks Natural Area
(WKNA), shown in Figure 11, consists of sandstone outcroppings over-
looking pasture lands, riparian zones, and small ponds and marsh
areas. White Rocks is considered ecologically sensitive for the
following reasons: (1) the rock outcrops support a small and fragile
ecosystem with slow-growing vegetation and some ephemeral forms of
biota adapted to the harsh environment; (2) the bluff areas provide
the only natural nesting niches in the area for the great horned owl
and barn owl; (3) the area contains several rare plant and insect
species, as discussed in the Biotic Communities section; (4) ecologi-
cal diversity in a small area associated with vertical variation, pro-
tected habitat, south facing cliffs, relative abundance of prey species
along creek and other factors; and (5) the close proximity of urban
and industrial activities may lead to a long-term degradation of the
local ecology.
In total, the WRNA represents a unique landform within the local
topography that harbors a distinct biotic community with many complex
interactions. Its high scientific and educational value has been
demonstrated in field studies and academic research, and it is used
by several departments of the University of Colorado. The aesthetic
qualities imparted by the White Rocks, both as a landscape feature
and as a site with a panoramic view of the floodplain, contribute
substantially to its value as a natural resource. This aspect is dis-
cussed in greater detail in the Visual and Aesthetics Environment
Section and in Appendix C.
A 1970 study of the White Rocks area (Reference 32) proposed a
one-half-mile buffer zone to protect the area from future degradation.
Recently approved revisions to the Boulder Valley Comprehensive Plan
designate a 450-acre Environmental Preservation area for the WRNA
consisting of 210 acres of rock outcrops and a 240-acre perimeter buf-
fer zone (Reference 34). Additional greenbelt and open space designa-
tions by the City Open Space Board of Trustees for land north, north-
west and east of the WRNA satisfy the proposed buffer zone.
The future of the White Rocks Natural Area is uncertain since
major changes in land use for adjacent areas are continually being
considered. A 1972 request to the U.S. Department of the Interior
for inclusion of White Rocks into the National Monument System was
49
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denied (Reference 35); however, the two current property owners of
the area covering White Rocks have stated their commitment to the
preservation and protection of the resource value of this site (Ref-
erences 36,37). A recent amendment to the Mined Land Reclamation
Act (Colorado HB 1529) prohibits permanent developments over commer-
cial gravel deposits and applies to parts of the WRNA and associated
buffer zone.
Walden Ponds—
The Walden Ponds Wildlife Habitat area is located near Boulder
Creek, immediately south of the Boulder sewage treatment plant on
75th Street. Under Alternative C, the polishing ponds will include
an area slated for reclamation by the Walden Ponds Wildlife Habitat
Reclamation Plan. When completed, the habitat area would cover ap-
proximately 110 acres and include 10 acres of shallow cattail marsh,
a large, 50-acre water-filled gravel pit, a 40-acre pasture area
and peripheral areas. In 1974, on the basis of a reclamation study
by Ms. Laudia Toburen (Reference 38), a program was implemented to
reclaim the gravel pit as a wildlife area. The large gravel pit
has been converted into a trout pond, with initial plantings of
native vegetation on banks and islands, installation of waterfowl
nest boxes and stocking with rainbow trout. The perimeter of the
pasture area has been planted with trees, shrubs and clusters of
fruit trees to attract birds. The pasture area is left untended
as a quail and pheasant habitat. A small portion is reserved as
a nursery area. The area is managed by the Boulder County Parks and
Open Space Department, with a full-time naturalist residing at the
site. At the present time, Walden Pond is in the partial stages
of reclamation, with sparse vegetation cover and many bare, exposed
areas. The trout pond and smaller duck pond/marsh areas attract a
large variety of waterfowl and shorebirds. Large numbers of mal-
lards and Canada geese utilize the ponds for resting and limited nes-
ting. The trout pond is currently being studied by the Colorado
Division of Wildlife for its potential as a cold-water ecosystem.
Treatment Plant and Proposed Land Application Sites
The proposed sites for Alternatives A through H are shown in
Figure 2. A comparison of the approximate biotic community compo-
sition of each alternative site is given in Table 6. The majority
of land application sites are within the pasture/agriculture unit.
The existing 75th Street treatment plant site, with its fencing,
paving and landscaping, is considered to be within the residential/
urban unit. Several facilities locations have changed from the
original facilities plan. The new infiltration/percolation pond
site has been moved 3,000 ft east to the 200 acres east of 75th
Street below Boulder Creek. The sludge injection fields under all
50
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Table 6. ALTERNATIVE SITES, APPROXIMATE BIOTIC COMMUNITY COMPOSITION
Alter-
native
System
Site
Biotic community,3 %
123156
Comments
Land treatment; infiltration-
percolation ponds
Sludge injection
Activated sludge following
trickling filters
Sludge injection
225 ac. south of Boulder Creek 95 2
and east of 75th St.
175 ac. south of Boulder Creek 95 5
and east of 75th Street.
Existing 75th St. treatment
plant
Same as Alternative A 95 5
100
Change in site location from that
shown in Facilities Plan. Ponds
now situated on fields site
planned for sludge injection in
Alternatives B-C. New sludge in-
jection field moved 3,000 ft south.
Aerated and polishing ponds
Sludge injection
Activated sludge before
trickling filters
Sludge injection
Multi-media filters
Sludge injection
Chemical coagulation
Landfill disposal of sludge
High-rate irrigation
Sludge injection
No project
Landfill disposal of sludge
330 ac. west and south of 50 5 5 10 30
75th St. treatment plant
Same as Alternative A 95 5
Existing 75th St. treatment 100
plant site
Same as Alternative A 95 5
Existing 75th St. treatment 100
plant site
Same as Alternative A 95 5
Existing 75th St. treatment 100
plant site
Boulder County landfill
3,360 ac. in northeast Boulder 80 5 10 2
County
Same as Alternative A 95 5
Existing 75th St. treatment 100
plant site
Boulder County landfill
Polishing ponds would include the
Walden Pond Wildlife Habitat area
Boulder County.
landfill outside of project area
Agricultural lands from 75th St.
east to County Line Rd. and from
Longmont south to Arapahoe Rd.
Landfill outside of project area
aBiotic communities: (1) Pasture/Agriculture (A) White Rocks Natural Area
(2) Riparian (5) Residential/Urban
(3) Ponds/Marshes (6) Gravel Pits
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alternatives have been relocated immediately south, to the area be-
tween the Union Pacific Railroad and Valmont Road.
SOCIAL AND ECONOMIC ENVIRONMENT
Visual and Aesthetic Environment
Boulder is located in an area that possesses a beautiful and dis-
tinctive scenery, and the scenic attractions associated with Boulder
are among the city's greatest assets. •
The proposed site for the infiltration/percolation basins under
Alternative A is a low-lying, level pasture area within the Boulder
Creek floodplain. This site lies between lands of higher elevation
to the north and to the south and thus is visible from numerous
points. The following paragraphs represent a landscape inventory
(see Appendix C) of the site as observed from the northern and sou-
thern areas that overlook the floodplain.
Observer Position from White Rocks, Looking South—
With the observer standing on the White Rocks looking south
toward the site, the landscape can be described as panoramic* where
the observer position is superior (above the visual objective). A
panoramic landscape is characterized by the absence of enclosure
and is a horizontally oriented arrangement of great stability. The
primary field of vision from the White Rocks is the middleground
distance. The panorama possesses a high degree of unity, vivid-
ness (expressed as the similarity of the landscape along a 180
field of vision) and variety (in the form of occasional trees and
small farm structures which are present in scattered locations on
the floodplain).
Observer Position from Valmont Road, Looking North—
With the observer in a superior position looking north toward
the site from Valmont Road, the landscape can be characterized as
a feature landscape. The white lines of the White Rocks and the
gentle rise in elevation cause the eye to be led to the feature.
The slight convexity of form of the bluffs provides a contrast to
the adjacent level plains, although the visibility of the Heather-
wood Estates structures provides an off-setting man-made contrast.
*Terms in italics are defined in Appendix C.
52
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Recreation Areas
Public Areas—
The Boulder area has excellent year-round recreational facili-
ties, including 14 parks and many residential areas within the city
boundaries.
The Boulder Valley Comprehensive Plan seeks to preserve and en-
hance recreational and open space areas. The plan designates the
vicinity of the 75th Street treatment plant as largely undeveloped
open space and parkland, with a tennis court facility to be construc-
ted approximately one-quarter mile west of the present plant during
the last phase of plan implementation. The Plan's projection period
is 1976-1991. The tennis courts would be reached by two hiking-bike-
and equestrian trails as well as by Jay Road; the trails are not
planned to go east of the tennis courts. A separate bikeways plan
developed for the City Department of Transportation proposes a bike
path, following Boulder Creek from 61st Street to 75th Street, and
passing just north of the plant site (References 5, 34).
Other existing and planned recreation sites in the vicinity of
the plant include the existing Boulder Reservoir recreation area
approximately one mile to the northwest; tennis courts; a country
club; and additional ball fields proposed for the residential area
north of the treatment plant.
Wildlife Areas—
Boulder offers a wide range of natural areas for the apprecia-
tion and utilization of wildlife resources. Within the project area,
the wildlife resources form the basis of waterfowl and gamebird hun-
ting, sportfishing and nature studies (Reference 39).
Within the project area, goose hunting is prohibited west of
75th Street although the boundary may vary yearly according to over-
all state wildlife policies. Common gamebird species include ring-
necked pheasant and mourning doves which favor open field areas.
Duck and gamebird hunting is allowed in most public areas and on pri-
vate property with the owner's permission. Hunting of any kind, how-
ever, is prohibited at the county-owned Walden Pond area and at the
city-managed Sawhill Ponds.
Animal hunting is limited to small mammals within the project
area and includes raccoons, ground squirrels, prairie dogs, jack-
rabbits, brushrabbits and to a lesser extent muskrats and marmots.
As with gamebirds, small mammal hunting is allowed on public lands
and private property with permission. No hunting is allowed at
Walden or Sawhill Ponds.
53
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Sportfishing enjoys a seasonal popularity throughout Boulder
County. The warmer waters of Walden and Sawhill Ponds are generally
fished for largemouth bass, shiners, crappies, bluegills and other
sunfish. Walden Pond has been designated as a fishing spot for
senior citizens and is stocked seasonally with rainbow trout. Boul-
der Creek is open to fishing wherever there is public access. How-
ever, within the project area the majority of the lands bordering
Boulder Creek are privately owned and inaccessible. In addition,
Boulder Creek from 55th Street downstream has poor fish productivity
due to stream pollution.
Boulder Creek and the adjacent floodplain areas offer several
"natural" areas for the observation and study of wildlife. Walden
and Sawhill Ponds afford an excellent opportunity for year-round
birdwatching. The riparian areas near Sawhill Ponds and along Boul-
der Creek are also utilized for observation of migratory songbirds,
raptors and resident bird species. The privately-owned White Rocks
area, where hunting activities are prohibited, offers unique oppor-
tunities for the observation of wildlife, particularly barn owls,
great horned owls and various raptors.
Noise
Boulder has many noise sources and attendant noise pollution
similar to those found in most large cities. Noise is virtually
an audible form of air pollution and has always been an unavoid-
able by-product of population growth and the machinery of urban
life.
In the rural areas beyond the city limits, noise sources are
predominantly from farm machinery, industrial operations and auto-
mobile traffic. At the 75th Street treatment plant, service vehi-
cles generate a negligible amount of traffic. However, the heavy
trucks which transport sludge from the treatment plant to the land-
fill several times a day generate a small but noticeable noise pol-
lution to the residents on 75th Street and Valmont Road. In the
adjacent gravel mining areas near the White Rocks and at Walden and
Sawhill Ponds, mining operations and gravel trucks generate a con-
stant background daytime noise level. Gravel trucks, in particular,
disrupt the farm areas with heavy traffic and loud back-up horns.
Odor
Background odors generally associated with the study area are
those normally associated with urban, suburban and farming com-
munities. Typical odorous materials are those commonly associated
with farming operations in the area. For example, a chicken farm
54
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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 40). 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 having been 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 agri-
cultural and manufacturing processes, providing the best practic-
able methods have been employed to control odors. For all odor
sources, however, there is an upper limit which must not be ex-
ceeded: odorous substances must not be detectable after having been
diluted with 127 volumes of odor-free air.
The existing Boulder wastewater treatment plant emits odors
during occasional periods of upset in the sludge handling facili-
ties and/or during adverse climatic conditions. Studies have
shown that the major sources of odor are the headworks, primary
clarifiers and existing sludge handling facilities (Reference 1).
Odor problems are particularly noticeable in the local area during
inversion periods when there is little air movement. Residents of
the adjacent areas on 75th Street and the Heatherwood Homeowners
Association (Reference 41) have periodically complained of pervasive
sewage odors. The 75th Street wastewater treatment plant was cited
for violation of Colorado State Odor Regulation No. 2 on 9 May 1975,
and as recently as 7 January 1977 (References 42, 43).
Plans for odor control facilities, sludge digesters and other
associated modifications to the existing plant have been submitted
to EPA. Due to the seriousness of the odor problems, the sludge-
handling and odor control facilities have been divided into a
separate phase from the main facilities plan in order to expedite
implementation. This first phase was issued a negative declaration
by EPA on 10 November 1976 (Reference 4), indicating that no major
environmental impacts were anticipated. Engineering designs for
these improvements are currently underway. When these facilities
are completed, the changes in the sludge handling and odor control
processes are expected to correct past odor problems associated
with the operation of the 75th Street plant.
55
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History
Boulder originated as a western frontier town that served as a
supply center for the mining towns in the mountains to the west and
for the farms to the east. An excellent account of Boulder's his-
torical background is given by Walter B. Lovelace in Boulder Yester-
day (Reference 44).
The Boulder Valley, particularly in those areas east of the
City of Boulder, has historically been devoted to agriculture, live-
stock grazing and gravel mining. Historical resources in the faci-
lities plan project area would consist potentially of pre-1900 farm-
houses and structures. A survey was conducted in 1975 (Reference
45) for structures of historic or architectural significance, or
environmental appropriateness. Ten buildings, mostly farmhouses,
were initially identified as potential resources. The Kolb farm-
house was the only building identified within the project area.
Further investigations in the 1975 study did not identify any one
building or group of buildings, as being of definite historical
significance.
A literature search and field reconnaissance for historical
structures and landmarks was conducted for this EIS in 1977
(Reference 47). The search revealed no significant historical re-
sources in the areas that possibly could be impacted by the pro-
posed wastewater treatment alternative sites.
Archaeological Resources
Existing archaeological site data within the proposed project
area are limited and cover only a few localized areas. Documenta-
tion of sites is largely a product of opportune surveying along
road cuts and selected areas such as promontory sites, rock-shel-
tered areas and water bodies. Seven sites have been identified
within the wastewater facilities planning area. Of these, only one
site occurs in the proximity of the proposed project area. The site
probably served as a campsite and rock shelter for Indian hunters.
The State Archaeologist has rated the priority of this site as high-
ly significant and indicated that it should be left undisturbed.
Since the time of the original site designation, the ownership of
the property has changed several times, and the status of the site
is now uncertain.
An extensive literature search and field reconnaissance of
proposed project sites (References 45, 46, 47) revealed no sites
or artifacts of archaeological significance. However, the possi-
bility of buried sites or artifacts in the project area exists,
particularly along Boulder Creek and in the White Rocks Natural
Area.
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Population
In 1950 the population of the City of Boulder was approximately
20,000; this number more than tripled in the succeeding twenty years.
According to U.S. Census figures, the City's population in 1970
was 66,870; that of the wastewater service area was 73,600; and of
Boulder Valley, 76,500. By 1974, the City Planning Commission esti-
mated that these figures had increased to 76,300, 81,800 and 81,000
respectively—a growth of approximately 14 percent since 1970 or 3.5
percent per year, for the City and 4.7 percent for Boulder Valley
(References 1, 48).
Boulder Valley accounts for roughly half of the total Boulder
County population, estimated in 1974 at 171,500. The County, itself
a fairly rapidly growing component of the greater Denver area, had
the second highest growth rate of the five-county Standard Metropoli-
tan Statistical Area (SMSA) in 1974—4.3 percent compared to 2.9 per-
cent for the SMSA as a whole. Both Boulder City and Boulder County
populations nearly doubled in the 1960's (References 49, 50).
In response to this rapid growth, both city and county are re-
examining goals with a view to planning and controlling future growth.
As a basis for land use decisions, the Boulder Valley Comprehensive
Plan was adopted in 1970, and reconfirmed in 1972, by city and
county governments. Both entities also jointly appointed a Boulder
Area Growth Study Commission (BAGSC), which subsequently devised
several working models of population growth for the area. On the
basis of these models, the BAGSC made a series of growth predictions
for the year 1990, ranging from a low of 83,000 to a high of 122,000
for the City of Boulder as shown on Table 7 (Reference 1)-
Present indications are that slow-growth policies will prevail.
In November 1976, the voters of the City of Boulder approved an
ordinance to limit the population to increases of 2 percent per an-
num by controlling the number of dwelling units to be built within
the City for a period of five years.
A study performed in 1975 (Reference 52) indicates an average
household size considerably smaller than that shown by U.S. Census
figures for the area. On this basis, the City Planning Department
and the Denver Regional Council of Government (DRCOG) now believe
that current Boulder population may be 7,000 lower than previously
estimated. Assuming that this is correct, and that the Boulder
Valley Comprehensive Plan will incorporate a long-range policy of
discouraging high growth rates as experienced since 1950, 1990 popu-
lation projections would be lower than Model 1, 3, or 4 estimates in
Table 7. Long-range estimates for the City of Boulder and the ser-
vice area, prepared on the basis of these assumptions, are shown in
Table 8 below:
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Table 7. FOUR POPULATION ESTIMATES FOR BOULDER CITY
AND BOULDER VALLEY FOR 1990
Wastewater Boulder
City of Boulder Service Area Valley
Model 1
Continuation of
existing trends 122,000
Model 2
Adoption of policy
to halt growth 83,000
134,200 160,000
91,300 122,000
Model 3
Emphasis on environment
quality, green belt,
open space,
agricultural expansion 118,200 129,800 170,500
Model 4
Diversified community,
industrial expansion 122,000 134,200 205,000
Source: Exploring Option for the Future; A Study of Growth in
Boulder Valley (Reference 51),
Table 8. POPULATION PROJECTIONS FOR BOULDER AND WASTEWATER
SERVICE AREA BASED ON 2.5% GROWTH RATE
Year
1976
1980
1985
1990
1995
2000
City of Boulder
73,000
80,600
91,200
103,000
116,700
Wastewater
Service Area
80,700
89,100
100,800
114,000
129,000
208 Service Area
Forecast
92,200
98,800
106,700
115,500
130,100
Sources: (References 52, 53).
58
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An annual growth rate of 2.5 percent for both the city and the
valley appears to be reasonable and conservative. It is assumed that
pressure within the city limits of Boulder to hold down population
growth will result in corresponding pressure for increased growth
elsewhere in Boulder Valley. Since the population of the wastewater
service area is the basis for projecting wastewater capacity needs,
the exact rate of growth within Boulder's City limits is not criti-
cal here.
Population in the Gun Barrel residential development immediately
north of the 75th Street treatment plant may present an exception to
the above projections. This development, which may be annexed to the
City of Boulder, has a present population of approximately 6,500;
this could conceivably expand to 14,500 when construction of currently
approved subdivisions is completed (Reference 54).
Under the Boulder Valley Comprehensive Plan, the city and
county have proposed to provide water and sewer line extensions only
to developments adjacent to the city limits. The Supreme Court has
ruled that because Boulder is the only utility supplier in the area,
it must grant new utility connections if there is enough capacity,
rather than using it as a growth-limiting tool. Thus the sizing of
the proposed project would set an ultimate limit on capacity for new
utility connections.
Demography
The population of the City of Boulder in 1970 was predominantly
young with 76 percent under 40 years of age and White with 97.7 per-
cent of the total. Most had non-Spanish surnames with 95.2 percent
of the total. Almost half of the total was under 21 years of age,
due to the large university population, which has an average enroll-
ment of approximately 20,000. Females outnumbered males very slightly:
50.1 percent versus 49.9 percent. Of all city residents 25 years ot
age or over in 1970, 83 percent had completed high school, compared
to 52 percent for the U.S., 37 percent were college graduates, ver-
sus 11 percent for the nation (Reference 48)-
Approximately half of the people in the Boulder Valley own
their own homes. One-third to one-half of all residents have lived
in the area for over 10 years.
Employment statistics for the Boulder area are compiled under
the Denver-Boulder Labor Market Area (LMA). As of August 1976, the
total labor force in the Denver-Boulder LMA was 692,800 with an over-
all unemployment rate of 6.5 percent. The main categories of
employment were: 1) non-agricultural: 85 percent; 2) agricultural:
2 percent; and 3) self-employed: 7 percent. The main non-agricultural
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types of employment were: services, retail trade, government and
manufacturing. Boulder has a high proportion of "professional and
related services" attributable of the University of Colorado and the
many private and government research-oriented agencies in the area.
According to the 1970 census (Reference 56) the median income
of the 14,366 families in Boulder, was $11,437. According to a
more recent estimate prepared by the Colorado Division of Housing,
median family income in Boulder County in 1974 was approximately
$14,550 (Reference 49).
Land Use
Regional Land Use—
Wastewater treatment plants are constructed to meet projected
user demand and water quality standards. The existing plant has an
in-place nominal capacity to treat 15.6 mgd, although it presently
satisfies an average demand of only 65 percent of capacity. The
present facility can treat overloads of up to 20 mgd, with result-
ing effluent of diminished quality. As elsewhere discussed, 1995
population in the service area will not likely exceed 130,000. This
is well within the present nominal capacity.
The proposed project will be constructed only to raise the
quality of effluent. If desired, the project could also be sized
to limit the capacity of the plant, and therefore, limit future
growth in the area. However, as the project is proposed, there
should be no effect upon regional land use patterns. The City of
Boulder is currently completing a major revision of its 1970 Compre-
hensive Plan (Reference 55). As discussed in the population section,
the Gun Barrel residential area immediately north of the 75th Street
treatment plant could sustain an increase of several thousand re-
sidents in the next 10 years. If the precedent established by the
Robinson Decision of the Colorado State Supreme Court is upheld, it
would appear that the City of Boulder will have to extend its service
area to include these future developments (Reference 54).
Local Land Use—
In this section, "local" is defined as that land lying within
an approximate one-mile radius of the existing 75th Street waste-
water treatment plant. The plant is sited on the floodplain adja-
cent to the southerly side of Boulder Creek.
Boulder Creek constitutes a general line of demarcation be-
tween (1) suburban residential and agricultural uses to the north
and (2) public works, mining and agricultural uses to the south.
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Between the creek and Jay Road to the north is an unincorporated
residential area that is generally rural in nature.
Immediately north of Jay Road and west of 75th Street is the
Gun Barrel area and, east of 75th Street, Heatherwood. These are
somewhat newer residential developments, including multi-use
planned unit developments. South of the 75th Street plant, land
use is typified by gravel mining west of 75th Street and agricul-
tural and grazing lands to the east. Scattered residences are al-
so found within the local area.
Tax Base - Assessed Values
The parcels presently being considered for purchase by the city
for the infiltration/percolation beds, the sludge-injection area
and plant expansion belong to tax jurisdictions 0460 and 0470. Ju-
risdiction 0460 covers the county fund, schools, transportation and
flood control districts, and the mill levy is $86.40 per $1,000 as-
sessed valuation. Jurisdiction 0470 includes the North Colorado
Water Conservation District with an additional $1.00/$1,000 assessed
valuation. Therefore, the total mill levy for parcels in that dis-
trict are $87.40 (Reference 56).
Land and Property Values
The Boulder real estate market has shown an annual appreciation
rate of 10 to 15 percent for a number of years. In 1975, even by
conservative estimates, the average was at least 15 percent (Refer-
ence 57).
There are three types of land in the project area: agricultural,
gravel mining and residential. Immediately surrounding the existing
plant and proposed sludge-injection and infiltration/percolation sites
are predominantly open fields with agricultural uses. Nearby are se-
veral residential developments, such as the Gun Barrel area which are
among the highest property value areas in the county (Reference 54).
The 75th Street treatment plant has had a history of complaints
about sewage odors from the surrounding neighborhood and the Gun
Barrel area (Reference 58). In general, local real estate sales and
land uses have not been greatly affected in the Gun Barrel area due
to the high housing demands (Reference 59). However, in the imme-
diate areas mostly strongly influenced by treatment plant odors, land
values and housing have been affected. Residents cite increasing
incidences of: 1) abandonment or rapid turnover of homes closest
to the treatment plant; 2) conversion of affected homes into rental
units; 3) slower rates of land and property appreciation near the
plant; and 4) deterioration of some homes near the plant due to
odor permeation and loss of owner or resident interest.
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Bonded Indebtedness and Subsidies
The City of Boulder's December 31, 1975 Financial Statement
shows a total bonded debt of $15.4 million. Of the outstanding
general obligation bonds totalling $12.5 million, $6.3 million for
waterworks improvements are considered to be self-supporting. In
addition, $2.9 million are outstanding on sewer revenue bonds is-
sued for projects other than the current wastewater treatment plant.
In 1974, the Boulder City Council made a policy decision not to
approve proposed capital projects requiring bonding (Reference 58).
Therefore it is assumed that the city will finance its share of con-
struction costs by other means. The Wastewater Utility Division of
the City of Boulder maintains a capital fund for required future
expenditures. Projected cash flow estimates as of December 2, 1976
indicate that there will be a total of $2,462,000 available from
this fund to finance the city's share of the costs. Based on the
established 75 percent federal participation, the City of Boulder is
presently able to finance all alternatives except G, which will re-
quire an additional $5.6 million in capital for the first phase of
construction, and another $650,000 in the second phase.
It was originally planned that the State of Colorado would par-
ticipate in the financing of the project through a State Water
Quality Control Commission Step II grant, amounting to approximately
5 percent of the total project capital cost. However, at this point
in time, there are no grant monies available. Therefore, it can be
assumed that the City of Boulder will receive no financial aid from
the State of Colorado (Reference 61).
Utility Services
Electric Power and Gas—
The 75th Street wastewater treatment plant is presently being
served by a primary meter, with customer ownership of all electric
facilities beyond the primary meter point. The highest electricity
demand by the plant since August 1975 has been 438 kW, experienced
in November 1976. Demand has remained fairly steady at 385 - 430 kW.
Total consumption for the 12-month period ending November 1975 was
2,657 x 10 kWh (Reference 60).
Natural gas consumption at the 75th Street treatment plant to-
taled 2,898 million cu ft for the 12 months ending November 1976
(Reference 60).
Water Supply—
The water utility of the City of Boulder, a city-owned utility
company, supplies water from high-elevation reserviors of the water-
shed. The city's current direct-flow water rights from the Big
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Thompson Froject, the Nederland Watershed, and various irrigation
ditches are adequate for current and projected needs, through raw
water storage rights may be inadequate to meet demands during a
drought year.
There are two existing water treatment plants: the Betasso
Treatment Plant, constructed in 1963, and Boulder Reservoir Treat-
ment Plant, constructed in 1972. These have nominal treatment ca-
pacities of 48 mgd and 8 mgd respectively. The nominal capacity of
the Betasso Plant was increased from 28 mgd to 48 mgd in 1977. Five
reservoirs for the storage of treated water have a total capacity
of at least 35 mgd. The city water distribution systems have re-
cently expanded and provide sufficient capacity to service a popula-
tion of 150,000. Present average consumption is 15.3 mgd; peak con-
sumption has been as high as 35 mgd, which was experienced in 1974.
Since 1965, when metered rate charges went into effect, per capita
use has varied from 134 to 175 gallons/day. Future per capita de-
mand under drought conditions is estimated at 175 gallons/day. This
is based on a worst-case average of approximately 26.3 mgd for a
population of 150,000.
The City Water Utility services the area of the 75th Street
treatment plant, as well as residential areas directly north of that
plant. Distribution to the vicinity of the plant is accomplished
through an existing 12" main along Carter Trail, ending at Jay Road.
Construction of an additional 16" main along Jay Road has been re-
commended by an independent study and is considered in county objec-
tives (References 50, 62, 63, 64, 65).
Solid Waste Disposal—
There is no municipal solid waste collection service, though
the city-authorized Urban Waste Resources Company operates a sani-
tary landfill for disposal of such waste. Collection is handled
by approximately 12 local private firms. It is estimated that the
Marshall Landfill site will have reached its capacity well before
1990, and recommendations have been made for acquisition of an
additional site (References 50, 66).
Storm Drain System—
Because of its topography and geographic location, the City
of Boulder is extremely vulnerable to flood damage. Recognizing
that existing storm drainage systems do not provide adequate pro-
tection, the city in 1973 took the first steps toward a major
flood control program and Master Drainage Plan, ultimately aimed
at providing facilities to handle storm and flood waters of up to
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100-year intensity. The program's first major drainageway improve-
ment project, Viele Channel, was completed in 1976 through coopera-
tive efforts by the City and County of Boulder (References 63, 64).
Transportation
Since January 1976, the Boulder City Bus System has been under
the management of the Regional Transportation District, Boulder
Division. The district now operates buses on a regular basis along
six routes within the city as well as into Denver. A long-range
Transit Development Plan, resulting from the Boulder Transportation
Study undertaken by the city in 1975, provides for several system
improvements. These include new and expanded routes to major traf-
fic generators outside the city, and inauguration of an extensive
bus shelter and bus pull-out lane program. There is presently no
regular service to the 75th Street wastewater treatment plant or
to the Gun Barrel residential development north of the plant
(References 50, 65, 66).
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SECTION III
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SECTION III
PROPOSED ALTERNATIVES
The wastewater facilities plan for which this EIS document has
been prepared is a joint effort of the City of Boulder Wastewater
Utility and CH2M-H111, Inc. The facilities plan analyzed a wide
range of unit treatment processes, presented in preliminary reports
(References 2 and 3), and selected seven alternatives for further
consideration on the basis of such factors as cost, environmental
impacts, effluent discharge requirements and utilization of existing
facilities. The facilities plan was submitted to the City of Boulder
in October 1975.
CHANGES TO THE FACILITIES PLAN
Several major changes have occurred to the facilities plan
since 1975. These changes were put forth in the February 1977
facilities plan supplement and have been incorporated into the
alternative plans of this EIS.
In February and March 1976, at the request of the City of
Boulder, the facilities planning consultant made the following
major changes:
1. The infiltration and percolation basins under Alternative
A were moved to the Kolb property with additional basins immediately
north of the railroad tracks and east of 75th Street, and also to
city property immediately west of 75th Street and adjacent to Boulder
Creek. The total land area occupied by the basins was changed.
2. The sludge-injection sites under all alternatives were
moved to the city-owned property west of 75th Street and south of
the railroad tracks, and to the Manchester property to the east of
75th Street and south of the railroad tracks.
3. Alternative B was modified to provide nitrification (removal
of ammonia).
4. Under alternative C, the three polishing ponds proposed
for the Walden Ponds County Wildlife Habitat area were eliminated
and an additional polishing pond was added between the main polish-
ing ponds and Boulder Creek. The flow pattern and pond arrangements
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were redesigned so that the effluent would flow in a southeastward
direction to discharge to Boulder Creek approximately 4,000 feet
upstream of the present discharge.
During preparation of the draft EIS in the fall of 1976, it
was learned that flow meter readings used to establish a baseline
wastewater generation rate had been erroneously high for several
years. The errors were found only after the infiltration/inflow
study (Reference 67) had been concluded. These meter readings,
used as a basis for design in the wastewater facilities plan, were
approximately 15 percent too high. In addition, recalculation of
population growth for this EIS (explained in Section II) indicated
that growth in the Boulder area would closely approximate projec-
tions made in 1975 by the Denver Regional Council of Governments
(DRCOG). These new population projections, and consequently waste-
water flow projections, are lower than those presented in the waste-
water facilities plan.
As a result of these factors, the facilities design flows and
sizes, along with the costs of alternatives, have been reduced.
This EIS presents the updated values for each alternative. As a
consequence of the delays associated with obtaining approval for a
recommended plan and the estimated time needed to design and con-
struct any new facility, the project planning period was redefined
to begin in 1980 and end in the year 2000.
Effective 31 January 1977, the stream classification of Boulder
Creek was changed from Bl to Al above the 75th Street treatment
plant, and from B2 to A2 below the treatment plant down to the Coal
Creek confluence. See Section II, Water Quality Management and
Regulations for explanation of classifications. Because of this,
some of the wastewater treatment processes that were optional under
the wastewater facilities plan have now become essential. Certain
alternatives can no longer meet the required effluent standards;
others, with modification, can. The descriptions of alternatives
presented in this chapter include revisions necessary to meet the
latest effluent discharge criteria.
DESIGN FLOWS AND POLLUTANT LOADINGS
Wastewater flows were calculated on the basis of population
projections developed by DRCOG as presented in Section II. The
base wastewater flow in 1975, corrected for meter error, was 12.5
million gallons per day (mgd) for a population of 92,200. This
flow included groundwater infiltration and storm water inflow. The
infiltration and inflow study concluded that a full-scale sewer
rehabilitation program was not justified on a cost basis. Therefore,
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the city would continue regular maintenance and repairs on the ex-
isting sewer system. On this basis, the wastewater flows from the
presently sewered population were assumed to remain unchanged. Future
service connections and new sewer lines would be constructed under
stringent infiltration requirements. Thus, it has been estimated that
incremental population growth would have an associated wastewater flow
rate of 120 gallons per capita per day (gpcd). This is a reasonable
value and well within accepted standards. Table 9 presents the re-
vised wastewater flows as calculated by the facilities planner and by
the Denver Regional Council of Governments in the Areawide Water Qual-
ity Management Plan.
Table 9. EXISTING AND PROJECTED WASTEWATER FLOWS (MOD)
Year
1975
1980
1990
2000
DRCOG
Population
Estimates
92,200
98,800
115,500
130,100
Population
Increment
From 1975
-
6,000
23,300
37,900
Incremental
Flow Using
120 gpcd
(mgd)
-
0.8
2.8
4.6
Wastewater Flows
Boulder
(mgd)
12. 5a
13.3
15.3
17.1
DRCOG
(mgd)
12.2
13.0
15.2
17.5
Base Flow Measured in 1975.
Source: Wastewater Facilities Plan Supplement, February 1977.
The wastewater flow rates developed by DRCOG are very similar to
those calculated by the facilities planner. In order to maintain
consistency with the Areawide Water Quality Management Plan, the DRCOG
estimates were used as a basis for facilities sizing and will also be
used for facilities evaluation.
Wastewater flow rates vary with time and season. The values
presented previously (October 1975) were based upon annual averages.
The facilities planner calculated that 95 percent of the wastewater
flows occurring in any year would be less than 1.3 times the annual
average flow and multiplied the flows (DRCOG estimates) in Table 9 by
1.3 to obtain 19.9 mgd and 22.8 for the years 1990 and 2000, respec-
tively.
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Most processes for the treatment of domestic wastewaters are
designed on the basis of three parameters: flow, 5-day biochemical
oxygen demand (BOD ) and suspended solids. Table 10 presents the
estimated future waste loads on the treatment system.
Table 10. ESTIMATED FUTURE WASTELOADS (LB/DAY)
Year
1975
1980
1990
2000
BOD5
13,400a
14,700
18,100
21,000
Suspended solids
13,100a
14,300
17,300
19,900
Measured values in 1975.
Source: Wastewater Facilities Plan Supplement, February 1977.
The 1975 waste loads were assumed to remain unchanged during the
study period. Waste loads atttributable to increasing population
were calculated on the production rates of 0.2 Ib of BOD per capita
per day and 0.18 Ib of solids per capita per day.
ALTERNATIVES
Following are descriptions of the updated alternatives based
on those developed in the wastewater facilities plan. Preceding
the descriptions is a presentation of the features shared in common
by all of the alternatives. A schematic presentation of the unit
processes within each alternative system is shown in Figure 12.
Common Features
All of the alternatives proposed would use the existing faci-
lities at the 75th Street plant to the fullest extent possible.
This plant is a secondary facility employing trickling filters.
The original plant, with a capacity of 15.2 mgd., was placed in
operation in 1968 and was expanded in 1972 to a capacity of 15.6
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FIGURE 12
CITY
COLLECTION
SYSTEM
SUBSURFACE
INJECTION
n EXISTING 75TH STREET
TREATMENT PLANT FACILITIES
\'"/\ PROPOSED PHASE [ ADDITIONS
r. ,'. A CURRENTLY BEIN8 DESIGNED
FOR T5TH STREET PLANT
COMMUN1 T Y
FARM LAND
LANDFILL
EXISTING TRICKLING FILTER PLANT
PLUS PHASE I ADDITIONS
(NO PROJECT-ALTERNATIVE H)
DIVERSION PRIMARY
INFILTRATION/
PERCOLATION
HEADWORKS
FILTERS CLARIFIERS CHLORINATION
"SLUDGE"
CITY
COLLECTION
SYSTEM
SUBSURFACE
INJECTION
TO COMMUNITY
OR FARMLAND
OR LANDFILL
ALTERNATIVE SYSTEM A
EXISTING TRICKLING FILTER PLANT
PLUS PHASE I ADDITIONS AND
INFILTRATION/PERCOLATION BASINS
69
-------
FIGURE 12 (Con'd)
CITY
COLLECTION
SYSTEM
x" TO COMMUNITY
/ OR FARMLAND
OR LANDFILL
ALTERNATIVE SYSTEM B
EXISTING TRICKLING FILTER PLANT
PLUS PHASE I ADDITIONS AND
ACTIVATED SLUDGE PROCESS
HEADWORKS
FLOW
DIVERSION
BOX
PRIMARY
CLARIFIERS
SECONDARY
r^xT?
EXISTING
TRICKLING SECONDARY
FILTERS CLARIFIERS
"SLUDGE
AERATED
LAGOON
PONDS
(WILDLIFE CHLORINATION/
REFUGE) OECHLORINATION^t*
CITY
COLLECTION
SYSTEM
\_y
SUBSURFACE
INJECTION
TO COMMUNITY
OR FARMLAND
OR LANDFILL
ALTERNATIVE SYSTEM C
EXISTING TRICKLING FILTER PLANT
PLUS PHASE I ADDITIONS AND
AERATED AND POLISHING PONDS
70
-------
FIGURE 12 (Con'd)
HEADWORKS
COLLECTION
SYSTEM
\
\
\
SLUDGE ANAEROBIC
THICKENING DIGESTION
EXISTING^
VACUUM
FILTERS
\
\
TO COMMUNITY
OR FARMLAND
OR LANDFILL
ALTERNATIVE SYSTEM D
ACTIVATED SLUDGE PROCESS AHEAD OF
EXISTING TRICKLING FILTER PLANT
PLUS DECHLORINATION
HEADWORKS
FLOW
DIVERSION
BOX
PRIMARY
CLARIFIERS
sTc ON"O
EXISTING
TRICKLING
FILTERS
SECONDARY
CLARIFIERS
SLUDGE"
FLOW
EQUALIZATION
MULTI-MEDIA
FILTRATION CHLORINATION
CITY
COLLECTION
SYSTEM
TO COMMUNITY
OR FARMLAND
OR LANDFILL
ALTERNATIVE SYSTEM E
EXISTING TRICKLING FILTER PLANT
PLUS PHASE I ADDITIONS AND
MULTI MEDIA FILTRATION
71
-------
FIGURE 12 (Con'd)
Fl OW
DIVE RblON
BOX
PRIMARY
CLARIFIERS
SECONDARY
EXISTING
TRIf.KI INC FLASH
FILTERS MIXER
"SUJOGE"
SECONDARY
CLARIFIERS
CHLORINATION
CITY
COLLECTION
SYSTEM
TO LANDFILL
ALTERNATIVE SYSTEM F
EXISTING TRICKLING FILTER PLANT
PLUS PHASE I ADDITIONS AND
ALUM ADDITION
CITY
COLLECTION
SYSTEM
TO COMMUNITY
OR FARMLAND
OR LANDFILL
ALTERNATIVE SYSTEM G
EXISTING TRICKLING FILTER PLANT
PLUS PHASE I ADDITIONS AND
HIGH-RATE IRRIGATION
72
-------
mgd. Basically, this plant consists of grit removal and shredding
of larger solids, followed by primary clarification using three
clarifiers which collect both primary sludge and the secondary
sludge recycled through the headworks. Four trickling filters con-
taining rock media follow the primary clarifiers. The wastewater
then enters a secondary clarifier and is subsequently chlorinated
prior to stream discharge. A portion of the effluent from the
trickling filters is recycled through the filters. The sludge
from the primary clarifiers is treated with lime in a holding tank,
and again with lime and polymers when the sludge is withdrawn for
vacuum filtration. Two rotating-drum vacuum filters dewater the
sludge. The resultant filter cake is disposed of to the county
landfill. This plant has met State discharge standards consistently
since 1973. However, the allowable level of BOD, ammonia nitrogen
and fecal coliforms under the previous B2 standards have had adverse
effects on Boulder Creek. The existing unit processes, with the pro-
posed additions to the sludge handling system under Phase I, are de-
picted in Figure 12 which would also represent the No Project Alter-
native.
The facilities planner has calculated that the existing primary
clarifiers have an average hydraulic loading rate of 700 g/ft *d
design criterion. The facilities planner has further calculated
that additional primary clarifier capacity will be needed during
Phase II construction. This increase in primary clarifier capacity
is envisioned for each alternative. This modification would allow
the treatment plant to handle a capacity of 17.6 mgd. The balance
of the existing trickling filter plant would require no expansion
of existing capacity.
Each of the alternatives except Alternative A (infiltration/per-
colation basins) and Alternative G (high-rate irrigation) would
have chlorination before discharge of the effluent to Boulder Creek.
Dechlorination (in Alternatives B, C and D) would be done by a
combination of aeration and treatment with sulfur dioxide. Dechlori-
nation was not proposed for Alternatives E and F because it has
assumed that any residual chlorine would combine with the ammonia
in the effluent. Effluent will have to be aerated prior to discharge
under alternatives A, E and F in order to meet the rather stringent
effluent dissolved oxygen requirements.
All alternatives except Alternatives F would have the same solids
handling system. The initial processes consists of sludge thickening
and anaerobic digestion. The final processing is divided into two
phases: (1) utilization of the existing vacuum filters to dewater425
percent of the sludge; and (2) subsurface injection of the remaining
75 percent to a local field site and subsequent cropping of the site.
The solids dewatered by vacuum filtration would be stockpiled for the
community, municipal and agricultural reuse.
73
-------
The solids handling for Alternative F would consist of sludge
thickening as described above, with anaerobic digestion, dewatering
by use of vacuum filters and final disposal through sanitary land-
filling.
EXPERIMENTAL INFILTRATION/PERCOLATION BASIN AT
75TH STREET TREATMENT PLANT SITE
Alternative A - Land Treatment by Infiltration/Percolation
This alternative system would use the existing 75th Street treat-
ment plant to provide the basic wastewater treatment functions. Chlo-
rinated secondary effluent from this plant would be pumped to infil-
tration/percolation basins for additional treatment. This process
would utilize the high infiltration and permeability capabilities of
the sands and gravels bordering Boulder Creek. Thirteen basins would
be formed by removal of ground cover and utilization of surface soils
74
-------
to build 4-ft high and approximately 55-ft wide berms around each
basin. The berms will be 15-ft wide at the top and will probably have
a 3:1 or 4:1 slope. The basins would be contoured to natural features
wherever possible, to preserve mature cottonwood trees growing on the
site. The basins would be filled on a 9- to 12-day rotation cycle. A
tile underdrain system beneath the basins would collect the effluent
as it filters down. This filtered effluent would flow to a main col-
lector drain and be discharged to Boulder Creek near the 75th Street
bridge.
The effluent from the trickling filter process alone could not
meet local wastewater treatment effluent limitations without further
processing. The facilities planner has calculated that infiltra-
tion/percolation ponds, with an area of 222 acres, would provide pol-
ishing of the effluent sufficient to meet effluent discharge criteria.
The area requirements were determined,by the facilities planner after
a study of soil characteristics on the Kolb property; which is pro-
posed for the infiltration basins. The storage lagoon for winter
flows envisioned in the wastewater facilities plan was subsequently
determined not to be necessary. The discharge temperature of the
treated effluent should prevent the freezing of the percolation pond.
The basic unit treatment processes of this alternative are
shown schematically in Figure 12. A site map showing the locations
of the treatment plant and revised sites proposed for the infiltra-
tion/percolation basins and sludge disposal area is presented in
Figure 13.
Alternative B - Activated Sludge Process Following Trickling Filters
The existing trickling filter treatment plant, with increased
primary clarifier capacity, would be a part of this alternative.
Effluent from the existing secondary clarifiers would flow to a new,
pure-oxygen-activated sludge treatment unit, as described in the
revised facilities plan. The oxygen-activated sludge would be de-
signed to oxidize any biodegradable organic matter leaving the
trickling filters and to convert the ammonia-nitrogen in the efflu-
ent to nitrate-nitrogen. This concept is a departure from the
October 1975 Wastewater Facilities Plan because in that document,
Alternative B was designed to oxidize organic matter but not to
produce a nitrified effluent.
The new oxygen-activated sludge units would consist of an on-
site oxygen-generation plant, aeration basins, and additional secon-
dary clarifiers.
Figure 12 shows a schematic representation of the unit treatment
processes of this alternative.
75
-------
SITE BOUNDARY
— —. — —GRAVITY EFFLUENT
PIPELINE
HEATHERWOOD (ESTATES
EFFLUENT FORCE MAIN
EFFLUENT TURNOUTS
EFFLUENT PU(4P'STATION
'SLUDGE FORCEy'tiAIN
StUOGE .FfitfCE LATERAL
-WITH HOSE RISERS
JAY ° ROAD
BASINS (TYP)
WALDEN PONDS |
WILDLIFE f 1 ."J|
HABITAT
AREA
FIGURE 13
PROPOSED ALTERNATIVE A
WITH SLUDGE INJECTION
-------
Alternative C - Aerated Lagoons and Polishing Ponds
Under this alternative, bacterial and algal ponds would be used
to polish the trickling filter plant effluent. Settled sewage from
the secondary clarifiers would first flow to aerated lagoons with a
two-day hydraulic detention time, x^here bacterial and algal action
would convert soluble BOD,- to cellular material and carbon dioxide.
Subsequent polishing ponds would capture residual organic matter,
nutrients and suspended solids, and would convert ammonia-nitrogen
to nitrate, with the intent of producing a clear effluent for direct
discharge to Boulder Creek.
The polishing ponds would be constructed with submerged rock
filters through which each pond's discharge would drain before pass-
ing to the next pond. It is envisioned by the facility planner
that the submerged filters would capture algae, discharging a clear
effluent to the next pond. Figure 12 is a schematic representation
of the treatment processes in Alternative C.
The aerated lagoons, polishing ponds and a small buffer zone
will require approximately 145 acres of additional land next to the
existing treatment plant. The proposed pond treatment site, as shown
in Figure 14 is scheduled for gravel mining in the near future. The
resultant gravel pits would be suitable for conversion to a treatment
pond system for Alternative C. It is envisioned by the facilities
planner that the polishing ponds could be used as an aquatic wildlife
habitat.
Alternative D - Activated Sludge Process Prior to Trickling Filters
A new activated sludge wastewater treatment system would precede
the existing trickling filters in this alternative. The activated
sludge treatment units would use pure-oxygen aeration to produce an
estimated 90 percent reduction in organic pollutants. The effluent,
low in carbonaceous pollutants, would be treated again in the exist-
ing trickling filters, where ammonia-nitrogen could be converted to
nitrate-nitrogen and a further reduction achieved in organic matter
and suspended solids.
The unit treatment processes for Alternative D are schematically
depicted in Figure 12. All new treatment units could be constructed
on the existing 75th Street treatment plant site.
Alternative E - Multimedia Filtration of Effluent
The basic trickling filter treatment processes would remain un-
changed. The secondary clarifier effluent, which is high in sus-
pended solids and BOD, would be subjected to multimedia filtration
77
-------
INJECTION SITE BOUNDARY
SLUDGE FORCE MAIN
HEATHERWOOD 1 ESTATES
BOULDER
FEEDER
DITCH
• • SLUDGE FORCE LATERAL
WITH RISERS
IRRIGATION PIPELINE ,„,
IRRIGATION
STP EXPANSK
JAY DROAD
EATJICNT _PLAN_1
WALDEN PONDS
WILDLIFE f L_
HABITAT
AREA
FIGURE 14
PROPOSED ALTERNATIVE C
WITH SLUDGE INJECTION
-------
to remove the suspended solids. Since much of the effluent BOD^ is
in the form of suspended organic matter, there would also be a de-
crease in total effluent BOD^. The facilities planner recommends
that the multimedia filters be preceded by a flow equalization basin
which would maintain a constant discharge rate to the filters and
would prevent sudden, excessive hydraulic loads.
This alternative could not meet the effluent discharge require-
ment for ammonia-nitrogen and was developed before the stream stan-
dards for Boulder Creek were revised. Conversion of this treatment
scheme to one that would remove ammonia-nitrogen would make it al-
most identical to one of the other alternatives. The treatment
processes of this alternative are shown in Figure 12.
Alternative F - Chemical Coagulation
This alternative would present, for formal comparison with
other alternatives, a practice employed for several years at the
75th Street plant, addition of aluminum sulfate (alum) to the trickl-
ing filter effluent in order to increase the efficiency of suspended
solid removal in the secondary clarifier.
Alternative F, like Alternative E, was developed to meet dis-
charge criteria less stringent than those now in existence and would
not meet present ammonia standards. The ability of this system to
meet suspended solids and BOD,, criteria without additional secondary
clarifiers is questionable. Also, just as with Alternative E, upgrad-
ing of this process would effectively make it identical to another
alternative.
Due to the anticipated chemical content of the waste sludges,
the facilities planner expects that anaerobic sludge digestion ef-
ficiency would decrease. Furthermore, the alum would preclude the
use of digested sludge for agricultural purposes, and the sludge
would in all probability have to be disposed to a landfill.
All wastewater treatment modification under this alternative
could be accomplished on the existing treatment plant property.
Figure 12 presents the process features of Alternative F.
Alternative G - High-Rate Irrigation of Effluent
The existing trickling filter treatment system would be used
in this alternative. Treated effluent from the secondary clarifiers
would be chlorinated and then conveyed to an 8,800 acre-ft storage
lagoon. During the 7-month growing season, water from the lagoon
would be used to irrigate approximately 2,100 acres of cultivated
grassland. The residual organic matter in the plant effluent would
79
-------
LONGMONT
PROPOSED EFFLUENT
STORAGE RESEVOIR
PLANNING AREA
BOUNDARY
POTENTIAL AREA FOR
HIGH RATE IRRIGATION
WASTEWATER FACILITIES
PLANNING AREA
FIGURE 15
POTENTIAL AREA FOR HIGH
RATE IRRIGATION
80
-------
have been oxidized in the storage lagoon. Nutrients passing through
the lagoon would contribute to crop growth in irrigated areas. Hay
harvested from the project area would be used for livestock feed.
The facilities planner has estimated that this alternative will
require an additional 3,360 acres for the irrigation fields, buffer
zones and a 350-acre storage lagoon. The site proposed for this system
is shown on Figure 15. The unit processes of this alternative are
presented in schematic form on Figure 12.
Alternative H - No Project
This alternative explores the ramifications of failing to up-
grade the existing treatment plant. Maintaining the present unit
processes, this plant currently meets the standards for secondary
treatment which all municipalities must comply with by 1 July 1977,
as defined by EPA. However, Boulder Creek would continue to suffer
from problems of poor water quality and deteriorated aquatic habitat
caused in part by the present sewage effluent, as discussed in Sec-
tion II under Water Quality.
Going beyond the secondary treatment goals, the State of Colorado
and many Boulder Valley residents desire to reestablish stream fisher-
ies and restore Boulder Creek close to its former pristine quality.
As mentioned earlier, an A2 stream classification for Boulder Creek
below the 75th Street treatment plant was adopted in January 1977.
Effluent from the existing treatment plant clearly will not meet A2
stream water quality standards and would strongly deter the develop-
ment of a warm-water fishery or primary-contact recreation. As the
existing wastewater effluents degrade Boulder Creek below A2 standards,
this no-action alternative is unacceptable and will not be considered
further.
ENGINEERING EVALUATION OF ALTERNATIVES
Common Features
The continued use of the existing 75th Street wastewater treat-
ment plant in the alternative wastewater management systems repre-
sents a continued use of a valuable resource. The original plant was
constructed in 1968, with an expansion in 1972. Since the typical
useful service life of a sewage treatment facility is from 30 to 35
years, the existing plant should remain functional until the end of
the planning period in the year 2000.
81
-------
The trickling filter process is generally less efficient than the
activated sludge process in removing pollutants. However; the strin-
gent criteria for discharge to Boulder Creek require a sequence of
treatment process to achieve desired effluent quality. Under this
circumstance, the existing trickling filter plant can be combined with
other unit processes.
The year-200 design flow would produce a 95-percentile hydraulic
loading on the clarifierg of 900 g/ft *d, which is higher than the
design limit of 800 g/ft "d established by the facilities planner.
Conventionally accepted mean hydraulic loading rates for primary
clarifiers followed by secondary treatment range from 800 to 1,200
g/ft *d, average daily flow (Reference 68). This range of loading
rates results in only small differences in treatment efficiency, which
become insignificant after subsequent secondary and tertiary treatment
processes. For this reason, expansion of primary clarifier capacity
does not appear to be essential for the successful wastewater treat-
ment in Boulder.
On the other hand, secondary clarifiers, when they represent the
final pollutant separation process in a treatment train, are critical
to the successful performance of a wastewater treatment facility. The
secondary clarifiers at the 75th Street treatment plant are the same
size as the primary clarifiers; thus their 95th percentile loading
would also be 900 g/ft *d in the year 2000. This is substantially
more than a typical loading rate of 400 to 600 g/ft *d for secondary
clarifiers and may result in excessive carry-over of wastewater solids
in the effluent (Reference 68). The facilities planner has not re-
commended an increase in secondary clarifier capacity in Alternatives
A, C, E and G. In Alternative F the effluent from these clarifiers
would be discharged directly to Boulder Creek. It may be desirable to
plan for a future expansion of trickling filter secondary clarifiers
for this alternative. In Alternatives B and D, the facilities planner
recommends new clarifiers with 14 ft and larger surface areas than the
existing clarifiers (two-145 ft diameter and one 80 ft diameter for
the future).
The sewage sludge disposal systems which consist of anaerobic
digestion followed by vacuum filtration or subsurface injection for
various portions of the total sludge production, will probably func-
tion satisfactorily. Sludge injection, as currently practiced at the
East Pearl Street treatment plant, should perform satisfactorily^.
82
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Table 11. PRELIMINARY ESTIMATES OF TREATMENT EFFECTIVENESS
CD
Effluent constituent concentration
Category
Colorado monthly standards
Boulder monthly guidelines
Raw wastewater estimate
Alternative effluent
A
B
C
D
E
F
G°
Suspended
solids,
rag/l
30
20
140
1-2
-10
20b
15
10
20
< 10
BOD 5,
mg/1
30
20
147
2-5
-10
20 b
10-15
20
20
< 5
NH3-N,
mg/1
weekly,
4.3
weekly,
4.3
30
0.5
< 1
10-15
< 1
20
20
< 1
Fecal
colif orm,
no./lOO ml
200
1,000
high
-v, 0
< 10
,0
< 10
< 10
< 20
< 20
Dissolved
oxygen,
mg/1
90% satu-
ration
(7-10)
low
2-5
7-10
7-10
7-10
2-4
2-4
7-10
Oil &
grease,
mg/1
10 at
any time
10
20
M)
< 1
.0
< 1
< 1
< 5
< 1
Cl re-
sidual,
mg/1
weekly,
0.04
-
0
•vO
< 0.04
< 0.04
< 0.04
< 1
< 1
0
Color,
units
-
< 20
high
-0
< 10
< 5
< 10
< 10
< 10
< 5
Turbid-
ity,
JTU
-
< 20
high
•v-0
< 10
< 5
«• 10
< 10
< 10
< 5
PH
6-9
6-9
6-9
6-9
6-9
6-9
6-9
6-9
6-7
6-9
Also see discussions in text.
Additional treatment between and after the polishing ponds could reduce BOD and SS to lower levels, but the amount
would vary according to operational and external factors.
No discharge - does not have to meet stream standards.
-------
Alternatives
The alternatives developed for the wastewater facilities plan
were generally intended to meet criteria for discharge to a creek with
a stream classification of B2. The classification of Boulder Creek
from the 75th Street treatment plant down to Coal Creek has been
changed to A2, and most alternatives, some with slight modificiation,
could meet the more stringent discharge criteria associated with the
new designation.
The effluent discharge criteria being applied to Boulder waste-
waters are stringent and require treatment processes or combinations
of processes not in common use. Since.much of sanitary engineering is
still an empirical science, the data base used for predicting the
performance of the alternatives under consideration is incomplete and
subject to revision. Estimates of the effectiveness of each treatment
system relied upon published technical information and the experience
of other sanitary engineers. A compilation of these estimates is
shown in Table 11, which compares the estimated effluent quality of
the systems. In view of the limitations of the analysis and the large
number of factors affecting treatment plant performance, minor dif-
ferences for specific parameters should not be used to differentiate
among alternatives; rather, all the data for a particular alternative
system, taken together, may be used as an indication of the possibili-
ty of its success.
Alternative A—
Alternative A appears to provide the best effluent considering
all of the criteria except dissolved oxygen. The relatively low dis-
solved oxygen should not be a major concern because the BOD,, would
also be extremely low. However, aeration would be required prior to
stream discharge in order to meet effluent standards. The effluent
quality estimates for Alternative A are based on the results from
experimental basins set up and operated by the City of Boulder and the
University of Colorado (Reference 69). These tests, however, were
made during the summer and used effluent with low concentrations (6 to
8 mg/1) of total nitrogen. Operation with higher nitrogen levels—
which is more typical during the winter—has not been reported and may
not produce such a highly nitrified effluent.
Construction and operation of the 13 infiltration/percolation
basins could be phased over the 20-year design period in accordance
with actual population growth. Presuming that all ponds handle an
equal portion of the design-year flow, then at least two-thirds of the
ponds must be built during the initial construction phase to be able
to handle 1980 flows. In actuality, the ponds are not uniformly sized,
and small differences in soil depth may affect the percolation rates
for individual ponds. The design criteria reflect loading rates which
84
-------
will allow adequate treatment from the types soils in the area. How-
ever, individual ponds under actual operating conditions may be able
to handle greater flows and still achieve desirable results.
Alternative B—
This system has the potential to meet all of the effluent cri-
teria. However, pure oxygen activated sludge systems do require a
higher level of operational skill than conventional activated sludge
systems, and a detailed evaluation of both systems should be made
before final selection of the treatment process.
The activated sludge unit and accompanying facilities would be
built during the initial construction phase. The units might be re-
duced in size to handle a smaller flow; however, future expansion
would be costly.
Alternative C^—
Alternative C could achieve the desired BOD and suspended solids
level of the Colorado monthly standards. The pond effluent would
probably also meet the Boulder monthly guidelines most of the time.
However, algal blooms, spillover and reductions in algal removal ef-
ficiency by the filters could occasionally lead to higher levels of
these two wastewater characteristics. Under the design conditions put
forth by the facilities planner, the aeration and polishing ponds
system probably cannot achieve sufficient ammonia-nitrogen removal to
meet discharge criteria. The projected 2-day detention times in the
aerated lagoons and subsequent polishing ponds detention times appear
to be insufficient to achieve nitrification down to 1 mg/1 ammonia-
nitrogen. Another design consideration would be lower winter tem-
peratures and pond freezing which will greatly inhibit nitrification.
Chlorination of the pond effluent will require a dechlorination
step to meet the 0.04 mg/1 residual chlorine limit. However, it is
not entirely certain that chlorination of the effluent would be neces-
sary, and it is possible that the combination of aerated lagoons and
ponds would effect a sufficient fecal coliform kill.
All of the new unit processes in this system require intensive
initial construction effort. The number of ponds probably cannot be
decreased, although their capacities may be altered if size phasing is
desired. With actual operation experience, it may be ascertained that
the desired performance may in fact be achieved by the use of fewer
polishing ponds.
85
-------
Alternative D—
There appears to be little reason for consideration of this alter-
native; it places major dependence on the trickling filter units as
the final treatment units. It may be difficult to maintain normal
growths on the trickling filter media with the little available carbon
from the activated sludge unit. Nitrification of the effluent during
the winter would also be difficult.
The potential need to increase secondary clarifier capacity fol-
lowing the trickling filters has been mentioned. The potential for
phasing the size of the unit processes is similar to that of Alter-
native B.
Alternative E—
Alternative E does not appear capable of achieving sufficient
ammonia-nitrogen removal to meet discharge criteria. Ammonia removal
through nitrification occurs aftaer the bulk of the BOD has been
removed and is accomplished by comparatively slow-growing bacteria.
The existing trickling filter does not appear to have the capacity to
achieve sufficient BOD removal to accomplish effective nitrification.
This alternative calls for an immediate initial expenditure for
filtration basins. The number of basins could be phased according to
need.
.Alternative F —
Like Alternative E, this alternative probably would not achieve
adequate ammonia-nitrogen removal, and the effectiveness of solids
removal with alum would be marginal, particularly with the present
secondary clarifier capacity. This system would expand plant capacity
from the nominal 15.6 mgd to 22 mgd. It is the only alternative which
includes expansion of the secondary clarifier.
Alternative G—
Alternative G does not involve direct discharge of treated ef-
fluent to any surface water course or irrigation upon food crops. It
therefore does not have to meet stringent effluent quality criteria.
The existing treatment facilities are adequate to produce an effluent
for irrigation where no contact between the effluent and portions of
the plant that are to be consumed would occur. These requirements are
more strict than those previously established by the various regula-
tory agencies but are necessary to achievement of the goals of the
community as stated by City Council.
86
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PROJECT COSTS
Capital Costs
Project implementation, as presented by the facilities planner,
will require physical construction in two separate phases. In all
seven system alternatives, capital costs for the first phase will be
incurred in the years 1978-1980, capital costs for the second phase
will be incurred in the years 1988 and 1989, and salvage values are
assumed for the year 2000. The design period allows for 20 years of
operation from first phase completion and, therefore, ends in the year
2000. A discount factor of 6-3/8 percent was used by the facilities
planner to make present worth calculations, and costs are presented in
January 1977 dollars. All costs presented in this analysis include
primary and secondary treatment, solids handling, support facilities
and engineering, legal, and administrative costs (References 1 and 5).
Total capital costs for both phases of construction range from a
low of $4,681,000 for Alternative F (chemical coagulation) to a high
of $34,875,000 for Alternative G (high-rate irrigation of effluent).
Assuming 75 percent federal participation in capital funding, cor-
responding costs to the City of Boulder would range from a low of
$1,170,000 (Alternative F) to a high of $8,718,000 (Alternative G).
Table 12 lists capital costs for each alternative system.
Operation and Maintenance (O&M)
Each project alternative represents a series of annual costs for
operation and maintenance (O&M) of the facility. These costs are
broken down into fixed annual charges and increasing variable charges
related to increased flow. Since O&M costs increase over time and
since they change after the second phase of construction, the facili-
ties planner has chosen specific O&M costs in 1987 and 1977 as mathe-
matically representative of annual costs in each phase. These annual
costs range from a low of $426,000 (Alternative C) to a high of
$1,785,000 (Alternative G) in the first phase of operation. They
range from a low of $504,000 (Alternative C) to a high of $2,594,000
(Alternative G) in the second phase of operation and are presented in
Table 12.
Cost Comparison of Alternatives
The present worth of all capital costs, annual operation and
maintenance (O&M) costs less salvage values discounted at 6-3/8 per-
cent annually, will range from a low of $8,896,000 (Alternative F) to
a high of $44,685,000 (Alternative G). Present worth of each alter-
native is presented in Table 12.
87
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Table 12. TOTAL PROJECT COSTS — ALL ALTERNATIVES
(In Thousands of Dollars)
Alternatives
Capital Costa
1978-1980
1988-1989
Total
Annual OSMb
1980-1990
1990-2000
Present worth of
all costsc
Salvage value of
A
9,247
642
9,889
487
565
12,764
853
B
8,341
1,931
10,272
670
786
14,652
853
C
7,244
588
7,832
426
504
10,712
579
D
9,515
2,029
11,544
633
766
15,646
940
E
6,524
402
6,926
524
604
10,889
534
F
4,033
648
4,681
573
669
9,336
350
G
32,263
2,612
34,875
1,785
2,594
48,738
4,053
facilities and
land3
Net present worth6
Ranking (net pre-
sent worth)
11,911 13,799 10,133 14,706 10,355 8,986 44,685
452631 7
From facilities planner.
Operating and maintenance costs are calculated on the basis of certain fixed charges per
year plus variable costs which reflect increased flow capacity. This method does not create
a linear yearly increase. Therefore, O&M costs for the years 1987 and 1997 were picked as
representative of average costs.
°Present worth (in January, 1977 dollars) is calculated at 6 3/8 percent for 30 years. The
useful life of various components of the facilities will vary; 30 years is an average.
From facilities planner.
g
Present worth of all costs less salvage value of facilities and land.
88
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A second method of comparing costs of alternatives is to use
the average annual cost i.e., the average of the annual costs of
amortization of the capital costs (capital recovery) plus the
annual 0 & M costs. These costs (assuming that 75 percent of the
capital costs will be paid by a federal grant) are presented in
Table 13.
The following tabulation shows the ranking of each alterna-
tive in terms of net present worth and average annual cost to
the City of Boulder.
Ranking
Average annual
Net present equivalent
Alternative worth cost to Boulder
*C
*F
*E 3
A 4
.11
G 7
B 5-1 5'
D 6 J 6-
The costs of the alternatives connected by brackets in the above
tabulations are within ten percent of each other. Considering the
approximate nature of the cost estimates there is no reason to dif-
ferentiate between the costs of these alternatives. Alternatives
marked with an asterisk will not meet effluent requirements as dis-
cussed in a previous section.
INTERACTION WITH OTHER PLANS
Regional Plans
The study area falls within the boundaries of DRCOG. This agency
has completed a Section 208 basinwide water quality management plan
which was released for review in May 1977 (Reference 70). The objec-
tives of the Boulder facilities plan should meet the majority of the
regional 208 goals for Boulder Creek. These 208 goals are:
1. closure of the East Pearl Street wastewater treatment
plant;
2. secondary treatment with trickling filters;
3. maximum effluent concentrations of 5 mg/1 BOD ,
1 mg/1 nitrate-nitrogen and 8 mg/1 phosphate;
4. nitrification of ammonia-nitrogen to below 1 mg/1 to
prevent fish toxicity;
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Table 13. CITY OF BOULDER PROJECT COSTS — ALL ALTERNATIVES
(In Thousands of Dollars)
Alternative
Capital Cost1
1978-1979
1988-1989
Total
Annual Capital
Recovery Cost^
1980-1990
1990-2000
Annual OiM3
1980-1990
1990-2000
A
2,312
161
2,473
175
187
487
565
B
2,085
483
2,568
158
194
670
786
C
1,811
147
1,958
137
148
426
504
D
2,379
507
2,886
180
218
633
776
E
1,631
101
1,732
123
131
524
604
F
1,008
162
1,170
76
88
573
669
G
8,065
653
8,718
610
659
1,785
2,594
Average Annual
Equivalent Cost
Ranking (Average
Annual Equivalent
Cost)
707
904
608
904
691
703
2,824
Assumes federal participation of 75 percent.
2
Annual payment required to recover Boulder's share of the capital costs at 6 3/8 percent
for 30 years.
3From Table 12.
4
Represents average of O&M charges plus average of annual capital recovery costs.
90
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5. disinfection by chlorination;
6. effluent aeration to ensure adequate dissolved oxygen
levels in the creek;
7. anaerobic sludge digestion, with ultimate disposal
in a regional land disposal site;
8. design flows for 18 mgd for the year 2010, assuming
complete elimination of infiltration;
9. establishment of Boulder Creek as a primary contact
recreation and warm-water fishery from the 75th Street
treatment plant east to its confluence with St. Vrain
Creek;
10. estimated costs (present worth 1977 dollars) of
approximately $24.2 million for facilities, inter-
ceptors and collection systems through the year 2000.
The new 208 basinwide water quality management plan recommends
more stringent water quality criteria than the facilities plan to meet
the 1983 national goal of achieving "fishable and swimmable" waters.
These goals are more stringent than the federal, state and local stan-
dards in regards to BOD,., ammonia-nitrogen, nitrates and phosphates.
Based on estimates made in Table 11, only Alternatives A and G
could meet a BOD standard of 5 mg/1. For ammonia-nitrogen, all sys-
tems except C, E and F could achieve sufficient nitrification of the
ammonia to meet the recommended ammonia level of 1 mg/1.
No federal, state or local standards have been set for phosphates
and nitrates in the Boulder treatment plant effluent. The 208 basin
plan is the first to recommend limits for these nutrients. In general,
all systems were judged capable of meeting the 8 mg/1 phosphate level.
Nitrates, however, represent the most difficult problem. In order to
reduce ammonia, all of the systems depend upon a process whereby am-
monia is converted to nitrates (nitrification). Thus effective am-
monia reduction necessarily implies an increase in nitrates. With the
present technology, removal of this nutrient is most effectively ach-
ieved by algal activity in lagoons, or by a denitrification process.
The polishing ponds under Alternative C incorporate algal growth,
however the ponds are inefficient for ammonia conversion to nitrates.
The algal blooms will also increase the BOD and suspended solids
levels. The efficiency of the proposed submerged rock filter systems
for suspended solids removal varies with operating conditions and
may not meet discharge requirements all the time.
Alternative systems A and G would probably not be able to meet
the recommended nitrate level and would probably have excess nitrates
in the percolates and surface run-off. Infiltration/percolation under
Alternative A will have no effect upon nitrate removal. High-rate
irrigation under Alternative G incorporates irrigation to the greatest
91
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level that the vegetation can tolerate. Nutrients in the wastewater
would exceed the amount required for plant growth and pass into the
groundwater table or to surface run-off. High-rate effluent irri-
gation practices in California have demonstrated excess accumulation
of nitrates in the groundwater (Reference 68). Alternatives B, D, E
and F are also judged ineffective at removing nitrates, unless sup-
plemented with a denitrification process.
The 208 management plan estimates the costs for Boulder to improve
their facilities and interceptors at approximately $24.2 million
(present worth). This amount greatly exceeds the projected present
worth of all alternatives except G. Net present worth of Alternative
G from Table 12 is $48.7 million. The additional estimated costs
would cover the addition of nitrate-removal facilities (denitrifica-
tion) to the existing Boulder system. Addition of a denitrification
unit to the above alternatives was not considered by the facilities
planner. Denitrification units are new, relatively untested and costly
to construct and operate. They could not be installed with a high
assurance of successful performance. System performance is generally
not as reliable as a lagoon system. Effective nitrate removal would
thus be best achieved by the addition of a lagoon system. In this re-
spect, Alternative C, which incorporates this system would be more
cost-effective and efficient.
County Goals
Boulder County has expressed no water quality objectives as of
this writing. The County does control the landfill sites which may be
used for ultimate sludge disposal. Possible land disposal or reuse of
wastewater sludge would be reviewed through the Special Use Review
process of the County Planning Board.
Implementation of Alternatives A and G requires the use of land
within the County's jurisdiction; a Special Use Permit must therefore
be obtained from the County. In addition, Alternative C proposes
reclamation of gravel pits which are currently scheduled to be mined
by the County. This alternative would commit the County to a land
reclamation arrangement which differs from that planned under the
Walden Ponds reclamation plan. These various land uses would be re-
viewed by the County Planning Board and ultimately by the Board of
Commissioners.
Local Water Quality Goals and Objectives
The Boulder Valley Comprehensive Plan has designated the Boulder
Creek corridor as a permanent open space and a connecting link within
the Greenbelt System. The community has a great deal of interest in
establishing and maintaining open areas and in preventing urban sprawl
in the Boulder area. Improvement of the water quality of Boulder
92
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Creek is essential for the establishment and maintenance of the creek
as a recreational resource. The Boulder City council articulated this
desire in a resolution passed on 17 June 1975 which commits the City
"... to upgrade and improve the quality of the stream of Boulder Creek
... [to an] Al or A2 classification down to the 75th Street plant, and
... it would be our hope and intention to do whatever we can to make
it a sport fishery" (Reference 1).
The Citizens Advisory Committee and the City of Boulder staff,
after studying the various guidelines and their financial implica-
tions, approved the general guidelines listed below.
(1) Provide treatment capacity sufficient to handle flows
expected in 1985, with consideration given to the ex-
pected flows of the next decade;
(2) Provide an acceptable method for the treatment and
disposal of septic tank pumpings (septage);
(3) Include odor control as a top priority in the evaluation
of any alternative;
(4) Consider nitrification to allow a game fishery, but not
such as to preclude further treatment to a higher
quality;
(5) Provide an acceptable method of sludge stabilization
and reuse of this valuable resource.
SCREENING OF ALTERNATIVES
Based on the estimated treatment effectiveness shown in Table 11
and the engineering evaluation of alternatives, three of the seven
proposed alternatives would not be able to meet state and local water
quality goals. These alternative systems are: E—multimedia fil-
tration; F—chemical coagulation; and H—no project. Alternatives E
and F were designed to meet the former B2 standards, and Alternative H
could not meet the upgraded stream standards. Modification of Alter-
natives E and F to bring treatment quality up to the A2 water quality
standards would have produced systems essentially the same as other
alternatives proposed. Therefore, in following sections of this EIS,
only those alternatives which can meet standards for the upgraded A2
stream classification for the central segment of Boulder Creek will be
considered. This narrowed range will include five alternatives: A—
infiltration/percolation; B—oxygen activated sludge after trickling
filters; C—aeration and polishing ponds; D—oxygen activated sludge
before trickling filters; and G—high-rate irrigation.
93
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94
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SECTION IV
-------
SECTION IV
ENVIRONMENTAL IMPACTS
AND MITIGATION MEASURES
The environmental impacts of the proposed alternatives are pre-
sented in this section. In Section III, eight alternatives were pre-
sented: A—infiltration/percolation basins; B—oxygen activated sludge
after trickling filters; C—aeration and polishing ponds; D—oxygen
activated sludge before trickling filters; E—multimedia filtration;
F—chemical coagulation; G—high-rate irrigation; and H—no action.
These alternatives were evaluated specifically for their anticipated
effluent quality and ability to meet the new, upgraded A2 stream clas-
sification for Boulder Creek below the 75th Street treatment plant.
In the engineering analysis part of Section III, Alternatives E,
F and H were judged as being unable to achieve the desired A2 water
quality standards. Therefore, in this environmental impact section
only those five alternatives which have a potential to meet the de-
sired standards are considered: A—infiltration/percolation; B—
oxygen activated sludge after trickling filters; C—aerated and po-
lishing ponds; D—oxygen activated sludge before trickling filters;
and G—high-rate irrigation.
These alternative courses of action will have both beneficial and
adverse impacts upon the natural environmental as well as on institu-
tions, economic factors and energy-utilization rates. These impacts
were assessed on the basis of available scientific knowledge, profes-
sional experience of the environmental team, consultation with local
experts in specific fields and familiarity with local conditions gain-
ed by the project team during field investigations.
The Environmental Protection Agency guidelines for the prepara-
tion of Environmental Impact Statements [40 CFS, Part 6, § 6.304 (c)]
require the evaluation of primary and secondary environmental impacts
for all alternatives. This section will discuss short- and long-term
direct (primary) impacts and long-term indirect (secondary) impacts.
SHORT-TERM IMPACTS
The direct short-term impacts and feasible mitigation measures,
shown in Table 14, are generally related to construction activities.
Supporting discussions for some individual impacts can be found in
Appendix E.
95
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Table 14. SHORT-TERM IMPACTS AND MITIGATION MEASURES
Alternative
Impacts
C
Comments
1) Soil erosion from con-
struction disturbed sites
3333
Greatest potential at sites re-
quiring lagoons and earthen berms
2) Disturbance of soil
profile at site or
modifications reduc-
ing agricultural
productivity
Greatest disturbance occurs at
construction of lagoon sites,
particularly Alternative G
3) Dust generation from
exposed ground surfaces
3 0 3 0
0"0"0"00"
Greatest potential during windy
periods
4) Increased aerial pollu-
tants (hydrocarbon
emissions)
By-product of equipment opera-
tion
5) Degradation of surface
water quality from
erosion and runoff
3030
Closely tied in with amount of
soil disturbed and erosion
potential
6) Depression of ground--
water table and effects
upon groundwater
quality
30303
Strong impact with systems re-
quiring excavation of deep la-
goon (s) or trenches and subse-
quent dewatering or construction
of barrier against groundwater
movement
7) Loss of groundcover and
disruption of wildlife
habitats
30303
Alternatives A, C and G may re-
quire removal of some cottonwood
trees
8) Disruption of wildlife
patterns within sites
and adjacent sensitive
ecological areas
30300
3~0"3"0"3"
0~0"0~0~0~
Alternative A will disrupt Walden
Ponds and Sawhill Ponds. Alterna-
tive C will temporarily disrupt
White Rocks area
9) Increased noise from
equipment and ground
vibrations
Unavoidable effects associated with
construction and earth-moving
10) Visual impact of con-.
struction equipment and
construction site
Temporary but unavoidable
96
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Table 14. SHORT TERM IMPACTS AND MITIGATION MEASURES
(Continued)
Mitigations
Effectiveness
• Schedule construction to dry season Very effective for all alternatives if
• Confine surface disturbances to timed- follow-up reseeding is conducted to elimi-
iate construction areas nate bare spots
• After construction, exposed soil areas
should be reseeded with native grasses
• Stockpile topsoil from site for reuse Unavoidable impact for lagoon site, Alter-
native G
• Keep soil wetted down in construction Very effective
area
• All vehicles and equipment should be Moderate effectiveness, unavoidable short-
fitted with pollution control devices term impact
that are properly maintained
• Interceptor ditches around construction Effective in minimizing impact if strictly
site to catch runoff enforced
• Settling basins to catch runoff waters
prior to discharge to creek
• Care should be taken not to discharge
petroleum or other pollutants to stream
• Limit areas for barrier construction Unavoidable adverse effect difficult to
and dewatering control
• Construct downstream recharge areas
• Supplemental surface irrigation
• Replanting with native vegetation where Can be effective in speeding up recovery
possible
• Mature cottonwood trees should be flag-
ged or fenced to minimize construction
damage
• Vegetation removal should occur during Difficult to control, should consult local
late summer or fall when nesting birds wildlife experts for assistance
are not present
• All equipment should have mufflers prop- Minor unavoidable impact
erly installed and maintained
• Limit activities to daylight hours
• Equipment should be stored in designa- Moderately effective, minor unavoidable
ted areas, all litter picked up impact
• Fence or otherwise screen construction
maintenance area
Key to Impacts:
Beneficial impact
o
CD
No change or minor adverse impact
( B Moderate adverse impact
Significant adverse impact
97
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Table 14. SHORT TERM IMPACTS AND MITIGATION MEASURES
(Continued)
Alternative
Impact
Comments
11) Spoil disposal from xTx xTN /TN /T\ /^ Includes lagoon and pipeline exca-
excavation UJ U/ U/ UJ LP vation
12) Stockpiling and stor- ST\ /TN /TN /TN /TN Increases erosion potential
age of spoil Uy vl/ U/ Uy Uy
13) Safety hazard ST\ /TN /TN /TN /TN °pen trenches' Ia8oon excavation
(I ) ( I / v|y \}J vLx and movement °f heavy equipment
14) Construction-related (|) {[) ( ) ( I ) (U Truc'c movements associated with
traffic \X/ VL/ Vix VLx \J delivery of equipment and mater-
ials along with transport of
spoil material. This will be
particularly noticeable in Alter-
native G
15) Disruption of through XTN ST~\ /T\ /T\ /TN Strongest impact during daylight
and local traffic (^J (^) \^J \J^J \^J hours, particularly during com-
mute times
16) Utility service dis- /T\ /T\ /TN /TN /TN Temporary effect causing local
ruption \Jy vl/ VLX \lx Vix inconvenience
17) Public fiscal effects /TN /TA /TN /TN /TN No benefit to either City or
sales tax revenue \^J \^J \^J \^J \^[J County of Boulder (see Appendix E)
18) Project employment x-v s~^. S~~\ s-~*. x-~x Estimated 70 to 100 additional
\J \^J \J V-X1 ^_J jobs (see Appendix E)
19) Business effects- ^-^ ^-^ .^-v ^-^ ^->^ Local portion of total construe-
direct (spending in ()()()()() tion purchases between $2-14 mil-
Boulder County) v_x v_x ^x \^s v^x li(jn (gee Appendlx E)
20) Business effects-in- x-v x~x x~N x~v x-v Estimated 44-240 job-years of in-
direct (Employment ( J (J (J ( ; ( ) direct employment (see Appendix E)
creased by project ^"^ ^"^ ^"^ ^~*
spending)
98
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Table 14. SHORT TERM IMPACTS AND MITIGATION MEASURES
(Continued)
Mitigations
Effectiveness
• Disposal of soil material should be co- No problems in Alternatives A and C which
ordinated with other ongoing projects require berm construction
requiring fill
• Spoil material not needed for back- Moderately effective
filling should be spread on ground and
seeded or covered to prevent dust and
erosion
• All open trenches should be covered or Effective in protecting all persons except
fenced at end of work day tresspassers
• All construction equipment should be
secured against unauthorized use
• Construction area should be well
marked and access restricted where
possible
• Scheduling to avoid peak traffic per- Strongest effect on 75th Street between Jay
iods in area and Valmont Roads
• Barricades and flagmen posted as nee- Poor-to-moderate effectiveness in preventing
essary to guide traffic through con- traffic congestion and delays
struction zones
• Notify local residents as to location,
nature and duration of construction
^•H^*— ^^^^«» ^^ _^^^_^^^^^^^^BH^^«W^^^^*~^ "~ ^^^~>BK*V^^^«»^^^*K.~^^>~^V*I_^^^^~— — «
• Advance notice of utility service dis- Effective in minimizing impacts
ruption should be given
• If disruption occurs over a long per-
iod, utility bypasses should be pro-
vided
• No mitigation measures are applicable
_^__^M^^^^^M«* ^ ^^.^.~__^MM__^~.^V_^~^~»'V^«»~— ^ "— •— ^ •— —» —" ^ ™• ^ ™- "— — — — -• ^ ^ ^ — ^ — ^ — •
• No mitigation measures are necessary
_ _ ^ ^ aw •— ^m~ _»^«H •— •_ •> — «^^ —«^—»^^ — —"^— — ^^ — ^^^^ — ^^^— ^— ^ — ^^ — ^^ — ^-^^— ^™_^^— ,^_«_—,^.
• No mitigation measures are necessary
• No mitigation measures are necessary
Key to Impacts:
C J Beneficial impact
( ) No change or minor adverse impact
( B Moderate adverse impact
Significant adverse impact
99
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LONG-TERM DIRECT IMPACTS
Physical Environment
Potential Impacts Upon Soils—
Impacts on soil characteristics are closely related to the method
of operation. In general, the application of secondary-treated effluent
to land can provide additional nutrients such as nitrates and phosphates
and can be beneficial to soil productivity. Areas of concern with this
method are possible accumulation of heavy metals and salts from the
effluent and variable system performance depending on loading rates.
Alternative A— 225 acres would be committed for infiltration/
percolation basins under this alternative. Soils at this site are pre-
dominately sand and aggregate overlain by a layer of topsoil. These soils
are satisfactory for this method of treatment. The permeable soils would
allow rapid water percolation while filtering the organic material and
other constituents. Effluent application rates of 150-200 ft/yr are
high enough to avoid toxic build-up of salts. However, loading of this
magnitude are too high to benefit soil productivity and excess nitrates
would leach through the soil column. Over the long-term, heavy metals
would gradually accumulate in the soil root zone.
Deterioration of soil characteristics can result from system over-
loading, poor management or both. Excessive concentrations of suspended
solids in effluent and organic matter loaded into the basins can lead to
clogging of the soil surface through several complex mechanisms. Surface
pore space can be reduced by deposition of suspended solids and bacterial
growth and slimes which lead to additional severe clogging problems.
The effectiveness of the infiltration/percolation basins treatment
method depends upon the permeability and filtering qualities of the
predominantly aggregate soil near Boulder Creek. Utilization of this
soil as a filtering medium precludes gravel mining in that area during
the lifetime of the facilities operation. However, this facility should
not impair the potential for gravel extraction at a future date if the
ponds operations are discontinued. Gravel resources are not limited to
this site, being fairly common along the Boulder Creek floodplain and
other watercourses. Within Boulder County, this site would represent
only a small percentage of the gravel resource.
Alternative G— A high-rate irrigation system would be operated to
maximize effluent application without causing damage to plants. Crop
growth and harvesting would allow assimilation of much of the organic
material and nutrients. However, the effluent application rate of 10
ft/yr provides more nutrients than can be assimilated by plant tissues.
As in Alternative A, salt build-up should not be a problem although there
would be a potential long-term accumulation of heavy metals. Nitrate
100
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effects are discussed under groundwater impacts.
Alternatives B, C, and P— These alternatives require no significant
commitments of soil or mineral resources. With all these systems but C,
sewage treatment processes would be contained within the existing plant
site. With Alternative C, Boulder County would extract gravel from the
prospective site before construction of the ponds which make up this
system. These ponds would be formed in the excavations remaining after
the gravel extraction.
Mitigation Measures for Soils Impacts—
The infiltration/percolation basins under Alternative A and the
storage lagoon under alternative G would remove 225 and 350 acres,
respectively, from pasture and crop production. The pond site for
Alternative A is not prime agricultural land and is suitable only for
pasturelands. No mitigation measures would compensate for this loss.
Similarly, the loss of agricultural productivity due to soil removed from
the storage pond cannot be effectively mitigated.
Maintenance of Infiltration/Percolation Basins— Problems of soil
clogging leading to anaerobic conditions and subsequent additional
clogging can be reduced or prevented by periodic drying of the basins.
As the soil dries out between application cycles, the pore spaces reopen
and aerobic soil conditions are reestablished. Attention to this im-
portant relationship can ensure effective operations of the basins and
also reduce the potential for odor problems.
Potential Impacts Upon Groundwater—
The groundwater resources in the project area occur typically 0 to
5 ft below the ground surface and extend approximately 15 ft deep.
This shallow aquifer is underlain by impermeable bedrock, generally 15
feet below the surface. The groundwater in the vicinity of the project
site flows toward Boulder Creek and at some locations runs parallel to
the creek. The main effects of the proposed alternatives can be divided
into the direct and indirect effects.
Alternatives A and G could directly impair groundwater quality.
Wastewater from the lagoons and application sites of Alternatives A and G
could percolate to the groundwater. The indirect effect of improved
wastewater treatment upon groundwater occurs in the zone where the
groundwater interacts with Boulder Creek. The creek has been described
as a losing reach (where stream water flows into adj acent groundwaters)
near the 75th Street treatment plant outfall and as a gaining reach
(where groundwater replenishes streamflow) near the White Rocks area.
Treated effluent from Alternatives B or D would be discharged to the
creek above 75th Street. Alternative A would discharge at or below
75th Street. The improved stream water quality would indirectly
101
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benefit the groundwater where it is fed by stream flows along the losing
reach of Boulder Creek. Alternatives A and C, which provide the highest
quality effluent, would be slightly more beneficial to groundwater
quality than the other "mechanical" systems.
Alternative A— Under Alternative A, the percolation ponds would be
for the most part isolated from the groundwater system by subsurface
drains. The drains would be designed to lower the water table to a
depth of five feet below the existing land surface of the site to speed
percolation from the ponds and prevent lateral movement of effluent into
areas east of the site. As the site extends across the width of the
alluvial aquifer, the drains will eliminate the majority of the under-
flow and recharge to areas immediately east of the site. In effect,
the drains will split the aquifer. The effectiveness of the drain system
in drawing out the percolated effluent depends upon the degree of soil
saturation. If the ponds are full and additional loading is caused by
heavy rainfall, the soil will be saturated from the surface to well
below the drains. Under this condition, the hydraulic capacity of the
underdrains may be exceeded and wastewater percolate may bypass the
drains entering the groundwater table. Groundwater contamination may
also occur during an extremely dry year. Water table drawn down below
the level of the underdrains could reduce the hydraulic effectiveness
of the drains. Wastewater may be drawn down to the water table past the
underdrains in this situation.
Groundwater level drawdown during normal pond operations will
occur in detectable amounts east of the site to a distance of 200 to
300 feet. Drawdown under the adjoining property east of the site will
be accelerated by the elimination of underflow and upgradient recharge.
The depth to water under the adjacent property will be lowered to as
much as five feet and will average approximately three feet below the
land surface. The principal factors controlling water levels under the
property would be the quantity of recharge the aquifer receives from
precipitation, the amount of irrigation on the property and the terraces
to the south and the water level of Boulder Creek and Green Ditch.
Increasing the depth to water east of the site will reduce the
subsurface irrigation of pasturelands overlying that area. At the
present time, the pasture receives approximately 50 percent of its
water demand through subirrigation. Reduced water levels will eliminate
shallow-rooted grasses in the pasture or severely restrict their growth.
Longer rooted species will survive but will exhibit reduced growth.
Alternative C— Under Alternative C, the aeration and polishing
ponds would not be lined. Groundwater movement would be controlled by
a groundwater cutoff drain surrounding the site, and the facilities
planner anticipates that the ponds would be self-sealing within a short
time after initiation of operations. Pond operation should not have
significant effects on the water table although groundwater movement
could affect the ponds operation if it seeps past the cutoff drain and
102
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overloads the system.
Alternative G— Under Alternative G, soil saturation in the upper
soil zone would occur immediately after high-rate irrigation. As
discussed under Alternative A, percolate may escape the drain system and
pass into the groundwater under saturated conditions. The pollutant
of greatest concern would be nitrates. High-rate irrigation generally
supplies more nutrients than can be immediately utilized by the
irrigated vegetation. Excess nitrates, in particular, would pass easily
down through the soil matrix. If nitrate levels in the groundwater exceed
45 mg/1, then domestic use (drinking and culinary) of this water source
should be prohibited.
Alternatives B & D— Alternatives B and D, in their operation phase,
should have no effects upon groundwater.
Mitigation Measures to Reduce Groundwater Impacts—
Supplementary Water Supply— In areas adjacent to land application
sites where the groundwater is used for domestic and livestock purposes,
arrangements could be made with the local water utility (City of Boulder)
to supply potable water. This would involve the installation of a city
water supply system to residences. For livestock, a determination of
well water quality would be made and, if necessary, water supply could
be augmented by transport of water from trucks. Pasturelands may also
require additional surface irrigation.
Underdrain System Design— Collection of percolates under the in-
filtration basins (Alternative A) could be impaired if the soil were
saturated and the hydraulic capacity of the underdrains exceeded. This
effect could be greatly reduced by oversizing the underdrain system so
that excess system loadings, to a certain level, could be handled.
Supplementary Recharge System— Groundwater drawdown would occur in
a shadow zone 200 to 300 ft east of the infiltration basins site. This
impact could be mitigated by the addition of a recharge system placed
along the eastern side of the site. The recharge facility should be de-
signed to duplicate existing underflow across the eastern boundary of the
site. The facility would be required to recharge 50 to 100 gpm. The
recharge mechanism could consist of a trench, a line of injection wells
or a series of recharge basins. The source of water for the facility
would need to be of high quality and contain little suspended or
settleable solids. A convenient water source of high quality would be
the underflow intercepted along the western side of the site. Pumping
would be required to transport this water to the recharge facility.
Boulder Creek would probably be unable to supply water to sufficient
quality. The potential for obtaining good quality water from an under-
lying aquifer is limited. The Pierre Shale Formation underlying the
alluvial aquifer'is several thousand feet thick.
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This measure would raise project costs and probably be more cost-
ly than other potential mitigation methods such as supplemental sur-
face irrigation. As the shadow zone of groundwater drawdown east of
the site would probably be small, the simple mitigation measures would
be adequate. If drawdown occurs to a much greater extent during oper-
ations, then a recharge system may become more feasible.
Potential Impacts Upon Surface Waters—
Under Boulder's existing wastewater treatment system, the secon-
dary-treated effluent contains significant levels of BOD5, ammonia-
nitrogen and dissolved nutrients. These pollutants have led to a
long-term degradation of water quality and of the aquatic environment.
Improvement of Surface Water Quality— All of the alternatives
under consideration would help Boulder realize its immediate waste-
water treatment goal of an effluent with 20 mg/1 of BOD5 and 20 mg/1
of suspended solids. As a result, the water quality of Boulder Creek
below the 75th Street treatment plant would be greatly improved.
The ultimate goal in improving stream water quality is the im-
provement or restoration of the aquatic environment itself. The clo-
sure of the Pearl Street treatment plant outfall in 1975 represented
the first step toward the restoration of Boulder Creek. Improved
water quality, and other improvements such as naturalization of chan-
nelized areas, revegetation of exposed stream banks and removal of
debris, would promote the potential of a trout fishery between 55th
and 75th Streets. Below the outfall of the 75th Street treatment
plant, the stream environment is presently not suitable for a trout
fishery; the water temperature is too warm, agricultural diversions
reduce streamflow, channelization has destroyed aquatic habitat and
treatment plant effluent introduces excess organic material and am-
monia, which is toxic to aquatic life. With the achievement of
20 mg/1 BOD5, 20 mg/1 suspended solids and less than 1 mg/1 ammonia-
nitrogen, a warm-water fishery could be developed below 75th Street.
This improvement in stream ecology would also benefit many species
of birds and mammals through increases in available food sources.
Surface Water Pollution— Overland water flow with high-rate
irrigation, under Alternative G, may contribute to surface water pol-
lution of irrigation ditches and possibly Boulder Creek. Excess ef-
fluent can run off the application site without significant treatment
in the soil column and contribute to high-nutrient levels and algae
growth in irrigation ditches. Under current farming practices, high
dissolved solids and nutrients, along with algal growth, occur season-
ally in all of the local ditches and storage reservoirs. Accidental
overflow from the ponds in Alternatives A and C also contribute pol-
lutants to surface waters, but the frequency of occurrence would be
much lower than in Alternative G. As discussed in the groundwater
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impacts section, nitrate pollution would be of the greatest concern
with run-off from these systems.
Decreased Dissolved Oxygen Levels— Under Alternative A, renovated
wastewater - collected from the underdrain system - would be pumped di-
rectly to Boulder Creek. As noted in Section III, Table 11: the per-
colate would contain low dissolved oxygen (D.O.) levels (2-4 mg/1).
These levels are too low to sustain normal fish and invertebrate life
and under certain conditions, may cause an anaerobic state in stream
bottom, leading to odor-generation and wildlife health problems. Mix-
ing of the effluent with aerated stream water, which typically contains
7-10 mg/1 dissolved oxygen (or higher under saturation conditions),
will reduce stream D.O. levels 20 to 25 percent, where effluent con-
tributes one-third of the streamflow. Dissolved oxygen levels will
fluctuate diurnally and seasonally depending on many factors such as
flow, temperature, BOD5, and volume of algal growth. In general, it
is estimated that the D.O. level would not drop below 5 mg/1, a thresh-
old limit for many fish and invertebrate species. However, the Boulder
monthly D.O. guidelines of 90 percent of saturation may not be met
consistently, particularly in the winter when the stream reaeration
potential is lower.
Mitigation Measures to Reduce Surface Water Impacts—
Surface Run-off Collection System— Construction of perimeter
ditches around the irrigation areas to collect surface runoff would
greatly reduce the potential for surface water pollution. The run-
off would be channeled to a settling basin or lagoon for reuse or
treatment prior to discharge. Under the June 1978 Colorado Dept. of
Health Guidelines, as presented in Appendix F, a surface water collec-
tion and monitoring system would be required in order to obtain a per-
mit for any land-application system.
Ponds System Design— The ponds system under Alternatives A and C
should be designed with adequate capacity to handle rainfall. System"
loadings and operations should also be designed to minimize overflow
and include emergency outlets and check devices.
Effluent Discharge and Mixing System— Effluent with low D.O.
levels under Alternative A should be reaerated prior to discharge to
Boulder Creek. This would require an active mixing system with aera-
tors, jets or other devices to oxygenate the effluent to a level that
will not deplete the total stream D.O. level below 90 percent of sat-
uration or some limit to be determined by the permit agencies.
Potential Impacts Upon Air Quality—
Local Climate— Under Alternatives B and D, no change in climate
is anticipated from project operation. The facilities are self-
contained and do not entail a large, exposed air-water or air-heat
interface.
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For Alternative G, and to a lesser extent Alternatives A and C, the
microclimate above the site would fluctuate continuously. Air moving
over the irrigated lands or ponds would increase slightly in moisture
content and decrease slightly in temperature along the downwind edge of
the sites during the summer. In winter, the temperature downwind of the
sites could be moderated by localized moisture differences. These micro-
climate effects are generally on a very limited scale and would probably
not be noticeable beyond the site boundaries.
Particulate Matter— Under Alternative A, the infiltration basins
would be subject to alternate wet and dry periods. Between loadings,
the soil would be allowed to dry out and reaerate to a depth of several
feet. During windy periods — especially "Chinook" episodes — surface
soils or particulates may be blown away from the basins site. This
effect would decrease as vegetation develops within the basins. Once
the vegetation becomes established, the roots will bind the basin surface
and prevent significant transport of soil particulates.
Fog Formation— Alternatives A, C and G are also expected to cause
local fog formation when the warmer effluent is exposed to relatively
cooler air. Based on calculations by McVehil (Reference 78), typical
conditions in Boulder where steam fog may occur in some quantity are:
Water Temperature Air Temperature
59°F 21°F
50 16
41 3
Steaming over open water in the pond areas proposed under Alter-
natives A, C and G could occur fairly frequently in Boulder's winter
weather. Some steam might be observed over the ponds up to 25 percent
of the time between November and March. Moderate or dense fog may
occur 5 to 8 percent of the time during the winter.
The fog or steam from the ponds would normally rise and evaporate
into the air or drift downwind and disappear within a short distance.
Under Alternative A, the potential exists for a ground level fog of
sufficient density to interfere with road visibility on 75th Street when
the prevailing winds are from the northeast and from the southwest and
west acrpss open fields. The distance to 75th Street is approximately
2500 ft and much of the fog would have dissipated over that distance.
The greatest potential for fog would result from the operation of
the 250-acre storage reservoir required for Alternative G. Traffic
on the roadways surrounding the site may be impaired by enveloping fog.
Because Alternative G involves effluent application during all of the
winter months, drifting fog generated from the ponds may also affect
surrounding areas. Local residents may find this condition bothersome
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Aerosols— Dispersion of spray-irrigated effluents under Alternative
G into the neighboring areas would be accentuated during windy periods,
particularly during "chinooks". Transmission of aerosols (microscopic
droplets) of wastewater origin may pose a health hazard as well as cause
a nuisance. Aerosol travel and pathogen survival rate are dependent on
several factors, such as wind, temperature and humidity.
Mitigation Measures to Reduce Air Quality Impacts—
Fog formation and microclimate effects are unavoidable impacts that
cannot be effectively mitigated without relocating the ponds in Alter-
natives A and C.
Aerosols from spray-irrigated effluent can be reduced by controlled
system operations but would be difficult to eliminate completely. Spe-
cifically, spraying should be curtailed during windy periods and directed
away from habitations. Night and morning irrigation would also reduce
aerosol potential. Alternately; irrigation methods such as furrow or
flood irrigation could be used. Irrigation practices would be subject to
the Colorado Department of Health June 1978 Guidelines for land-applica-
tion systems (see Appendix F).
Biological Environment
Potential Impacts Upon Vegetation and Habitats—
Alternative A— The creation of infiltration/percolation basins under
Alternative A would result in the removal of approximately 200 acres of
pastureland from production. The construction of an impermeable barrier
around the basin site to depress the groundwater table by approximately
two feet would have some negative impacts on the pastureland adjoining
the site to the east. This area currently depends on the high ground-
water table to supply water for plants. The impermeable barrier would
cause a "shadow zone" on the groundwater regime of the adjacent site
whereby the water table would be depressed to some extent into the
pasture. Some groundwater would continue to flow around the barrier,
and the depressed water table would have the hydraulic effect of drawing
some groundwater into the shadow zone from surrounding areas. The pro-
ductivity of the pasture would probably decline within the shadow zone
because of the interruption of the water supply to the shallow-rooted
grasses and forbs. Deeper-rooted grasses, legumes and forbs may become
more dominant in this zone. Riparian vegetation, including several ma-
ture cottonwood trees, should not be affected. A comparison of the ex-
isting pasture species and the plant species expected to colonize the
percolation basins are shown in Table 15.
Alternatives B and D— These alternatives would require only a few
acres for the actual plant additions. The main impact would be during
construction. The operational phase of these alternatives represents
insignificant long-term changes to the local environment.
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Table 15. EXISTING AND EXPECTED PLANT SPECIES
AT ALTERNATIVE SITE A
Common name
Scientific name
Existing species that will
be affected by construction
Alkali sacaton
Big bluestern
Bluegrass
Canada wild rye
Clover
Inland saltgrass
Kochia
Milkweed
Orchard grass
Plantain, English
Sand dropseed
Smooth brome
Tall wheatgrass
Thistle
Western wheatgrass
Expected species colonizing
infiltration basins
Alfafa*
Angelica
Barnyardgrass*
Bindweed*
Bluegrass
Bluejoint
Bulrush
Cordgrass
Cottonwood*
Cow parsnip
Curly dock*
Cutgrass
Dandelion*
Downy chess*
Filaree*
Green foxtail*
Italian ryegrass*
Kochia*
Mannagrass
Milkweed
Perennial ryegrasa*
Plantain, common*
Plantain, English*
Poison hemlock
Reed canary grass
Reed grass
Rush*
Sedge
Sloughgrass
Smartweed
Smooth brome*
Spikerush
Sunflower*
Water hemlock
Willow
Sporobolas giroides
Andropogon gerardii
Poa ap.
Elymus canadensis
Trifolium sp.
Distichis stricta
Kochia iranica
Asclepias speciosa
Dactylis glomerate
Plantago lancecJ.ata
Sporobolus cryptandrun
Brorous inermis
Agrostis elongatum
Carduus nutans
Agropyron smithii
Medicago sativa
Angelica sp.
Echinochloa crusgalli var. mitis
Convolvulus arvensis
Poa sp.
Calamagrostis canadensis
Scirpus sp.
Spartina sp.
Populus sargentii
Heracleum lariat urn
Rumex crispus
Leers la oryzoides
Taraxacum officiriale
Bromus tectorum
Erodium cicutarium
Setaria viridis
Lolium nwltiflorum
Kochia iranica
Glyceria sp.
Asclepias speciosa
Lolium perenne
Plantago major
Plantago lanceolata
Conium maculatum
Phalaris arundiancea
Calamagrostis sp.
Juncus sp.
Carex sp.
BecJonannia syzigachne
Persicaria sp.
Brormis inermis
Eleocharis macrostachya
Helianthus annuus
Cacuti douglasii
Salix sp.
Plant species observed on experimental basins at treatment plant site, 1976.
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Alternative C— Under Alternative C, the main impact to vegetation
on the site would have already occurred during gravel extraction prior to
construction. Operation of the polishing ponds would remove 30 to 50
acres from the agricultural/pasture unit. However, the productivity in
this area is marginal due to the high water table and disturbed
surroundings. Under this alternative, the perimeter areas would be land-
scaped and planted. Particularly, the planting of cottonwood trees and
other vegetation would increase the diversity of the area. Reclamation
plans for this alternative, however, would not provide as diverse and
rich an environment as the Walden Ponds Wildlife Habitat area presently
planned for the site.
Alternative G— Operation of Alternative G would effect the greatest
change upon local vegetation. The 350-acre storage reservoir site would
be lost from future crop or pasture production. An even greater effect
would be the high-rate irrigation (10 ft/yr) of effluent over 2,100 acres.
A marked change in plant composition would occur with the application of
water and wastewater nutrients. The current upland grassland species
would be replaced by a monoculture of water-loving forage crops such as
fescue or coastal bermuda grass.
The possibility exists for harm to plant growth from excess hydraulic
loadings or poor soil aeration, or a combination of the two, if the
sprinkler system is not adequately maintained and properly operated.
Heavy metals, bacteria and viruses from effluent can enter the ecosystem
and food chain. This hazard is somewhat reduced by wastewater stabili-
zation and the filtering effects of the soil. However, the nutrient
resource in wastewater would promote a beneficial increase in agri-
cultural productivity. This could be maximized by proper crop selection
and control of irrigation rates to limit excess buildup of heavy metals
and salts.
Mitigation Measures to Reduce Vegetation and Habitat Impacts—
Construction Practices and Reclamation Program— Construction of
treatment facilities under all alternatives, particularly those which
are land intensive such as Alternatives A, C and G, will involve ex-
tensive removal of natural and introduced vegetation from construction
sites. Wildlife utilizing these areas would also be disturbed from their
normal patterns.
The population growth and land development which would be accommodated
as a result of availability of sewerage capacity in the planning area
would have an even greater destructive impact on local vegetation. Not
only would removal of existing vegetation be an adverse impact, but the
ensuing increased erodibility of the soils would further reduce aesthetic
qualities of the utilized sites and degrade stream water quality with
transported sediments and nutrients. Mitigation measures to reduce
this impact or facilitate habitat restoration are listed below. The
first three are fairly specific to the wastewater facility construction.
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site, while the fourth measure applies to overall construction within
the planning area.
1. Limit construction activities, stockpiling of materials and
construction personnel to the construction site. This action would
minimize adverse effects on adjacent areas.
2. Design and place structures in areas of marginal habitat or areas
that are already committed to human uses. This type of planning minimizes
disturbance of natural areas by using existing roadways and urbanized
areas.
3. Construction practices which preserve on-site vegetation and
habitats to the maximum extent possible should be employed. The
integration of existing natural vegetation into the project area would
preserve some wildlife habitat as well as facilitate recovery after
construction. Retention of trees and groundcover, where possible, would
also help stabilize the soil structure. Channel work, where necessary,
should not be based on "high" velocity flows, but in general upon design
velocities similar to the natural stream characteristics.
4. A reclamation program for construction sites should be required.
As soon as it is feasible after completion of construction, the exposed
terrain could be regraded to a natural or semi-natural land form and
revegetated. Restoration of groundcover, particularly native species
would facilitate return of some wildlife species. Due to the initial
construction disturbance, sensitive species may migrate permanently to
other areas. Thus, the level of success for this mitigation action is
dependent on the return and colonization of species tolerant to an
altered human environment.
Moisture Tolerant Species Selection— High-rate irrigation upon crop-
lands in Alternative G would lead to the selection of moisture tolerant
herbaceous plants. The shift from crop and pasture species to predomi-
nantly water-tolerant grasses also implies a shift in the associated
invertebrate and wildlife species. This effect would be reduced slightly
during winter when no irrigation would occur but is, nevertheless, un-
avoidable.
A similar situation exists under Alternative A where operation of the
infiltration/percolation ponds would tend to select plant species that
would be tolerant of intermittent wet and dry cycles. Some species may
exhibit rapid growth rates, producing a large biomass and subsequent die-
off and impairing system operation. Mitigation of this effect would
include careful selection of vegetation species and, in the event of
heavy biomass accumulation, the basins should be periodically cut or
scraped.
Potential Impacts Upon Wildlife Patters—
Alternative A would alter present low-lying pasture areas into
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moist meadow and wetland areas with moderate to tall vegetation. During
the wet stages, shorebirds such as killdeer and sandpipers would be
attracted to the perimeter areas. Waterfowl would utilize the wetlands
for resting and supplemental feeding areas although the changing water
levels would not be suitable for protection during nest-building.
Amphibians such as leopard frogs and chorus frogs may also utilize the
ponds although breeding would not be possible. During the semi-dry and
dry stages, raccoons and muskrats would be occasional visitants.
Cottontail rabbits and meadow voles would temporarily be found in these
areas as they have been observed frequenting dry irrigation ditches. For
all of the species mentioned, during both the wet and the dry stage,
nesting and breeding would be highly unlikely in the percolation pond
areas due to variable water levels. Small mammals in particular would
not tolerate well the 8- to 12-day fluctuating cycles within the 13 com-
partmentalized pond-meadow environments. The necessity for frequent
migration between basins would probably preclude the settlement of per-
manent inhabitants. The compatibility of these ponds with the nearby
White Rocks Natural Area (WRNA) and the on-going reclamation project by
Flatiron Sand and Gravel Company adjacent to the site is difficult to
ascertain. The constantly fluctuating percolation basins would contrast
sharply with the proposed riparian and meadow environment planned for the
gravel mining area. The WRNA ecology would also depend upon the type of
vegetation growing in the basins and the type of maintenance, such as
mowing or harvesting. Annual or seasonal maintenance operations in them-
selves could have a strong detrimental impact on the reestablished vege-
tation and wildlife. At the present time, hay grown on the site is har-
vested twice a year. If vegetative cover is not established, the infil-
tration/percolation basins would provide no valuable wildlife habitat.
Operation of the polishing ponds under Alternative C should not cause
significant wildlife disease problems. During the winter, when waterfowl
may be confined in large numbers to shallow, poorly circulating or
anaerobic pond margins, the potential for "limberneck" disease to occur
among waterfowl is present. This disease is caused by toxins from the
bacterium Dostrium botulinum and occurs when an infected bird is intro-
duced into an area where large numbers of waterfowl are congested in
unsanitary conditions. Limberneck disease is generally not a problem in
large deep pond system. The polishing ponds should be designed to main-
tain a minimum flow through the system to reduce conditions for the
production of this bacterium. Further design of the ponds to incorporate
relatively steep banks, minimizing shallow waterfowl standing areas, would
preclude large concentrations of waterfowl along the pond margins. Thus,
the operation of the polishing ponds should not contribute a greater
potential for limberneck disease than is already present in the area with
other existing ponds.
Spring and summer algal blooms present another problem for wildlife
usage. Heavy algal blooms and the consequent decrease in water quality as
the algae decay degrades the aquatic environment significantly and reduces
wildlife habitat. Extreme conditions may lead to large fish kills in ponds
and depletion of food supply.
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Alternatives B and D— These alternatives would involve only small
portions of land around the existing 75th Street plant. This area is
presently affected by noise, vibrations, vehicular movements and visually
dominant structures. Operation of these alternatives would not effect
significant differences in wildlife patterns or numbers.
Alternative C— This proposed system would create a series of pond
environments attractive to waterfowl and semi-aquatic wildlife. The
downstream polishing ponds would be suitable for fish stocking and would
draw significant numbers of mallards, Canada geese, redheads, teals,
gadwalls and pin-tail ducks. The landscaped and revegetated berm and
buffer areas would provide shelter for small mammals and songbirds.
Because portions of the project would be open to the public, wildlife
species tolerant of human presence would be most likely to occur.
Alternative G— This system calls for the operation of a 350-acre
storage lagoon surrounded by approximately 3,000 acres of cropland. The.
large, moderately deep storage lagoon has the potential to experience
algal blooms as in Alternative A. With the steep banks of the lagoon,
waterfowl congestion and limberneck disease are not likely to occur.
The commitment of a large acreage in northwestern Boulder County to
high-rate irrigation ensures the preservation of the open space amenity
and facilitates a large wildlife refuge. A monoculture of forage grasses
would attract primarily rodents, small birds and associated predators.
Operation and harvesting of the field areas, however, would deter the
optimum wildlife production potential.
Mitigation Measures to Reduce Wildlife Impacts—
Alternative A will result in vegetated basins with an altered wild-
life community tolerant to wet and dry cycles. Some reduction of rodent
species and numbers will occur while an increase in aquatic bird species
may be experienced. The reduction of some cottonwood trees will remove
perching and nesting sites for birds. Mitigations for this effect are the
same as those discussed under the Disturbance or Loss of Vegetation
Section.
In winter, pond environments utilized heavily by waterfowl have the
potential to develop limberneck disease. The potential for this disease
in the polishing ponds can be greatly reduced by eliminating the causitive
factors. Control measures to eliminate shallow areas where waterfowl may
become congested such as steep bank areas and adequate circulation within
the pond system.
Potential Impacts Upon the Aquatic Environment—
All of the proposed alternatives would improve*tWe water quality of
Boulder Creek and benefit the riparian zone to varying degrees. Dis-
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continuation of the Pearl Street outfall in May 1975 has already resulted
in a demonstrated improvement in water quality, as discussed in the
section on environmental setting. Invertebrate and fish sampling con-
ducted since May 1975 confirms the improvement in stream conditions.
The appearance of largemouth bass and crappies in waters near Boulder
Creek (such as the Flatirons gravel pits) also confirms the presence of
warmwater fish species.
Alternatives A, C and G— These alternatives would produce the
highest quality effluents, with BOD and suspended solids ranging from
5 to 10 mg/1 or less. The high quality effluent would be compatible
with the development of a warmwater fishery below 75th Street in Boulder
Creek. However, nitrates from runoff and percolates in Alternatives A
and G may continue to cause a seasonal stimulus to algal growth. Improved
water quality, in itself, is not enough to restore the creek to its
original state. Full restoration of Boulder Creek requires the re-
vegetation of disturbed banks, naturalization of channelized areas,
correction of agricultural pollution and restraints on water diversions
in addition to the improvement of stream water quality. These actions
are beyond the scope of this project but would fit in with a regional
plan.
The polishing ponds in Alternative C could also provide a limited
aquatic habitat. The initial pond receiving secondary treated effluent
would not be suitable for fish culture. The intermediary and final
polishing ponds, however, could support a warm-water fishery. Ammonia
levels from Alternative C may be seasonally high enough to be toxic to
aquatic life. The success of these ponds would also be dependent upon
the control of algal growth and preclusion of anaerobic conditions. The
large storage reservoir under Alternative G receives secondary-treated
effluent as in the initial polishing pond and therefore would not be
suitable for fish culture.
Alternative G would result in the selection of moisture-tolerant
vegetation species as discussed above. The conversion of varied crop and
pasturelands to limited types of monoculture would alter the habitat
and lead to a shift in wildlife species. Although the habitat type would
be altered, some agricultural techniques could be utilized to mitigate
this impact to the benefit of wildlife. Residual and surplus areas, such
as streambanks, road edges, fencerows, corners and woodland patches, when
left uncultivated, provide important wildlife habitat (Reference 93).
Unharvested strips, stubble and fallow areas would also provide an
important supplement.
Alternatives B and D— These alternatives would produce an improved
quality effluent, with BOD and suspended solids ranging from 10 to 15
mg/1. The suspended solids load would lead to warmer ambient temperatures
in the summer and promote a warmwater fishery. The BOD load would also
cause a localized degradation in stream habitat downstream of the outfall
during low flow periods. Nitrates from the effluents would also promote
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seasonal algal growth. As in Alternative A, the ability to restore a viable
fishery to Boulder Creek is not solely dependent upon improved water quality
but rather on a combined improvement of physical, chemical and biological
stream factors. As streambanks, road edges, fencerows, corners and woodland
patches, when left uncultivated, provide important wildlife habitat (Ref-
erence 93). Unharvested strips, stubble and fallow areas would also provide
an important supplement.
Social and Economic Environment
Noise Impacts—
The operating equipment and treatment processes associated with all the
treatment alternatives would be relatively quiet and should not significantly
increase the ambient sound level. Construction activities with their atten-
dant noise generation would last up to 18 months. Mitigations should include
use of vibratory hammers instead of pile drivers, where practical, and si-
lencers on compressors and other equipment. Construction activities would
generally be scheduled during the daylight hours, although dewatering pumps
and other equipment may operate for extended periods.
Odor Impacts—
As mentioned in the section on environmental setting, the existing 75th
Street treatment plant causes intermittent odor problems in the vicinity of
the plant site. These odors emanate mainly from the sludge processing fac-
ilities and to a lesser degree from the trickling filters. Phase I of the
Boulder wastewater facilities improvement project is the addition of an an-
aerobic digester and other sludge-handling facilities to control odor. This
phase has received a separate negative declaration on environmental impacts
(Reference 4) and should be implemented in the near future. All the proposed
systems would continue to use the existing trickling filters. The odors
presently associated with the treatment plant should be greatly reduced.
Further control will include covering the trickling filters.
Alternatives A, C and G involve components that could cause additional
odor problems. These alternatives are significant because they involve the
greatest exposure of wastewater effluent to land and air. The remaining
physical and chemical treatment alternatives would have a low potential for
producing additional odors.
Alternative A— Odor problems from an infiltration/percolation basin are
usually associated with system overloading, poor management, or both. Ex-
cessive concentrations of suspended solids and organic matter in the waste-
water loaded into the basins can lead to clogging of the soil surface through
several complex mechanisms. Surface pore space is reduced by deposition of
suspended solids and bacterial growth which results in the development of
slimes and leads to more severe clogging and odor problems. Also, excessively
long application periods can lead to the development of anaerobic conditions
in the soil with the resulting odor and infiltration problems. These pro-
blems can be prevented by periodic drying of the basins which allows the
clogged pore spaces to reopen and aerobic conditions to be maintained (Ref-
erence 80).
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Odors should not be a significant problem in this alternative for
two reasons. The quality of the influent to the basins will be
relatively good (effluent from a secondary-treatment plant). Secondly,
nitrification will be necessary in order to meet NPDES permit require-
ments. This means that application periods must be short in order to
maintain oxygen levels in the soil sufficiently high for nitrification
of the ammonium in the wastewater. By monitoring the ammonia level in
the discharge and the percolation rates in the basins, the treatment
plant operators should be able to anticipate any problems in the basins
and take corrective action before any odor problems develop.
Another potential source of odor may be derived from vegetation
growing within the basin. Some plant species with a fibrous or matted
root system could reduce the soil percolation rate. Other plants have
a rapid life cycle and produce a large biomass within a short period of
time. Their subsequent decay, if they are not removed, could also af-
fect percolation rates and produce odor. Clearly, the type of vegeta-
tion growing in the infiltration basins would play an important role
in this alternative and should be studied carefully.
Alternative C— The polishing ponds required for Alternative C may
produce odors during two periods. During the winter, pond water may be-
come stratified and an anaerobic layer form on the pond bottom. As the
ponds thaw out in the spring, the turnover of the bottom layer could
bring odorous elements to the surface. The second period for odor
generation would be during the summer. The ponds would be rich in nutrients
and could develop heavy algal blooms. The subsequent algal decay and
deterioration of water quality may cause objectionable odors. The mag-
nitude of this impact would be dependent on temperature and wind.
Harvesting and removal of algae during peak growth period would reduce
the potential for odor.
The odor dispersion potentials for Alternatives A and C would vary
with the season and the time of day. In the winter, winds are from the
east during the day 65 percent of the time and from the west during the
night 75 percent of the time. During these periods, wind movement
parallels the valley and could possibly carry odors to the southern
fringe of Heatherwood when it blows from the east. During the day and
night, southerly winds prevail 15 percent of the time, while northerly
winds prevail 10 percent of the time. Southerly winds would have the
greatest potential for carrying odor toward the Heatherwood development,
but effects on Gunbarrel Green are anticipated to be limited. Residences
and farms to the south of the ponded areas could be affected by northerly
winds.
During the summer, wind distribution remains much the same, with
a slight percentage increase in northerly and southerly winds. The most
serious odor condition would occur on a summer day accompanied by a
southerly wind and unstable air. The condition could occur daily, but
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for limited time periods. This condition, however, would affect the
area of development surrounding the site. Once again, source strengths
are not known, and it may be that concentrations perceivable to the
human nose would occur only a few hundred feet from the downwind edge of
the source. An estimate of odor movement by an air quality consultant
(Reference 81) indicated a minimum 100-fold dilution of odors between
the site for Alternative A and the southermost row of homes in Heather-
wood.
Alternative G— Three principal odor sources are associated with
the storage lagoon required for Alternative G. First, the 350-acre
impoundment would be 30 feet deep, so maintenance of aerobic conditions
throughout the water column would be difficult. Consequently the anaerobic
status of the lower strata of water would generate odor during fall and
spring pond turnovers. Second, because the water would be nutrient-rich,
odorous algal blooms would develop. The algae would cause odorous con-
ditions not only in the vicinity of the impoundment but throughout the
irrigation area as well. Because no economical way has been devised to
remove algae from the irrigation water, algae would be spread on the
application site. As the algae dry and decompose on the land, odors may
be expected, especially during warm weather. Third, algae produced in
the reservoir would die and settle to the bottom. During pond drawdown
(in summer), these and other settled deposits may be exposed, possibly
causing objectionable odors.
Mitigation Measures to Reduce Odor Impacts—
Even the most sophisticated wastewater treatment facilities can
emit unpleasant odors if precautions are not taken. Mitigation measures
that may be considered are discussed with each alternative.
Alternative A - Infiltration/Percolation Ponds— The infiltration
basins themselves should emit minimal odors under proper operation.
If ponds become inoperative due to soil clogging and wastewater re-
mains long enough to allow an algal bloom, adverse odor conditions
may result. Similarly, excessive vegetation growth and die-off in
the basin may produce odors. Control measures include harvesting
vegetation in the basins or scraping the upper soil and vegetative
layer of the site. The pond operations should be closely controlled
on a cyclical schedule. Allowing the ponds to dry out and reestablish
aerobic conditions will greatly minimize odor problems. Monitoring of
ammonia levels to determine the extent of nitrification and bacterial
growth would also allow early control of potential odor conditions.
Alternatives B and D, Activated Sludge Systems— Some of the
mitigative design features for odor control include:
1. Scrubbing air from the influent pump station wet-well by
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pumping it into the aeration basin, the activated sludge process or into
oxidizing baths ;
2. Provision of covers over primary clarifiers, drawing air from
under the cover and scrubbing, as above;
3. Provision of separate enclosures over trickling filter or
activated sludge units with scrubbing or ventilation of the air space;
4. Use of deodorizing mists downwind of the wastewater treatment
plant during periods of particularly bad odor formation or during mal-
functions. These mists have been used in the past at the Boulder
treatment plant with limited success. In some cases, the scented mists
were repellant also to the public. This may be used as an emergency
measure, but is no substitute for an actual solution or consideration
prior to proper design.
Alternative C - Aeration/Polishing Ponds— The ponds may become
anaerobic in the lower depths during winter. Subsequent spring thaws
and mixing could bring odors to the surface. The ponds would also be
rich in nutrients and develop algal blooms in summer, possibly caus-
ing objectionable odors. Odors may be partially controlled by the
addition of aeration units to preclude anaerobic conditions and fil-
tering systems to remove filamentous algae where practicable. With
rigorous control on algal mass in the ponds, odor problems can be
greatly controlled. No mitigation measures exist to completely con-
trol or limit the dispersion of generated odors.
Alternative G - High-Rate Irrigation— This system suffers the
same odor problems as mentioned under Alternative C. In addition,
algae generated from algal blooms applied with the irrigation water
to crops may cause widespread odors as it dries and decomposes on the
application site. Settled and decaying algae in the storage lagoon
may also be exposed during pond drawdown in summer. The mitigation
effects discussed under Alternative C are effective for smaller sys-
tems. However, odor conditions are much harder to control in large
systems and are unavoidable.
Potential Energy Consumption Effects—
Fuels used directly to operate the proposed facilities or indi-
rectly to generate electricity for treatment equipment must be con-
sidered a limited resource. Wastewater treatment facilities general-
ly use both electricity and natural gas as opposed to fuel oil, gaso-
line or coal. About 35 percent of the electric power used in Colorado
is generated by burning natural gas. Thus both directly and indirect-
ly, wastewater treatment plants are dependent on natural gas. Sup-
plies of this fuel in particular will not be sufficient to meet user
demand in Colorado by 1980 with a shortfall of as much as 15 percent
by 1985.
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In the 1975 facilities plan, an estimate of energy demand by the
various alternatives was made based on higher population estimates than
those used in this EIS. Although the population and resultant wastewater
flows were revised downward in 1977, energy use estimates were not revised.
Table 16 presents these estimates based on the higher 1985 population
of 116,300 and a 1995 population of 154,000. The energy requirement could
be adjusted downward to account for lower population and flows; however,
the ranking of the alternatives would remain the same.
The alternatives with the lowest energy demand are A and C which
are estimated within 10 percent of each other. Based on relative com-
parisons with the projected demand at the existing facility, Alternatives
A and C would require 50-60 percent more energy while Alternative B would
require 138 percent more energy. Alternatives D and G would be most
energy intensive requiring 4-5 times more energy than projected operations
for the existing facility-
Table 16. MARGINAL ENERGY CONSUMPTION
(KWH/YR x 103, ESTIMATED)
System Alternative Gross Energy Consumption3 Ranking
Existing Treatment Plant 3,663
1965
A - Infiltration-Percolation
Basins
1985 5,300
1995 6,100 (1)
B - Activated Sludge after
Trickling Filters
1985 7,000 (2)
1995 8,700
C - Aerated/Polishing Ponds
1985 4,300 (1)
1995 5,600
D - Activated Sludge before
Trickling Filters
G -
1985
1995
High-rate Irrigation
1985
1995
15,600
19,900
9,400
14,500
(4)
(3)
aTotal operating energy dry weather flow.
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However, peak demand, rather than total consumption, is the critical
factor to be considered in evaluating impact on the electric utility
system. The highest demand by the 75th Street treatment plant in the past
14 months has been 438 kW. The existing facility of the Public Service
Company of Colorado can fully accommodate a demand of up to 2,000 kW, or
over 4-1/2 times the peak to date. According to advice from PSC, it is
unforeseeable that demand under any of the proposed systems, even System D,
could rise to such a level. Therefore, none of the proposed alternatives
would be expected to have a significant negative impact on the electric
utility system.
Mitigation Measures to Reduce Energy Consumption—
The anaerobic digestion process produces methane gas which can be
used directly as a fuel or to generate electricity. Although Alternatives
B and D would generate the largest amounts of methane, their total energy
demand would still be high. The Alternative with the largest percentage
reduction in total energy demand attainable through use of process-
generated methane gas is Alternative C.
Potential electric energy generation with process-generated methane
gas could contribute up to 3,000 kWh/yr in 1995, which would supplant
as much as 50 percent of the energy demand of Alternatives A and C. If
Alternatives B and D utilized an aerobic digestion process, no methane
would be generated.
Since Colorado faces a potential shortage in natural gas supply,
serious consideration should be given to replacing natural gas use with
methane gas generated from the treatment facility. Natural gas use in
1995 would be projected in the order of 4-5 million cu ft/yr. This
amount could be significantly reduced by using the methane gas for space
heating and for process operations such as heating of the anaerobic
digesters.
Local Land Use Impact—
Land use in the vicinity of the 75th Street treatment plant is
characterized by single-family residences to the north, sparsely settled
and agricultural uses immediately east and west, and a mixture of
agricultural and mining to the south. Northeast Boulder County is pre-
dominantly agricultural with some residential and mining areas. The
Boulder Valley Comprehensive Plan recommends generally that land in the
vicinity of the Boulder Creek floodplain be maintained for open space
uses. The 75th Street treatment plant was constructed prior to the open
space recommendation. Under present criteria, it has been considered
by some persons as marginally compatible with surrounding land uses.
Some of the proposed alternatives would have an effect on agricultural
and mining land uses, while the others generally would not affect
existing land use.
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Alternatives B & D— These systems call for physical additions to
the present treatment plant and are mostly within the existing site.
Their presence should not affect adjacent land uses although additional
structures may to a limited degree reduce the open-space usage. Potential
odor problems would be negligible except in the case of a plant upset.
If the condition were recurrent, then the facility would not be com-
patible with residential land uses north of the plant. Monitoring and
control of operations could reduce this effect.
Alternative C— The project site has been scheduled for gravel mining
by Boulder County. Upon the completion of mining activities, the Boulder
County Parks and Open Space Department has proposed a reclamation plan
in conjunction with the Walden Ponds Wildlife Habitat Area. The proposed
alternative would convert this site at the completion of gravel mining
into a series of polishing ponds that may be suitable for waterfowl and
warmwater fish. While these ponds would provide additional wildlife
habitat to the area, they would not be as productive as the plan proposed
for the Walden Ponds area. In the context of the local environs, the
ponds would be compatible with agricultural and open space uses. Potential
odor from the ponds, as discussed in the odor impact section, may have
indirect adverse effects on residential land use to the north of the
facility. Rigorous control of potential odor situations and the visual
appearance of the facility would reduce this effect.
Alternative G— The operation of a large 350-acre lagoon and ex-
tensive irrigated crop areas would generally be compatible with surround-
ing land uses in northeastern Boulder County. The area is predominantly
under agricultural and pasture usage and would not undergo a significant
land use change. If the city and county determined that purchase of the
proposed irrigation lands is necessary to ensure system operation, then
existing land uses should be reconsidered. The purchase and incorporation
of private farms into the high-rate irrigated cropland would ensure the
continuation of open-space/agricultural land uses. However, some land-
owners may not agree with these land use goals, while others may have
alternate plans such as commercial development or gravel mining.
Impacts Upon Local Water Supply—
Operation of the proposed alternative systems would generally have
a negligible impact on properties within the proposed area drawing upon
the municipal water supply system. Residences and farms depending on
groundwater supplies (wells) however, may be affected under Alternatives
A and G.
Alternative A— Operation of underdrains in the infiltration basins
would depress the groundwater table several feet and have a tendency to
draw out groundwater from a small area around the site as well. This
could slightly lower the well water level on the property east of the
infiltration basin and reduce the amount of pasture sub irrigation as
discussed in groundwater impacts. Potential contamination of the well
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water supply to this residence, which is also discussed in groundwater
impacts, may render this well unsuitable for domestic use and require a
conversion to municipal water supply.
Alternative G— High-rate effluent irrigation and collection by drain
pipes would have similar effects to those described under Alternative A.
Since this alternative covers a much greater area and could affect more
than one residence dependent on well water supplies, facilities planning
should be more extensive. In the event that leachates cause local wells
to exceed drinking water quality standards, the city may have to consider
extension of municipal water supply to this area.
Impacts Upon Municipal Service Costs - Utilities—
Based on EPA guidelines, operation and maintenance costs for the
wastewater facility will be financed through increased user charges.
The present cost is $2.86 per household per month for sewer services.
This figure is an average based on a flat $1.50 charge plus 18c per
thousand gallons (Reference 58).
Rate increases will vary, depending on population growth and inflation
rates. In current dollars, billing increases will range from $0.96 to
$4.45 per household per month, depending on which alternative is selected.
The plant investment fee, a one-time service fee for hookup, will also
be adjusted accordingly. It currently stands at $450 per hookup. This
money is for capital investment (Reference 58).
Impacts Land and Property Values—
Although it is difficult to generalize from the experience of other
wastewater treatment plants, land values have not historically decreased
as a result of project implementation (Reference 82). The proposed pro-
ject will upgrade the existing treatment plant, rather than introduce a
new plant; therefore, the impact on land values should not be signifi-
cant.
The main concerns voiced by local residents focus upon potential
odor problems of the alternatives. The degree to which each alternative
addresses the odor abatement for these situations will largely determine
the effect on land values, if any (Reference 54, 58). Under Phase I of
the facilities plan, which is not covered in this EIS, sludge digestion
and stabilization facilities are currently being designed to control the
existing odor problems. All of the alternatives may have the potential
to produce odor as discussed in the odor impacts section, with Alterna-
tives A, C and G being of greatest concern.
If land values can be affected by odor problems, Alternatives C and
G would have the greatest adverse effect. In contrast, Alternative D
would have the least effect. For a more detailed analysis, see the
impact section on Odor.
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The overall question of land values in the immediate and surrounding
areas will be affected by a recent ordinance passed by the City of
Boulder intended to effectively reduce population growth in the city
through limitation of residential building permits. Included in the
ordinance is a recommendation that the city work directly with the county
commissioners to extend this "growth-limiting" policy to the entire
Boulder Valley. In a market which has recently seen low vacancy rates
(Reference 57, 83), a slowdown in construction will produce higher market
values throughout the valley. Project implementation should cause no
significant net reduction in the value of surrounding property.
Property Tax Impacts—
Implementation of the proposed project will result in a net re-
duction of land from the tax rolls. For all of the alternatives
which use more land than is presently available, the City of Boulder
will purchase the necessary parcels from private individuals, thus making
this land tax exempt (Reference 84).
The exact land areas which will be purchased cannot be determined
until actual negotiations have been completed. Therefore, for the
purpose of this analysis, three assumptions have been made:
(1) That entire parcels will be purchased, not portions
thereof;
(2) That the improvements and personal property presently
on those parcels will be removed; and
(3) That a worst case will apply to Alternative G requiring
city purchase of all necessary land.
Table 17 presents the potential loss in assessed valuation (AV)
and the associated reduction in tax revenue. Boulder County Assessors'
Office 1976 assessments were used for the parcels involved and tax
rates for 1975 were applied (References 58, 85, 86). Some parcels
are not taxed by the North Colorado Water Conservation District Juris-
diction, therefore the AV reductions in that column are smaller than
the figures for the other jurisdictions.
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Table 17. POTENTIAL LOSSES IN ASSESSED VALUATION
AND TAX REVENUES TO AFFECTED JURISDICTIONS
Alternatives0
Assessed valuation of facility
sites in Tax Jurisdiction 0460a
Revenue loss In Tax Jurisdiction
0460 ($86.40 Total Mill Levy)
Assessed valuation in North
A B C
$23,200 $12,000 $16,550
2,004 1,036 1,430
9,760
D GQ
$12,000 $298,984
1,036 25,832
297,544
Colorado Water Conservation Dis-
trict (NCWCD), Tax Jurisdiction
0470b
Revenue loss to NCWCD ($1.00 10 - - 298
District Mill Levy)
Total Revenue Loss $2,014 $1,036 $1,430 $1,036 $26,130
"The assessed valuations for parcels not subject to taxation by this district have been
subtracted.
1975 Abstract of Assessment and Summary of Taxes, Boulder County, Colorado.
CBoulder County Assessor's Office. These figures reflect assessed valuations as of
November, 1976 of actual parcels under consideration.
Because the land for this alternative has not been selected, an average of $85.65/acre
assessed valuation was applied to the 3,360 acres required in the Facilities Plan.
The average is based on assessment figures for 3,154 acres in tracts 23 and 24 of
Township 1N40 and tracts 16-21 of Township 1N69 which include the other potential sites
and surrounding area.
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Although the revenue figures involved are less than one-tenth of
a percent of the total collected for each jurisdiction, a relative
comparison of the alternatives is possible. Alternative G represents
the largest potential dollar charge and Alternative A the second lar-
gest, corresponding with relative estimated capital costs. Alterna-
tive G, however, creates the third largest change in AV because it in-
volves purchase of some land at the 75th Street site. Alternatives B
and D both utilize existing city property and require land purchases
for the sludge-injection site only. These two alternatives represent
the smallest assessed valuation losses.
Employment Impacts—
The 75th Street plant currently employs twenty-two people. The
Pearl Street facility, which will be phased out, employs one person.
Below are the additional personnel requirements projected for each
alternative (Reference 58).
Alternative Additional Personnel Required
A One person
B Two to four people
C No new employment. However, the
city would like a county environ-
mental employee to transfer to the
facility.
D Two to four people
G No net new public employment.
However, additional private man-
power may be required by additional
farming activity. The city will
lease the land and not be directly
involved in the agricultural reuse
operation.
Net new employment would be relatively low and would probably have
a negligible effect on unemployment in the Boulder area.
Impacts Upon Loans, Bonds and Subsidies—
In 1974, the Boulder City Council expressed the objective not to
approve proposed capital projects requiring bonding (Reference 58).
Therefore it is assumed that the city will finance its share of con-
struction costs by other means. The Wastewater Utility Division of
the City of Boulder maintains a capital fund for required future ex-
penditures. Projected cash flow estimates as of December 2, 1976 in-
dicate that there will be a total of $2,462,000 available from this
fund to finance the city's share of the costs. This projection indicates
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that, by 1977, service charges will no longer be sufficient to cover
operating expenses. A rate increase will be considered. Modification
of the existing rate structure will be affected by the choice of alterna-
tive and the city's current ability to finance its portion from the
reserve fund (Reference 58). Based on the established 75 percent federal
participation, the City of Boulder is presently able to finance all
alternatives except G, which will require an additional $5.6 million in
capital for the first phase of construction and another $650,000 in
the second phase.
The facilities plan indicates that the State of Colorado may
participate in the financing of the project. Discussions with the
State indicate that funds are not now available for this purpose.
Consequently, State participation is not incorporated into this
analysis.
Impacts Upon Public and Social Services—
In the event of a major accident at the treatment plant site—
whether in the course of construction or during operation—the private
ambulance service would be augmented by the Fire Department's rescue
squad, the Emergency Preparedness Program, the community hospitals,
and other disaster response groups.
Despite the potentially large quantities of methane to be handled,
the likelihood of explosion during operation is small. This is due in
part to the advanced state of container tank and gas-collection system
design. Further, the gas is produced in anaerobic digester tanks where
no combustion can occur. If leakage should develop in the tanks, it
would result in outflow of methane rather than inflow of air, since
the gas pressure would be higher than the atmospheric pressure. Ad-
ditional safeguards are provided by flame traps to prevent the spread
of fire within the gas collection system after it leaves the digester
tanks (Reference 87).
Therefore, regardless of the alternative selected, operation of the
proposed project should not have any significant impact on local health
care facilities, given the present capability of the community health
service systems.
Public Health Impacts—
Provisions of sewerage systems and modern methods for sewage treat-
ment are aimed at the basic goal of public health protection. Health
hazards associated with sewage treatment, although greatly reduced by
processing and treatment, are always of concern. Several fungi present
in sewage are capable of causing disease in humans. Pathogens involving
bacteria, viruses and parasites, which are found in both sludge and
effluent, can be spread through air transmission, vectors, water, or
direct contact.
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The major bacterial diseases are satisfactorily controlled by the
secondary-treatment processes. Statements about viral health problems
must be more guarded because of the difficulty in detecting viruses
and the lack of standards for virus levels. In general, however, vi-
ruses are more short-lived than bacterial pathogens (References 88,
89). Intestinal parasites may also be present in various forms of
sludge. Parasites and their eggs or cysts are only partially destroy-
ed by traditional treatment processes. Other biological hazards as-
sociated with sludge are such disease-carrying vectors as flies, mos-
quitoes and rats.
The possibility of the contraction of disease through any of the
alternative sewage treatment methods is relatively low. Incidents of
disease contraction related to sewage treatment have been undocumented,
even for personnel working around municipal treatment works. Chlorination
of effluents, digestion of sludge and limited survival of pathogens in
soil are some of the factors that reduce the threat of pathogens to
humans. Nevertheless, some pathogens, even in very small numbers may
survive over long periods of time. Therefore, all systems which in-
corporate sludge and effluent recycling should consider potential public
health problems.
The potential for pathogen transmission would be greater under
Alternatives A, C and G because these alternatives allow the greatest
exposure of effluent to land and air. Of the three, Alternative C would
present potential health problems because public use of the site would
be allowed in the proposed park. Pathogens from blowing soil particulates
within the basins in Alternative A would be insignificant when the basins
become vegetated. However, in the history of treatment plant operations
in Boulder, no personnel have ever contracted diseases of sewage origin.
Alternatives B and D, which are basically enclosed systems, would present
the least chance of pathogen transmission.
Mitigation Measures to Reduce Public Health Hazards—
Pathogen transmission through the air and through surface runoff
waters and nitrate contamination of groundwaters are the main threats
to public health. They can be detected through continuous monitoring
of pathogen longevity and goundwater quality under the land applica-
tion sites. Mitigation measures for public health hazards could in-
clude :
1. Provision of special medical services for the employees
at the facility;
2. Restriction of public access to the site;
3. Maintenance of optimal digestion conditions in anaerobic
digesters;
4. Provision of special medical monitoring and preventive treatment
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to persons frequenting the site for taking delivery of sludge
loads.
Potential pollution of groundwater could pose a public health hazard
under several alternatives. The primary chemical constituent of concern
is nitrate. Nitrate levels over 45 ppm (measured as nitrate) in drinking
water are considered to be harmful to infants (Reference 91). As in-
dicated in the section on water quality, groundwater contamination would
require serious consideration under Alternatives A and G where wells are
used for domestic water supply.
Recreation Impacts—
Without the improvement of the existing wastewater treatment facili-
ties, effluent with excessive BOD,- and suspended solids would continue
to enter Boulder Creek. This would continue to degrade the creek near
75th Street and endanger its recreational resource value. The City of
Boulder in its 1975 and 1976 recommendations has strongly sought to
restore this resource.
Alternatives A through G would upgrade the water quality of Boulder
Creek through discharge of a higher quality effluent. Limitation of
BOD,- and suspended solids in the effluent would be a strong step toward
restoration of the warmwater fishery recreational potential below 75th
Street. However, the successful restoration of fisheries to these
stream segments depends not only upon improved water quality but upon
an improved stream habitat as well.
In terms of commitment of land resources, Alternatives A, C and G
require large parcels of land for wastewater treatment, with limited
or no recreational usage. The final polishing ponds in Alternative C
would be capable of supporting a warmwater fishery and may be open to
the public. The buffer zone around the pond areas and along Boulder
Creek may be suitable for wildlife observation. Application areas
within Alternatives A and G would probably have limited public access
because of the potential for exposure to secondary effluent. The
maintenance of these areas as wildlife refuges would probably also
preclude hunting of waterfowl and small mammals. The slight potential
for development of an odor problem, as discussed in the odor impact
section, under any of these alternatives would negatively affect the
local recreational potential.
Alternatives B and D, require little or no land commitment beyond
the existing treatment plant site.
A possible benefit from the implementation of the facilities plan is
the provision of a public recreation area along Boulder Creek immediately
above the 75th Street bridge. This area is relatively flat and affords
a good view of the creek. Small picnic facilities, fishing and look-
out areas would encourage public usage of the area. Fishing access is
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particularly important since Boulder Creek is surrounded typically by
private lands which limit public access.
Visual and Aesthetic Impacts—
Minor visual changes would accompany most of the alternatives. Two
alternatives, A and C, however, could visually influence a large area.
Alternatives B and D would generally increase the infra-structure
within the 75th Street treatment plant site and would not have any sig-
nificant effects on the existing visual and aesthetic setting.
Alternative A— As presented in the system layout in Figure 13
(Section III), the infiltration basins would be clustered within 225
acres on the Kolb property east of 75th Street. From 75th Street.
the panorama would be characterized by a series of low 4-ft berms en-
casing ponds of varying small acreages. Within the ponds would be thick
vegetation such as tall grass or sedge simulating to some degree a marsh
or sedge meadow area. The basins would be designed to integrate the
existing mature cottonwood trees. Basin operation would have a varying
8-12 day cycle where the basins would have water in them for 2-3 days.
The layout of the basins and the temporal change in water levels would
definitely present a conspicuous man-made feature to the landscape.
Viewed from the Heatherwoods and White Rocks area to the north, the
basins would also present a cluster of artifically-preduced pond areas.
Some persons may view the pond and tall grass system as variety to the
existing landscape while others may consider it incompatible.
Alternative C— The polishing ponds would be between Boulder Creek
and the Sawhill Ponds area. In comparison to the rough gravel pits in
the Sawhill Pond area, the polishing ponds would probably have a
"softer" appearance with ponds contoured around existing trees and
plantings. Although the polishing ponds would not have a natural wild-
life setting as in the riparian zone, it would still present a park-like
setting with open views and walkways. As the ponds would be behind the
treatment plant, they would be removed from sight of the nearest road
(75th Street). Viewed from the Gunbarrel area above Jay Road, the
polishing ponds would probably be similar to the Sawhill Ponds in per-
spective and provide relief from the gravel mining areas.
Mitigation Measures to Reduce Visual/Aesthetic Impacts—
Alternative A - Infiltration/Percolation Ponds—
1. The shape of the basins should be contoured so as to appear
more natural. Where possible, existing cottonwood trees should be re-
tained. While this would reduce the visual impact of straight and
abrupt edges, the basins would still exist as a conspicuous man-made
feature because of their water surface and clustered appearance.
2. The planting of vegetation in the basins would diminish the
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visual surface contrast when dry. Vegetation would not provide a sig-
nificant reduction in surface contrast when the basins were filled.
3. Cottonwoods and willows could be planted around the edges of the
basins to provide screening and variety.
Alternative C - Aeration/Polishing Ponds— The ponds would be con-
toured to harmonize with natural features where possible. Mitigation
measures would include retention of cottonwood trees where possible and
plantings to accent the pond areas. Buffer zones around the pond will
be allowed to grow native vegetation species that would also benefit
wildlife.
Alternative &— The storage lagoon for this alternative would re-
present the greatest change in the visual setting. Operation of the
lagoon would have the appearance of a large irrigation pond or diversion
storage reservoir. High-rate irrigation and growth of seasonal crops
would not present a change in visual and aesthetics greater than irri-
gated farmland.
Potential Impacts in Archaeological/Historical Resources—
There is always the possibility that subsurface or buried archaeo-
logical resources may be within a project area, especially when that
project area is adjacent to a stream or river where fluvial deposits
can quickly obscure a resource.
Construction and operation of the infiltration/percolation basins
would require the removal of some or all of the buildings on the Kolb
property. These buildings may be eligible for inclusion in the National
Register.
Mitigation Measures to Protect Archaeological/Historical Resources—
If any indicators of archaeological resources (artifacts, human
remains, concentrations of ash, charcoal, thermally-fractured rocks,
bones, etc.) are encountered during project activities, all work
should be halted within a 50-yard radius of the find. A qualified
archaeologist should be retained or the Office of the State Archaeolo-
gist should be contacted to ascertain the nature of the discovery and
recommend mitigation measures as necessary.
Archaeological resources encountered during project-related activ-
ities should be reported to the Office of the State Archaeologist.
This would put the responsibility for reporting archaeological re-
sources on the individuals concerned with completing project activi-
ties. If this is done, the construction workers and tractor operators
should be familiarized with indicators of archaeological resources.
This measure may be the most desirable considering that there is a low
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probability of any archaeological resources within those unexamined por-
tions of the survey area. Provision for recovery of archaeological
resources or measures to protect them would be part of the EPA grant
condition.
Should it be determined that the Kolb buildings need to be altered,
removed, or modified in any way because of the proposed project, they
should be examined by a qualified historic architect to determine if they
are in any way significant because of their architecture. The Baldwin
Report (Reference 45) would suggest that the structures are not signifi-
cant, and the project plans as proposed would not appear to create any
impacts on the buildings.
LONG-TERM INDIRECT IMPACTS
Long-term indirect impacts of the proposed action are those resulting
in new growth made possible by an expanded and improved wastewater
treatment facility. Modification of the treatment plant to provide advance
treatment meeting the upgraded effluent and stream standards would facili-
tate growth up to the limit of treatment capacity.
Based upon the 1974 Robinson Decision under the Colorado Supreme
Court, the City of Boulder must provide utility hook-ups to new construct-
ion developments within the county that are within the proximity of exist-
ing utility feeder lines. This implies a continued short-term impetus
for secondary growth until areas within the proximity of existing utility
lines are developed fully. For the remaining areas, the possibility of
continued land development and population expansion, especially in the
northern and eastern parts of the planning area, depends in part upon
the ability of the wastewater treatment facilities to handle these
additional waste flows. Hence, even though wastewater facilities may not
have a direct growth-inducement potential, they are nonetheless essential
for such growth. The potential future service area of such facilities
therefore necessarily becomes the scene of the secondary impacts described
below. In the following paragraphs, the secondary impacts of greatest
significance are discussed.
Soils
The construction of residential communities and the associated parks,
schools and other land uses necessarily consumes open space and, in most
cases, agricultural lands. Productive agricultural lands are a dwindling
resource in Boulder County as well as in Colorado. The main control on
conversion of agricultural lands are city and county zoning ordinances
and the development of a regional land-use plan. The Boulder Valley
Comprehensive Plan, which identifies the integrity of subcommunities and
tne preservation of open space t>y greenbelts and greenways, has taken
strong steps towards the conservation of agricultural soils.
Another secondary effect of the continued provision of sewer services
is the improvement of local soils and water tables by the discontinuance
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of septic systems. As identified in the environmental setting, se-
veral areas in Boulder County experience septic systems problems.
Orderly growth and provision of sewerage services to these outlying
areas would remove the public health hazard and soil degradation po-
tential of septic tanks and drain fields.
Water Quality
All alternatives will have similar potential for secondary water
quality impacts. Additional residential development in the Boulder
area will cause some pollution due to nonpoint sources of runoff. For
example, the runoff from streets and other paved areas will contain
pollutants. Erosion from graded hillside and valley areas that are
not stabilized by vegetation will cause sediment to be discharged into
the drainage network. Measures can be employed to reduce these ef-
fects through land use controls such as density and slope restrictions.
Generally, secondary impacts upon water quality will be amenable to
mitigation with proper design of the conveyance structures and treat-
ment of runoff. It is important that regulatory controls be estab-
lished, implemented and rigorously enforced so that the necessary
mitigative measures are actually designed and built into the develop-
ments that are permitted. The Areawide Water Quality Management Plan
(Reference 70) that has been recently completed for the Denver Metro-
politan area addresses these issues and offers a plan to accomplish
these needs
Biotic Communities
The construction and operation of a wastewater treatment facility
with nominal capacity of 17.6 mgd would make available an important
utility for future developments and subdivisions in the Boulder area.
Secondary effects resulting from the proposed action would be impacts
associated with development and human habitation of valley areas and
the potential for future development of open space areas.
Developments, such as land subdivision, generally involve the
division of large areas into small parcels, with open space and re-
creational sites interspersed among clustered homesites. Heatherwood,
Gunbarrel Greens and the Table Mesa area are examples of this type of
subdivisions are briefly described below.
1. Lands suitable for urban development are frequently areas of
agricultural potential with fertile, well-developed soils. Although
they may not currently be under agricultural use, these areas are
effectively removed from the agricultural land base by subdivision and
development. A further impact of subdivision involves the removal of
open space lands from the Boulder Valley.
2. Subdivision and development can lead to changes in the visual
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and aesthetic quality of the surrounding agricultural areas by the
creation of buildings and structures in former open and undisturbed areas.
The replacement of natural features by man-made structures causes a
general decrease in visual and aesthetic quality.
3. Soil erosion resulting from vegetation removal during road
construction, building site clearing and fire-control activities is a
major short-term impact of subdivision. This impact is compounded in
steeply sloping areas. Soil erosion may become a long-term effect in
the highly erodible areas which are graded and not stabilized.
4. Loss of wildlife habitat because of the reduction of food and
shelter available to wildlife as well as increased population density is
a long-term secondary impact.
5. Increased population density causes an increase in the potential
for accidental wildfires. In dry agricultural areas with a high fire
potential, wildfires are difficult to control and can result in the
destruction of human life and property as well as in the loss of
vegetation and wildlife. On the other hand, increased population
will result in higher priority being given to fire prevention and pro-
tection.
6. Sediments and fertilizer leachates can enter streams, particu-
larly where housing sites and park areas are located near watercourses.
Fertilizer and pesticide residues, such as nitrates and phosphates,
provide a nutrient source for algae and can lead to stream pollution.
7. Several areas along the Boulder Creek floodplain are important
vegetation and wildlife habitat areas. These habitats, discussed in the
Sensitive Environmental Areas section, include the White Rocks Natural
Area, Sawhill Ponds and Walden Ponds. Of these, the White Rocks Natural
Area represents the most fragile unit due to its unTque characteristics
and presence of several rare and endangered plant and animal species. All
of these environmentally sensitive areas are recognized in the City and d
County Master Plans and specifically reserved as permanent open-space
areas. However, the surrounding lands may be zoned agricultural, 'light'
industrial or even residential, depending upon the area. Thus, encroach-
ing human occupation or disturbance from human activities may have an
indirect effect upon sensitive vegetation and wildlife areas.
Even if sensitive environmental areas have been degraded, the absolute
effect on wildlife is not known. For example, if 20 percent of the White
Rocks buffer zone is used for human purposes, it is not clear that the
raptors or endangered fern species inhabiting the cliffs may be reduced
by 20 percent. The effect of the habitat loss may not become apparent
until a severe winter or exceptionally dry spring occurs. Even if the
raptors did decrease by 20 percent, it is not known if the birds have
actually died or migrated to new areas with a suitable habitat. However,
it may generally be stated that as sensitive areas are consumed or de-
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PROPOSED INFILTRATION/PERCOLATION PONDSITE
WITHIN PASTURE/AGRICULTURE UNIT
graded, greater pressure may result in a lowering of habitat quality in
adjacent areas. This trend is often difficult to assess and its
potential to occur should be recognized ,by the local planning agencies.
Air Quality
Air quality in the Boulder area at the present time is greatly in-
fluenced by traffic in the central area of the city. On days with stable
atmospheric conditions air pollution will generate to a point that ex-
ceeds the standards in this area. Throughout the remainder of the study
area, traffic is relatively freeflowing resulting in less congestion, less
emissions and better air quality. Carbon monoxide (CO) levels in excess
of the standards are normally unexpected. As winds pick up or frontal
activity takes place, pollutant levels, even in the central city, are
reduced with the standards being met through the area.
This trend is expected to continue through 1980 after which vehicle
emissions will result in a sharp decline in CO concentrations. Based on
information developed in the Denver area, the decline in CO levels should
be well established and the standards met by 1985.
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Oxidants such as ozone frequently exceed the standards in the Boulder
area. However, since these data are not available at this time, a photo-
chemical oxidant simulation model could not be used. These high ozone
levels are expected to continue as long as the source pollutant (reactive
hydrocarbons) are emitted into the air. As EPA emission controls reduce
vehicle emissions, ozone levels will be reduced similar to CO. However,
there are sufficient reactive hydrocarbons naturally emitted into the air
that the ozone standards may be exceeded in the future.
Resources
The secondary effects caused by increased population growth in
the area accommodated by the improved treatment facilities implicitly
involve the gradual loss or deterioration of the following resources:
1. Soils eroded from construction sites;
2. Wildlife habitats altered by the presence of residences and
commercial activities;
3. The aesthetic quality of the valley and mesa areas marred by
structures built for residences and other activities;
4. Use of fossil fuels and other non-renewable resources in the
development and maintenance of new communities; and
5. The quality of rural life in the outlying areas gradually
changing toward an urban condition with its associated problems.
Socio-Economic Conditions
Growth-inducing impacts are secondary effects of a project which
either (1) lead directly to growth, such as by attracting a large work
force to an area, or (2) remove an obstacle to growth, such as construct-
ion of a highway which provides physical access for development.
The proposed project will employ 70 to 100 people during the con-
struction. It will further create indirect local employment through
project spending depending on the alternative selected and the propor-
tion of construction materials purchased locally. With current unem-
ployment in excess of 45,000 in the Denver-Boulder area, the proposed
project should have a beneficial impact in reducing unemployment.
Wastewater flow capacity for the 20-year project planning period
was determined from the service area population projections used by the
Denver Regional Council of Governments (DRCOG) for the ongoing Water
Quality Management Plan. The City of Boulder is attempting to limit
growth within the city through a building permits limitation (see sec-
tion on Population Setting). Sizing the improvements to the Boulder
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wastewater facility to handle a specified flow volume could set the
capacity of the plant to an arbitrary level.
For several of the alternatives, the limiting factors are the
primary and secondary clarifiers in the treatment process. Present
nominal plant capacity is 15.6 mgd. With modifications to the clari-
fiers, plant efficiency would be ensured, and the capacity could be
increased to 17.6 mgd. This capacity would be adequate to handle the
1995-2000 DRCOG projections. The additional treatment facilities pro-
posed under each alternative are also sized to handle this capacity.
As discussed in Section III, the majority of the alternative systems
could be phased or reduced in size to accommodate only planned growth.
Reduction in treatment plant capacity could imply that sewer connec-
tions may become limited in the Boulder area by the year 2000. This
may severely limit growth within the City of Boulder. However, growth
within areas under county jurisdiction may continue independently of
this project.
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SECTION V
-------
SECTION V
UNAVOIDABLE ADVERSE IMPACTS
Environmental impacts and feasible measures to mitigate or
eliminate adverse effects of each alternative were presented in
Section IV. Those impacts which cannot be avoided, even with the im-
plementation of mitigation measures are presented in Table 18. Al-
ternatives A and C have many similar types of impacts as systems
utilize shallow ponds in the vicinity of the 75th Street treatment
plant. Alternative G would have the most significant impacts of all
the proposed systems.
ALTERNATIVE PLANS
Alternative A - Infiltration/Percolation Basins
Construction and operation of this land-treatment system would
depress the groundwater table to approximately 5 ft below the site
surface. Groundwater would also be drawn down 3 to 5 ft in a 200-
to 300-ft "shadow" zone east of the site. Pastureland within this
shadow zone would lose the natural subirrigation and suffer adverse
effects. Domestic wells within this shadow zone would be drawn down
as much as 5 ft below ground surface. In the event that wastewater
bypasses the system underdrains under certain conditions, groundwater
quality may be degraded.
Pond operation during the winter could generate localized steam
fogs that may be a nuisance to motorists and nearby residences.
Aerosol generation during windy periods is also a possibility. Odor
potential is generally low, but may be significant if a pond becomes
clogged and anaerobic conditions arise. Nitrate levels in the effluent
will not be significantly reduced by this land treatment system.
The existing pastureland habitat will be altered to a contin-
uously changing wet and dry condition with attendant vegetation and
wildlife shifts. The site occurs within the county-designated White
Rocks Natural Area and the project may effect changes in the local
ecology.
Public acceptance of this alternative varies widely. The system
could perform effectively with low energy and capital requirements.
However, many local residences are concerned about the odor genera-
tion potential and side-effects of groundwater drawdown. The proximity
of the ponds system immediately south of a major housing development
will be visually prominent and incompatible with community desires.
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Table 18. ENVIRONMENTAL SUMMARY OF UNAVOIDABLE ADVERSE
IMPACTS OF PROJECT ALTERNATIVES
00 01
*rj 4J
3 rH
3«
00
c
o
Cu
01
o
01
pa
01
00 0)
3 rH
rH -H
W PL<
•O 00
o> e
c
o
•H
01
JJ
eg
I
5
I
Soil stability and erosion hazards
Changes in groundwater quality/quantity
Surface water quality (ditches etc.)
Local air quality/climate
Vegetation and wildlife habitats
Wildlife patterns
Odor generation potential
Impact on land and property values
Loss in property tax revenues
Increase in municipal service costs
Consumptive use of energy
Impact on recreation facilities
Impact upon aesthetic qualities
Public health concerns
Community acceptance
Degree of Impact: ^B Major impact
/"^ Moderate impact
0
3
0
3
3
3
3
3
0
3
3
0
0
0
3
O
o
o
o
o
o
0
0
0
3
•
O
0
O
0
0
3
0
3
0
0
3
3
0
0
3
0
0
0
3
O
O
O
O
O
O
0
0
0
3
•
O
0
O
0
0
0
3
3
0
0
3
•
•
•
•
O
0
0
3
( ) Minor impact
O *
138
impact
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Alternatives B and D - Activated Sludge Systems
Adverse impacts associated with these two alternatives are sim-
ilar and addressed together in this section. The most significant
impact associated with this alternative will be the large expenditure
of gas and electricity to run the activated-sludge system. System D
will consume 2 to 5 times more energy than the other alternatives.
Gas consumption can be reduced by recycling methane gas generated by
the digestors, but nevertheless, energy and resource use will still
be significant. In terms of treatment efficiency and reliability,
alternative system D would be more energy-intensive and methane gas
reclamation would be lower than Alternative B. Capital costs for
these systems would be 15-30 percent higher than the land-treatment
systems.
Alternative C - Aeration/Polishing Ponds
The major unavoidable impact associated with this system is the
potential for algal growth in the ponds and subsequent odor problems.
Due to the large air/water interface, winter occurrences of steam fog
from the ponds would become a nuisance to local residences and motor-
ists.
The polishing ponds would also be incompatible with Boulder
County reclamation plans for the Walden Ponds Wildlife Habitat Area
and would require a special use permit from the county.
As with Alternative A, public acceptance of a ponds system in
the vicinity of 75th Street treatment plant is variable. The greatest
concern is the odor potential and aesthetic impacts for the residences
adjacent to the site. Due to these large housing developments down-
wind, any odor production would probably be incompatible with commun-
ity interests.
Alternative G - High-rate Irrigation
The major impact of this system is the high capital expenditure
required to purchase the 3360 acres for facilities and irrigation.
This would be 3 to 4 times greater than the other alternatives.
Construction and operation of a storage reservoir would commit
350 acres of farmland. The reservoir would experience significant
algal blooms and attendant odor problems. Steam fog generation in
the winter would also be significant. However, the location of the
reservoir in a rural area would tend to make these effects less
noticeable.
High-rate irrigation of crops would require intensive management.
Excess hydraulic loadings can lead to surface water runoff and pollu-
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tion, as well as salt accumulations in soils. Pumping of effluent to
the storage reservoir and later to the irrigation sites, would require
twice as much energy use compared to Alternatives B or D.
Public acceptance for this plan would be mixed. While wastewater
could effectively be recycled with this system, massive land purchases
would essentially put the city into the farming business and reduce
individual farm ownership. A new and complex administration would
be required to handle purchases, water rights, leasing and other
activities related to system operations.
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SECTION VI
-------
SECTION VI
IRREVERSIBLE AND IRRETRIEVABLE RESOURCE COMMITMENTS
The creation and construction of an advanced wastewater treatment
system for the Boulder Wastewater Facilities Planning Area will impose
on future generations the necessity for a strong commitment to the
maintenance, potential expansion and continuation of the wastewater
management systems now being developed. The selection of future al-
ternatives for wastewater collection, treatment and disposal will,
to a large extent, be limited by implementation of the selected plan.
Four major commitments of resources have been identified with the
implementation of a wastewater treatment facilities plan. The extent
of resource commitments varies among the alternatives considered and
is discussed below.
IRRETRIEVABLE LOSS OF WILDLIFE HABITAT
Alteration and loss of wildlife habitat will be least for the con-
struction of an additional activated sludge unit (Alternatives B and
D) and greatest for the high-rate irrigation system proposed under
Alternative G.
The land application alternatives will effect great changes in
wildlife habitat. Alternatives A and C both involve pond systems
that will be significantly different from the former habitat. The
loss of pasture habitat will be traded for an increase to aquatic and
semi-aquatic habitat. There is already much aquatic habitat in the
adjacent Walden and Sawhill Ponds. Under Alternative G, the 350
acres required for the storage lagoon will permanently remove that
area from the natural environment. The impacts of spray irrigation of
wastewater on vegetation are discussed in Section IV. Short-term
vegetation changes are largely reversible. However, the long-term
practice of wastewater irrigation could physically, as well as
functionally, change the composition of the local biotic community.
The secondary impacts of all alternatives include increased pop-
ulation growth and its resultant effects upon the environment.
Development of outlying areas would lead to physical habitat degrada-
tion such as erosion and functional deterioration of habitats due to
barrier construction, excessive noise, alterations in predator-prey
relationships, vegetation changes and human presence.
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IRREVERSIBLE DESTRUCTION OF SOIL PROFILE
Destruction of the soil profile on 350 acres of land at the site
of the proposed storage lagoon under Alternative G is irreversible.
These areas would be forever altered as agricultural areas.
IRREVERSIBLE AND IRRETRIEVABLE ENERGY AND
ECONOMIC RESOURCE COMMITMENT
Alternatives B and D are the most energy-intensive with the opera-
tion of a pure-oxygen activated sludge treatment unit. The land treat-
ment alternatives are the least energy-intensive; of these, Alternative
G requires the most energy, requiring sewage to be pumped several miles
to a storage lagoon at a higher elevation. This alternative will re-
quire increasing amounts of energy as population, and thus sewage
volume, increases.
Any wastewater treatment system requires a commitment of energy
resources for operation. Electricity would be used to power equip-
ment and, in some plants, generate gases for wastewater disinfection.
This commitment is permanent for energy expended. However, if a dollar
value could be placed upon the improved stream water quality, such
commitment of resources would be easily viewed as, at least in part,
transferable.
The proposed project will require permanent commitments of con-
struction materials and a 1 1/2 year commitment of construction workers
for a combined value of $8 - $12 million under Alternatives A through
D and $34 million under Alternative G. The materials would consist
of concrete, steel, fabricated machinery, electrical components, wood
forms, framing and pipe. The supply of these materials is not known
to be critically short, and their purchase and use would be beneficial
to the regional and national economies.
The employment of construction workers for the regional facility
would draw on a large labor pool at a time of high national unemploy-
ment in the construction trades. It cannot be predicted from where the
workers might come, but their employment would be of national and
state benefit, and they would reinvest some portion of their earnings
in the City and County of Boulder.
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SECTION VII
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SECTION VII
RELATIONSHIP BETWEEN SHORT-TERM USES OF THE
HUMAN ENVIRONMENT AND THE MAINTENANCE AND
ENHANCEMENT OF LONG-TERM PRODUCTIVITY
The mechanical and land treatment systems proposed in the
Boulder Wastewater Facilities Plan will probably have a duration of
20 or more years. This is a rather long period of time, given the
rapidity of change in today's technology. Nevertheless, fair
and important questions to ask are: What might be the implications
of the project for the next few hundred years? What are the total
benefits? What are the potential long-term damages that may
occur to the specific sites? What would be the net effect upon the
environment?
The three land treatment alternatives (A, C and G) would
probably require the most in-depth evaluation with the broadest
perspective. All of the proposed alternatives incorporate various
advanced wastewater treatment methods that will produce a high
quality effluent deemed consistent with the long-term interests of
environmental preservation. However, these solutions that seem
efficient for long-term productivity at this time might not
be viewed as such by the year 2000. There will be progressively
improved technology and, perhaps, breakthroughs that could alter
our whole perspective of wastewater management. Several considerations
regarding productivity of the existing and future environment are
discussed below.
ENHANCEMENT OF SOIL PRODUCTIVITY
Recycling of wastewater under Alternative G represents an initial
step toward the conservation of non-renewable and renewable resources.
In the long term, the recycling of nutrients to the soil represents
a forward-looking step for a society that will have to recognize
the finite limitations of its natural resources. At present, the
bulk of our commercial fertilizers is produced from fossil fuels,
particularly natural gas and, to some extent, coal.
At present, the primary source of phosphorus fertilizer is
deposits of phosphate that are extremely limited. Because phosphates
in wastewater are concentrated in sludge as a result of the treatment
process, land recycling can be an important long-term mechanism for
reuse of this element, providing soils with one of the macronutrients
essential for crop production.
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POTENTIAL CUMULATIVE LONG-TERM ENVIRONMENTAL DAMAGE
A long-term view of land application of effluent must include po-
tential harmful effects. Because wastewater contains elements that
may be toxic or harmful if accumulated in significant quantities, the
potential exists for some long-term damage to the productivity of
that soil for growing crops.
An undesirable aspect of high-rate irrigation with effluents is
the addition of salts to the soil profile. Over long periods of time,
salts can have an inhibitory effect on plant growth. This problem is
not confined to the Boulder operation but is common to all irrigated
agriculture. Increased salinity of soils has an extremely 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 requirement for flushing
these salts below the root zone. This is accomplished through
application of additional irrigation water which commonly is sub-
sequently collected in subsurface drains.
The chief measure for avoiding the detrimental long-term effects
of soil salinization is control of wastewater application to levels
considered safe for that type of soil and land use. Recommended safe
levels are still somewhat tentative; any long-term assessment of this
project must recognize that some effects may occur in a manner
different from that stated here. However, an on-going monitoring
program and assessment of effects will provide the basis for any
changes necessary during the project life.
THE LONG-TERM ENVIRONMENTAL PERSPECTIVE
None of the alternatives considered here can be viewed strictly
as a short-term use of the human environment. Any unmitigated adverse
impact of an action, no matter how small, will be incorporated into
the ecosystem and may be magnified over time. Thus, it is necessary
to view the utilization of stream and/or land as receiving media not
in terms of short-term use of the human environment, but in its true
perspective. An immediate consequence of such a view is that there
must be minimal conflict between effluent disposal practices and en-
vironmental productivity.
The Boulder Valley Comprehensive Plan, the Areawide 208 Water
Quality Management Plan and the 1972 Water Pollution Control Act Amend-
ments all incorporate a serious analysis of long-term water quality and
environmental goals. The primary goal to restore Boulder Creek to its
original high quality stream environment is a short-term goal with
potential long-term benefits. Restrictive limits on treatment plant
effluent discharge quality and receiving water quality have been set
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URBAN GROWTH ALONG BOULDER SKYLINE
for this purpose. Implementation of treatment and control measures at
the present time requires considerable capital investment to effect an
immediate improvement in the stream environment. Maintenance of these
immediate short-term improvements into long-term enhancement and pro-
ductivity require careful future area-wide planning to ensure compati-
ble land uses.
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146
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SECTION VIII
-------
SECTION VIII
COMMENTS ON THE DRAFT ENVIRONMENTAL
IMPACT STATEMENT AND RESPONSES
PUBLIC HEARING
The Environmental Protection Agency held a public hearing on
the Boulder Wastewater Treatment Facilities Draft Environmental Im-
pact Statement on October 3, 1977 at the Boulder City Council Cham-
bers in Boulder, Colorado. The hearing was attended by approximately
15 people of which seven presented testimony for the record on the
EIS. Because of the length of the official hearing record and the
printing costs involved, it is not reproduced here. The document is
available for public review at the City of Boulder Wastewater Utili-
ties and at the EPA Region VIII Office in Denver, Colorado.
A brief summarization of the major concerns voiced at the hear-
ing are presented below:
1. Mr. Phil Stern, a Boulder resident (parts of his presenta-
tion were endorsed by PLAN-BOULDER and P.U.R.E.), expressed his con-
cerns about flood-proofing of the present 75th Street plant, inade-
quate descriptions of flood hazards in the EIS and the ability of
the project to meet President Carter's Executive Order 11988 - "Flood
Plain Management" and Governor Lamm's Executive Order - "Evaluation
of Flood Hazard in locating state buildings, roads and other Facili-
ties and in reviewing and approving Sewage and Water Facilities and
Subdivisions". Mr. Stern pointed out that the EIS needed an in-depth
discussion of the ability of each alternative to meet the A2 stream
standards. Land treatment costs, as developed by the facilities
planner, did not appear to be accurate for some alternatives based
on previous Deports, and should actually be the most economical. He
also questioned the sludge generation rates and consequent high dis-
posal rates that could lead to sludge dumping rather than beneficial
reuse. Mr. Stern concluded by endorsing the Alternative C lagoon
system.
2. Mrs. Martha Weiser, a Boulder County resident, called for
a more accurate description and definition of the White Rocks Natural
Area in the EIS and read the legal description in the recently rev-
ised Boulder Valley Comprehensive Plan along with the definition of
"environmental preservation" in the plan. Mrs. Weiser opposes Alter-
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natives A and C for environmental reasons and supports Alternative B.
She questioned the sludge injection method and expressed difficulty
in comprehending Appendix F in the EIS on effects of sludge applic-
tion. A letter was presented from the District 6 Water Users (Feb-
ruary 22, 1977), stating their opposition to sludge injection for
reasons of: 1) water quality degradation; 2) health hazards associ-
ated with pathogens in sludge; and 3) potential changes in ground-
water flow patterns and volumes from the sludge injection practice.
Mrs. Weiser emphasized the potential long-term effects of sludge in-
jection and questioned some of the City of Boulder's statements. She
suggested a compromise solution to the sludge injection problem:
wherein, sludge injection could be allowed on the existing city-owned
property for a short-term (3-5 years) to test impacts before making
it into a full-scale project. Mrs. Weiser concluded by clarifying
her opposition to Alternative C due to potential odor problems, pro-
blems with the county wildlife refuge area and inconsistency of the
project with adjacent land uses such as the Celebrity Homes north of
Jay Road.
3. Ms. Nancy Sheffield, a representative of the City of Boulder,
stated the position voted on by the Boulder City Council to: 1) adopt
Alternative B - activated sludge nitrification and explore methane
recovery to reduce the greater energy costs associated with this al-
ternative; and 2) to support the sludge injection proposal.
4. Mr. A. W. Nelson, a Boulder County resident, questioned the
effects of sludge injection on the local groundwater and property
values; as well as right-of-way restrictions and proximity to his pro-
perty. Mr. Nelson stated that his home on the east side of 71st
Street has not been affected by odor problems from the 75th Street
treatment plant. He concluded by restating his concerns for ground-
water contamination and the need to know more about groundwater flow
patterns prior to sludge injection.
5. Mr. James R. Williams, a Boulder County resident, lodged a
strong complaint against the location of the existing treatment faci-
lities and the associated odor problems. He suggested that any
treatment facilities should be located farther east and be isolated
from homes and people. Based on the past performance of the 75th
Street plant, Mr. Williams questioned the reliability of any new fa-
cilities on the same site and the credibility of the City's claim
that they could control the odor problem. He concluded by restating
Mr. Nelson's concerns about groundwater contamination and its effects
on local wells and their users.
6. Ms. Shelly Murphy, a representative of the League of Women
Voters of Boulder, expressed concerns about Alternative B regarding:
1) ineffectiveness at removing nitrate-nitrogen down to 1 mg/1; 2)
energy consumption that would be twice as much as Alternatives A or
C; and 3) higher capital and annual costs than Alternatives A or C.
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Ms. Murphy questioned the appropriateness of funding an expensive ter-
tiary treatment facility at Boulder when many communities in Colorado
still need funds to upgrade their facilities to the secondary treat-
ment level. She stated that the odor discussion was unclear for the
various alternatives and that they should be compared against odor
potential from reclaimed gravel pits as well. The wildlife poten-
tial between the proposed project and Walden Ponds also needed clari-
fication. In conclusion, Ms. Murphy, on behalf of the League of
Women Voters urged the Environmental Protection Agency to fund Alter-
native C as the best choice for Boulder's future wastewater facili-
ties.
7- Mr. Keith Bell, a Boulder resident, stated that he supported
Alternative B and brought up two points regarding treatment alterna-
tives: 1) more attention was needed on potential groundwater problems
with Alternatives A and C relating to bedrock geology; and 2) more
concise comments were needed on the odor potential of Alternative C
with a reference to Chapter 9 of the facilities plan. Mr. Bell also
related, in his experience as a sanitary engineer, icing problems
in aerated lagoons that had damaged aeration equipment and disrupted
treatment systems for weeks at a time. He suggested an analysis for
this type of problem should also be included in the EIS.
The Environmental Protection Agency Region X wishes to express
its appreciation to all commenting agencies, groups and individuals
for the time and effort spent in reviewing the draft EIS. Issues
raised at the public hearing have been readdressed in the final EIS.
All comments were presented to the Regional Administrator and were
considered by him in EPA's decision making process.
LETTERS OF COMMENT
This section contains letters of comment from individuals and
groups to the Boulder Wastewater Facilities Plan Draft EIS. Where-
ever a response is required of EPA to the letter, a response page
follows that letter.
Table 19 presents a listing of the comment letter received dur-
ing the 45-day review period, the page in this section in which the
letters appear, and a general category listing of their contents.
Comment categories are shown in an attempt to indicate those aspects
of the proposed action about which the commentors were most inter-
ested and concerned.
149
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Ul
o
Table 19. COMMENTS RECEIVED,
BOULDER WASTEWATER FACILITIES
PLAN — DRAFT EIS
1977
Date
9/24
9/28
9/29
10/3
-J~\J / -J
10/4
10/8
No
Date
10/12
10/19
10/24
10/25
From
Denver Regional Council
of Governments
Department of Housing
and Urban Development
Boulder County Planning
Department
Roeer Fell
United States Department
of Interior
Mr. /Mrs. A. W. Nelson
Mrs. Martha Weiser
Colorado Department
of Highways
Office of the State
Archaeologist
Colorado Department
of Health
Department of the Army
Corps of Engineers
EIS
Page
No.
151
152
161
164
175
181
184
195
197
199
203
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// ^ DENVER REGIONAL COUNCIL OF GOVERNMENTS
1776 SOUTH JACKSON STREET . DENVER. COLORADO SO21O . 738-3186
f
September 24, 1977
John A. Green
Regional Administrator
United States Environmental Protection Agency
1860 Lincoln Streeet
Denver, Colorado 80203
Re: EIS/021-77, Boulder Waste water Treatment Facilities - Draft EIS
Dear Mr. Green:
In accordance with Office of Management and Budget Circular A-9 5
procedures, the Denver Regional Council of Governments' staff has
reviewed the above captioned project and offers the following comments:
The Denver 208 Plan, as prepared by the DRCOG, calls for upgrading
and expansion of the Boulder Wastewater Treatment Plant between 1977
and 1980 and again in 1986 to 1990. The Draft EIS appears to adequately
address the environmental impacts for a number of alternative methods
for plant expansion and upgrading.
The Council of Governments appreciates this opportunity to be of service
to you.
Sincerely,
Robert D. Farley
Executive Director
RDF/bJs
Richard Brown, Colorado State Division of Planning
The Hon. Robert G. Trenka, Councilman, Boulder COG Representative
OON 01 0«CKt» n I JAMKI J NOI_>N * r, C*a,~mM WILLIAM TMOMMTO
EXECUTIVE COMMITTEE
-OMH • MU«*"IT' CMAWLH A "irrl" WH.L.IAI. H UCMICHOLY J» •OIIBT
151
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DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT
REGIONAL OFFICE
EXECUTIVE TOWER • 1405 CURTIS STREET
DENVER, COLORADO 80202
September 28, 1977
REGION VIII IN REPLY REFER TO:
8DE
Mr. Alan Merson
Regional Administrator
Environmental Protection Agency
1860 Lincoln Street
Denver, Colorado 80203
Dear Mr. Merson:
We have reviewed a copy of the Draft Environmental Impact Statement (EIS)
dated August 1977, prepared by the U.S. Environmental Protection Agency
(EPA) on the city of Boulder's proposed project for expansion and
additions to the city's waste water treatment facilities.
We have determined from this draft EIS that expansions and additions
must be made to the city of Boulder's waste water treatment facilities.
Your justification for this expansion and addition to the present
system has been necessitated by projected population increases and the
desire of the local population to upgrade Boulder Creek. However, the
Draft EIS does not include the fact that this proposed project will
stimulate growth. This impact of growth should be addressed. Additionally,
we feel it would be appropriate to .include the justification for upgrading "
Boulder Creek so that it will support cold water fish. This discussion
should include increased benefits (recreational or other) which will
occur with this stream upgrading. The adverse impact to downstream water
users of encouraging phreatophytes (cottonwoods) to continue along this
stream should also be discussed.
We feel that the following items should be clarified in the Final EIS:
1. Your planning area boundary, first mentioned on page 3 of the
draft EIS, does not agree with the service area described in
your Regional EIS (Denver Regional Environmental Impact
Statement for Wastewater Facilities and the Clean Water Program,
June 1977). Specifically, the Gun Barrel Area has been
overlooked.
2. On page 66 you dismissed repair to the sewer lines as too
costly to reduce infiltration and eliminate the need for
enlargement to the treatment plant. However, no estimates
of cost are included to form the basis of this statement.
Insuring Offices
Casper, Wyoming- Denver, Colorado- Fargo, North Dakota • Helena, Montana- Salt Lake City, Utah-Sioux Falls South Dakota
152
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3. On page 33 of the draft EIS you state that "A definite flood
hazard exists at Boulder, and includes a portion of Central
Boulder, residential and commercial areas of Arapahoe Road..." _
Please clarify whether this proposal will allow or support ©
incompatible development within these known flood hazard areas.
Also, describe how you have complied with the requirements of
Executive Order 11988, Section 2-(2)(3)(4) regarding floodplain
management.
4. On page 56 you mentioned doing a "literature search and field
reconnaissance for historical structures." It is recommended O
that the State Historic Preservation Officer (SHPO) be contacted
concerning this project. We understand that the SHPO has the
most current information available.
5. On pages 14, 15 and 16 a discussion of capital costs is
presented, using 1995 population, salvage values for the year
2000, and a discount factor for 30 years. Shouldn't all
figures have the same base year?
6. On page 63 you mention that the Betasso Plant is "expected to
be increased by 20 mgd by the Spring of 1977." Since this
date has passed, the current status should be included.
Thank you for the opportunity to provide these comments.
Sincerely,
Robert J. Matusenek
Assistant Regional Administrator
Community Planning and Development
153
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Response to Department of Housing and Urban Development,
letter of 28 September 1977:
1. Based on estimates of projected population and flow in
Section III, Table 9 of the EIS, the Boulder Wastewater
treatment plant served 92,200 persons with an average
flow of 12.5 mgd in 1975. Assuming that all future growth
would generate wastewater at the rate of 120 gpcd and that
the nominal capacity of the plant - without any changes - is
15.6 mgd, then the remaining average capacity of 3.1 mgd
would support an additional 25,800 persons or roughly 10
percent lower than the 2000 projection of 130,000 by DRCOG.
It should be kept in mind that the year 2000 projections
were developed by DRCOG accounting for many complex exo-
genous and endogenous growth factors in the Boulder plan-
ning area. The design flows for the proposed project would
accommodate DRCOG population projections and would not
necessarily have a stimulatory effect. The contention that
this or any other single service can function as a stimu-
lant to unbridled growth, ignores the realities of the
growth-regulating, decision-making processes operating in
Boulder.
2. Upgrading of the Boulder Creek Stream classification was
approved in January 1977 by the Colorado Water Quality
Control Commission. The new A2 stream classification was
promulgated by the strong desire of many interest groups
in Boulder and their written and spoken testimony is re-
corded in the Boulder Wastewater Facilities Plan and Public
Participation Records. There appears to be some confusion
in your statement referring to a cold water fishery. Class
A2 is a warm water fishery with primary contact recreation.
The new Stream classification had legal status prior to
the Draft EIS and thus discussion of its justification was
not considered relevant. Recreational effects of the pro-
ject are discussed in the Environmental Impacts Section.
Encouragement of phreatophytes (cottonwoods) downstream
of the treatment plant would not be considered to change
significantly from the present conditions and processes.
3. The planning area boundary in the EIS and the facilities
plan has been officially designated as the 201 planning
area for the DRCOG Water Quality Management Plan. Your
reference to Figure IV-B in the Denver Regional EIS for
Wastewater Facilities and the Clean Water Program.
154
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Responses to Department of Housing and Urban Development
Page Two
is for "Future Service Areas". These are recommended
service areas, many of which are not officially recog-
nized. Also, "Service Areas" as discussed in the Re-
gional EIS, refers to areas that may be considered for
utility, public and social services, and does not speci-
fically imply sewer services throughout.
4. Based on the report "Infiltration/Inflow Analysis, Sani-
tary Sewer System - Boulder, Colorado" (EIS, Reference
67), the following 1975 present worth values were made:
1) Treatment of I/I with existing treatment
Plant: $21,873,700
2) Improvement of sewerage system to remove
I/I: $22,033,900
Although these figures are no longer current, neverthe-
less, by comparison, it can be seen that continuation of
the present sewerage system is less costly than removal
of I/I.
5. Development accommodated by the proposed project, such
as structures and roads, would be subject to Boulder
Valley Comprehensive Plan. Types of compatible, as well
as incompatible development, would be controlled by the
local planning authorities.
A copy of Executive Order 11988 is included at the end
of this response. In the planning stage of the facili-
ties plan, the general public and interest groups were
notified of the project and its location in the flood
plain. This was prior to Executive Order 11988, but in
essence, fulfills Section 2(2). For all alternatives,
except alternative G, location in the flood plan was
most cost-effective as well as essential for treatment
effectiveness.
The Boulder Wastewater Facilities Plan and the Draft
EIS were both submitted to the State Division of Plan-
ning which serves as the state and areawide A-95 clear-
inghouse. Both reports identified project locations in
the flood plain and design considerations to withstand
the "base flood". The facilities plan also identified
the alternative project locations and the rationale for
their selection. This in essence, fulfills Section 2(3)
of Executive Order 11988.
155
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Responses to Department of Housing and Urban Development letter
(28 September 1977)
Page Three
Section 2(4) of the Executive Order relates to appropri-
ate planning, regulations and procedures by agencies to
effect flood plain management. The Boulder Valley Com-
prehensive Plan and other related policies of Boulder
City and County have identified flood plain areas and ap-
propriate land use designations and regulations. All ex-
isting buildings and proposed structures at the 75th Street
treatment plant have or will be designed to meet the 100-
year flood conditions. In addition, design of structures
to withstand 100-year flood conditions is requisite for
EPA grant conditions and federal flood insurance programs.
6. The SHPO has been contacted regarding this project and an
archaeologist's report has been submitted to them. The
comment letter from the SHPO appears in this section of
the EIS.
7. Project cost figures on pages 14, 15 and 16, are based
on the February 1977 supplement to the Boulder Wastewater
Facilities Plan (EIS, Reference 5). These costs were re-
vised for the 2000 population and salvage values were es-
timated for the year 2000. The facilities planner chose
a 30-year period to calculate capital recovery costs, as
this was the estimated useful life of the facilities. The
present worth values for several of the alternatives would
change slightly if the capital costs were discounted over
20 years. In the cost comparison of alternatives, project
costs are considered accurate within 10 percent. Thus,
ranking of alternatives would remain at roughly the same
level.
8. The Betasso Plant was increased from 28 mgd to 48 mgd in
1977, and has been revised in the final EIS.
156
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FOR IMMEDIATE RELEASE ^y 24, 1977
Office of the White House Press Secretary
THE WHITE HOUSE
EXECUTIVE ORDER -
FLOODPLAIN MANAGEMENT
By virtue of the authority vested In me by the
Constitution and statutes of the United States of-America,
and as President of the Unl ^d States of America, In
furtherance of the National Environmental Policy Act of
1969, as amended C*2 U.S.C. 14321 e£ seq.) the National
Flood Insurance Act of 1968, as amended (42 U.S.C. 4001
et seq.). and the Flood Disaster Protection Act of 1973
TTubTTc Law 93-231, 87 Stat. 975), in order to avoid to
the extent possible the long and short term adverse impacts
associated with the occupancy and modification of flood-
plains and to avoid direct or Indirect support of floodplain
development wherever there is a practicable alternative, It
Is hereby ordered as follows:
Section 1. Each agency shall provide leadership and
shall take action to reduce the risk of flood loss, to
minimize the impact of floods on human safety, health
and welfare, and to restore and preserve the natural and
beneficial values served by floodplalns in carrying out its
responsibilities for (1) acquiring, managing, and disposing
of Federal lands and facilities; (2) providing Federally
undertaken, financed, or assisted construction and improve-
ments; and (3) conducting Federal activities and programs
affecting land use, including but not limited to water and
related land resources planning, regulating, and licensing
activities.
Sec. 2. In carrying out the activities described in
Section 1 of this Order, each agency has a. responsibility to
evaluate the potential effects of any actions it may take in
a floodplain; to ensure that its planning programs and
budget requests reflect consideration of flood hazards and
floodplain management; and to prescribe procedures to
Implement the policies and requirements of this Order,
as follows:
(a)(l) Before taking an action, each agency shall
determine whether the proposed action will occur in a
floodplain — for major Federal actions significantly
affecting the quality of the human environment, the
evaluation required below will be included in any statement
prepared under Section 102(2)(C) of the National Environ-
mental Policy Act. This determination shall be made
according to a Department of Housing and Urban Development
(HUD) floodplain map or a more detailed map of an area, if
available. If such maps are not available, the agency shall
make a determination of the location of the floodplain based
on the best available information. The Water Resources
Council shall Issue guidance on this information not later
than October 1, 1977.
(2) If an agency has determined to, or proposes to,
conduct, support, or allow an actisn to be located in a
floodplain, the agency shall consider alternatives to avoid
adverse effects and incomnatible development in the flood-
plains. If the head of the agency finds that the only
practicable alternative coni-.stent with the law and with
more
157
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the policy 3et forth In this Order requires siting in a
floodplaln, the agency shall, prior to taking action,
(i) design or modify its action in order to minimize potential
harm to or within the floodplaln, consistent with regulations
issued in accord with Section 2(d) of this Order, and
(11) prepare and circulate a notice containing an explanation
of why the action is proposed to be located in the floodplain.
(3) For programs subject to the Office of Management
and Bucket Circular A-95, the agency shall send the notice,
not to exceed three pages in length including a location
map, to the state and areawlde A-95 clearinghouses for the
geographic areas affected. The notice shall include:
(1) the reasons why the action is proposed to be located
in a floodplain; (11) a statement indicating whether the
action conforms to applicable state or local floodplain
protection standards and (ill) a list of the alternatives
considered. Agencies shall endeavor to allow a brief comment
period prior to taking any action.
CO Each agency shall also provide opportunity for
early public review of any plans or proposals for actions
in floodplalns. in accordance with Section 2(b)of Executive
Order No. 1151*1, as amended, including the development of
procedures to accomplish this objective for Federal actions
whose impact is not significant enough to require the
preparation of an environmental Impact statement under
Section 102(2)(C) of the National Environmental Policy Act
of 1969, as amended.
(b) Any requests for new authorizations or appropriations
transmitted to the Office of Management and Budget shall
Indicate, if an action to be proposed will be located in a
floodplaln, whether the proposed action is in accord with
this Order.
(c) Each agency shall take floodplain management into
account when formulating or evaluating any water and land
use plans and shall require land and water resources use
appropriate to the degree of hazard involved. Agencies
shall include adequate provision for the evaluation and
consideration of flood hazards in the regulations and
operating procedures for the licenses, permits, loan or
grants-in-ald programs that they administer. Agencies
shall also encourage and provide appropriate guidance to
applicants to evaluate the effects of their proposals in
floodplains prior to submitting applications for Federal
licenses, permits, loans or grants.
(d) As allowed by law, each agency shall issue or
amend existing regulations and procedures within one year
to comply with this Order. These procedures shall incorporate
the Unified National Program for Floodplain Management of
the Water Resources Council, and shall explain the means
that the agency will employ to pursue the nonhazardous use
of riverine, coastal and other floodplalns in connection
with the activities under its authority. To the extent
possible, existing processes, such as those of the Council
on Environmental Quality and the Water Resources Council,
shall be utilized to fulfill the requirements of this Order.
Agencies shall prepare their procedures in consultation
with the Water Resources Council, the Federal Insurance
Administration, ar.d th" Council on Environmental Quality,
and shall update such procedures as necessary.
Sec. 3. In addition to the requirements of Section 2,
agencies with responsibilities for Federal real property
and facilities shall take the following measures:
(a) The regulations and procedures established
under Section 2(d) of this Order shall, at a minimum,
require the construction of Federal structures and
more
158
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3
facilities to be in accordance with the standards and
criteria and to be consistent with the intent of those
promulgated under the National Flood Insurance Program.
They shall deviate only to the extent that the standards
of the Flood Insurance Program are demonstrably inappro-
priate for a given type of structure or facility.
(b) If, after compliance with the requirements
of this Order, new construction of structures or
facilities are to be located in a floodplain, accepted
floodproofing and other flood protection measures shall
be applied to new construction or rehabilitation. To
achieve flood protection, agencies shall, wherever
practicable, elevate structures above the base flood
level rather than filling in land.
(c) If property used by the general public has
suffered flood damage or is located in an identified
flood hazard area, the responsible agency shall provide
on structures, and other places where appropriate, con-
spicuous delineation of past and probable flood height
in order to enhance public awareness of and knowledge
about flood hazards.
(d) When property in floodplains Is proposed for
lease, easement, right-of-way, or disposal to non-Federal
public or private parties, the Federal agency shall (1)
reference in the conveyance those uses that are restricted
under identified Federal, State or local floodplain
regulations; and (2) attach other appropriate restrictions
to the uses of properties by the grantee or purchaser and
any successors, except where prohibited by law: or (3)
withhold such properties from conveyance.
Sec. 4. In addition to any responsibilities under this
Order and Sections 202 and 205 of the Flood Disaster
Protection Act of 1973, as amended (42 U.S.C. U106 and 1)128),
agencies which guarantee, approve, regulate, or Insure any
financial transaction which is related to an area located
in a floodplain shall, prior to completing action on such
transaction, inform any private parties participating in the
transaction of the hazards of locating structures In the
floodplain.
Sec. 5. The head of each agency shall submit a reoort
to the Council on Environmental Quality and to the Water
Resources Council on June 30, 1978, regarding the status
of their procedures and the imoact of this Order on the
agency's operations. Thereafter, the Water Resources
Council shall periodically evaluate agency procedures and
their effectiveness.
Sec. 6. As used in this Order:
(a) The term "agency" shall have the same meaning as
the term "Executive agency" in Section 105 of Title 5 of
the United States Code and shall include the military
departments; the directives contained in this Order,
however, are meant to apply only to those agencies which
perform the activities described in Section 1 which are
located in or affecting floodplains.
(b) The term "base flood" shall mean that flood which
has a one percent or greater chance of occurrence in any
given year.
(c) The tern "floodplain" shall mean the lowland and
relatively flat areas adjoining inland and coastal waters
including floodprone areas of offshore islands, including
at a minimum, that area subject to a one percent or greater
chance of flooding in any given year.
more
159
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Sec. 7. Executive Order ^fo. 11296 of August 10, 1966,
is hereby revoked. All actions, procedures, and Issuances
taken under that Order and still In effect shall remain In
effect until modified by appropriate authority under the
terms of this Order.
Sec. 8. Nothing In this Order shall apply to assistance
provided for. emergency work essential to save lives and
protect property and public health and safety, performed
pursuant to Sections 305 and 306 of the Disaster Relief
Act of 1974 (88 Stat. 148, 42 U.S.C. 5145 and 5146).
Sec. 9. To the extent the provisions of Section 2(a)
of this Order are applicable to projects covered by
Section 104(h) of the Housing and Community Development
Act of 1974, as amended (88 Stat. 640, 42 U.S.C. 5304(h)),
the responsibilities under those provisions may be assumed
by the appropriate applicant, if the applicant has also
assumed, with respect to such projects, all of the respon-
sibilities for environmental review, decisionmaking, and
action pursuant to the National Environmental Policy Act
of 1969, as amended.
JIMMY CARTER
THE WHITE HOUSE,
May 24, 1977.
* # # #
160
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P.O. bo* 471 13ffi ana IDMJC* it. Dould«r. eoto. 80302 441-3930
September 29, 1977
Mr. Alan Merson
Regional Administrator
Environmental Protection Agency
1860 Lincoln Street
Denver, CO 80295
•-• --
°OCT04 19/7
Viaier
RE: Draft Environmental Impact Statement of August 1977/Boulder
Wastewater Treatement Facilities
Dear Mr. Merson:
Please be informed that the Boulder County Long Range Planning Com-
mission, following public hearing on September 28, 1977, approved
the following recommendations in response to your August 11, 1977
invitation for comments on the draft environmental impact statement
on the City of Boulder's proposed project for expansion and additions
to the City's wastewater treatment facilities:
1. That Alternative B, activated sludge process following
trickling filters (as amended to provide nitrification),
is recommended to the EPA for funding.
2. That the final EIS and "Wastewater Facilities Plan"
emphasize the need for a comprehensive program for odor
control to include minimally: the identification and
monitoring of all odor-producing sources associated
with the sewage treatment facilities; a plan and schedule
for odor abatement; the evaluation of sludge handling and
disposal systems for odor-producing elements; and an
expanded public information and input process in order
to effectively relate to all problems associated with the
operation of sewage treatment facilities.
3. A great deal of public concern has been expressed over
the location of a relatively new sludge disposal technique
so close to existing residential development and the White
Rocks Natural Area. Items of major concern include odor
control, vector control, groundwater contamination, heavy
metals buildup, and pathogen transmission. Sludge in-
jections of the site(s) proposed cannot be endorsed with-
out the resolution of the specific and technical concerns
to the satisfaction of the City/County Board of Health.,
161
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Mr. Alan ,Merson
Regional Administrator
Environmental Protection Agency
September 29, 1977
Page two
City of Boulder Planning Board, Boulder City Council,
Boulder County Long Range Planning Commission, and Boulder
County Board of Commissioners.
4. That the selected treatment alternative(s) include pro-
visions so that constructed facilities will absorb unexpected
shock loadings and provide backup during system failure, so
that the primary emergency procedure during system failure
will be other than wastewater plant bypass and sewage flow
directed into Boulder Creek.
5. Facilities must be designed to be in compliance with Section
18.5 of the Boulder County Zoning Resolution, Flood Plain.
Particular attention should be given to protection against
erosion, backwater and downstream effects. Water rights
issues should be resolved prior to Use by Special Review,
with emphasis placed on maximizing the opportunities for
agricultural reuse of municipal effluent.
6. That the EIS depiction of the wastewater facilities planning
area and White Rocks Natural Area be changed to be consistent
with the '77 Boulder Valley Comprehensive Plan.
7. That it be noted in the environmental impact statement that
the Boulder 201 EIS is not intended to and does not satisfy
the requirements of PL 92-500, Section 208 relating to
Boulder County.
I would be happy to discuss these recommendations with you further,
if necessary, and look forward to working with the EPA on this matter.
Finally, I would like to take this opportunity to express our appreciation
for the efforts of Mr. Gene Taylor, project officer, in facilitating
public and local government response on this project.
Sincerely
EC
Planning Director
ET/JB/da
xc/Mr. Doug Smith, Director - Utilities Division - City of Boulder
Mr. Bryan Miller, Director - Environmental Health - Boulder City/
County Health Department
162
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Responses to Boulder County Planning Department
letter of 29 September 1977:
1. Recommendation has been noted.
2. The need for a comprehensive program for odor control has
been noted in the Final EIS. Recommendations for odor
control will become part of the EPA grant conditions.
3. Items of major concern regarding the sludge-injection
technique such as odor control, vector control, groundwater
contamination, heavy metals build-up and pathegon trans-
mission will be addressed in a newly-revised addendum to
the Final EIS to be issued at a later date. An additional
sludge injection site is currently being investigated.
4. Provision for facilities to absorb shock loadings and include
back-up systems will be part of the EPA grant conditions.
5. Ability of the project to meet Boulder County Flood Plain
Zoning requirements and resolution of water rights will be
made as part of EPA grant Conditions.
6. The text and figures depicting the White Rocks Natural Area
have been changed to conform to the 1977 Boulder Valley
Comprehensive Plan.
7. This has been noted in the Introduction of the Final EIS.
163
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October 3, 1977
Mr. John A. Green
Regional Administrator, EPA
1860 Lincoln Street
Denver, Colorado 80295 Re:
EIS - Boulder Waste-water
Treatment
August 1977
Dear Sir:
This letter is written in response to EPA letter 8W-EE dated
August 8, 1977 regarding modifications to the City of Boulder's 75th Street
sewage plant and the addition of a sludge disposal system to a land area
near the present plant.
On September 20, 1977 the City Council of Boulder approved modifi-
cation Plan B which includes a sludge disposal system by injection on a
land area located 1-1/2 miles from the present plant designated by para-
graph 5 of the EIS Summary as a field of "170 acres" including City owned
property west of 75th Street and south of the UPRR tracks (Page 65-EIS,
Para 2).
According to this plan 50$ of the sludge will be pumped to the
injection site as a slurry and injected below the ground surface using a
series of force mains, pipelines, underground drains and an expensive
pumping system.
As a peripheral land-owner immediately adjoining the "Manchester"
property which has been designated as a sludge injection site I would like
to express my objections and those of other landowners so situated to the
inclusion of sludge injection disposal systems to any land areas near or
adjoining the present sewage plant.
In reviewing the details of the EIS regarding the proposals for
sludge injection on adjacent land area sites the following conments are
submitted for consideration:
1. Past planning by the City of Boulder for treatment of sewage
has generally been short-sighted and restricted by factors of
expediency and pressures by political interest groups.
The present 75th Street sewage plant on a site of approxi-
mately 80 acres was newly constructed and became operative in 1968.
In only 9 years of existence it has proved to be grossly inade-
quate to function properly, to meet the needs of the service area
and to conform to State and Federal standards regarding air and
water pollution.
2. There is little reason to believe that the proposed new
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Page 2.
planning by the City of Boulder and their consultants, CH.M-H111,
offer any assurance that the proposed modification alternatives
will result in a plant operation that will meet either the Odor
Emission Regulations of the Colorado Department of Health or the
stringent water pollution controls imposed by the highly restric-
tive Federal Regulations of the EPA under Sections 208, 402 and
303 of the Water Pollution Control Act of 1972.
Rather than providing an effective long range solution to present
problems the plan to add a sludge injection disposal system merely dis-
tributes the treatment activity from an enclave of 80 acres to a non-
contiguous land area of an additional "170 acres" which happens to be un-
developed and is nearby.
This is another example of expediency and short-term planning
based on an experimental unproved sludge disposal system which will be
expensive to develop, to operate and which well may be in direct conflict
with all of the provisions of Sections 208, 402 and 303 of the Water
Pollution Control Act of 1972.
Consideration has to be given to the question of how much liquid
sludge can be imposed on a finite amount of land over an infinite period
of time. In a continually expanding service area the amount of sludge
produced will increase year by year to be injected on a limited designated
site.
If the present sewage plant which has already been modified (1973)
and cannot presently meet current State and Federal standards only 9 years
after initial construction it is impossible to believe that the proposed
modifications can be effective through the next 18 years until 1995—
the projected planning date to accommodate a population of 129,000.
It must be noted that during the planning stages of the present
75th Street sewage plant an offer was made to the Boulder City Council to
provide a substantially larger site on the "Cannon" property approximately
2 miles further downstream immediately west of 95th Street. This proposed
site in a large open undeveloped area was rejected as being "too expensive"
by the City Council because it required the construction of an additional
2 miles of semge trunk line.
However at a meeting of the Boulder County Health Board held on
September 13, 1977 the Utilities Director of the City of Boulder offered
direct assistance to Board of Health Members in resolving sewage problems
along South Boulder Creek adjacent to Eldorado Springs by proposing to
submit a request for an EPA grant of approximately $1,000,000.00 to con-
struct a sewage trunk line connecting directly to the present inadequate
75th Street sewage plant.
It is difficult to reconcile the goals of the City of Boulder who
on one hand are now asking for Federal funding to upgrade the present
sewage plant to meet required standards and are at the same time offering
to provide facilities that will encourage immediate urban growth to further
strain an already overloaded, inadequate sewage plant.
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Page 3.
The proposed site for field Injection of liquid sludge MS not
Included In the original Wastewater Facilities Plan of October 1975
OUM-H111, but was changed by the City of Boulder during March and April
of 1976 and the designated area varies from "170 acres" to "225 acres"
(EIS - Page 104, Para 4) depending on the EIS reference reviewed.
The EIS draft does not address the problems generated by the
sludge injection disposal system as a separate concise topic, but scatters
various comments throughout the 160 pages and appendices in at least 25
references running from 1 to 4 or more paragraphs.
In reviewing these references it 1s not possible to cite a single
example where the EIS concerns itself with successful operations of
sludge Injection disposal systems Initiated by other municipalities within
the State of Colorado or even on an experimental basis by any agency within
Colorado or at any other location.
Relocation by the City of Boulder of a sludge disposal system on
the "Manchester" property immediately adjacent to my farm and residential
property imposes adverse conditions to me and the surrounding residential
owners that did not exist under the location proposed by C^M-Hill when
this system was designated for the "Kolb" property in a less developed area.
If this system of sludge disposal is approved at this site designated
by the City of Boulder it will have to be considered as an expedient,
experimental process limited in useage by the land available, the con-
tinual increase of sludge produced and the capacity of the land for sludge
assimilation.
The EIS has addressed its review to a number of factors which affect
this process of sludge disposal with very few positive or clear-cut resolu-
tions of problems generated by the plan.
It is highly important to me and to those Boulder valley residents
similarly situated that due and fair consideration be given to positive
solutions of problems created by the Imposition of any experimental plan
of sludge disposal on the areas near which we live.
Specific concerns which do not seem to be clearly resolved are
itemized below along with comments on specific notations in the EIS along
with reference pages:
1. Odor
Merely an extension of the present problem from the 75th
Street plant to the sludge injection site.
2. Alteration of surface and groundwater flows:
a. Amount - Decrease in present flows by Installation of
underground drains.
b. Quality - Deleterious effects of heavy metal, salts and
nitrates.
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Page 4.
c. Effect on intermittant stream flow in pastures. Re-
duction of flow and possible contamination.
d. Effect on grass production 1n sub-Irrigated pastures.
Reduction 1n growth.
e. Effect on domestic and stock wells. Contamination and
reduction of water quantity available.
3. Pathogens
Sludge Injection sites become pathogen transmission areas.
4. Reduction 1n land values and re-sale value of farm and farm-
stead and adjacent residential areas.
A careful study and review of the EIS does not Indicate that the
proposal for sludge disposal by Injection has been endorsed positively
In any way as a proven, practical method of secondary sewage treatment by
the EPA.
To the contrary most of the comments dwell at length on the negative
aspects of sludge disposal by Injection.
Because of the limited scope of the study and the absence of proven
practical data along with the need for longer range planning 1t 1s hoped
that funding to the City of Boulder will not be approved or granted for
any system of sludge injection.
There are a few portions of the Boulder Valley that still retain
the high quality natural rural environment once common to all of Boulder
County. The City of Boulder's plans would only add to the continuing
degradation of this beautiful area.
ly yours,
Roger C. Fell
7861 Valmont Drive
Boulder, Colorado
Addenda enclosed
cc: Jack Murphy, Chairman—Boulder Co. Commissioners
Edward A. Tepe, Planning Director, Boulder Co
Frank Buchanan, Mayor, City of Boulder
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Addenda
Comments on EIS Draft
EIS - Page 13, Para 1, Items 3, 4 and 5 — Sludge Injection
Item 3. "Long-term sludge application to the site will result in the
build up of heavy metals and salts within the soil."
Conflicts with Sec. 303, PL 92-500. RCF
Page 14, Items 4 and 5 — Sludge Injection
Item 4. "Heavy metals concentration and potential contamination by
pathogens may render some crops grown on the sludge—amended field
unsuitable for human consumption etc ."
Item 5. "Soluble salts, particularly nitrates will gradually leach
into the groundwater reservoir, etc ——."
In direct conflict with Water Pollution Control Act of
1972 (PL-92-500). The sludge injection sites become sludge
dump areas. RCF
EIS - Pages 54 and 55, Paras 1 through 5 — Odor
Para. 5. "When these facilities are completed, the changes in the
sludge handling and odor control processes are expected to correct
past odor problems associated with the operation of the 75th Street
plant."
Citizens have a right to expect positive solutions for odor
control which conform at least to regulatory standards.
Approval of plans and funding grants for odor control should
be based beyond "expectancies."
EIS - Page 63, Para 2 — Sludge Disposal
"The East Pearl Plant utilizes soil injection and soil conditioning."
No pilot study of this operation by the U.S.E.P.A., no monitoring,
no results, conclusions or useful recommendations. Why not? RCF
•
EIS - Page 82, Para 1 —Sludge Disposal
•
"The sewage sludge disposal systems i.e. subsurface injection for
various portions of the total sludge production will probably
function satisfactorily."
"As the City experiments with each system and selects a preferred method-
ology, a future commitment will probably be made to one or two
systems."
O
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Addenda Page 2.
There 1s nothing positive 1n the above statements that warrants
any approval of expenditure of taxpayer's funds for proposals
based on probabilities. RCF
EIS - Page 91, Para 1 - Removal of Nitrates
"Alternatives B, D, E, and F are also judged Ineffective at removing
nitrates."
Conflicts with Sec. 208 and 303, PL 92-500.
How can this plan be approved if it does not meet required standards?
-- RCF
«
EIS - Page 91, Para 3 - County Goals
"The County does control the landfill sites which may be used for
ultimate sludge disposal. Possible land disposal or reuse of
wastewater sludge would be reviewed through the Special Use Review
process of the County Planning Board."
This is an important recommendation. The power of review
should be carefully exercised by the County before any site
approval or system plan is ever granted. RCF
EIS - Page 99, Para 2 through Page 104, Para 1 — Soils at Sludge Inspection
Sites.
Describes adverse impacts of sludge Injection on land site
in terms of concentration of salts, heavy metals and ground
water impairment in terms of quality and quantity.
Details limitations of sludge site to absorb impact of 1500
tons of sludge per year. (This is a conservative estimate
of sludge production. Sludge production will Increase each
year as service area is expanded.)
EIS - Page 103-104, Paras 4 through 7 -- Groundwater below Sludge Injection
Sites.
Describes adverse impacts of sludge Injection on groundwater
quality.
The injection site becomes a point source of pollution in
direct conflict with the provisions of Public Law 92-500,
Water Pollution Control Act of 1972.
EIS - Page 115, Para 1 — Sludge Injection Fields
"Subsurface injection of liquid sludge under all alternatives (except F)
would produce minimal odor."
J
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169
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Addenda Page 3.
There is no experimental or current operational evidence
presented in the IRS to substantiate this statement. RCF
EIS - Page 123, Para 4 — Public Health
•Health hazards associated with sewage treatment, although greatly re-
duced by processing and treatment, are always of concern."
I am in accordance with this statement and it is one of many
reasons that disposal of sludge by injection is not a de-
sirable plan. RCF
EIS - Page 124, Paras 1 through 4 — Pathogens
A four paragraph description of the presence and possible
deleterious effects of pathogens associated with sewage
treatment.
Para 4.
"The sludge injection fields proposed under all alternatives except F,
present a greater concern because of the more concentrated elements
in the sludge and their cumulative effects."
I share the concern of both the City/County Board of Health
and Boulder County Long Range Planning Commission who have
published concerns regarding the methods and sites for
sludge injection.
EIS - Page 136, Para 3 — Loss of Gravel Resource
Random acquisition of sludge injection sites may impair
the potential for gravel extraction and conflict with mining
laws, State of Colorado.
EIS - Page 137, Para 1 through 6 — Accumulation of Salts and Heavy Metals -
An eight paragraph description of the adverse impact on
sludge injection sites caused by discharge of salts and heavy
metals into the sub-soil and leaching into the groundwater
system.
This operation conflicts with Sections 208, 402 and 303 of
PL 92-500. RCF
EIS - Page 148, Para 2 — Sludge Injection Site Soil Commitment.
Irreversible damage to sludge injection site caused by impact
of heavy metals and soluble salts.
In direct conflict with Section 303, PL 92-500. It must be
O
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170
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Addenda Page 4.
noted that all of the proposed sludge injection sites are
located on remnants of highly porous, permeable alluvial
terraces of sand, gravel and rocky rubble with only a thin
top-soil layer overlying an Impermeable layer of shale
approximately 20' below the surface. (Figure 5, Page 25
EIS).
Under these conditions there will be continual leaching
of the disposal sites with soluble salts, heavy metals and
nitrates returned directly by underground water flows back
to the stream basin.
EIS - Pages 150 and 151, Paras 1 through 4 — Potential Cumulative Long-
term Environmental Damage.
Para 1. "A long term view of sludge injection to fields must include
potential harmful effects." Etc.
These paragraphs detail the adverse effects of sludge
injection caused by the addition of soluble salts and heavy
metals into a permeable soil site.
While there is no positive endorsement of this process by
the EIS it must be noted that there must be consideration
given to the conflict of such process with Sec. 303, PL 92-
500.
EIS - Page 149, Para 3 -- Enhancement of Soil Productivity
Throughout the EIS and 1n all of the public presentations
by the City of Boulder there are continual allusions to the
beneficial uses of sludge 1n application to agricultural
lands as a substitute for commercial fertilizers and as
method of conservation of natural resources.
Members of the City/County Board of Health and the
Boulder County Long Range Planning Commission have suggested
that additional study and planning be given to processes that
effectively dry and modify sludge to provide a fertilizer
product that can be effectively used by farmers on agri-
cultural lands throughout eastern Colorado and which will
compete with conrnercial fertilizers now used.
Response to these suggestions by the City of Boulder has been
less than enthusiastic although statements have been made
that there 1s a great demand by City and County entitles for
sludge to be used in governmental park systems.
The EIS should insist that full consideration be given to all
171
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Addenda Page 5.
of the long range Implications of any sludge disposal system
and be reluctant to approve the sludge Injection system which
obviously has serious limitations.
It 1s felt that technology does exist to provide advantages
for approval of a sludge product that does have potential
for resolving the present enigma of the high cost of
commercial agricultural fertilizers produced from petroleum
derivatives.
It seems that much more consideration has been given to the
quality of sewage effluent resulting from plant discharge
Into Boulder Creek and the provisions of Sec. 208 than to the
consequences of sludge Injection and the potential pollution
to Boulder Creek in conflict with Sec. 303 of Public Law
92-500.
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Responses to letter from Mr. Roger C. Fell of 3 October 1977
1. Past short-range planning and operational problems regarding
Boulder wastewater treatment have been less than desirable. The
task of EPA, prior to awarding grant monies for wastewater im-
provement projects, is to determine the most cost-effective, re-
liable and environmentally acceptable treatment method under the
given conditions. Where adverse effects can be mitigated by
recommendations in the EIS, EPA can make these part of the grant
conditions. The role of the wastewater facilities plan and the
EIS is thus to work out the most reasonable and effective solu-
tion.
2. The amount of sludge that will be generated in the future and
land requirements for disposal will be discussed in the sludge-
injection addendum to be published separately after the final
EIS. As far as long-term reliability. EPA requires, under P.L.
92-500, that the proposed project must adequately meet federal
water quality standards through the planning period ending in
the year 2000.
3. The Boulder City Council voted to accept the 75th Street treat-
ment plant under conditions at that time. Reference to the
sewage trunk line extension to El Dorado Springs at the Board
of Health meeting on 13 September 1977, would be for a separ-
ate project with a separate EPA grant. The ability of the pre-
sent 75th Street treatment plant or of the proposed project to
handle the additional load from a possible El Dorado Springs
sewer extension is not considered in this EIS. This would be
the subject of a separate facilities plan and EIS.
4. "170 acres" is the correct figure and has been revised in the
final EIS. Evaluation of sludge injection and its impacts will
be gathered into a separate addendum to the final EIS to make
discussion of this item more concise.
5. Citation and comparison of other sludge-injection operations are
presented in a separate addendum to the final EIS.
6. Specific concerns regarding sludge-injection that you have men-
tioned, particularly: odor, alteration of surface and ground-
water flows, pathogens and effects on land values, will be
gathered together and readdressed in a separate addendum to the
final EIS.
7. At the time that the draft EIS was prepared in July 1977, the
Denver Regional Council of Governments came out with a new set
of water quality standards for the Denver 208 planning area.
These standards were rather stringent and at the end of 1977,
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Responses to letter from Mr. Roger C. Fell of 3 October 1977
Page Two
the final.adopted standards pertaining to Boulder Creek had
dropped the 1 mg/1 nitrate-nitrogen limitation in wastewater ef-
fluent. Thus, the statement on Page 91 of the draft EIS is no
longer applicable and has been revised.
The proposed sludge injection site, south of the railroad tracks,
has a potential for gravel extraction. No detailed studies have
been made of the quality or quantity of the gravel resource on
that site. Based on information from other mining areas in the
flood plain, the gravel resource could be 7- to 10- feet thick
with an overlying soil layer of 5- to 10-ft. The area between
the Sawhill Ponds and White Rocks generally contains a good-
quality aggregate. The feasibility of mining this resource
would have to be based on further detailed testing.
Colorado mining laws prohibit development over gravel resources
that would preclude extraction of this resource. The sludge
injection operation is essentially an agricultural crop usage
and does not involve conversion of land use. Thus, at any time
after sludge injection is discontinued, the land could be mined
for its gravel resource.
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United States Department of the Interior
OFFICE OF THE SECRETARY
MISSOURI BASIN REGION • n • VJ
DENVER. COLORADO 80225 lU ' '
ER 77/814
October 4, 1977
Mr. Alan Her son
Regional Administrator
Environmental Protection Agency
Region VIII, Suite 900
1860 Lincoln Street
Denver, CO 80203
Dear Mr. Merson:
This is in response to your August 11, 1977 request for Department of the
Interior review of the Draft Environmental Statement for the Boulder
Wastewater Treatment Facilities, Boulder, Colorado. We have completed the
subject review and have the following comments:
General Comments
1. The Environmental Impact Statement (EIS) adequately addresses the
potential impacts on fish and wildlife for all alternatives presented. From
the information presented it would appear that Alternative B (activated sludge
process following trickling filters) would have the least impact on such
resources.
2. Infiltration rates for the various soils are not mentioned nor is the
method of irrigation with the effluent, e.g., sprinkler, gravity. In addition,
at least mi'n-fmaT downgradient monitoring of ground-water quality should be
included in planning—just as surface—effluent monitoring will be required—
in order to provide a basis for detecting impacts before downgradient ground-
water users suffer damage. This monitoring will be especially needed if well
owners in the vicinity reject the offer of a municipal water supply.
3. You should be aware that Sawhill Ponds has received matching assistance
monies from the 7>r"4 and Water Conservation Fund (L&WCF). Encroachment upon
Sawhill Ponds would constitute a conversion of recreation use under Section
6(f) of the L&WCF Act, as amended. Section 6(f) requires that any change
from recreational land use be approved by the Secretary of the Interior and
also requires the substitution of other properties of at least equal fair
market value and reasonably equivalent usefulness and location for the
recreation lands to be taken. There is no -provision under this section for
acceneapeg of cyih in payment for recreation lands converted to other uses.
175
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Information presented in the statement indicates that Alternates A
and C could adversely Impact the Sawhill Ponds, If either alternate
is selected, we suggest that you consult with the Boulder City Parks
Department concerning project Impacts on this area.
•
4. The statement fails to evidence consultation of either the
National Register of Historic Places or the State Historic Preservation
Officer for Colorado, Mr. Stephen H. Hart, Chairman, State Historical
Society, Colorado State Museum, 200 14th Avenue, Denver, Colorado 80203,
concerning the effects of the proposed action on archeological or
historical properties that are listed on, or may be eligible for, the
National Register of Historic Places, Documentation of such consulta-
tion is required by the Code of Federal Regulations, both Title 36,
Part 800.2 and Title 40, Part 1500. Evidence of such consultation,
including relevant appended correspondence, should appear In the final
environmental statement. The final statement should also provide
documentation of compliance with the Advisory Council on Historic-
Preservation's "Procedures for the Protection of Historic and Cultural
Properties" (36 CFR, Part 800), as necessary.
The discussion of archeological and historical resources in the project
area, particularly the pertinent paragraphs on pages 55-56 and 144, is
confusing and fails to clearly describe the nature of cultural resources
in or near the project area and define their relationship to the proposed
action.
Also, the extent of earlier archeological and historical surveys of
affected areas is not delineated, nor is the methodology employed in
such surveys described. We suggest that information of a more specific
nature be extracted from the referenced archeological and historical
reports (preference 45, 46, and 47 on page 156} and be incorporated in
subsequent draft and final versions of this environmental statement to
facilitate reviev. -
5. The environmental impact statement almost completely ignores the
potential mineral impacts of the proposed action. It is true that
the amount of land involved is small—a Tng-g-tmTm of 3,360 acres under
one alternative—and that the amount of minerals involved is likely
to be correspondingly limited. Nevertheless, the proposed action
involves a flood plain that is known to have a sand and gravel resource,
is currently being mined for sand and gravel in the project area, and
is immediately adjacent to a rapidly growing city with a strong demand
for construction minerals.
Half a dozen references in the statement pertain to past and present
gravel mining activity in the project area, but they all seem to be
rather offhand and to be related to things such as environmental aspects
of gravel pits, using gravel pits as settling ponds or trout ponds, etc.
Nowhere is the question of potential loss of a mineral resource squarely
176
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and adequately addressed. In the most extensive reference to minerals,
one short paragraph on page 136 titled "Loss of Gravel Resources," it
is stated that "... utilization of this soil as a filtering medium
precludes gravel mining in that area during the lifetime of the facil-
ities operation.", and that gravel resources are ". . . fairly common
along the Boulder floodplain and other watercourses." These statements
are true enough, but are simply not adequate by themselves.
Good-quality aggregate is somewhat limited in the Boulder area, and
the fact that sand and gravel is currently being mined in the project
area implies that good-quality gravel occurs there. The environmental
statement does not indicate that any attempt fra-? been made to assess
the quality and quantity of the resource that would be affected by the
project. Irreversible and irretrievable resource commitments are
identified as loss of wildlife habitat, destruction of soil profile,
sludge injection site soil commitment, and energy and economic resource
commitment. Adverse impacts are considered on soils, landforms, water,
biotic communities, noise, odors, and air quality. We believe that
sand and gravel should be included.
To be complete, this statement should include an evaluation of the type
and volume of gravel (and other possible minerals) underlying the
proposed project site, the extent to which this resource will be mined
before the project is constructed, the potential mineral values foregone
In construction of this project, and the relative level of importance
the affected mineral resource might play in the Boulder market for con-
struction minerals.
6. The Draft Environmental Impact Statement addresses seven alternatives.
The final environmental statement should address the impacts of the
selected alternative. In this way the impacts would be more site specific
and could be more fully addressed.
Specific Comments
1. Page 9, Alternative G: There is the beginning of an inconsistency
here. It is stated that the total land requirement for the project is
360 acres, including the lagoon, buffer zone, and irrigation lands. On
page 79, it is stated that irrigation lands would total 3,360 acres,
which is more realistic. On page 107, the requirement is given as
2,500 acres.
2. Page 17, paragraph 3: This discussion should be clarified. The
second sentence presents several comparatives; however, it is unclear
as to what is being compared.
3. Page 34, Table 2: The footnote to this table indicates that the
waste loads are a total of either or both 50D5 and suspended solids.
Since the two are not exactly additive, the waste loads are meaningless.
The amounts of each should be delineated and two separate totals given.
177
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4, Page 34, last paragraph.: Excessive irrigation also causes surface
erosion., carrying soil particles and adsorbed salts and nutrients to
streams,
5. Page 35, 2nd full paragraph: The inference here is that the instream
BOD5 rises to 28 mg/1. While this may meet effluent standards, these
are not applicable to the receiving stream. Based on this, the effluent
would have to Be considerably greater in BODg than 28 mg/1, and most
likely more important ffia" temperature, which was discussed in the pre-
ceding paragraph, in maintaining D.O. levels above the instream standard.
6. Page 37, 1st full paragraph: The Colorado-Big Thompson was built by
and is operated and maintained by the Bureau of Reclamation, with the
repayment obligation undertaken by the NCWCD.
7. Page 37, last paragraph: This discussion is extremely confusing and
should be revised.
8. Page 40, 3rd full paragraph: The DRCOG 2Q8 Plan is not basinwide,
in that the mountain South Platte reach is included in the State's 208
Plan for nondesignated areas, while downstream the Larimer-Weld COG
is conducting the 208 planning. The 1973 DRCOG effort was conducted
under the authority of Section 303,
&, Page 43, 1st paragraph: This discussion would be more appropriately
included in the preceding description of the physical components of the
environmental setting.
10, Page 107, Alternative G: Irrigation application rates of 10 acre-
feet/acre are mentioned here. The irrigated crops mentioned are fescue
and Bermuda grass. At the application rate mentioned above, it might
be desirable to consider more hydrophytic plants as the principle crop.
In addition, it may be necessary to consider subsurface drains, since
the application rate will be so great.
11. Page 145, paragraph 1: Particular attention should be paid to
assessment of both (1) the significance of the "Kolb buildings" and
the archeological site mentioned on page 45, and (2) the specific
effects of the proposed action of these properties.
12. Also, the discussion on pages 144-145 of measures to be tak^n in the
event the previously unknown archeqlogical resources are encountered during
construction should be modified to state in more positive terms those
actions that will be taken in such a case, rather than retaining the present
terminology reflecting measures that should be implemented. _j
Sincerely yours,
JOHN E. RAYBOUKN-
Regional Environmental Officer
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Responses to U. S. Department of Interior letter
of 4 October 1977:
1. Statement noted, no comment necessary.
2. Infiltration rates for the infiltration basin site in
Alternative A are documented in the facilities plan -
Appendix C, Table 4. Infiltration rates along the peri-
phery of Boulder Creek vary from 3.7 to 36 in./hr. In
the central portion of the site, the rates vary from 31
to 50 in./hr. In the south portion, near the railroad
tracks, the rates vary from 26 to 50 in./hr. These rates
are based on laboratory tests from individual observa-
tion wells and may vary a great deal throughout the site
according to soil composition and thicknesses.
High-rate irrigation of effluent, under Alternative G,
would be accomplished with a pump system and spray irri-
gation.
Downgradient groundwater monitoring, as mentioned in your
statement, would be appropriate for Alternatives A and G.
This has been added to the final EIS.
3. Alternative A would not encroach upon the Sawhill Ponds
or require changes in recreational land use. Alternative
C would utilize one pond within the northwest corner of
the Sawhill Ponds area. This would be incompatible with
the Land and Water Conservation Fund Act, unless an ac-
ceptable trade-off was made. In the course of this EIS,
Alternative C was not selected.
4. The SHPO has been contacted regarding this project and
an archaeologist's report submitted to them. The comment
letter from the SHPO appears in this section of the EIS.
The description of potential historical resources on pages
55 and 56 has been revised to include information relevant
to the project area. Archaeology resource information is
generally sketchy and difficult to define. All surveys
mentioned in the EIS covered all of the alternative pro-
ject sites except for the 3,360-acres outlined in Alterna-
tive G. The methodology employed in all surveys was an
examination of the site surface, where accessible. Due
to the low potential for archaeological resources at the
sites, no soil cores or excavations were made. The text
of the archaeologist's report is added to the final EIS
as Appendix H.
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Responses to U. S. Department of Interior letter
of 4 October 1977
Page Two
Detailed site descriptions and location of the archaeo-
logical site mentioned on page 56 is not included in this
EIS. The State Board of Archaeologists wishes not to re-
lease survey data for public reports in order to protect
these resources. In relation to the proposed project,
qualified archaeologists have determined no existing cul-
tural resources within the facilities site and a low po-
tential for their occurrence.
5. An assessment of the gravel resources in the project area
has been added to Section II of the final EIS. Additional
discussion on impacts upon gravel resources and long-term
commitments have also been added to the final EIS.
6. Specific comments 1 through 12, referring to text clarifi-
cations, have been noted and will be corrected and incor-
porated in the final EIS.
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7101 Valmont Drive
Boulder, Colorado 80301
October 8, 1977
Regional Administrator
Environmental Protection Agency
Lincoln Towers Building
1860 Lincoln
Denver, Colorado 80295
Dear Sir,
We are strongly opposed to the possibility of having a sludge Injection site on
the city owned property west of 75th street. Should this become a reality, it would
lower our property value and contaminate our two shallow wells. They are scooped wells,
one is 15' deep add the other 18' deep and are located 45' and 180' from the city
property line. Every year the city property is irrigated for farming purposes at least
one time arid every year the wells are contaminated. We bring in water for domestic use
until we get them cleaned up.
We would also like to bring out the following points:
1. Our neighbors received copies of the Draft Environmental Impact Statement in the
mail but we did not. Our East and South property lines adjoin the city property.
We have 4.4 acres.
2. The map on the other side of this page does no£ Show a study has been made on water
table contours and flow direction for the proposed sludge injection site on city
owned property West of 75th.
3. The Public Service Co. has two high towers on the right of way that cuts through
the city owned property. Soil erosion could become a problem for these towers.
4. How many acres does the city actually own? Reference is made to City owned property
but how many acres are left when you deduct the right of ways for the Union Pacific
Railroad and the Public Service Co? Also there is a big drainage ditch that cuts
into the city property. On Oct. 7, 1977, I went to the Assessors office to find
out how much land the City of Boulder bought^from L. A. Biddle)west of 75th Street.
This information was not readily available. The description on the micro film
did not have this information on the record.
5. The maps in the Impact Statement do not even come close to showing the number of
homes on land that adjoins the city property. Directly across the road in Section
23 there are two homes, a trailer, a duplex, an apartment building, and a church.
The population of that area ranges from 20 to 25 people none of whom wish to
live across the street from a sewage injection site.
6. Do the Manchester's have any say as to whether they want to give up their property
East of 75th Street? They say all they know is" what they read in the news media
and that they have not been contacted by anyone as yet...it is hard to believe that
situations such as this exist.
Thank you for your interest in this matter.
Sincerely,
Mr. & Mrs. Arthur W. Nelson
181
-------
Mr. & Mrs. A. W. Nelson, 7101 Valmont Drive, Boulder, Colorado 00301
Oct. 8, 1977
0 MO 1000
LUle~OF~eOUAL GROUND
00
NO
FIGURE 7
WATER TABLE CONTOURS AND
FLOW DIRECTION
-------
Responses to Mr. and Mrs. A. W. Nelson letter
of 8 October 1977:
1. Your name has been added to the mailing list to re-
ceive reports and information on the Boulder EIS.
Thank you for bringing this to our attention.
2. Additional studies on water table contours and flow
direction have been performed to augment the data shown
in Figure 7. This additional information will be pre-
sented in an addendum to the final EIS and should give
more specific information on groundwater characteristics
under the sludge injection site.
3. Sludge injection as proposed in the facilities plan is
similar to normal farming operations involving discing
or tilling, irrigation and harvesting. The sludge in-
jection operation should not cause any erosion problems
for the two electrical transmission towers near the site.
4. The map of the project area has been revised to include
all dwellings adjacent to the proposed treatment and
sludge injection sites.
6. If the Manchester property is used for sludge injection,
the City of Boulder will make arrangements to purchase
the necessary acreage from the Manchesters at fair market
value. Residents will probably not be required to re-
locate as house and farm building sites will probably
not be acquired. In the event that the owners do not
wish to negotiate, the City would exercise its right of
eminent domain.
183
-------
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-------
Responses to letter from Martha Weiser:
1. The base map in Figure 2 and subsequent figures have
been revised to include all houses around all of the
alternative treatment and sludge injection sites.
2. Except for the short period when sludge is being in-
jected, the site will be used as a conventional agri-
cultural field with periodic soil and groundwater moni-
toring. After discontinuation of sludge injection, the
site will continue to be monitored periodically.
3. Text revision - the resultant topography of the White
Rocks is what influences plant and animal distribution.
4. Corrections, additions and recommendations were noted
and revised in the final EIS.
5. The description of the WRNA has been expanded, to include
pasture and riparian elements in the text and Appendix
B. The discussion on page 45 is necessarily brief as it
presents an overview of biotic communities in the area.
The separate discussion of the WRNA as a Sensitive Eco-
logical Area on pages 49-50 was viewed as an appropriate
place for more detail.
7. Your comments on treatment plan effects on local land
values are valid. That section of page 61 has been re-
written to reflect those concerns.
8. The sand-drying beds have been removed from the Phase I
design of odor and sludge handling facilities. The City
plans to use the existing vacuum filtration units and
surface spreading on land to dewater sludge for reuse.
9. Winter wastewater volumes are generally the lowest and
thus, loading rates on the infiltration basins would be
lower. In order to prevent ground freezing and obstruc-
tion to infiltration, the operation cycle would be shortened.
The City estimates that the effluent would be 8-9°C or
greater. Smaller loading rates on a shorter cycle - 3-4
days - would be used to prevent the ground from freezing
completely. The effluent itself would be warm enough to
thaw out the surface partially. Operation of this system
in the winter would require close attention to temperature
and percolation rates. Excessive loadings or a longer time
between loading cycles could allow the basins to freeze
sufficiently to disrupt infiltration.
192
-------
Responses to letter from Martha Weiser
Page Two
10. The proposed site of Alternative G is the same area as
that depicted in Figure 9.2 of the facilities plan with
some exclusions for residences and existing ponds and
reservoirs.
11. The Boulder County Planning Department and the County
Commissioners also play an active role in determining
the goals for Boulder Creek. This has been added to
the text of the final EIS.
12. The EIS reflects the most recent costs, as revised by
the facilities planner in the February 1977 Supplement
to the facilities plan (EIS, Reference 5). Although
an increase in secondary clarifier size would be ad-
visable, Alternatives A and C would function satisfac-
torily with the existing clarifiers. The pond systems
at the end of the treatment system for Alternatives A
and C would compensate for the inadequate secondary
clarifiers.
13. No reclamation costs have been developed for the sludge
injection site. With appropriate operation procedures,
no site restoration activities were planned. With a
periodic monitoring program, the site would be discon-
tinued if direct pollution effects were resulting from
the operations. It would seem appropriate, however,
for the City to continue a monitoring program on the
site after the termination of sludge injection opera-
tions .
The facilities planner did not develop specific costs
for items such as changes in access roads and purchase
of irrigation rights. These were assumed to be covered
by an estimate of "contingency costs" worked into each
alternative. In the event that costly mitigation mea-
sures are required with the recommended plan, this would
change project costs.
14. The groundwater level under the sludge injection site
is not as shallow as the pond sites under Alternatives
A and C. Operation of the sludge injection fields also
does not involve massive water infiltration as with
Alternative A and would not necessarily have the same
characteristics. More discussion on this topic will be
presented in an addendum to the final EIS.
193
-------
Responses to letter from Martha Weiser
Page Three
15. The 200 acres mentioned Is specifically the perco-
lation pond site. No estimate was made of additional
acreage in adjacent fields that would be lost to pasture
production, although a discussion is included estimating
the potential extent of groundwater effects.
16. Three of the existing pasture vegetation species were
observed colonizing the experimental infiltration basins
near the 75th Street plant. The two other species: blue-
grass and milkweed, are of such ubiquity, that they could
be expected to colonize the basins. The fact that these
5 species are already in pasture areas should not preclude
them from colonizing the infiltration basins.
17. The effect of underdrains at the sludge injection site will
be discussed in a separate addendum to the final EIS.
18. Comments on deodorizing mists have been added to page
143. It should be noted that mists are a temporary
solution that cannot substitute for proper considera-
tion during project design.
19. The effect of pathogen hazards from blowing dust is
negligible as the infiltration basins would be vege-
tated and, thus, have little exposed soil surfaces.
20. Your comments are valid. Since few systems can be
absolutely proven to have no damaging effects, the
role of the EIS is to make the best assessment of the
given situation.
The statement "assuming no change in sludge heavy metal
content" is unclear and should read: "assuming that the
type and concentration of heavy metals in the sludge re-
mains the same throughout the project". This assumption
is reasonable, considering that the Boulder treatment
plant is projected to receive mainly domestic sewage
which has a relatively constant, low heavy metals content.
194
-------
STATE DEPARTMENT OF HIGHWAYS
JACK KINSTL1NGER
'
DIVISION OF HIGHWAYS
E. N. HAASE
CHIEF ENGINEER
EXECUTIVE DIRECTOR
COLORADO STATE PATROL
COL. C. WAYNE KEITH.
CHIEF
October 6, 1977
Mr. Philip H. Schmuck, Director
Colorado Division of Planning
520 State Centennial Building
1313 Sherman Street
Denver, Colorado 80203
Dear Mr. Schmuck:
RECEIVED
OCT121977
DIV. OF PLANNING
The Colorado Department of Highways has reviewed the Boulder Wastewater
Treatment Facilities Draft Environmental Impact Statement prepared by
the U.S. Environmental Protection Agency and has the following comments.
The project does not cause any conflicts with the State Highway system in
this area. There does, however, appear to be an error in the definition
of 100-year flood on page 33, paragraph 5.
Thank you for the opportunity to review this document. We would appreciate
receiving future information which is relevant to our interests regarding
this project.
Very truly yours,
Jack Kinstlinger
Executive Director
Harv|y R. Atchison
Staff Environmental Manager
BSC/rg
195
-------
Response to State Department of Highways letter
of 6 October 1977:
The 100-year flood, was calculated by the Army Corps
of Engineers in 1969 to be 11,000 cfs at the Boulder
treatment plant. Based on later studies in 1976 by
the Corps, the 100-year flood was re-calculated to
be 18,000 cfs. This has been revised in the final
EIS.
196
-------
OFFICE OF THE STATE ARCHAEOLOGIST
1300 Broadway
Denver, CO 80203
303-892-3391,2,3
October 7, 1977
Mr. Philip H.. Schiuuck »-»-M.—)
Department of Local Affairs n
Colorado Division of Planning OCT14 1977
520 State Centennial Bldg.
Denver, CO 80203 DIV. OF FLKNNIHG
RE: DEIS Boulder Wastewater Treatment Facilities (EPA):
archaeological resources
Dear Mr. Schmuck:
The Office of the State Archaeologist of Colorado has
received and reviewed the Draft Environmental Impact Statement
for Boulder Wastewater Treatment Facilities.
Archaeological resources have been adequately addressed,
and the mitagative measures outlined on pages 144 and 145 are
generally appropriate.
It should be noted that this Office's role is consultive,
and the Environmental Protection Agency (EPA] is responsible ^
for arranging the proper evaluation of any archaeological f
resources identified by encounter Cv. 36 CFR 800.4(a) C2); cf.
p. 144) . After developing the eligibility data, EPA should seek
our consultation—for the State Historic Preservation Officer—
in determinations of eligibility or effect C36 CFR 800.4 (bl), or
in planning for the avoidance or mitigation of adverse impacts
(36 CFR 800.5 (e) and (f)I.
If we can be of continued assistance, please call upon
Staff Archaeologist David R. Stuart. (The State Historical
Society's Department of Historic Preservation will independently
comment regarding architectural/historical resources.)
For the State Historic
PreseE»*fc*an Officer
Bruce
State Archai
eau, Ph.D.
ist Colorado
BER(DRS):ng
cc: Hart, SHPO
197
-------
Response to the Office of the State Archaeologist letter
of 7 October 1977:
The archaeologist's survey report of the project site
has been included in the final EIS as Appendix H. No
eligible archaeological or historical sites were found
during the literature search or field survey of the
sites. Provisions for the evaluation of archaeological
resources that may be encountered during construction and
appropriate mitigation measures will become part of the
EPA grant conditions.
198
-------
COLORADO DEPARTMENT OF HEALTH
4310 EAST 11TH AVENUE • DENVER, COLORADO 80220 • PHONE 388-6111
Anthony Robbina, M.D.. M.P.A. Eiecutiv* Director
October 24, 1977
Mr. Phil Schmuck
Division of Planning
Dept of Local Affairs nr»r o r
INTERDEPARTMENTAL (J(j ' « 0
RE: DEIS, Boulder Uastewater Facilities DIV- OF
Dear Mr. Schmuck:
The Colorado Department of Health has reviewed the above
mentioned document and offers the following comments:
Air Pollution Control: The DEIS adequately addresses the primary
air pol1ution impacts associated with the construction and opera-
tion of the alternative wastewater treatment facilities studied
for the city of Boulder- However, minimal discussion is provided
with respect to secondary or growth related impacts.
Although the Division does not question this level of discus-
sion, it should be noted that it represents a marked contrast to
the discussion of secondary impacts for other wastewater facility
proposals in the Denver AQCR and AQMA. _
More specifically, discussions in the Boulder DEIS emphasize
odorous emissions and the available control measures for the alter-
native facilities studied. The discussion of secondary impacts in
the Boulder DEIS is limited to the following on page 144, "Air qual-
ity caused by the secondary impact of induced growth can be consid-
erable." Also, on page 19 an interesting indication of the air
pollution levels to be expected in the future is given. That is,
"there are sufficient naturally occurring emissions of reactive hydro-
carbons that ozone standards may be exceeded in the future."
A very limited discussion was given to primary air quality
impacts in the DEIS prepared by EPA for was tewater treatment facilities
in the Denver region. However, over $200,000 was spent in evaluating
secondary air quality impacts caused by growth induced by the avail-
ability of adequate wastewater treatment facilities. This study
also duplicated, to some degree, the Denver region Air Quality
Maintenance analysis efforts of the APCD which were requirements
of EPA. Neither of the studies performed for the Denver region con-
cluded that there are sufficient naturally occurring emissions of
reactive hydrocarbons that could cause ozone standards to be violated
in the future. Further, it is not clear how EPA's position on the
Foothills project is reflected in the Boulder DEIS.
The Division does not fault the level of discussion of secondary
impact in the Boulder DEIS since: (1) the growth projections utilized
were consistent with local and regional planner's projections; and
lo
199
-------
Mr. Phil Schmuck
October 24, 1977
page 2
(2) indications are that Boulder city and county growth control
policies will prevail. The Division seriously questions the
apparent inconsistency in EPA's requirements for the treatment
of air quality impacts from one EIS to another, for similar pro-
jects, which are located in the same AQCR and the same AQMA.
«P
Radiation and Hazardous Wastes Control: The sludge injection fields
proposed in the DEIS should comply with the Department's "Guidelines
for Sludge Utilization on Land" (Draft copy) until the adoption
of regulations by the Departments of Health and Agriculture. The
objectives of these guidelines are to insure stabilization of the
sludge and to allow for its beneficial use.
Water quality & Engineering Division; (1) The main environment ~
to be impacted by any alternative will be the human population which
is in sparse to moderate density within a half mile radius of the
plant site. Therefore, any selected alternatives' main secondary
function will be to minimize to the maximum extent possible, offen-
sive odor generation. Since Phase One has already been funded
to include covering the existing trickling filters with air scrubbers,
the most predictable and reliable alternative would be one which
includes conventional, mechanical treatment processes in which odor
generation is controllable, in this case Alternative B or D.
(2) The advanced ammonia treatment required by the A£ stream classi-
fication eliminates Alternative A as a viable alternative since its
ammonia reduction capability is questionable. Also, the design life
of these basins can be highly variable and the odor generation
potential is high.
(3) While being the lowest cost alternative, Alternative C has odor
generation potential during extended periods of ice cover and
eventually as nutrient levels rise in the ponds during algae decay
after a bloom. Also, the effluent quality remains questionable
with this Alternative for the effectiveness of algae harvesting
has thus far not proved effective.
(4) Considering the plant setting and the upgraded stream classi-
fication, the only viable alternative would be B or a conventional
advanced treatment process. Going further with the conventional
treatment alternative, the activated sludge process is less compat-
ible to the trickling filter and anaerobic digestion process;
the use of the rotating biological disc process would be a more
compatible and reliable advanced treatment process.
•V
Sincerely,
/K
rtl
Ron Simsick
Program Administrator
200
-------
Responses to Colorado Department of Health letter
of 24 October 1977:
1. The statement: "There are sufficient naturally occurring
emissions of reactive hydrocarbons that ozone standards
may be exceeded in the future", refers to turpenes and
other reactive hydrocarbons that are naturally emitted
from conifers and other trees. These natural emissions
typically result in background reactive hydrocarbon levels
of 0.02 ppm or greater, depending on the location. This
effect was considered by the Colorado Department of High-
ways, to be more significant in the Boulder area than in
the Denver region due to Boulder's close proximity to the
Rocky Mountains and forest ranges.
The most recent and pertinent air quality projection for
the Boulder area was published in 1976: "Air Quality
Analysis for the Boulder Metropolitan Area", (EIS, Refer-
ench 12). Base conditions were taken from local air
quality monitoring data recorded from 1974 through 1976.
Air quality projections were based on the year 2000 popu-
lation projections developed by DRCOG. Carbon monoxide
was simulated with an APRAC model, while ozone data which
was incomplete for model use, was evaluated qualitative-
ly, assuming proportional relationships between emissions
and concentrations. This covered a slightly larger plan-
ning area than the EIS over the same planning period and
gives a good indication of secondary air quality impacts
caused by urban growth that had been accommodated by utili-
ties expansions projects such as sewer and water service.
Discussion of air quality impacts related to increased
growth in the Boulder Valley has been added to Section IV
under Long-Term Indirect Impacts (Page ), and also in
the summary in Section I.
2. The Boulder Wastewater Facilities EIS cannot be directly
compared with the recently completed Denver Regional EIS,
although both projects are located in the same AQCR. The
Boulder EIS covered a single facility in an area non-
contiguous with the Denver area. The Denver Regional EIS
evaluated eight separate wastewater projects in the Denver
metropolitan area as well as the 208 areawide non-point
source pollution control program. The Denver EIS presented
an opportunity to evaluate regional growth and development
impacts cumulatively for the Denver region. For this rea-
son, a large-scale analysis of secondary air-quality im-
pacts from growth induced by provision of utilities was
undertaken in the Denver EIS.
201
-------
Responses to Colorado Department of Health letter
of 24 October 1977
Page Two
For the Boulder EIS, EPA evaluated the local conditions
and on-going comprehensive planning activities and de-
cided that the Boulder wastewater facilities warranted
a separate EIS. The assessment of air quality projec-
tions in the previously mentioned air quality analysis
report was considered acceptable for evaluating secon-
dary impacts in the Boulder EIS.
3. Design of the sludge injection fields and operations
specifications to comply with the Department's "Guide-
lines for Sludge Utilization on Land" will become part
of the EPA grant conditions.
4. Comments on the treatment efficiency of alternatives A,
B and C have been noted and have been considered by EPA
in the selection process.
202
-------
DEPARTMENT OF THE ARMY
OMAHA DISTRICT. CORPS OF ENGINEERS
6014 U.S. POST OFFICE AND COURTHOUSE
OMAHA NEBRASKA 68IO2
MROPD-M 25 October 1977
Mr. John A. Green, Regional Administrator
United States Environmental Protection Agency
Region VHI, i860 Lincoln Street
Denver, Colorado 80203
Dear Mr. Green:
This responds to your letter notice cf 29 August 1977 with which you
transmitted a copy of the draft EIS for the Boulder Wastevater
Treatment Facilities, Boulder, Colorado for our review and comment.
We have completed our review of the draft EIS and have the following
comments.
Details are not provided on infiltration-percolation ponds, aeration
ponds or the storage lagoon. If these facilities are diked above the
existing ground level, it should be recognized they will create an
obstruction to flood flows and that flood levels may be raised. We
recommend that flood obstructions, if any, be analyzed and designs
developed that will not raise flood elevations more than 1 foot above
flood elevations without the facilities.
On Page 33 of your report, you state that the 100-year flood discharge
at the 75th Street sewage treatment plant is 12,000 c.f.s. Our 1972
flood hazard information report for the portion of Boulder upstream
of 28th Street is referenced as the source. Our 1969 Flood Plain
Information Report for the Boulder Metropolitan Region is the correct
source for the vicinity of the sewage treatment plant. The 1969 report
indicates a. 100-year discharge of 11,000 c.f.s. at the sewage treatment
plant.
We performed a new hydrology study for Boulder Creek upstream of
Boulder in 1976, and have determined that our 1969 discharge estimates
are too low. Although discharges downstream of Boulder have not been
reevaluated, preliminary indications are that the 100-year flood
203
-------
MROPD-M 25 October 1977
Mr. John A. Green, Regional Administrator
discharge may be on the order of 18,000 c.f.s. in the vicinity of
the sewage treatment plant. However, this number has not been
verified and the final figure may be somewhat lower. We do not
anticipate that flood elevations for the revised discharge would be
more than 1 foot higher than our 1969 report indicates.
The draft EIS is environmentally acceptable and mitigative measures
have been adequately addressed. Since the proposed project is located
in the flood plain and not in a wetland area, no permit will be
required; however, the discharge structure may involve a subsequent
permit.
We appreciate having had the opportunity to review this draft document.
We would also appreciate a copy of the final environmental statement
when it becomes available.
Sincerely yours,
Inclosure /'YoHN E. VELEHHADSKI, P.E.
Special Note C/Chief, Planning Division
204
-------
SPECIAL ::oTg
Our reviev notes that this proposed project may involve vor>: in
or adjacent to one or several strear.s or wetlands. Either under
Section 10'of the niver and Harbor Act of March 3, 1899 (30 Stat.
1151; 33 USC 1*03) or under the provisions of Section I»OU of the
Federal Water Pollution Control Act Ac-.endaent of 1972, a permit
cay ba required fros the Corps of Engineers prior to the start of
construction.
i.'either our letter of reviev nor this special r.oto is intended to
co.-.vey or r.jve Corps of Engineers approval to the document or the
proposed projects therein you sub-.itted for our reviev.
Additional project details and other information nay be needed
to Ea>;e an environmental assessment and/or prepare or supplement an
environmental impact statement in connection vith the perait
process. If you are not familiar vith the pernit regulations,
additional inforcation can be obtai-ed fro.-a this office upon request
Please vrite to: District Engineer
Onaha District, Corps of Engineers
ATT!!: Operations Division
P. 0. Box 5
Onaha, Nebraska 63101
205
-------
Responses to Department of the Army, Corps of Engineers letter
of 25 October 1977:
1. The infiltration-percolation ponds would be diked
above the existing ground level on the north end of
the site nearest Boulder Creek. In ponds that are
farther to the south, the berms would be designed so
that the top would not significantly exceed existing
ground levels. Thus, in total, the percolation ponds
would be designed not to raise flood elevations more
than one foot above flood levels without the ponds.
To a small degree, this would increase flood velocities
in the lowest part of the flood plain due to the re-
strictions of dikes from the percolation ponds near
Boulder Creek. However, as the flood level rises, flood
water would overtop the percolation pond berms and ex-
tend through the natural flood plain area.
The aeration ponds under Alternative C would have similar
effects to those discussed under percolation ponds. The
aeration ponds would be designed to allow flood flows to
exceed the berms and inundate the pond area.
The storage lagoon site under Alternative G will not be
within the Boulder Creek flood plain.
2. The 100-year discharge of 11,000 cfs from the 1969 report
has been noted and revised in the final EIS. The revised
18,000 cfs figure has also been noted and will be included
in the final EIS.
The 75th Street treatment plant was designed with all
doors and openings at least 2 feet higher than the maxi-
mum 100-year discharge of 11,000 cfs. This would still
be able to meet a revised flood elevation of one foot
higher than that projected for 11,000 cfs. Additional
facilities under Alternative B - construction of a new
activated sludge unit would be designed to withstand a
maximum discharge of 18,000 cfs.
206
-------
SECTION IX
-------
SECTION IX
REFERENCES
1. City of Boulder, Colorado Wastewater Utility Division and
CH^M-Hill, Inc., "Wastewater Facilities Plan for Boulder,
Colorado," October 1975.
2. Ci^M-Hill, Inc., "Comparative Study of Wastewater Treatment,
City of Boulder," July 1974.
3. Bauer Engineering, Inc., "Wastewater Management Opportunities,
Boulder Colorado-a study of alternatives," July 1974.
4. U.S. Environmental Protection Agency, "Negative Declaration
on the Proposed Wastewater Treatment Facility at Boulder,
Colorado," 10 November 1976.
5. CH^M-Hill, Inc., "Wastewater Facilities Plan for Boulder
Colorado, Supplemental Costs," February 1977.
6. Paddock, Mark IV. , "The Climate and Topography of the Boulder
Region," Natural History of the Boulder Area, Leaflet No. 13,
University of Colorado Museum, Boulder, Colorado, August 1964.
7- Berry, Joseph IV., "The Climate of Colorado," in Climates of
the States, Vol. 2, Water Information Center, Port Washington,
N.Y., 1974.
8. Brinkmann, W.A.R., "A Climatological Study of Strong Downslope
Winds in the Boulder Area," NCAR Cooperative Thesis-Institute
of Arctic and Alpine Research, Occasional Paper 7, University
of Colorado, Boulder, Colorado, 1973.
9. Bradley, R.S., "Natural Hazards—Wind," Environmental Inven-
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11. Bradley, R.S., "Air Pollution," Environmental Inventory and
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207
-------
12. Boulder City/County Health Department, "Air Quality Analysis
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13. MacPhail, Donald D., Helen L. Young & Dennis I. Netoff, White
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14. Moreland, Donald C. and Ronald E. Moreland, Soil Survey of
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15. Boulder City-County Health Department, Unpublished map showing
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to pollution by sewage systems, May 1975.
16. Thorne Ecological Institute, "Boulder Creek Project Environ-
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of Engineers, Omaha, Nebraska, 15 November 1972.
17. Dept. of the Army, Omaha District, Corps of Engineers, "Special
Flood Hazard Information Report, Boulder Creek, City of Boulder,
Colorado," Prepared for the City of Boulder and the Urban
Drainage and Flood Control District, 1972.
18. Madole, R.F. & A.E. Mears, "Floods" in Environmental Inventory
and Land Use Recommendations for Boulder County, Colorado,
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University of Colorado, Boulder, 1973.
19. Heffington, William and Michael Surlette, Personal Communica-
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December 1976.
20. Stocker-Keammerer and Assoc., "The Ecology of Boulder Creek:
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21. Blatchley Associates, "Water Rights Aspects of Boulder's
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22. Colorado Department of Health, Water Quality Control Commis-
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23. Denver Regional Council of Governments, Water Quality Manage-
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208
-------
24. Rodeck, Hugo G., Editor, Natural History of the Boulder Area,
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26. Ramaley, Francis, Colorado Plant Life, University of Colorado,
Boulder, 1927.
27. Olmsted, Frederick Law, Jr., The Improvement of Boulder, Colo-
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28. Thorne Ecological Institute, Boulder Creek Project, Environ-
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29. "States Lists of Endangered and Threatened Species of the
Continental United States," in Federal Register Volume 40,
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30. "Colorado Legislature S.B. 142 - Nongame and Endangered
Species Conservation Act," 1973.
31. Colorado Native Plant Society, "Provisional List of Endangered
or Threatened or Sensitive Vascular Plants of Colorado",
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Endangered Plant Subcommittee, May 1976.
32. Weber, Dr. William A., Professor of Natural History, Curator
of the Herbarium, University of Colorado Museum, Boulder,
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33. Netoff, D.I. and H.L. Young, White Rocks Natural Area Study,
D.D. MacPhail (ed.) Department of Geography, University of
Colorado, Boulder, 1970.
34. Boulder County Parks and Open Space Department, Open Space
Plan for Boulder County - draft map, 1976.
35. Flatiron Sand and Gravel Company, "Review Data for Special Use
Permit," Boulder, October 1972.
36. Weiser, Martha, Property owner, White Rocks area, Personal
Communication, October 1976.
37. Mrs. Tell Ertl, Property owner, White Rocks, Personal Communica-
tion, December 16, 1976.
209
-------
38. Toburen, Claudia, "Reclaiming Boulder County Gravel Pit as
a Wildlife Area," Western Interstate Commission for Higher
Education, Boulder County Dist. No. 1, Boulder, Colorado,
April 1974.
39. Maxwell, Paul, Boulder County Parks and Open Space Department,
Personal Communication, October 1976.
40. State of Colorado Department of Health, Air Pollution Control
Commission, "Regulation No. 2 in Odor Emission Regulations,"
20 April 1971.
41. "Materials Relating to Public Review of Wastewater Facilities
Plan," 1976.
42. Boulder City-County Health Department "Notice of Violation on
5 May 1975-Boulder 75th Street Treatment Plant: Sewage Odors,"
May 1975.
43. Boulder City-County Health Department "Notice of Violation on
7 January 1977-Boulder 75th Street Treatment Facility:
Sewage Odors," January 1977.
44. Lovelace, Walter B., Boulder yesterday and the Pioneer Trail,
Boulder Historical Society, 1968.
45. Baldwin, Susan, Report prepared for City of Boulder Sewer
Department concerning historical resources which might be
impacted by the proposed Boulder Wastewater Facility Plan.
City of Boulder Planning Department, 1975.
46. Seydel, Karle, An Inventory and Assessment of Known Archae-
ological Sites in the Affected Area of the City of Boulder
Sewer Utility. City of Boulder Sewer Department, 1975.
47. Archeological Consulting and Research Services, Inc., "Report
of Archeological Reconnaissance for the Boulder, Colorado
Wastewater Facility Plan," December 1976.
48. U.S. Government, Department of Commerce, Bureau of the Census,
1970 Census of Population and Housing.
49. Christiansen, N.J. (publisher), "The Boulder Market," a
publication by The Daily Camera, Boulder, Colorado 1976.
50. United Banks of Colorado, Inc., Economic Development Depart-
ment, Boulder, Colorado: An Economic Overview—1975. Denver,
Colorado, no date.
210
-------
51. Boulder Area Growth Study Commission, Exploring Options for
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52. R.L. Polk & Co., Urban Statistics Division, "Profiles of
Change," Detroit, Michigan 1974-1975 Edition, August 1975.
53. Denver Regional Council of Governments, "Clean Water Program,"
(Denver 208 Non-point Source Pollution Control Program),
October 1976.
54. Brouillette, Jason, Assistant Director, Boulder County Plan-
ning Department, Personal Communication, 26 October 1976 and
8 December 1976.
55. Ryan, Richard, City of Boulder, Planning Department, Personal
Communication, 19 November 1976.
56. Boulder, County of, County Assessor, 1973 through 1975 Abstract
of Assessment and Summary of Taxes, Boulder, Colorado.
57. Cottingham and Wells, Inc. Where to Live in Boulder County,
Boulder, Colorado, October 1976.
58. Smith, Douglas, Director, Wastewater Utility, Department of
Public Facilities, City of Boulder, Colorado, Personal Com-
munication, October-November 1976.
59. Ekberg, Chuck, Multiprop Corporation, Boulder, Colorado,
Personal Communication, October 1976.
60. Carson, Kermit, Public Service Company of Colorado, Personal
Communication, 9 December 1976 and 13 December 1976.
61. Colorado Department of Public Health, Water Quality Control
Commission, correspondence with Socio-Economic Systems on
6 January 1977-
62. Black & Veatch, Consulting Engineers, Comprehensive Study of
Water Works Facilities, Boulder, Colorado, Denver, Colorado,
March 1975.
63. Boulder, City of, Objectives and Programs 1976, Boulder,
Colorado, 1975.
64. Boulder, City of, Objectives and Programs 1977, Boulder,
Colorado, 1976.
65. Douglas, Donald, Director of Water Utilities, Boulder,
Colorado, letter, 28 October 1976.
211
-------
66. U.S. Government, Department of Housing and Urban Development,
Habitat: A Planned Unit Development, Title X, Draft Environ-
mental Impact Statement, Denver, Colorado, October 1976.
67. Black & Veatch, Consulting Engineers, "Infiltration/Inflow
Analysis, Sanitary Sewer system, Boulder Colorado," 30 May 1975.
68. U.S. Environmental Protection Agency, "Process Design Manual
for Suspended Solids Removal," EPA Technology Transfer 625/1-
75-003a January 1975.
69. University of Colorado, Experimental Infiltration-Percolation
Pond studies at the Boulder Wastewater Treatment Facility.
Preliminary Results January 1977.
70. Denver Regional Council of Governments, "Clean Water Program,
Technical Report and Summary-Draft" March 1977.
71. Engineering-Science, Inc., "Pipeline Transport of Digested
Sludge to Strip Mine Spoil Site for Spoil Reclamation",
August 1975.
72. 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 Bemuda Grass", Journal of
Environmental Quality, Vol. 1, No. 3, 1972.
73. 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.
74. Chaney, Rufus L., "Land Application of Sewage Sludge, Benefits
and Problems", Proceedings of the 1973 Lime and Fertilizer
Conference, 5:15-23, 1973.
75. 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.C., 1967.
76. Smith, Douglas G., Director of Wastewater Utility, City of
Boulder, Colorado, letter "Re: Environmental Impact State-
ment, Boulder Wastewater Treatment Plant" to G. Taylor,
U.S. Environmental Protection Agency, Region VIII, dated
April 26, 1977.
77. Easton, Eric B., Ed., "FDA, OSWMP seek Limits on Metals in Sludge
Bound for Land Application" in Sludge, Vol. 1,-No. 7, pg. 51,
October 1976.
212
-------
78. McVehil, George E., "Fog Formation Over a Warm Pond", consul-
tant report to the City of Boulder, undated.
79. 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.
80. Vodehnal, Dale, "Comments on Odor Potential of Proposed Boulder
Wastewater Treatment Facility, Alternative A", Control Techno-
logy Section, U.S. Environmental Protection Agency, Region VIII,
memorandum dated June 2, 1977.
81. Morris, Alvin L., "Dilution of Gaseous Effluents from Boulder
Wastewater Treatment Plant at 75th Street", consultant re-
port to the City of Boulder, January 15, 1976.
82. Roll, John L., Metropolitan Sanitary Districts of Greater
Chicago, Personal communication, September 15, 1975 (As
quoted in Metro Denver Sludge E.I.S.).
83. Boulder Chamber of Commerce. In Boulder, Colorado, Vol. 1. ,
Ed. 1, Summer 1976.
84. Holland, Dale, Boulder County Assessor's Office, Personal
communication, October, 1976.
85. Boulder, County of, Office of the Assessor, Assessment Records,
October-November, 1976.
86. Lane, Gordon, Chief Personal Property Assessor, Boulder County
Assessor's Office, Personal communication, November, 1976.
87. Metcalf & Eddy, Inc. Wastewater Engineering, New York: McGraw-
Hill Book Company, 1972.
88. Berve, Donn W., Chief of Environmental Health Services, Tri-
County District Health Department, personal communication on
September 4, 1975.
89. Council on Environmental Quality in association with the
Environmental Protection Agency, "Evaluation of Municipal
Sewage Treatment Alternatives", February 1974.
90. Dotson, G.K., "Constraints to Spreading Sewage Sludge on Crop-
land", from "News of Environmental Research in Cincinnati",
Environmental Protection Agency, May 31, 1973.
213
-------
91. Feth, J.H., "The Urban Environment", U.S. Geological Survey,
Circular 601-1, 1973.
92. Hotes, F.L., K.H. Ateshian and B. Sheikh, "Comparative Costs
of Erosion and Sediment Control - Construction Activities,"
Engineering-Science, Inc. - U.S. Environmental Protection
Agency, July 1973.
93. CH2M HILL, "Metro Denver District Sludge Management, Volume I;
Summary Report", February 1975.
214
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APPENDICES
-------
APPENDIX A
SOIL CHARACTERISTICS OF THE PROPOSED PROJECT AREA
CHARACTERISTICS OF SOIL SERIES AT THE 75TH STREET PLANT
Soils of the Niwot series are made up of deep, somewhat poorly
drained soils that are shallow over gravelly sand. These soils, like
the Loveland series soils, were formed on low terraces and bottomlands
in loamy alluvium superimposed over sand and gravel. Slopes are 0 to 1
percent. The native vegetation is mainly brome and water-toleriint
grasses. These soils are best suited for use as pasture or meadow be-
cause of high, seasonal water table and shallow depth (10 to 2) in.) to
sand or gravel. Some small areas are used for irrigated crops, and an
increasing number of areas are used for sand and gravel pits.
The dark-grayish-brown and grayish-brown surface layer is variable
in texture. It ranges from sandy clay loam to light clay loam or loam
and is about 14 in. thick. The underlying material, extending to a
depth of 60 in. or more, is pale-brown gravelly sand containing many
mottles. In the surface layer, soil reaction is mildly alkaline; below
the surface it is neutral.
Niwot soils have moderate permeability. Available water capacity
for the profile is low to moderate. Roots can penetrate to a depth of
60 in. or more, and the seasonal high water table is at a depth of be-
tween 6 and 18 in. Runoff is slow, and the erosion hazard is slight ex-
cept for bank-cutting near channels. Because of their position in the
landscape, these soils are frequently flooded. The soils are inter-
spersed with small, almost barren gravel bars and small areps of Love-
land soils as well as some unnamed sandy soils (Reference A-l).
CHARACTERISTICS OF SOILS AT THE INFILTRATION-PERCOLATION BASIN SITE
PROPOSED FOR THE 75TH STREET PLANT
Nearly all of the area of the infiltration-percolation basins is
made up of the Niwot and Loveland soils described above. However, the
Loveland soils of the southern edge of the basin area are adjacent to
Manter sandy loam, 0 to 1 percent slopes, and the two thus are likely
to be found together in a transitional complex. Manter sandy loam (0 to
1 percent slopes) is described in the succeeding section (Reference A-l).
CHARACTERISTICS OF SOILS AT THE SLUDGE INJECTION AREA SITE
PROPOSED UNDER ALTERNATIVE A
Manter Series
The Manter series is made up of deep, well-drained soils. These
soils were formed on terraces and uplands in loamy eolian and outwash ma-
terials. The native vegetation is mainly short grasses. These soils are
used for irrigated and dryland crops and for pasture.
A-l
-------
In a representative profile, the surface layer is brown sandy loam
about 6 in. thick. The subsoil, about 10 in. thick, is brown and pale-
brown sandy loam. The substratum is strongly calcareous, very pale-brown
sandy loam and loamy sand extending to a depth of 60 in. or more. In
the surface layer and subsoil, soil reaction is neutral; in the underly-
ing material, it is moderately alkaline.
Manter soils have moderate permeability, and available water capac-
ity for the profile is moderate. Roots can penetrate to a depth of 60
in. or more (Reference A-l) . The Manter soils can further be differen-
tiated into Manter sandy loam 0 to 1 percent, 1 to 3 percent, and 3 to
9 percent slopes.
Ascalon Series
The Ascalon series is made up of deep, well-drained soils. These
soils were formed on terraces and uplands in loamy mixed alluvium and
wind-laid materials. The native vegetation is mainly blue grama. Most
of the acreage of these soils is used for irrigated and dry cropland.
In a representative profile, the surface layer is grayish-brown
sandy loam about 8 in. thick. The subsoil reaches to a depth of 26 in.
It is brown sandy clay loam in the upper part and strongly calcareous,
light yellowish-brown sandy loam in the lower part. The substratum, to
a depth of 60 in. or more, is strongly calcareous, very pale brown sandy
loam. In the surface layer, soil reaction is neutral, but with increas-
ing depth the reaction becomes moderately alkaline.
Ascalon soils have moderate permeability. Available water capacity
for the profile is high. Roots can penetrate to a depth of 60 in. or
more (Reference A-l). Ascalon soils can further be differentiated into
Ascalon sandy loam 1 to 3 percent and 3 to 5 percent slopes.
Calkins Sandy Loam, 1 to 3 Percent Slopes
The Calkins series is made up of deep, somewhat poorly drained soils.
They were formed in loamy alluvium. This soil is found on stream ter-
races and bottoms. In most places, it occurs as long, narrow areas more
than 20 acres in size. The native vegetation is mainly meadow grasses.
All of this soil is used for irrigated crops.
In a representative profile, the surface layer, about 40 in. thick,
is grayish-brown sandy loam. Underlying this to a depth of 60 in. or
more is light brownish-gray coarse sandy loam that contains many brown
mottles. Soil reaction is neutral.
Calkins soils have moderate to rapid permeability. Available water
capacity for the profile is moderate to high. Roots can penetrate to a
depth of 60 in. or more, and the seasonal high water table is at a depth
of three ft or less. Runoff is slow on this soil. The erosion hazard
ard is moderate (Reference A-l).
References A-l. USDA, Soil Conservation Service, "Soil Survey of
Boulder County Area, Colorado, January 1975.'
A-2
-------
Table A-l. ENGINEERING INTERPRETATIONS OF SOIL PROPERTIES
Soil series and
map symbols
Soil features affecting
Pond reservoir areas
Embankments and dikes
Drainage of cropland
and pasture
Irrigation
Ascaion
Calkins
Loveland
Manter
McClave
Niwot
Moderate permeability;
0 to 3 percent slopes.
High water table;
moderately rapid per-
meability.
High water table;
rapid permeability
below depth of 3 feet;
0 to 1 percent slopes.
Rapid permeability be-
low depth of 3 feet; 0
to 3 percent slopes.
Rapid permeability be-
low depth of 3 feet; 3
to 9 percent slopes.
Water table at depth of
1/2 to 1 1/2 feet;
rapid permeability be-
low the surface layer.
Medium to low permea-
bility; fair to good
compaction; medium
piping potential.
Medium permeability;
fair to good compac-
tion; medium to high
piping potential.
High compacted permea-
bility below depth of
3 feet; medium to low
shear strength; fair
compaction in the
upper 3 feet.
Medium compacted per-
meability; medium shear
strength; fair compac-
tion; high to medium
piping potential.
Medium compacted per-
meability; medium shear
strength; fair compac-
tion; high to medium
piping potential.
High permeability;
medium shear strength;
good compaction.
Moderate permeability.
High water table; mod-
erately rapid permea-
bility.
Rapid permeability
below depth of 3 feet;
some outlet problems-
Moderately rapid per-
meability.
Moderately rapid per-
meability.
Water table at depth
of 1/2 to 1 1/2 feet;
outlet problems; sub-
ject to flooding.
Rapid intake rate;
high available water
capacity; 0 to 3 per-
cent slopes.
Rapid intake rate;
high available water
capacity.
Moderate intake rate;
moderate available
water capacity.
Rapid intake rate;
moderate available
water capacity; 0 to
3 percent slopes.
Rapid intake rate;
moderate available
water capacity; 3 to
9 percent slopes.
Water table at depth
of 1/2 to 1 1/2 feet;
low available water
capacity; subject to
flooding.
Source: Reference A-l.
-------
Table A-2. LIMITATIONS OF THE SOILS FOR USES RELATED TO WASTEWATER TREATMENT PLANTS
Degree and kind of limitation
Soil series and
map symbols
Septic tank
absorption
fields
Sewage
lagoons
Shallow
excavations
for
Local
roads and
streets
Sanitary
landfill
Ascalon Slight.
Calkins Severe: water table
at depth of 2 to 3
feet.
Loveland Severe: flooding
hazard; water table
at depth of 2 to 4
feet.
Manter Slight.
McClave Moderate to severe:
water table at depth
of 2 1/2 to 5 feet.
Moderate: moderate
permeability; slopes.
Severe: water table
at depth of 2 to 3
feet.
Severe: flooding
hazard; rapid per-
meability below a
depth of 3 feet.
Severe: rapid per-
meability in sub-
stratum.
Moderate to severe:
water table at depth
of 2 1/2 to 5 feet;
moderate permeabil-
ity.
Slight.
Moderate to severe:
water table at depth
of 2 to 3 feet.
Severe: flooding
hazard; water table
at depth of 2 to 4
feet.
Slight above depth
of 3 feet; severe
below depth of 3
feet; sandy substra-
tum.
Moderate: clay loam
texture; water table
at depth of 2 1/2 to
5 feet.
Moderate: moderate
shrink-swell poten-
tial.
Moderate: water
table at depth of
2 to 3 feet.
Moderate: flooding
hazard; moderate
shrink-swell poten-
tial.
Slight.
Moderate: moderate
shrink-swell poten-
tial.
Slight.
Severe: water
table at depth of
2 to 3 feet.
Severe: flooding
hazard; sand and
gravel at depth of
20 to 40 inches.
Slight: pollution
hazard in some
places because of
rapid permeability.
Severe: clay loam
texture; water ta-
ble at depth of
2 1/2 to 5 feet.
Niwot
Severe: flooding
hazard; water table
at depth of 1/2 to
1 1/2 feet.
Severe: flooding
hazard; water table
at depth of 1/2 to
1 1/2 feet; rapid
permeability.
Severe: water table
at a depth of 1/2 to
1 1/2 feet.
Moderate to severe:
flooding hazard;
water table at depth
of 1/2 to 1 1/2 feet.
Severe: flooding
hazard; water ta-
ble at depth of
1/2 to 1 1/2 feet.
Source: Reference A-l.
-------
APPENDIX B
BIOLOGICAL ENVIRONMENT
BIOTIC COMMUNITIES
Pasture/Agriculture
Vegetation—
Much of the plains area in eastern Boulder County is currently
under agricultural use. Dryland wheat farming is practiced on upland
sites which are sloping or unsuitable for irrigation by gravity flow
(Reference B-l). Irrigated cropland is used for the production of
corn (grain and silage), alfalfa, beans, barley, beets, hay and oats.
Irrigated pastureland comprises the third major agricultural land use
in the country.
The low-lying land south of Boulder Creek and east of 75th Street
is situated within the floodplain, and much of this area is currently
being utilized as pastureland. Approximately 200 acres of this unit
is under consideration for land treatment facilities under the proposed
project. Areas within the floodplain are generally not suitable for
use as cropland because of poor drainage, stoniness and related prob-
lems (Reference B-l). The high groundwater table and the generally
moister floodplain conditions cause some of these pastures to be
sub-irrigated, which fosters good plant growth and allows for a greater
grazing pressure than on drier areas. Other parts of the pasturelands
are served by irrigation ditches. Further toward the south, between
the Union Pacific Railroad tracks and Valmont Road, the soil is deeper,
and there is a change in land use from pasture to irrigated cropland.
Wildlife—
A large variety of animals is associated with the Pasture/Agri-
culture unit, which serves primarily as a feeding and resting area.
The most abundant animals are small rodents such as the eastern and
desert cottontail rabbits, thirteen-line ground squirrels, deer mice,
pocket mice and meadow voles. These form the typical diet of predator
species such as the coyote, great-horned owl, barn owl, red-tailed
hawk and other raptors. Other mammals which depend on the Pasture/
B-l
-------
Agriculture unit are the plains pocket gopher, western harvest mouse,
black-tailed prairie dog and striped skunk.
The Pasture/Agriculture habitat in the study area is often bor-
dered by the Riparian habitat and shares many of its bird species.
Common species occurring in the Pasture/Agriculture unit are the west-
ern meadowlark, black-billed magpie, grasshopper sparrow, savannah
sparrow, house finch and lark bunting. The lark bunting is the offi-
cial Colorado State Bird. Migrant birds common in the spring and
early summer include the American goldfinch, western and mountain
bluebirds, kingbirds and the predatory sparrow hawk.
Riparian
Boulder Creek and the tributary seasonal streams and ditches re-
present the main Riparian habitat; areas. All alternatives will con-
sider some form of wastewater discharge to Boulder Creek. Some con-
struction activity may occur immediately adjacent to Riparian zones.
Vegetation—
Riparian vegetation occurs along Boulder Creek and is character-
ized by the presence of cottonwoods, willows, shrubs and herbaceous
plants. Cottonwoods generally grow along watercourses, and their large
size provides shade and thus modifies the microclimate in the under-
story. Willows frequently become established on exposed, moist or
sandy sites, stabilizing the soil and allowing for the later estab-
lishment and growth of cottonwoods. Other tree species such as box
elder, alder, hackberry and ash are characteristic of the Riparian
zone. Major shrub species include hawthorn, chokecherry, golden
currant and snowberry. Herbaceous vegetation is often dense and con-
sists of many native and introduced mesophytic species. In those
riparian areas where grazing occurs, vegetation is subject to tramp-
ling and other disturbances that often result in a poorly developed
groundcover and stream bed erosion.
Wildlife—
The Riparian habitat generally provides an interface between
aquatic and terrestrial ecosystems. This "edge" effect is important
not only for its diversity but also for its value as food, shelter and
a corridor for wildlife passage. The creek traverses several distinct
areas as it flows from the foothills through the city and down onto
the plains and agricultural areas. Thus, in a regional context, the
narrow watercourse, lined with trees and shrubs, serves as a corridor
B-2
-------
for wildlife movements by provision of water and shelter. Boulder
Creek has been the subject of recent as well as historical investiga-
tions (References B-2, B-3).
Insect and fish populations within Boulder Creek depend strongly
upon stream conditions and the seasonal quality and quantity of waters
entering the creek. Within the upper reaches of Boulder Creek above
the Pearl Street treatment plant, the bottom substrate consists of
gravel and rock, with some siltation in the pools. Benthic insects
are fairly diverse, with up to 15 species, dominated by Ephemeral la
mayflies, midge larvae, caddis fly nymphs and aquatic beetles (Ref-
erence B-2). A record of benthic invertebrate sampling is presented
in the latter part of Appendix B. Fish habitat is abundant, and pre-
dominant fishes are white sucker, long-nose dace and rainbow trout.
A listing of fish in the study area is also given in the latter part
of Appendix B. Historically, the Boulder Creek environment changes
markedly after 55th Street. When the Pearl Street treatment plant
outfall was operational, excess organic matter, nutrients and other
pollutants depressed the dissolved oxygen level and encouraged in-
festations of sewage fungus, degrading the stream habitat. Fish and
several major categories of insects typically disappeared from these
polluted areas, leaving mainly tolerant organisms such as moth fly
larvae, midge larvae and sludge worms, which tolerate low dissolved
oxygen levels. With the cessation of effluent disposal from the Pearl
Street outfall in May 1975, Boulder Creek has shown signs of recovery.
However, organic and sediment loads from agricultural return flows,
channelization and the 75th Street sewage outfall continue to make the
creek a shallow, turbid, warm-water ecosystem.
Mammals living within the Riparian habitat include the beaver,
muskrat, badger, marmot, skunk, prairie dog, rabbit and raccoon.
While the beaver is rather rare in Boulder Creek, the muskrat and
raccoon appear to utilize even highly polluted watercourses and water
bodies. Other mammals favoring the Riparian zone include the harvest
mouse, deer mouse, red fox and occasional mule deer.
The Riparian habitat harbors a wide diversity of bird species. A
detailed listing of species probably occurring in Boulder Creek is
given in Appendix B. Common species include several swallow species,
loggerhead shrike, song sparrow, belted kingfisher and migrant warblers,
Copper's and sharp-shinned hawks nest in the cottonwood trees near
the creek and hunt small birds and rodents.
Ponds and Marshes
Former gravel mining operations along the Boulder Creek flood-
plain have left numerous water-filled gravel pits that have created an
B-3
-------
extensive pond and marsh environment. Within the project area, the
major pond areas are the Walden Pond Wildlife Habitat Area and the
Sawhill Ponds area. Both pond areas border the 75th Street treatment
plant and Alternative C treatment site from the south.
Vegetation—
The pond areas are characterized by large areas of standing water,
peripheral zones of emergent vegetation and steep banks. Principal
plant species include cattails, bulrushes, sedges and rushes. The
lack of topsoil adjacent to the ponds has led to the development of
many bare areas consisting of compacted sandy soil and gravel. Vege-
tation is sparse in these areas and, where present, consists mainly of
reeds such as Russian thistle and summer cypress.
Wildlife—
The extensive pond areas, maintained by the high groundwater
levels, provide a stable year-round aquatic environment for waterfowl
and other water-associated birds and animals. Records from the Walden
Pond area (Reference B-4) indicatq a large resident population of pied-
billed grebes, Canada geese, mallards and American coots. Great blue
herons are also common year-round visitants. Common shorebirds include
killdeer, solitary and spotted sandpipers, greater yellowlegs and sev-
eral gull species. Migrants and visitants from other ponds and reser-
voirs include the blue-winged teal, redhead, pin-tail and gadwall
ducks.
Few mammal species utilize the pond areas because of the steep
banks and sparse shore vegetation. Animals tolerating this environ-
ment are the muskrat and raccoon. Species which occasionally frequent
the periphery of the pond areas may include the coyote, red fox and
striped skunk. Reptiles and amphibians observed in the Walden Pond
areas are the snapping turtle, painted turtle, garter snake and,
rarely, the northern water snake.
Walden pond is artificially stocked with rainbow trout. Other
fish species which have been introduced into the ponds are white suck-
er, plains sand shiner and western gambusia.
White Rocks Natural Area (WRNA)
The area known locally as the White Rocks is located north of
Boulder Creek between 75th Street and 95th Street. The steep 100-ft
bluffs rising directly above the creek bed contrast sharply with the
flat pasturelands. This is a unique and ecologically sensitive area
B-4
-------
recognized for its unusual geologic formations and as an ecological
asylum for several species of rare and endangered plants and animals.
The western portion of the White Rocks area overlaps the proposed
land treatment site under Alternative A.
Vegetation—
The White Rocks have been the subject of many ecological and mon-
itoring studies in recent years (References B-5, B-6, B-7). The White
Rocks area is generally within the plains grassland region, although
its expansive sandstone outcroppings and its abrupt transition to the
riparian zone at Boulder Creek provide many varied habitats for plant
life. Typical dry uplands vegetation occurs along the upper reaches
of the White Rocks where there is adequate soil development. Extensive
exposed sandstone areas provide a harsh environment for plant growth,
with hardy plants such as yucca, prickly pear, big bluestem and needle
grass precariously established in pits, cracks and other areas of soil
accumulation. A few ponderosa pine and some shrubs such as skunkbrush,
fourwing saltbrush plum, currant, chokecherry and Bessey cherry are
found in scattered locations along the bluffs. Many more plant species
are found on the rocks. At the base of the White Rocks, cottonwoods
and other riparian vegetation occur within the WRNA.
The extremely rare fern Asplenium andrewseii occurs underneath
overhanging ledges of a particular stratum on the cliffs. Formerly
identified as Asplenium adiantum-nigrum, this fern was recently re-
cognized by the Department of the Interior, Endangered Species Program
in 1977 as an endangered species. Its occurrence is dependent on the
unique environmental conditions found at this site. Human activities
such as generation of dust and gaseous pollutants (smog), changes in
microclimate or physical disturbances may affect this species ability
to survive. Two other rare plants, forktip three awn grass (Aristida
basiramea) and American potato bean (Apios americana) also occur at
the WRNA (References B-8, B-9).
Wildlife—
The White Rocks area provides a distinct wildlife habitat within
the project area. The juxtaposition of tall bluffs overlooking the
lowlying Boulder Creek and pasture areas creates an important "edge"
effect. Resident cliff-nesting species include the barn owl, great
horned owl, kestrel, and several swallow species. The two owl species
are not common to the area, depending largely upon the White Rocks
for nesting sites. The bluffs are also used as resting and surveil-
lance points by resident red-tailed hawks and migratory hawks such as
Swainson's hawk, ferruginous, rough-legged and Harlans hawks as well
as immature golden and bald eagles. (Reference B-10). Cottonwood
B-5
-------
trees at the base of the White Rocks, adjacent to the creek, also har-
bor flickers, eastern kingbirds, western meadowlarks, numerous migrant
warblers and sparrows, kestrels and wrens. (Reference B-8).
Small rodents such as mice, squirrels and rabbits are common.
These mammals occupy niches along the cliff base and under brush and
fallen trees in the floodplain. Other mammals include skunks, marmots,
badgers and raccoons. The main predators are the red fox and coyote.
The red fox has been observed in the WRNA and probably nests within
sheltered rock hollows.
Several unusual and rare animals have been found at White Rocks.
Dr. Robert Gregg, an entomologist at the University of Colorado, has
collected several rare ant species at the WRNA (Reference B-ll).
Aphaenogaster fulva, an ant species common east of the Mississippi
River, occurs along the bluffs. Three other rare western species found
in the area are A. huachucana, Formica oriniventris and Lasius occi-
dentalis. The mining bee, Perdita opuntiae, is also found along the
lower rock faces. This species is unique to the area, drilling narrow
burrows into the sandstone cliffs to accommodate its hives (Reference
B-12). The face of the White Rocks is marked by numerous depressions
which gather rainwater and dry up shortly afterwards. Due to evapora-
tion, water in the pits becomes relatively saline. An interesting
phenomenon is the ephemeral fairy shrimp found in these pits which com-
plete their life cycle in the duration of a few days to a few weeks
when these "solution pits" occur.
Residential/Urban
Vegetation—
The Residential/Urban unit refers to that land which is currently
being utilized for some form of human activity other than agriculture
or mining. Within the vicinity of the proposed project, areas that
can be characterized as Residential/Urban are the Heatherwood Estates
Gunbarrel Greens and the 75th Street sewage treatment plant. The
Heatherwood Estates is a recent development occupying approximately
200 acres within a former dryland farming area. The 75th Street sewage
treatment plant is situated south of Boulder Creek within a floodplain
meadow that consists of grasses, weeds and a few cottonwoods along the
riparian interface. Several farm homes scattered along 75th Street
Road and Valmont Road supplement the Residential/Urban unit. In the
past, residential areas, particularly Heatherwood Estates and Gunbarrel
Greens, have been subject to odor problems downwind of the 75th Street
treatment plant.
B-6
-------
Wildlife-
Birds and animal species found within the proximity of residential
or urban developments are generally those species which are either (1)
tolerant of human disturbances, (2) dependent upon human activities,
(3) introduced by humans or (4) some combination of the three. Bird
species occurring near residential and urban areas are Stellar's jay,
robin, mockingbird, starling, house finch and several sparrow species.
Small mammals occasionally found in and around buildings include
the house mouse, Norway rat, plains pocket gopher and fox squirrel.
The raccoon, striped skunk and red fox are infrequently observed in
populated areas.
Gravel Mining Areas—
Within the project area, gravel mining operations are currently
conducted by the Flatiron Sand and Gravel Company on approximately 250
acres east of 75th Street within the Boulder Creek floodplain. Much
ecological and monitoring study has preceded the present operations,
and the principals are firmly committed to restoring that part of the
floodplain to an ecologically sound condition (References B-7, B-8) .
The proposed land treatment site under Alternative C will be subject
to gravel mining by a private firm prior to usage as a treatment area.
Vegetation—
The gravel mining operations by Flatiron generally proceed from
October through March. Reclamation of the bare gravel pits with trees
and grasses occurs annually during March and April. The master plan
for the reclamation project will be staged over nine years and calls
for the recreation of riparian woodlands, dry grasslands, wet sedge
meadows and numerous lakes. At present, the revegetation program has
had limited success, with scanty cottonwood regeneration and numerous
bare areas. In the last two years, young tree plantings have been sub-
ject to beaver depredations. A portion of the site has been reserved
as a nursery area for cultivating native trees and shrubs.
Wildlife—
The gravel mining area represents a highly disturbed environment.
Mining activities, equipment noise and particulate emissions during
the operating season are partial wildlife deterrents. From March
through September, when mining operations are idle, wildlife move more
freely from the adjacent areas. Annual wildlife monitoring programs
B-7
-------
and maintenance of test plots are conducted on the reclamation sites.
Aquatic bird species frequenting the groundwater-filled gravel
pits are the pied-billed grebe, blue-winged teal, ring-necked duck,
killdeer, spotted sandpiper and several gull species. Birds observed
in the vicinity of the pond areas include red-winged blackbird, west-
ern meadowlark, barn swallow, mourning dove and several sparrow species
(Reference B-7).
Within the gravel pits area, mammals are represented by species
tolerant to human presence such as muskrats and raccoons. Prairie dogs
have colonized one dry gravel pit area where the water table was lower-
ed and vegetation succeeded toward upland grassland species. These
rodents have been reported in numbers of 10 per acre and appear to be
a stable population (Reference B-13). Some concern has been expressed
by the local residents and by Flatiron Company that these animals may
be a reservoir for "prairie-dog plague," which can also affect humans.
Future control measures may include dusting the animals to kill plague-
carrying fleas. Reptiles and amphibians recorded in the gravel pit
ponds are the leopard frog, western chorus frog, snapping turtle and
northern water snake. Fish species successfully introduced into the
ponds include the largemouth bass, white sucker, green sunfish, bluegill
and pumpkinseed (Reference B-7).
B-8
-------
Sample Locations
Table B-l. BENTHIC INVERTEBRATES OF BOULDER CREEK
Upstream E. Pearl Downstream Upstream 75th Downstream
WWTP E. Pearl WWTP St. WWTP 75th St. WWTP
—
95th St.
Bridge
Mayflies Ephemcroptera
Ephemeral la sp.
Baetls sp.
Rhithrogena sp.
Stoneflles Plecoptera
Isoperla sp.
Pteronarcella sp.
Acroneuria sp.
Caddlsflles Trichoptera
HydropsycTie sp.
Brachycentrus sp.
Lepldostoma sp.
Dlptera
Midges Tendipedidae
Snipe flies Atherix sp.
Moth flies Psychodidae
Crane flies Tipula sp.
Freshwater shrimp Amphipoda
Hyalella azteca
Beetles Coleoptera
Stenelmis sp. (larvae)
(adult)
Elmldae (larvae)
Annelida
Sludge worms Tubificidae
Sow bug s Isopoda
Asellus militaris
Leeches Hirudinea
Helobdella nepheloidea
TOTAL
N/m
270
7
10
67
3
10
690
17
53
23
g/m2 N/m2 g/m2 N/m2 g/m2 N/m2 g/m2 N/m2 g/m2
6.930
O.S30
0.190
0.017
0.850
0.327
1.050
0.003
0.010
0.307
0.343
0.020
0.040
0.030
0.360
0.115
257
0.040
0.003
0.423
270
0.590 145
20 0.115
0.040
0.175 375 0 765
5 8.120
370 2.045
5 0.130
13 0.007 3 0.007 400 2.645 80 0.130 525 0.215
S 0.240 90 2.190
10 1.565 225 26.830
1187 10.177 273 0.833 700 3.735 240 1.880 1585 40.230
(1) N/m number per meter square; g/m grams per meter square
Source: From Stoecker-Keammerer £ Associates, "The Ecology of Boulder Creek: Environmental
Inventory and Evaluation of Sewage Treatment Alternatives, " prepared for CH2M HILL.
B-9
-------
Table B-2. BIRD SPECIES AND THEIR PROBABLE OCCURRENCE
WITHIN STUDY AREAa
'Biotic
communities
Common name
Scientific name
M £ a H og
00 01 ji a u
< U U T-l
SO* C -rt 0) CO
•rt O J3 01 U
Hi ee PU 3 « o
12345 6
GREBES
Horned grebe
Eared grebe
Pied-billed grebe
Western grebe
WATERFOWL
Canada goose
Snow goose
Mallard
Pintail
Gadwall
American widgeon
Northern shovelor
Blue-winged teal
Cinnamon teal
Green-winged teal
Wood duck
Redhead
Canvasback
Ring-necked duck
Common goldeneye
Barrow's goldeneye
Bufflehead
Greater scaup
Lesser scaup
Ruddy duck
Common merganser
Red-breasted merganser
VULTURES, HAWKS
Turkey vulture
Cooper's hawk
Sharp-shinned hawk
Marsh hawk
Swaison's hawk
Rough-legged hawk
Ferruginous hawk
Red-tailed hawk
Golden eagle
Osprey
Prairie falcon
Pigeon hawk
Sparrow hawk
Harlan's hawk
Bald eagle
GALLINACEOUS BIRDS
Ring-neck pheasant
PODICIPSDIPOROES
Podicaps auritus
Podicaps caspicus
PodHymbua podiceps
Aechmophorua occi den tails
ANSERIFORMES
Sranta canadensis
Chen hyperborea
Ritas platyrhynchos
Anas acuta
Anas strepera
Mareca ajnerlcana
Spatula clypeata
Anas discors
Anas cyanoptera
Anas carollnenais
Aix sponsa
Aythya araericana
%tftya vallsinsria
Ay thy a collaris
Bucephala clangula
Bucsphala islandica
Bucephala aiieola
Aythya marila
Aythga affinis
Oxyura jamalcansls
Mergus merganser
Margus ssrrator
Cathartes aura
Aocipiter cooparil
Accipitar striatus
Circus cyanaus
Butao swainsoni
Buteo lagopus
Butao regalls
Butao Jamaicans is
Aguila cnrysaeCos
Pandion hallaotus
Falco majflcanus
Falco eolujnbarius
FaJco sparverlus
Suteo harlani
ffallaeetus laucophalus
GALLIFORftES
Phasianus coJ.chi.cus
C
0
A C
R
R 0 A. C
000
C
0 0
0
C 0
0
000
R
C
R
0
0
R
0
0
0
0
0
0
0
0
0
0
000000
oo OR
00 R R
0 0 C C
0 0
00 0
OR R
C R C
R R 0
R
R R 0
R R a R
A R C
R R R
R
0 C C C
B-10
-------
Table B-2 (continued). BIRD SPECIES AND THEIR PROBABLE
OCCURRENCE WITHIN STUDY AREAa
•H
U
41
3
Common name Scientific name 1
Blotlc
communities
o -a
JS » H
S
•H
U
0.
2
2
a jtf
w o
| S
a h us
Laucophoyx thula
Ardoa haxodias
Butoridas vires cons
Wcyticorax nycticorax
Nyctanassa violacea
Sotaurus lentdginosus
Ixobrychus exilis
Plegadis chihi
GRUIFORMES
limicola
Porzana Carolina
Cot urni cops noveboracensis
Gallinula chloxopus
Fulica anaricana
CHARADRII FORMES
Recnrvi rostra amsricana
Char a dri us voci farus
T ring a sol it aria
Acitia macularia
Catoptrophorus samipalmatus
To tan us malanoleucus
Totanus flavipes
Ijjnnodromus scolopaceus
Erolia fuscicollis
Ereunetes pus il las
Ereunates mauri
Srolla bairdii
Phal aropus fuli cari us
Steganopus tricolor
Philohela minor
Capella gallinago
Larus aro-entatus
lartis californicus
Laxus dalawaransis
Larus pipixcan
Sterna forsteri
COLUMBIFORMES
Colunba fasciata
Col umba livia
Zenaidura macrouia
R
0 0 R
0 C 0
0 C 0
C 0
R
C
R
R
C
C
R
R
0 C 0
0
0 0 A
0
0
0
C
0
0
C
0
0
R
R
R
R
C
R 0
0
R C
0 C
R
0
0
C
0
0
0
0
0
R
R
0
0
0
0
R
R
0 0 C
A 0 A C 0 0
B-ll
-------
Table B-2 (continued). BIRD SPECIES AND THEIR PROBABLE
OCCURRENCE WITHIN STUDY AREA3
Bio tic
communities
O 99
•H 11
U J3 09 >-4 Q9
M 0 M a "
< hi O -H
a a. e •* a a
Common name
OWLS
Screech, owl
Great horned owl
Long-eared owl
Short-eared owl
Barn owl
Burrowing owl
HIGHTHAWKS
Common nighthawk
Lesser nighthawk
Scientific name
STRIGIFORMES
Otus asio
Bubo virginianus
' Asio otus
Asio flaontaua
Tgto alba
Spaotyto cunicularia
CAPRIMOLGIFORMES
Chordeiles minor
Chordeiles acutipennis
s, a
1 2
0 0
0 R
R R
R
0
R
C
0
o .a v u
CU 3 Pfi 09
3.456
R 0
C R
0
R
0
R R
0
HUMMINGBIRDS, SWIFTS
Broad-tailed hummingbird
KINGFISHERS
Belted kingfisher
WOODPECKERS
Red-shafted flicker
Yallow-ahafted flicker
Red-headed woodpecker
Lawia ' woodpecker
tallow-bellied sapsucker
Hairy woodpecker
Downy woodpecker
PERCHING BIRDS
Eastern kingbird
Western kingbird
Cassia's kingbird
Eastern wood peewee
Western wood peewee
Say's puoebe
Dusky flycatcher
Horned lark
Barn swallow
Cliff swallow
Violet-green swallow
Tree swallow
Bank swallow
Rough-winged swallow
Black-billed magpie
Stellar's Jay
Common raven
Common crow
APODIFORMBS
Selasphorus platycercus
COPACIIFORHES
Megaceryla alcyon alcyon
PICIFORMES
Colaptes cafer collaris
Colaptes auratus
Melanarpes arythrocephalus
Asyndosmus letfis
Sphyrapicus varius
Dendiocopos villosus
Dendrocopos pubescans
PASSERIFORHES
Tyrannus tyrannus
Tyramus verticalis
Tyrannus vocifarans
Contopus virens
Contopus sordidulus
Sayornis saya
Empidonax obholaeii
Eremophila aipeatris
Hi rundo tuatica
Petrodialidon pyrrhoaota
Tachycineta taalassina
Iiodoprocna bicolor
Riparia eipaxia
Stalgidopteryx ruflcollis
Pica pica
Cyanocitta stalled
Conrus corax
Corvus brachrhynchos
0 0
COO
0 0 0 C C
R R
R 0
OR R
R
0 R
R 0 R 0
C CO
C 00
0
0
0
00 0
R a R
OR R
C C C C
0 0 C 0
C C
C C
C C
CCO R
C A 0 0
R 0
0 00
00 0
B-12
-------
Table B-2 (continued). BIRD SPECIES AND THEIR PROBABLE
OCCURRENCE WITHIN STUDY AREA3
Biotic
communities
U •H
a
a. a
Conmon name'
Scientific name
a
o>
1234
rj o
Of Ow
u u
OS U
5 6
Black-capped chickadee
Mountain chickadee
Dipper
Brown creeper
Pygmy nuthatch
Red-breasted nuthatch
White-breasted nuthatch
Long-billed marsh wren
Winter wren
Mockingbird
Catbird
Robin
Townsend'3 solitaire
Hermit thrush
Swainson's thrush
Western bluebird
Mountain bluebird
Euby-crowned kinglet
Golden-crowned kinglet
Water pipit
Bohemian waxwing
Cadar waxwing
Water pipit
Northern shrike
Loggerhead shrike
Starling
Red-eyed vireo
Warbling vireo
Bell's vireo
Tennessee warbler
Orange-crowned warbler
Nashville warbler
Virginia's warbler
Yellow warbler
Myrtle warbler
Audobon's warbler
Yellowthroat
Wilson's warbler
Ovenbird
Northern waterthrush
Yellow-breasted chat
Macgillivray's warbler
Hooded warbler
American redstart
House sparrow
Western meadowlark
Yellow-headed blackbird
Red-winged blackbird
Brewer's blackbird
Common grackle
Parus atricapillus
Parus gaabeli
Clnclas attxicanas
Cartha familiaris
. Sitta pygnaaa
5itta canadensis
Sitta carolinansis
faimacodycss palustris
Troglodytes troglodytes
Minus polgglottos
Dumetella carolinensis
Turdus migratorius
Myadestas towns end!
Hylocichla mustslina
Hylocichla ustulatia
Si alia mexicana
Sialia currucoidas
Regulus calendula
Regulus satropa
Arthus spinoletta
Bombycilla grarrulus
Bomiycilla cadorium
ArtAus spinoJatta
Lanius excubitor
I-anlus ludovicianus
Sturnus vulgaris
Vireo olivaceus
Virao gilvus
Vireo bellii
faraiivora peregrina
Varmivora caJata
fermivora ruficapilla
Varmivora virginiae
Dendroica petechia
Dandroica coronata
Dendroica auduboni
Gaothlypis trichas
Hilsonia pusilla
Saiurus aurocapillua
Seiunis novaioracansis
Tcteria sirens
Oporornis tolmiei
tfilsonia citrina
Setophaga ruticilla
Passer domesticus
5turnella neglecta
Xanthocephalus xanthocephalus
Agelaius phoeniceus
Euphagus cyanocephalos
Quiscalus quiscula
R
C
C
0
0
0
0
C
C
C
0
C
A
0
0
0
0
R
0
0
R
0
0
R
C
0
0
0
R
0
R
C
C
R
0
0
0
0
0
0
0
C
0
0
C
0
0
0
0
R
R
0
0
0
R
R
0
0
0
0
0
C
C
C
0
0
0
0
C
0
0
C
0
0
R
C
C
C
0
C
0
R
0
0
R
0
0
C
0
0
0
0
R
0
R
0
R
0
C
A
0
R
C
0
0
0
0
0
0
0
R
R
C
A
R
A
C
0
0
R
0
C
R
0
R
0
C
0
0
0
0
R
R
C
0
0
0
R
R
0
0
0
R
R
B-13
-------
Table B-2 (continued). BIRD SPECIES AND THEIR PROBABLE
OCCURRENCE WITHIN STUDY AREAa
Biotic
communities
3 3
M .£ 03 •-* 03
00 09 .tt C8 U
-< M O -H -rt
->• £ fl o u cu
OJ <8 Z 03 B
Common name
Brown-headed cowbird
Bullock's oriole
Western tanager
Scarlet tanager
Blue grosbeak
Evening grosbeak
Indigo bunting
Lazuli bunting
Cassin's finch
House finch
Pine siskin
American goldfinch
Lesser goldfinch
Rufous-sided towhee
Green- tailed towhee
Savannah sparrow
Grasshopper sparrow
Baird's sparrow
Lark bunting
Vesper sparrow
Lark sparrow
Slate-colored junco
Oregon junco
Gray-headed junco
White-winged junco
Tree sparrow
Chipping sparrow
Clay-colored sparrow
Brewer's sparrow
Harris ' sparrow
White-crowned sparrow
Gambel's sparrow
Le Conte's sparrow
Fox sparrow
Lincoln's sparrow
Song sparrow
Swamp sparrow
Scientific name
Molothrus ater
Icterus bullockii
Piranga ludoviciana
• Piranga ollvacea
Guiraca caeruilea
Uesparipnona vespartina
Passarina cyanea
Passarina aooana
Carpodacus cassinii
Carpodacus maxicanus
Spinus pinus
Spinus tristis
Spinus psaltria
Plpllo arythrophthalmus
Chlorura chlorara
Passerculus sandtfichansis
Aooodramus savannarum
Amaodramus bairdii
Calamospiza melanocorys
Pooecates gramineus
Chondastes granoiacus
Junco hyenalis
Junco oraganus
Junco canlceps
Junco aiken
Spizella arborga
Splzalla passerina
Spizella pallida
Spizella brewed
Zonotrichia querula
Zonotrichia leucophrys
Zonotrichia leucophrys gaabeli
Passarherbulus caudacutus
Passaralla iliaca
Malospiza lincolnii
Melospiza melodia
Malospiza gaorgian
H >H ~-
3 U 09
U OS -3
mac
a -H o
a, 2 ft.
123
0 0
C
0 R
0 0
0 R
0
0
0
0 R
C 0
0
C C
0 0
0
0
C
C
R
0
0
0
0 R
0 A
R
0
A A
0
0
0
R A
R
0 C
0
0 C
R A A
R
OJ r-t
•^ DO <8
456
o"
C
R
0 0
R
0 R
0
0
C C
C
C 0
0
0 0
0
R
0 R
C A
0 R
0
C R 0
0
0
0
0 R 0
0
0
R 0
0
C 0
R
Key to occurrence: A = abundant C ~ common 0 - occasional R - rare
b
White Rocks Natural Area as Defined in Boulder County Comprehensive Plan
B-14
-------
Table B-3. ANIMAL SPECIES AND THEIR PROBABLE OCCURRENCE
WITHIN STUDY AREA
Biotlc
communities
Connaon name
RABBITS
Blacktail jackrabbit
Eastern cottontail
Desert cottontail
Mountain cottontail
RODENTS
Yellow-bellied marmot
Thirteen- lined ground squirrel
Rock squirrel
Black-tailed prairie dog
Fox squirrel
Colorado chipmunk
Plains pocket gopher
Hispid pocket mouse
Beaver
Western harvest mouse
Deer mouse
Mexican woodrat
Meadow vole
Prairie vole
Muskrat
House mouse
Norway rat
CARNIVORES
Coyote
Red fox
Raccoon
Badger
Striped skunk
HOOFED ANIMALS
Mule deer
Scientific name
LAGOMORPHA
Lepus californicus
Sylvilagus floridanus
S. audubonii
S. nuttalli
RODEHTIA
Marmota flaviventris
Spermophilus tridecemlineatus
S. variegatus
Cynomys ludoricianus
Sciurus niger
Eutamias quadrivattus
Oeomys bursarius
Pergonathus hispidus
Castor canadensis
Reithrodontomys megalotis
Peromyscus maniculatus
Neotoma mexicana
Microtus pennsylvanicus
M. ochrog aster
Ondatra zibethicus
Mus musculus
Rattus norvegicus
CARNIVORA
Canis latrans
Vulpes vulpes
Procyon lotor
Taxidea taxus
Nephitis mephitis
ARTIODACTYLA
Odocoileus hemionus
u
u o
00 01
^-. c a
u ra -J
U T-* ^
3 p H
o u a.
3- C
0) i-H
a) *^
*H (D (0
f
-------
Table B-4. REPTILES AND AMPHIBIANS AND THEIR PROBABLE
OCCURRENCE WITHIN STUDY AREA
Common name
FROGS AND TOADS
Leapord frog
Western chorus frog
Rocky Mountain toad
Biotic
communities
•
o
M co 01 •-) o)
to Cl) AS c« -U
Sex C i-t w ra
•H O ,rt 0) Jj
h (6 AH & PS O
Scientific name 123456
ANVRA
Rana pipiens C 0
Pseudacris triseriata 0
Bufo woodhousel woodhousei R R P.
SALAMANDERS
Utah tiger salamander
TURTLES
Snapping turtle
Painted turtle
SNAKES AND LIZARDS
Six-lined racerunner
Red-lipped rock lizard
Garter snake
Bull snake
Northern water snake
Prairie rattlesnake
Hog-nosed snake
Western smooth green snake
Wandering garter snake
Western plains garter snake
URODELA
Ambystoma tigrinum nebulosum R R R
CHELONIA
Chelydra serpentina 0 C -0
Chrysemys picta 0 0
SQUAMATA
Chemidophorus sexlineatus
Sceloporus undulatus R
crythrocheilus
Thaomophis sirtalis 000
Pituophis catenifer 0 COO
Natrix sipedon R R R
Crotalus viridus R C R
Heterodon nasicus hasicus 0 0
Opheodrys vernalis R R
blanchardi
Thamnophls elegans R R R
vagrans
Thamnophis radix haydeni R R R
B-16
-------
Table B-5. FISH SPECIES AND THEIR PROBABLE OCCURRENCE
WITHIN STUDY AREA
Common name
Rainbow trout
Brown trout
Largemouth bass
White sucker
Longnose dace
Northern creek chub
Plains sand shiner
Green sunflsh
Pumpkinseed
Bluegill
Western gambusia
Scientific name
Salao gairdneri
Salmo trutta
Micropterus salmoides
Catostomus commersoni
Rhinichthys cataractae
Semotilus atromaculatus
Notropis deliciosus
Lepomus cyan eJ Jus
Lepomus gibbosus
Lepomus macrochirus
Gambusia affinis
o in u"t CB
1 1 I H
01 HI 01 B
0) 01 01 T3 T>
ti U hi C C
O U CJ O O
EX. &4
01 o) oi c i-i
•O T3 T3
333^0)
O O O (0 Wi
in « DO 3 o
123*5
X X
X
X
X XX
X
X
X
X
X
X
X
on records of Stoecker-Keammerer Associates, 1974.
bBased on records and personal conmunication with Boulder County Parks
and Open Space Department, 1975-1976.
"TJased on data from ERTL property special use permit, 1976.
B-17
-------
REFERENCES FOR APPENDIX B
B-l Dept. of the Army, Omaha District, Corps of Engineers, "Special
Flood Hazard Information Report, Boulder Creek, City of Boulder,
Colorado," Prepared for the City of Boulder and the Urban Drainage
and Flood Control District, 1972.
B-2 Stocker-Keammerer and Assoc., "The Ecology of Boulder Creek:
Environmental Inventory and Evaluation of Sewage Treatment
Alternatives," in "Comparative Study of Wastewater Treatment, City
of Boulder," CH2M-Hill, May 197A.
B-3 Beidleman, Richard G., "The Vertebrate Ecology of a Colorado Plains
Cottonwood River Bottom," Unpublished MA thesis, University of
Colorado, Boulder, Colorado, 1948.
B-4 Boulder County Parks and Open Space Department, Unpublished records,
Bird and Wildlife Census at Walden Ponds Wildlife Habitat, April
1974 to September 1976.
B-5 Krebs, P- V., "Vegetation" in Environmental Inventory and Land Use
Recommendations for Boulder County, Colorado, Occasional Paper No.
8, Institute of Arctic and Alpine Research, University of Colorado,
Boulder, 1973.
B-6 Netoff, D.I. and H.L. Young, White Rocks Natural Area Study, D.D.
MacPhail (ed.) Department of Geography, University of Colorado,
Boulder, 1970.
B-7 Flatiron Sand and Gravel Company, "Review Data for Special Use
Permit," Boulder, October 1972.
B-8 Flatiron Paving Company, "ERTL Property Special Use Permit,
Monitoring Report" Boulder, August 1976.
B-9 Colorado Native Plant Society, "Provisional List of Endangered or
Threatened or Sensitive Vascular Plants of Colorado", Compiled from
Dr. W. A. Weber's list with modifications by the Endangered Plant
Subcommittee, May 1976.
B-10 Beidleman, Richard G., "Guide to the Winter Birds of Colorado,"
University of Colorado Museum, Boulder, Colorado, 1963.
B-18
-------
B-ll Gregg, Robert E., Interview by Netoff and Young in "White Rocks
Natural Area Study", University of Colorado, Department of
Geography, Boulder, Colorado, 1970.
B-12 Byers, Loren F., "An Ecological Study of the Ants of Boulder
County, Colorado", unpublished masters thesis, Department of
Biology, University of Colorado, Boulder, Colorado, 1936.
B-13 Mr. Guy Leonard, Ground Water Hydrologist, Leonard Rice Con-
sulting Water Engineers, Personal Communication on 23 Decem-
ber 1976.
B-19
-------
APPENDIX C
THE AESTHETICS OF A LANDSCAPE AS A RESOURCE COMMODITY
The National Environmental Policy Act of 1969 clearly expressed the
objective of treating aesthetic resources on an equal level with natural
and social resources. The Act states that all Federal agencies shall
"utilize a systematic, interdisciplinary approach which will insure the
integrated use of the natural and social sciences and the environmental
design arts in planning and in decisionmaking which may have an impact
on man's environment" (Reference C-l). Unlike the natural and social
resources (such as soils, vegetation, wildlife, air quality, population,
traffic circulation, etc.) , aesthetic resources are dTfficult to measure
in standard or meaningful units that not only describe the aesthetic re-
source, but that also enable a specific determination to be made of a
project's impact on that resource. Aware of this difficulty and re-
emphasizing its objective of equal treatment of aesthetic resources,
NEPA goes on to state that all Federal agencies shall "identify and de-
velop methods and procedures...which will insure that presently unquanti-
fied environmental amenities and values may be given appropriate consid-
eration in decisionmaking along with economic and technical considera-
tions" (Reference C-l).
Techniques for measuring the aesthetic resource are still evolving.
A recent Forest Service bibliography entitled "Measuring Scenic Beauty"
(Reference c~2) lists 165 entries, of which 95 percent were written
after 1965. The aesthetic consequences of public land management de-
cisions are often the most immediate and noticeable, yet planners have
difficulty assessing scenic resources equally with natural and social
resources because the latter are more easily measured (Reference C-2).
An additional practical concern with aesthetics in project planning
stems from two primary sources: (1) the planner's concern to ensure
the ultimate success or acceptance of the project by the community; and
(2) the concern to meet the requirements outlined in regulatory guide-
lines for publicly funded projects (Reference C-3).
A starting point for the measurement of the aesthetic resource, as
developed by Litton (References C-4, C-5 and c-6), comes from the recog-
nition of the landscape as a resource in its own right. Thus, as with
other natural resources, such as timber, soil and wildlife, the land-
scape is inventoried and thereby integrated into the overall land manage-
ment plan. Litton has developed parameters for studying the landscape
as a resource, and a brief outline of these is presented in the following
paragraphs (Reference C-4).
In discussing the landscape as a visual resource, certain land man-
agement terms suggest the scope of objectives available to the planner.
These terms include: Preservation, Protection, Maintenance, Enhancement,
Degradation, Rehabilitation, Restoration and Remodeling. Within the con-
text of these general land-management concepts, the following Attributes
C-l
-------
of the Landscape are identified:
A. Factors of Recognition
1. Form
2. Space ^- Primary
3. Time Variability
4. Observer Position^
5. Distance > Secondary
6. Sequence J
B. Landscape Compositional Types
1. Panoramic
2. Feature
3. Enclosed
4. Focal
5. Forest or Canopied
Primary factors of recognition are those which are beyond the capa-
city of the observer to change, but can be degraded. Secondary factors
describe relationships between the observer and the landscape, and can
be manipulated. Form relates particularly to the convex elements of land
form, and space is made up of concave elements. Some kind of contrast
must be present if form or space are obvious. Kinds of contrast include:
Isolation, Dominance by relative size or scale, Contour Distinction and
Surface Variance. Space is further modified by four factors: Propor-
tions, Constitution, Configuration and Scale or Relative Size. Time
Variability represents the primary factor of short-term change and in-
cludes (1) Light and Color and (2) Ephemeral Influences, which are sea-
sonal, diurnal or momentary.
Observer Position can be characterized as (1) observer inferior,
(2) observer normal and (3) observer superior, these terms indicating,
respectively, whether the observer is below, level with or above the
visual objective. Distance relationships are relative and can be ex-
pressed as Foreground, Middleground and Background. Middleground is
critical as the area where man-made changes may blend in or intrude upon
the landscape. Sequence describes the way in which the landscape is
seen bit by bit.
A Panoramic landscape is characterized by the absence of enclosure,
and is a horizontally-oriented placid arrangement of great stability.
A Feature landscape is one in which a single thing or cohesive set of
related elements dominates their surroundings. The Enclosed landscape
is marked by its concavity, and the Focal landscape is composed of ele-
ments that appear to converge upon a point. The Forest or Canopied
landscape refers to that arrangement within the forest itself, under
C-2
-------
the envelopment of the leaf canopy and upon the ground plane.
Having established the above Attributes of the Landscape, Litton
presents several means of evaluating the landscape for aesthetic quality.
Three basic aesthetic criteria are recognized: unity, vividness and
variety.
Unity is that quality of wholeness in which all parts cohere as a
unit. The five Landscape Compositional Types represent compositions
that illustrate this cohesive state. Man-made changes have the potential
for breaking unity and diminishing quality. The absence of unity (i.e.,
fragmentation) indicates the absence of aesthetic quality.
Vividness is that quality in the landscape which gives it distinc-
tion and makes it visually striking. Similarity and Contrast are two
ways vividness can be expressed. Similarity involves the repetition of
like or similar characteristics. Man-made changes that depend upon con-
cepts of similarity have maximum potential of maintaining this particular
kind of vividness. Contrast puts sharply different things or qualities
together. Man-made changes in the landscape are apt to be noticed for
their contrast, but are often negative in quality. Litton states that
the greatest care must be exercised in designing changes that will be-
come conspicuous because of contrasts.
Variety represents how many different objects and relationships are
present in a landscape. Greater variety often is an indication of higher
aesthetic quality. The five Landscape Compositional Types represent
frameworks into which variety may be visually integrated.
The above presentation of Litton's methodology is not intended to
be a definitive summary of his work, nor does it represent a summary of
the state of the art. This methodology has been used in this EIS to
evaluate the Aesthetic Resources as they are affected by the proposed
Boulder Wastewater Facilities Plan.
C-3
-------
REFEEENCES FOR APPENDIX C
C-l The National Environmental Policy Act of 1969, Public Law 91-190,
Sec. 102, January 1, 1970.
C-2 Arthur, Louise M. and Ron S. Boster, "Measuring Scenic Beauty:
A Selected Annotated Bibliography," U.S.D.A. Forest Service
General Technical Report RM-25, May 1976.
C~3 Redding, Martin J., Aesthetics in Environmental Planning, Socio-
economic Environmental Studies Series, U.S. Environmental Protec-
tion Agency, EPA-600/5-73-009, November 1973.
C-4 Litton, R. Burton, Jr., "Aesthetic Dimensions of the Landscape,"
in Natural Environments: Studies in Theoretical and Applied
Analysis, John V. Krutilla, ed., Johns Hopkins University Press,
Baltimore, Maryland, 1972.
C-5 Litton, R. Burton, Jr., "VisuaJ. Vulnerability of Forest Landscapes,"
Journal of Forestry 72(7): 392-397, July 1974.
C-6 Litton, R. Burton, Jr., "Forest Landscape Description and Inven-
tories - A Basis for Land Planning and Design," U.S.D.A. Forest
Service Research Paper PSW-49, Pacific Southwest Forest and Range
Experiment Station, Berkeley, California, 1968.
C-4
-------
APPENDIX D
EVALUATION OF INFILTRATION/PERCOLATION BASINS
AT THE 95TH STREET SITE AND
AN AGRICULTURAL REUSE PROGRAM
INTRODUCTION
This appendix presents additional detail on two areas of
investigation in response to comments made on the August 1977
Draft Environmental Impact Statement (EIS) on Wastewater Treatment
Facilities, Boulder, Colorado. This new information, in conjunc-
tion with the earlier analyses in the EIS, will be used by the City
of Boulder, Boulder County and the U. S. Environmental Protection
Agency (EPA) to select a new wastewater treatment system for the
Boulder Wastewater Facilities Planning Area.
Background
The draft EIS evaluated eight alternative projects to modify
existing treatment facilities to meet newly-upgraded water quality
standards in Boulder Creek. The eight alternatives were: (A) in-
filtration/percolation basins, (B) activated-sludge process following
existing trickling filters, (C) aeration/polishing ponds, (D) acti-
vated-sludge process prior to trickling filters, (E) multi-media
filtration, (F) chemical coagulation, (G) high-rate irrigation upon
agricultural land, and (H) no action. Except for alternatives F and
H, all projects involved sludge injection for agricultural reuse.
A preliminary screening eliminated E, F, and H from further considera-
tion since they were technically unable to meet state and local water
quality goals. Thus, the draft EIS primarily examined the five re-
maining alternatives and their environmental impacts.
In August 1977, EPA distributed the draft EIS to federal, state,
and local agencies as well as to interested groups and individuals
for review and comment. Attention was focused on Alternatives A, B
and C as the most cost-effective treatment systems. After numerous
public meetings, local agency meetings, and a public hearing, the
majority of Boulder City and County residents favored Alternative B
for the wastewater treatment processes but were undecided as to the
acceptability of sludge injection. Alternative B represented a com-
promise agreement; for although it would be more costly and energy-
intensive, it did not have the controversial environmental impacts
associated with Alternatives A or C.
In February 1978, EPA decided that further work was needed before
one alternative could be recommended for design and construction
under federal funding. Subsequently, EPA contracted Engineering-
Science to perform the necessary follow-up.
D-l
-------
Project Development
The review process revealed two areas requiring further work.
They are: (1) an investigation of a new site for infiltration/perco-
lation basins, (2) the development of an agricultural reuse program.
The draft EIS shows Alternative A, infiltration/percolation basins,
to be a cost-effective method of providing high quality effluent; the
proposed site, however, was unacceptable to local residents and probably
to units of local government. EPA believed that relocation of the ba-
sins could possibly resolve this conflict without sacrificing the tech-
nical or economical effectiveness of this alternative.
An agricultural reuse program, which uses treated wastewater for
irrigating agricultural land, is being developed because it is an at-
tractive solution that can satisfy both water quality and reuse goals.
The Boulder facilities plan discusses this landbased system only as a
possible upgrading process to follow any of the more conventional treat-
ment alternatives. Boulder County residents and district water users,
however, feel that such a system warrants further study at this time.
Feasibility of the reuse program should be based on water exchanges
rather than on massive land purchases as evaluated in the preliminary
assessment.
Description of Alternative Sites and Systems
The three alternative wastewater and sludge management systems
evaluated in this appendix are:
1. Infiltration/Percolation Basins, 95th Street Site—Secondary
effluent from the existing plant would be pumped 2-1/2 miles to infil-
tration/percolation basins where further polishing would occur before
discharge to Boulder Creek. The basic unit processes are the same as
those in Alternative A in the EIS; only the site of the basins differ.
Soil characteristics at the new 95th Street site will determine the
need for a tile underdrain system and area requirements.
2. Agricultural Reuse Program—A pump station and force main would
convey secondary effluent from the existing plant to one or more local
irrigation ditches. Individual farms within the ditch companies would
then draw treated effluent for crop irrigation. During the non-irriga-
tion season, treated effluent would be conveyed along the irrigation
ditch(es) and/or pipeline(s) to a new storage reservoir or to an exist-
ing one such as Panama Reservoir for future irrigation uses. The City
of Boulder would thus exchange treated effluent for water that would
normally have been drawn from Boulder Creek by the ditch companies.
This agricultural reuse program would work towards fulfilling the EPA
goal of zero discharge to surface waters.
D-2
-------
INFILTRATION/PERCOLATION BASINS AT 95TH STREET SITE
System Description
Treatment Processes^—
This system would use the existing facilities at the 75th Street
plant to the fullest possible extent for primary and secondary
wastewater treatment. This consists basically of grit removal,
primary clarification, trickling filters, and secondary clarifica-
tion. Further treatment of liquid wastes, however, will be neces-
sary to meet the upgraded stream standards.
This alternative proposes to convey secondary effluent from
the existing treatment plant 2-1/2 miles east to infiltration/
percolation (I/P) basins near 95th Street for land treatment. A
schematic layout is shown in Figure D-l. As the effluent percolates
through the basins, the high infiltration and permeability capabili-
ties of the sand and gravel bordering Boulder Creek would provide
the additional polishing necessary. This "renovated" effluent would
then be collected in an underdrain system and discharged to Boulder
Creek.
The I/P basins site covers approximately 228 acres between
Leggett Ditch and Boulder Creek. This acreage includes not only the
basins, but 50-ft. wide perimeter berms between basins and a buffer
zone around the entire site. Thirteen basins will be formed by
removing the ground cover and using the excavated surface soil to
build protective berms around each basin. Wherever possible, basins
will be contoured to conform with natural features and to preserve
mature cottonwood trees growing on the site. In addition, hydro-
philic vegetation may be planted in the basins for visual appearance.
Underdrains would probably be installed at intervals of 80 feet to de-
press the groundwater table and to collect the filtered effluent. Dis-
charge will occur in Boulder Creek above the 95th Street Bridge and
at the east end of the site as shown in Figure D-l.
Shifting the point of effluent discharge from above 75th Street
to near 95th Street would significantly reduce the flow in that
reach of Boulder Creek and affect legal water rights. This alterna-
tive would have to include water replacement to meet the decreed
water rights of the two ditch companies immediately west and east of
95th Street. A separate pump station and pipeline would be construc-
ted to convey renovated effluent to the ditches as shown in Figure
D-l.
The system would operate year-round on an 8 to 12 day loading/
drying rotation cycle, allowing time for soils to dry between
loadings. The discharge temperature of the effluent should be
warm enough to prevent freezing during the winter and to eliminate
the need for cold weather storage.
D-3
-------
LEGEND
RENOVATED EFFLUENT LINE
TO IRRIGATION DITCHES
RENOVATED EFFLUENT
DISCHARGE POINTS
EFFLUENT PUMP STATION
EFFLUENT TURNOUTS
SCHEMATIC LAYOUT CF
PROPOSED INFILTRATION/
PERCOLATION BASINS AT
95th STREET SITE
-------
System Evaluation—
Successful infiltration/percolation systems have been operating
throughout the United States for many years. However, variations
in many factors such as climate, soil, and pre-application treatment
make it difficult to compare the performance of other systems with
the one proposed for Boulder.
Lake George, New York has been successfully applying 0.3 - 1.0
mgd of unchlorinated trickling filter effluent to a 644-acre I/P
system since 1936 (References D-l, D-2). Both ground and surface
water in the vicinity of the plant have consistently met local and
state water quality standards. In this system, rocks and glacial
till sands interspersed with bedrock range from 20- to 72-feet deep
beneath the percolation beds; the annual loading rate is 65 ft/yr.
In comparison, the proposed system for Boulder will have to handle
design flows up to 22.8 mgd; chlorinated secondary effluent would
percolate through seven to fifteen feet of underlying sand and gra-
vel, with an annual loading rate of about 101 ft/yr. Thus, despite
the similarities in climate and quality of applied effluent, the
differences in soil types and loading rates invalidate a comparison
of engineering effectiveness.
Fort Devens, Massachusetts has also been operating an I/P
system for more than 30 years to treat unchlorinated primary effluent.
Investigations done in 1973 showed that the treatment process greatly
reduces levels of COD, BOD, organic nitrogen, ammonia-nitrogen,
phosphorus, and total coliform bacteria, although nitrate removal
was not as successful (Reference D-3). Climatic conditions are
comparable to Boulder, but the difference in quality of applied efflu-
ent again makes it difficult to compare systems.
Another successful I/P system is at Whittier Narrows, California
in which chlorinated tertiary effluent mixed with imported water
percolates through 10-20 feet of sandy loam and enters the ground-
water table (Reference D-4). Here renovated wastewater meets drinking
water standards. However, this sytem is designed to recharge the
groundwater, rather than to polish wastewater, and is much more
sophisticated than Boulder's proposed system.
Results from existing systems, nevertheless, show that infiltra-
tion/percolation basins can be a technically feasible method for
meeting Boulder's water quality goals.
D-5
-------
To determine the effectiveness of I/P basins under local climatic
and soil conditions, the City of Boulder is conducting a pilot
program adjacent to Boulder Creek at the 75th Street treatment plant.
In the initial two years, unchlorinated secondary effluent was
applied twice a week to three experimental I/P basins ranging in
sizes between 0.6 and 0.9 acres. To date, results of this study
have shown that an I/P system has excellent treatment capabilities
for polishing secondary effluent and for meeting water quality goals
year-round, provided that appropriate hydraulic loading rates and
loading/drying cycles are maintained.
During the first year of operation of the experimental basins,
the following data on the quality of the renovated wastewater were
collected:
1. Suspended solids and coliform organisms were consistently
reduced by over 96%. (Reference D-5.)
2. Organic and ammonia-nitrogen removal was nearly complete.
(Reference D-6.)
3. Phosphorous removal was generally excellent; concentrations
in renovated wastewater collected in the underdrains were
consistently less than 1.5 mg/1 PO.-P- (Reference D-5.)
4. Concentration of wastewater organics (measured as chemical
oxygen demand) was effectively reduced by 70 to 80% throughout
the study period. (Reference D-5.)
5. Total nitrogen removal was highly variable, between 9 to 59%,
during the study period. Quality of influent, weather condi-
tions, and seasonal vegetation affected nitrification,
denitrification, and volatilization processes which caused
wide variations in treatment effectiveness. (References D-5,
D-6.)
6. I/P treatment did not demonstrate any salt removal capabi-
lities during the study period; salt concentrations general-
ly increased as the wastewater percolated through the soil.
However, the leaching out of salts naturally present in
the soil seemed to decrease over the study period, possibly
indicating that equilibrium conditions can be achieved.
(Reference D-6.)
Significant seasonal variations were observed in the treatment
performance during the first year, particularly for nitrogen and
phosphorous removal. Extremely high nitrate discharges were record-
ed during April and May, apparently due to the accumulation of
ammonia-nitrogen in the soil during the winter. During the spring
the ammonia is oxidized and then released as nitrate. Phosphorous
removal was also inhibited during the winter when the adsorptive
D-6
-------
capacity of the soil is saturated, so that increased levels of
phosphate leached through the soil. Nevertheless, water quality of
the renovated wastewater was maintained above current and projected
discharge standards throughout the entire one-year study period.
Appropriate hydraulic loading rates and loading/drying cycles
were critical for successful operation of the I/P basins. (Reference
D-7.) Two of the experimental basins initially exhibited ponding
conditions due to hydraulic overloading. To correct this, it was
necessary to remove the surface layer of soil which had a high clay
content. Other hydraulic characteristics of the basins were also
highly site-specific. Loading rates for two basins only 500 feet
apart varied four fold. During the loading portion of the cycle,
accumulation of suspended solids and low temperatures slowed the in-
filtration rates. Drying and scarification of the basins between
loadings reliably resotred high initial infiltration rates. (Experi-
mental basins had no vegetative cover.)
The soils at the 95th Street site are generally suitable for
I/P basins based on the Soil Conservation Service Survey (Reference
D-8). Depending on the loading rate and presence or absence of a
vegetative cover, limitation of the soils on the proposed site are
only slight to moderate.
At this time, there is no way to assess long-term reliability
of I/P basins at the proposed site. If results of the pilot studies
are indicative, then usefulness of the I/P basins may extend beyond
the 20-30 year design period. Success of the first two years of the
pilot study has instigated another study to test effectiveness of
I/P treatment on primary effluent.
Project Costs—
The project implementation schedule for I/P basins at the 95th
Street site is projected to remain the same as outlined in Section
III of the EIS. Construction would occur in two phases: 1978-1980,
and 1988-1989. Salvage values are assumed for the year 2000 and
the design period is 1980-2000 or 20 years. To be comparable with
costs estimates made by the facilities planner, a 6-3/8 percent
discount factor was used and costs are presented in January 1977
dollars.
The cost estimate for I/P basins at the 95th Street site was
calculated using the costs developed for the former 75th Street
site as a base and adding new costs for the additional facilities
required. The physical details of the I/P basins at the new site
was assumed to be roughly the same as those described in pages 11-30
and 11-31 of the original facilities plan. (Reference D-l.) Perti-
nent changes to the system will be as follows:
D-7
-------
1. Rather than a 6000-ft., 36-in. diameter force main from the
plant, there will be a 14,600-ft. force main (additional
8,600 ft.).
2. Rather than a 575 horsepower (hp) pump station, there will
be a 715 hp pump station—in order to overcome additional
friction loss in the longer pipeline.
3. In addition to the underdrain/low-lift pump stations pro-
posed in the original report, additional Dumps and lines
would probably be necessary to return flow from the I/P basins
to the Leggett and Lower Boulder Ditches. It will be necessary
to return 12,600 acre-feet (AF) of flows (3,800 AF to Leggett
and 8,800 AF to Lower Boulder at design flow) to satisfy water
rights.
4. The additional pipeline length will require construction of
a stream crossing for the 36-in. force main that was not
included in the facilities plan.
The additional capital costs associated with the above-mentioned
changes are presented in Table D-l. The incremental increase in
capital cost at the 95th Street site is $1,115,000. With an allowance
of 15 percent for legal, engineering and administrative costs, the
actual incremental cost would be approximately $1,282,000.
The estimated incremental annual operation and maintenance (O&M)
costs for the revised facilities are:
Main plant pump station $11,500
Pumping to Leggett Ditch 7,300
Pumping to Lower Boulder Ditch 3,800
Additional pumping costs total $22,600
For estimation purposes, the additional O&M cost is assumed to be
$25,000/year. This reflects basically increased electrical energy
usage for pumping and maintenance required for the new transmission
lines. Using the revised figures presented above, the new costs
for Alternative A —including a sludge-injection system — are pre-
sented in Table D-2. Project costs for the City of Boulder are
shown in Table D-3. The net present worth of $13,130,000 represents
an approximate 10 percent increase over the 75th Street site.
Correspondingly, Boulder's average annual equivalent cost of
$754,000 represents an approximate 7 percent increase.
D-8
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Table D-l. CONSTRUCTION COST ESTIMATES, INFILTRATION/
PERCOLATION BASINS - 95th STREET SITE
(In Thousands of Dollars)
Item Estimated Costs
Construction of I/P basins3 $3,639,000
(includes effluent transmission and
distribution, site preparation, basin
construction, underdrains and effluent
pumps, water quality monitoring
and miscellaneous)
Additional facilities required for
95th Street site
Effluent transmission (includes larger 672,000
pump, additional pipeline and structure
for creek crossing)
Renovated effluent return pipelines 443,000
and pumps to irrigation ditches
I/P basin construction subtotal 4,754,000
Legal, administrative and engineering
fees (15%) 713,000
I/P Basin Construction Total $5,467,000
aBased on February 1977 Facilities Plan Supplement for 75th Street
Site (Kolb property). (Reference D-9.)
D-9
-------
Table D-2. TOTAL PROJECT COSTS, INFILTRATION/
PERCOLATION BASINS - 95th STREET SITE
(In Thousands of Dollars)
Item
Capital Cost
1978-1980
1988-1989
Total
Annual 0 & M
1980-1990
1990-2000
Present Worth of
All Costsc
Salvage Value of
Facilities and Land
Net present worth
Feb. 1977
Estimate3
9,247
642
9,889
487
565
12,764
853
11,911
b
Increment
1,282
0
21
24
1,312
93
Total
(95th St Site)
10,529
642
11,171
508
589
14,076
946
13,130
From Table 12 of EIS, based on 75th Street site costs.
See text for development of costs.
Q
January 1977 dollars at 6-3/8 percent for 30 years.
Present worth of all costs less salvage value of facilities and land.
D-10
-------
Table D-3. CITY OF BOULDER PROJECT COSTS, INFILTRATION/
PERCOLATION BASINS - 95th STREET SITE
(In Thousands of Dollars)
Item
Capital Costa
1978-1979
1988-1989
TOTAL
Annual Capital Recovery Cost
1980-1990
1990-2000
Annual 0 & M
1980-1990
1990-2000
Average Annual Equivalent Cost
75th Street
Site
2,312
161
2,473
175
187
487
565
707
95th Street
Site
2,632
161
2,793
199
211
508
589
754
f\
Assume 75 percent federal grant.
Annual payment required to recover Boulder's share of capital costs at
6-3/8 percent for 30 years.
°From Table D-2.
Represents average of 0 & M charges plus average of annual capital
recovery costs.
D-ll
-------
Site Setting
Physical Environment—
The proposed site for I/P basins lies in the floodplain of
Boulder Creek, encompassing areas north of the creek up to Leggett
Ditch and extending one-half mile to the east and to the west of
95th Street. The land slopes gradually downward from the 75th Street
treatment plant to the site, averaging about 0.5% slope. The site
covers 228 acres and is relatively flat with occasional depressions
and mounds from previous gravel mining.
The floodplain is composed of sands and gravels overlain by 3.5
to 6.5 feet of fine-grained alluvial soils. Soils on the site are
of two main types, Loveland and Niwot soils, which are characterized
in Appendix A of the EIS. The underlying sands and gravels origi-
nated from igneous and metamorphic rocks eroded from the mountains
west of Boulder. They range in thickness from as little as seven
feet to as much as fifteen feet. Under the 228-acre site, is an
estimated 3.3 million cubic yards of aggregate. According to the
U. S. Geological Survey report on aggregate materials in the Front
Range Urban Corridor Area, terrace and floodplain deposits of Boulder
Creek contain the best quality gravel for concrete aggregate and
road metal (Reference D-10).
The Pierre Shale bedrock formation underlies the sands and gra-
vels. The Pierre Shale can be as thick as 4500 to 5000 feet. The
upper part of the Pierre Shale contains interbeds of shale and silt-
stone. The upper siltstones are known locally as the Pierre Shale
transition zone (Reference D-ll).
The sands and gravels beneath the floodplain contain large
amounts of groundwater in storage. Recharge to and discharge from
the sands and gravels supports water levels in Boulder Creek, wells,
and lakes on the floodplain. Recharge to the groundwater system
occurs principally by leakage from irrigation ditches and laterals
and by infiltration of precipitation. The direction of groundwater
flow is generally to the east, parallel to Boulder Creek, as shown
in Figure D-2. Depths to groundwater on the site range from less
than one foot to as much as five feet beneath the land surface.
Water levels will be highest during the irrigation season and low-
est during the late winter and early spring months. Annual fluc-
tuations as much as four feet have been recorded in other similar
hydrologic situations. The depth to groundwater, based on observa-
tions in July 1978 is shown in Figure D-3.
The permeability of the sand and gravel aquifer is low and
varies from less than two feet per day to as much as 60 feet per
day. The average permeability of the material on the site is
probably on the order of 33 feet per day. As a result of this low
permeability, wells completed in the sands and gravels yield only
20-30 gal/min or enough water for stock and domestic purposes.
D-12
-------
.'.^ ^5050
TREATMEN
PLANT
BOULDER V
VALMONT DRIVE
GROUNDKATER CONTOURS
AND FLOW DIRECTION
JULY 1976
GROUND SURFACE E
CONTOUR OF EQUAL HATER TABLE
ELEVATION IN FEET
PROPOSED PROJECT|SITES
ARROWS DENOTE DIRECTION OF
GROUNDWATER FLOW
-------
> ^<=T
I. LOWER BOULDER x
DEPTH TO GROUNDKATER,
PROPOSED PROJECT AREA,
JULY 1978
LINE OF EQUAL DEPTH
TO WATER. IN FEET
PROPOSED PROJECT SITES
-------
There are wells registered with the Division of Water Resources per-
mitted for as much as 700 gal/min. These "wells" are not vertical
tube wells but are pumps set into sand and gravel excavations. The
"wells" pump large amounts of water because of a large effective
radius.
The siltstones in the upper part of the Pierre Shale subcrop
in the valley of Boulder Creek east of Boulder. The siltstones
are considered an aquifer in the eastern part of Boulder County and
are believed to be present in the vicinity of the infiltration/
percolation pond site. There is evidence of a fracture in the
bedrock formation and that there is a commingling of the alluvial
water with the deeper siltstone water. The State Water Resources
Department and the U. S. Geological Survey have initiated a study
of groundwater flow and losses in the 95th Street area. A report
describing aquifer coefficients of the siltstones is in preparation
(Reference D-ll) .
Boulder Creek is the predominant surface water on the site.
Flow ranges from approximately 5 cubic feet/second (cfs) to 1,000 cfs
during peak spring and summer runoff. During the dry season, much of
the flow is controlled by upstream uses, including the 75th Street
plant which can contribute up to one-third of the total flow. The
quality of the stream formerly complied with the Class B2 Standard
(waters suitable for non-contact recreation and warmwater fishery),
but does not meet the newly revised A2 Standard (primary contact re-
creation and warmwater fishery). Other surface waters include several
shallow ponds which are remnants of former gravel mining operations.
Biological Environment—
The proposed I/P basins site is situated within a Pasture/
Agriculture biotic community* along the Boulder Creek floodplain.
In spring 1978, approximately one-fourth of the site on the nor-
thern end was planted to alfalfa hay production while the remainder
was used as pasture. The pasturelands support two distinctive
types of groundcover depending on the relative elevation on the
floodplain. In low-lying areas where land contours are nearly
equal to or several feet above Boulder Creek, lush vegetation occurs.
Sedges, particularly Nebraska sedge (Carex nebraskensis) and
prairie cordgrass (Spartina pectinata) flourish in these areas
where the groundwater table is within 2 feet or less of the ground
surface. This "sedge meadow" locally provides nearly 100 percent
groundcover and is most dominant west of 95th Street adjacent to
Boulder Creek. Wildlife associated with the wet sedge meadow are
typically red-winged blackbirds, barn swallows, rough-winged
swallows, meadowlarks, cottontail rabbits, and meadow voles.
*As defined in Appendix B of the EIS
D-15
-------
The second type of groundcover along the topographically higher
portions of the floodplain is a short grassland dominated by Kentucky
bluegrass (Poa pratensis). This grassland covers the largest areal
extent and is subject to light to moderate cattle grazing. In closely-
cropped areas, considerable amounts of bare ground are exposed, and
numerous weed species such as filaree, prickly lettuce, plantain and
mullein are present. Near fenceposts and in isolated spots, weed
species are dominant, particularly Russian thistle, milkweek, gumweed,
dock and various thistle species. A listing of plant species observed
on the site is shown in Table D-4. Due to the low groundcover, wildlife
diversity is limited, and in all' cases, is dominated by domestic cattle
and their grazing activities. In areas where tall weeds provide some
cover are found cottontail rabbits and several mice species. Isolated
small prairie dog colonies exist on the fringes of the pasture area
where the groundcover is low and the earth not severly trampled by
cattle. A listing of wildlife species that probably occur within the
area, although not necessarily at the site, is shown in Table D-5.
Within the project area, no rare, endangered or threatened plant or
wildlife species have been recorded.
Within the pasture area are several small ponds formed during pre-
vious gravel mining operations. The ponds are frequented by cattle and
are generally shallow and filled with algae. Black-crowned night herons
and killdeer have been observed in these ponds; however, use appears to
be limited.
Social/Economic Environment—
The proposed 95th Street site lies in eastern Boulder County, ap-
proximately six miles east of the City of Boulder. This rural area is
predominantly agricultural with a few scattered residences and inter-
mittent gravel mining along the floodplain. The I/P basin site is part
of Boulder Valley Farm, Inc. and is currently used as pastureland for
raising purebred cattle. Approximately 10 to 15 residences are within
a one-half mile vicinity of the site.
In the past, sand and gravel mining has occurred at isolated loca-
tions on the site, and recently, the owner of Boulder Valley Farm has
entered into a contract for more extensive mining of the gravel re-
sources. As of July 1978, the mining company is awaiting state approval
to start sand and gravel extraction on the 97-acre parcel of land to the
west of 95th Street. In addition to the mining operation, the owner of
the property has long-term plans to construct a 50-unit housing develop-
ment on the terraces to the north, overlooking Boulder Creek (Reference
D-12).
Neither the State Historic Preservation Office nor the Boulder
County Comprehensive Plan has identified any part of the proposed site
as an archaeologically sensitive area. However, the White Rocks
area, immediately northwest of Boulder Valley Farm, has been designated
D-16
-------
Table D-4. VASCULAR PLANT SPECIES WITHIN PROJECT AREA
Scientific Name
Common Name
Scientific Name
Common Name
i
Agropyron elongatum
Agropyron smithii
Andropogon gerardii
Arctium minus
Artemisia ludoviciana
Asclepias speciosa
Bromus tectorum
Carduus leiophyllus
Carex nebraskensis
Carex spp.
Cirsium arvense
- -
Distichlis stricta
Elaeagnus angustifolia
Erodium cicutarium
Glycyrrhiza lepidota
Grindelia squarrosa
Iva xanthifolia
Kochia iranica
Lactuca serriola
Lepi'dium dens if lor urn
Medicago sativa
Tall Wheatgrass
Western Wheatgrass
Big Bluestem
Burdock
Sagewort
Showy Milkweed
Cheatgrass
Thistle
Nebraska Sedge
Sedges
Canada Thistle
Inland Saltgrass
Russian Olive
Filaree
Wild Licorice
Curly-cup Gumweed
Marsh Elder
Summer Cypress
Prickly Lettuce
Peppergrass
Alfalfa
Melilotus sp.
Oenothera caespitosa
Opuntia polyacantha
Panicurn virgatum
Plantago lanceolatum
Plantago major
Poa pratensis
Polygonum sp.
Populus sargentii
Prunus americana
Rosa woodsii
Rumex sp.
Salix amygdaloides
Salix exigua
Salsola iberica
Sorghastrum nutans
Spartina pectinata
Symphoricarpos occidentalis
Taraxacum officinale
Tragopogon dubius
Typha latifolia
Verbascum thapsus
Sweetclover
Evening Primrose
Prickly Pear Cactus
Switchgrass
Narrowleaf Plantain
Common Plantain
Kentucky Bluegrass
Knotweed
Plains Cottonwood
Wild Plum
Wood's Rose
Dock
Peach-leaved Willow
Coyote Willow
Russian Thistle
Indian Grass
Prairie Cordgrass
Snowberry
Dandelion
Salsify
Cattail
Common Mullein
Based on observations on 15 March 1978, as presented in vegetation report for Boulder Valley Farms Pit
Mining Application and EIS staff observations on 18-21 July 1978.
-------
Table D-5. WILDLIFE SPECIES PROBABLY OCCURRING
a h f
WITHIN PROJECT AREA ' '
Scientific Name
MAMMALS
Can! 3 latrans
Castor canadensis
Citellus tridecemlineatus
Cynomys ludovicianus
Geomys bursarius
Marmota flaviventris
Mephitis mephitis
Microtus ochrogaster
Microtus pennsylvanicus
Mus musculus
Odocoileus hemionus
Ondatra zibethica
Perognathus hispidus
Peromyscus .maniculatus
Procyon lotor
Rattus norvegicus
Reithrodontomys (megalotis^)
.Sylvilagug auduboni
Sylvilagus (nuttali?)
Sylvilagus floridanus
Vulpes fulva
REPTILES AND AMPHIBIANS
Chelydra serpentina
Chrysemys picta
Pituophis melanoleucus
Rana pipiens
Thamnophis sirtalis
Common Name
Coyote
Beaver
Thirteen-lined ground
squirrel
Blacktail prairie dog
Plains pocket gopher
Yellowbelly marmot
Striped skunk
Prairie vole
Meadow vole
House mouse
Mule deer
Muskrat
Hispid pocket mouse
Deer mouse
Raccoon
Norway rat
Western harvest mouse
Desert cottontail
Mountain cottontail
Eastern cottontail
Red fox
Snapping turtle
Painted turtle
Bull snake
Leopard frog
Common garter snake
Scientific Name
BIRDS
Agelaius phoeniceus
Anas discors
Anas platyrhynchos
Ardea herodias
Branta canadensis
Bubo virginianus
Buteo jamaicensis
Buteo swainsoni
Calamospiza melanocarpa
Cathartes aura
Charadrius vociferus
Colaptes cafer
Columba livia
Corvus brachyrhynchos
Ealco sparverius
Geothlypis trichas
Hirundo rustica
Icterus bullockii
Megaceryle alcyoin
Melanerpes erythrocephalus
Nycticorax nycticorax
Paserina amoena
Phasianus colchicus
Pica pica
Quiscalus quiscula
Stelgidopteryx ruficollis
Sternella neglecta
Sturnus vulgaris
Troglodytes aedon
Turdus migratorius
Tyrannus tyrannus
Tyto alba
Xanthocephalus
xanthocephalus
Zenaidura macroura
Common Name
Red-winged blackbird
Blue-winged teal
Mallard
Great blue heron
Canada goose
Great horned owl
Red-tailed hawk
Swainson'3 hawk
Lark bunting
Turkey vulture
Killdeer
Red-shafted flicker
Rock dove
Common crow
Sparrow hawk
Yellowthroat
Barn swallow
Bullock's oriole
Belted kingfisher
Red-headed woodpecker
Black-crowned night heron
Lazuli bunting
Ring-necked pheasant
Black-billed magpie
Common grackle
Rough-winged swallow
Western meadowlark
Starling
House wren
Robin
Eastern kingbird
Barn owl
Yellow-headed blackbird
Mourning dove
'"'Species list taken from Wildlife Report in Boulder Valley Farms Pit Mining Application.
Nomenclature follows Burt and Grossenheider (1964).
Nomenclature follows Robbins e£ ^1 (1966).
D-18
-------
as a state archaeological site which probably served Indian hunters as
a campsite and rock shelter (References D-13, D-1A).
Based on 1978 information (Reference D-15), the assessed value of
the 228-acre site is estimated to be $18,000 or less than one percent of
the total project cost. Revenues from property tax for this land
parcel accounts for $1,500 or less than one tenth of the assessed
value.
Water rights in Boulder Creek are divided between senior and
junior rights, based on the concept "first in time, first in right."
Lower Boulder Ditch (senior right) and Leggett Ditch (junior
right) both draw water from Boulder Creek in the reach between the
treatment plant and the site for irrigation purposes. The junior
water rights are largely dependent upon the discharge from the
treatment plant, although during low streamflow, senior rights may
also be partially dependent on Boulder's wastewater effluent. A
detailed discussion by Blatchey Associates on water right aspects
of Boulder's proposed land treatment systems can be found in
"Comparative Study of Wastewater Treatment, City of Boulder"
(Reference D -16).
Regional Setting
Land Us e—
The proposed I/P basin site lies within the Lefthand/Niwot/
Boulder Creek Subregion, as defined in the Boulder County Compre-
hensive Plan. In March 1978, County policy officially designated
the existing land use character as being "agricultural in nature"
(Reference D-17). County policy discourages further subdivision of
lands and aims to preserve agricultural lands within the subregion.
In addition, the site itself has been identified as significant
agricultural land of local importance, surrounded almost entirely
by significant agricultural land of statewide importance. The
site has also been identified in the Open Space Element of the
Boulder County Comprehensive Plan as a critical wildlife habitat/
wetland area and part of the Boulder Creek scenic corridor.
Residents in the Boulder Creek area near 95th Street receive
their water from Lefthand Water Supply Company. Use of wells for
domestic supply is limited because of the erratic watertable level,
and potential contamination from nearby septic disposal systems.
Community services are primarily provided by the cities of Long-
mont, Brownsville and Niwot as well as by Boulder County (Reference
D-18). (The proposed site lies immediately outside the boundaries of
the Boulder Valley Comprehensive Plan.)
D-19
-------
Environmental Features—
The project site occurs within an area designated as a "critical
wildlife habitat" in the March 1978 Boulder County Comprehensive
Plan. The environmental features within the area of significance
(Figure D-4) are the Boulder Creek watercourse and riparian zone
to the south, a heron rookery or colony on Boulder Creek, immediately
southeast of the site, and the White Rocks Natural Area 3/4 miles
east of the site.
Boulder Creek forms the southern boundary of the site. West of
95th Street, the stream banks are low with overhanging vegetation and
small segments support thick growths of cottonwood and willow trees
which shade the streamcourse. The interface of water and bank
vegetation provide an important wildlife habitat. East of 95th Street,
the northern bank rises 3 to 8 feet above the creek and is relatively
exposed with no overhanging vegetation. The stream channel has been
straightened by the county in some areas leaving high cut banks and
oxbow ponds. Boulder Creek typically sustains thick algal mats in
the summer due to upstream nutrient enrichment and supports limited
aquatic fauna due to historic discharges of wastewater effluent from
the 75th Street treatment plant upstream. Characteristic riparian
vegetation and wildlife are discussed in Appendix B of the EIS.
A heron rookery is established in a large cottonwood grove
immediately east of the project site. The grove extends approximately
one-half mile along Boulder Creek with mature cottonwood trees
standing 60- to 80-feet tall and a relatively open understory. The
grove sustains a large nesting population of great blue herons and
black-crowned night herons. Approximately 100 nests are occupied by
each species, making this rookery the largest one in the state
(Reference D-19). The great blue herons migrate from the south and
nest in the rookery from March through early August. The black-
crowned night herons arrive somewhat later and leave by late-August.
Both species subsist predominantly on fish supplemented by small
animals and insects. The herons utilize a large feeding area that
extends beyond the project site to nearby ponds and reservoirs such
as Sawhill Ponds and Valmont Reservoir. The birds have adapted to
many changes in the area including stream channelization activities
beneath the rookery, gravel mining upstream, and vehicular traffic
on 95th Street. The limit to their tolerance is difficult to deter-
mine but would probably be greatly affected by human activities
such as land development and destruction of nesting areas.
D-20
-------
o
I
CRITICAL WILDLIFE
HABITAT AREAS
-------
The White Rocks Natural Area (WRNA) has been discussed in de-
tail in Section II of the EIS and consists of approximately 210
acres of sandstone outcroppings and bluffs overlooking the Boulder
Creek floodplain. The WRNA contains unique local landforms har-
boring a distinct biotic community with eight rare and endangered
plant and animal species. The White Rocks also form an integral
part of the floodplain ecosystem providing nesting, resting and
observation sites for predatory birds and animals as well as an
important land/water interface area for resident wildlife.
Near the White Rocks formation south of Boulder Creek and
southwest of the project site is a current gravel mining and recla-
mation operation. The ambient noise level is increased during mining
operations by haul trucks on 95th Street and an on-site rock
crusher. The mining activities are conducted with stringent air
and water quality control measures and followed-up by an intensive
reclamation program to transform the gravel pits into a high quality
wildlife habitat. As of spring 1978, the reclamation of the gravel
pits and revegetation program were proceeding well and attracting
great blue herons to feed in the area.
In total, the designation of the project area and the local
region as a "critical wildlife habitat" recognizes a number of
significant environmental conditions. Preservation of these
resources implies that they should be considered in the early
phases of local planning activities where careful planning can
minimize disturbances and in some cases enhance the environment.
Potential Impacts and Mitigation Measures
Environmental impacts and mitigation measures are discussed in
two groups: short-term impacts associated with construction acti-
vities and long-term impacts which accompany operation of the treat-
ment system.
Site-specific Impacts—
Site preparation for the infiltration/percolation basins and
the installation of a 2^ mile pipeline to the site would cause
moderately adverse impacts during the limited period of construction
activities, some of which can be effectively mitigated. Excava-
tion of groundcover and topsoils on 228 acres will expose large
areas for possible erosion and dust generation. Water quality down-
stream in Boulder Creek may be affected by the increased sedimen-
tation caused by erosion on the site. Removal of groundcover will
also destroy the pasture/agriculture habitats on the site, and
construction dust, noise, and activities may temporarily disrupt
wildlife habitats adjacent to the site. This includes the aquatic
and riparian communities along Boulder Creek, the heron rookery
to the east, and to a minor extent, the White Rocks Natural Area
to the west. Mature cotto.nwood trees on the site may also be jeopard-
ized.
D-22
-------
Construction of the underdrain system would require dewatering
to a depth of eight- to ten-feet and installation of an impermeable
barrier around the perimeter of the site. This would divert ground-
water flow and depress groundwater levels on and near the site, partic-
ularly areas to the east. Groundcover and vegetation may suffer from
the lowered groundwater table.
When construction is completed, the initial start-up of opera-
tions may create some difficulties. Since hydraulic characteristics
are site-specific, as d
-------
Seasonal variation in treatment efficiency is expected due to
variations in both influent quality and ambient weather conditions
and type and volume of vegetation growing within the basins.
Ammonia-nitrogen is stored within the soil column during the winter,
is oxidized into nitrate in the spring, and then discharged. Winter
conditions will also reduce phosphorous removal, and significantly
higher discharge concentrations of phosphate can be expected from
November through January. This uneven loading may disrupt stream
habitats and lead to sporadic algal grows. High spring flows,
however, may dilute the peak discharges and mitigate any adverse
effect.
Water quality in Boulder Creek downstream of 95th Street would
be significantly improved with the additional land treatment; however,
relocating the point of discharge from 75th Street to 95th Street
would decrease the flow in the 2%-mile reach. This could amount to
a substantial portion of the flow during the dry season and alter
riparian and aquatic habitats if remedial measures are not taken.
The creation of infiltration/percolation basins would remove
about 220 acres of pastureland from production, as well as a small
area to the east of the site which would be affected by the depressed
groundwater table. A different habitat, consisting of intermittently
wet and dry areas, will replace the pastureland. This habitat would
be likely to attract the nearby bird populations, several species of
frogs and other amphibians, as well as insects and animals tolerant
of wet conditions. Moderate to tall vegetation should become
established in the area of the basins.
The proposed mining of sand and gravel on this site would be
halted during the lifetime of the infiltration/percolation basins,
presently being designed for 20 years. Future options of continuing
this method of treatment at the site would postpone mining even
further. The treatment system, however, should not affect the
quality of the gravel for mining at a later date.
During cold weather, the moisture from the warm effluent may
create fog at the site and inconvenience travelers on 95th Street.
Site-specific Mitigation Measures—
Many of the short-term impacts can be effectively abated by
proper scheduling of construction activities. Both soil erosion and
disruption of bird habitats can be minimized if construction occurs
during the late summer and fall, when the dry season coincides with
the non-nesting time of year. Restricting construction activities
to the daytime would lessen the disturbances to local residents from
noise and vibration, but a temporary disturbance is unavoidable.
D-24
-------
Dust generation can be controlled by wetting the soil in
the construction area. Careful grading control and constructing
interceptor ditches around the site would protect Boulder Creek
from any erosion problems. Use of mufflers on the equipment and
machinery would reduce noise. Temporary impacts on vegetation
and wildlife can be diminished by phasing construction activities.
Supplemental irrigation on land adjacent to the site can compensate
for the depressed water table and maintain vegetation. Proper
planning in the design of the basins would not only preserve the
mature cottonwood trees on the site but also enhance the aesthetic
appearance of the treatment system.
Start-up of the I/P basins should occur only after intensive
soil surveys and preliminary tests to avoid overloading and soil
clogging. Design of loading rates, capacities, and drying times
should be flexible to allow for variations in weather, vegetation
in basins, influent quality, and soil capacities. In addition, an
intensive geohydrologic study is needed to assess impacts on the
deep aquifers before regular operation begins.
Long-term impacts can be mitigated by periodic and/or continuous
monitoring of water and soil resources. Effluent quality. Boulder
Creek, alluvial and deep groundwater should all be monitored to
assure water quality goals are maintained. Soil should also be
analyzed regularly for salt content, build-up of heavy metals, and
stability of general soil characteristics. Loading rates and
drying times can be adjusted as necessary to reduce and possibly
eliminate adverse effects.
Vegetation lost due to the lower groundwater table can be replaced
by species with longer roots or species requiring less water. If
necessary, supplemental irrigation can restore some of the vegetation.
Regional Impacts—
Beyond the immediate vicinity of the 95th Street site, regional
effects of I/P basins will occur. Social and economic as well as
environmental aspects must be considered.
In the short-term, construction of such a large facility would
benefit the local economy by creating jobs (see Appendix E in EIS)
and by directly and indirectly supporting local businesses. In the
long-term, the major beneficial effect would be the significant
improvement of water quality in Boulder Creek downstream of 95th
Street, making waters suitable for primary contact recreation and
a warm water fishery.
D-25
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Another long term social impact will be the aesthetic aspects
of the I/P basins, including odors, visual appearance and noises.
Because the effluent will be chlorinated and infiltration rates are
rapid, odor should not be a problem. Only malfunctioning of the
basins caused by hydraulic overloading would create the possiblity
for unpleasant odors. From 95th Street the basins should appear
as large ponds, possibly with tall grasses growing in them, and
conform with the open, rural character of the area. Once construc-
tion is complete, there will be little machinery on site other
than a few scattered pump stations. Noises should be minimal.
Downstream water rights will be impacted by the operation
of infiltration/percolation basins at the 95th Street site. The
water rights will be impacted because evaporation from the ponds
will decrease groundwater flow to Boulder Creek which, in turn, will
deplete streamflows. Assuming net evaporation rates in the Boulder
area to be 1.6 ft/yr, evaporation from 228 acres of basins is
estimated to be 363 acre-feet annually.
The evaporation of sewage effluent from the pond will be an addi-
tional use of water from the Boulder Creek system. Historically, sewage
effluent was returned directly to Boulder Creek from the 75th Street
treatment plant and no evaporation or additional losses to the system
occurred. The use of the infiltration/percolation basins will increase
the total water use in the stream basin by allowing an additional 360
acre-feet of water to be evaporated each year.
Other water rights on Boulder Creek, specifically Leggett and
Lower Boulder Ditches, will be altered by the change in treatment
plant effluent return flows to Boulder Creek. Diversion of waste-
water discharge to 95th Street will significantly reduce flows in
Boulder Creek between the existing treatment plant and the 95th
Street bridge. Historically, the effluent was available to the
Leggett and Lower Boulder Ditches for diversions. The new point of
return flow from the ponds is downstream of the two ditches and
transporting the effluent in a pipeline for treatment in the ponds
will make less water available to the two ditches. The amount of
depletion is equivalent to the design flow, or approximately 20,000
acre-feet per year.
The project design would incorporate a subsystem to replace
ditch diversions during the irrigation season. Renovated water
from the I/P basin underdrains would be collected at several points
for discharge to Boulder Creek. During the irrigation season, a
separate pump and pipeline system would convey renovated water
north to Leggett Ditch and upstream to Boulder Creek at the 95th
Street bridge as shown in Figure D-l. The headgate/stream
diversion point for Leggett Ditch is actually 1% miles east of the
proposed replacement point; however, no irrigation use occurs in
that interval. The second replacement point, at the 95th Street
bridge, will assure adequate stream flow for downstream diversions
D-26
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to the Lower Boulder Ditch. The volumes of renovated water pumped
to these two replacement points would vary with irrigation demand
and stream flow, equaling at least 60 percent of the system
design flow. Thus, Leggett Ditch will receive water at a slightly
different point than the historical intake point, but this should
not greatly affect the ditch operations. With an efficiently
functioning flow replacement system, Lower Boulder Ditch flows
should not be affected.
Environmental conditions in the local area that may be affected
by the operation of the I/P basins are the Boulder Creek watercourse
and riparian zone, and the heron rookery east of the site. Opera-
tion of the I/P basins as mentioned earlier, will require that:
1) wastewater formerly discharged to Boulder Creek near 75th Street
will now be diverted to the new I/P basin site, treated and discharged
near 95th Street; and 2) underdrains below the I/P basins will split
the groundwater table and remove the upper layer to a surface dis-
charge.
The first condition leads to a reduction in stream flow between
75th and 95th Streets. Depending on the season and system loadings,
the reduction would be 12 to 17 mgd, which in the summer would com-
prise 1/3 to 1/2 of the total stream flow. Aquatic flora and fauna
would probably be stressed or reduced in this 2^ mile stretch. The
flow reduction would not only reduce stream levels but also diminish
stream flow into the groundwater table and subsequent subirrigation
of adjacent low-lying pasturelands. The area of land most likely
to be affected are pasturelands south of Boulder Creek up to
approximately the Union Pacific Railroad tracks. Reduction of
subirrigation by several inches to a few feet could dry up some of the
shallow-rooted forage species and lead to the selection of deeper-
rooted plant species. Patchiness in the ground cover would also be
likely to occur. This impact is offset partially by the current
irrigation practices on the terraces above the floodplain. Inter-
mittent flood irrigation on local farm and pastureland contribute
to the variable groundwater level in the low-lying floodplain area.
The second condition of groundwater diversion at the site, would
reduce subirrigation of pasturelands in a "shadow" zone of 200 to 300
feet east of the site. Within close proximity to the site is the
cottonwood grove which provides critical habitat for the heron
rookery. Potential groundwater drawdown of 5 to 8 feet would reduce
subirrigation of the cottonwood grove. However, the effect on the
trees from the proposed I/P basins is anticipated to be minor as the
root system for mature cottonwood trees extends beyond that depth*
and the trees also draw water from the adjacent Boulder Creek-
An example of effects on a heron rookery through damage to nesting
trees occurred in 1974-1975 at Chatfield Reservoir, south of Denver.
Dewatering of gravel pits in an adjacent mining area (300 to 400 feet
from the rookery) lowered the groundwater table 30 feet leading to
D-27
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seventy-five percent mortality among the trees. The rookery was small
(initially 9 herons) and managed to survive the habitat damage with meas-
surable population increases through in-migration. In a larger colony,
debilitation of over three-quarters of the nesting sites would have a
serious effect on a rookery.
Day-to-day operation of the I/P basins, which would be manifested
in a series of full, partially full and dry water basins, would pro-
bably have minor effects on the adjacent heron rookery or the farther
White Rocks Natural Area. Predator food supply for the herons and
local raptors (hawks and owls) would be reduced by the removal of
the small mammal population on the site, particularly mice, rabbits
and prairie dogs. While the site represents only a small percentage
in the feeding territory of local predators, nevertheless it is a
reduction. The presence of the basins themselves, while a great
departure from the former pastureland, would be similar in form
to local ponds and wet meadow areas. The basins and the changing
water levels should not adversely affect the rookery. The attrac-
tion of insects and amphibians to the basins would probably form
a new food supply for the herons. This heron rookery near 95th
Street has been shown in the past to be remarkably adaptable to
changes in local conditions. In 1966, Boulder Creek beneath the
rookery was channelized extensively for flood control. Figure D-4
shows the former stream meanders. The rookery was well-established
at that time and did not appear to be affected. Since 1962, gravel
mining—forming seven lakes within a one-half mile vicinity of the rook-
ery— has occurred. Most, if not all of the mining was done, in the
spring and summer and has not appeared to alter the birds' residency.
The herons also appear to have adapted to cattle grazing at the base
of the trees, irrigation water jets, occasional trespassers and
even lowflying helicopters.
Regional Mitigation Measures—
Impacts on water rights will have to be addressed in some form
of replacement water. Evaporative losses, estimated to be 363 acre-
feet/year, should be replaced to Boulder Creek on a one-to-one
basis to compensate downstream users. Since most of the evaporation
occurs during the growing season, about 313 acre-feet of water should
be released to Boulder Creek during the summer and about 50 acre-feet
released during the winter. To compensate Leggett and Lower Boulder
Ditches, the projected streamflow between April and October, or
about 12,600 acre-feet/year, would have to be replaced. This volume
may be reduced if water derived from outside of the Boulder Creek
basin was used in the City's system.
No winter replacement water is required because the Leggett and
Lower Boulder Ditches do not divert water during the winter months. Re-
turn flows from the ponds will ensure that the flows of Boulder Creek
will remain intact below the 95th Street bridge. Replacement water
D-28
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would also serve to recharge the groundwater and make up for the
diverted flows in the surrounding areas. The reduction in flow
in the Z^-mile reach between 75th and 95th Streets is unavoidable.
Interactions with Other Plans
Currently, there are four entities with future plans involving
the 95th Street site: (1) the owner of the property, (2) a sand
and gravel company, (3) City of Boulder, and (4) Boulder County.
The property owner has done extensive studies on future uses
of Boulder Valley Farm, including studies by a planning consultant.
His detailed plans include mining the gravel resources, enlarging
a 25-acre tree farm to 50 acres, and building a 50-unit housing
development. All of this is in addition to the ongoing cattle breed-
ing '(Reference D-12). With the I/P basins alternative, the city
would purchase all or part of the property for the basins site.
Purchase of the entire Boulder Valley Farm would require a higher
capital expenditure by the city. Purchase of only the 228 acres for
the basins site would curtail the mining options on that site and
may require modification of future use plans on the other parts of
the Boulder Valley Farm.
The sand and gravel company has also established detailed plans
at the proposed I/P basin site. The sand and gravel company has
bought the gravel rights from the property owner and performed exten-
sive studies on the western half of the site as part of a formal
mining application to the state (Reference D-13). To use the area
west of 95th Street, the City of Boulder would have to acquire the
gravel rights from the sand and gravel company through purchase
and/or exchange of properties and mining rights. The Company also
has intentions to mine the eastern portion at a later date (Reference
D-20). Though use of the soils for I/P basins would not damage the
quality of the sands and gravels, it would delay any mining operations
by a minimum of 20 years.
The Boulder Valley Comprehensive Plan (BVCP) provides policies
for future growth and development in the City of Boulder and sur-
rounding areas (Reference D-21). Though under County jurisdiction,
the site is within the influence of the Boulder Valley Comprehensive
Plan and is not planned to accommodate urban development. If the I/P
basins were established, it could alter or eliminate future housing
development plans and would conform with the rural character of the
area.
The Boulder County Comprehensive Plan which incorporates the
BVCP, has identified the Boulder Creek area, including the proposed
site, as a critical wildlife habitat/wetland area and as a proposed
area to be maintained as open space (Reference D-22). Design of the
I/P basins could be coordinated with the County Parks and Open Space
Department and possibly achieve this open space goal.
D-29
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Other Environmental Considerations
Irreversible/Irretrievable Commitments of Resources—
With the construction of the I/P basins, irreversible destruc-
tion of vegetation and habitat will occur. The present pasture/
agriculture habitat will be replaced by a cyclic wet-and-dry eco-
system of vegetated basins. The pasture/agriculture habitat is im-
portant for wildlife forage, cover and hunting range for predators
and covers much of Boulder County. Loss of the pasture resource at
this site is considered irreversible, but would have only a small
effect on the local system.
Short-term Human Use vs. Long-Term Productivity—
Short-term human use of the 95th Street site for I/P basins may
have three implications on the long-term productivity of the
floodplain environment: (1) possible contamination of deep aquifers;
(2) temporary loss of gravel resources; and (3) possible disruption
of the heron rookery adjacent to the site.
The State Water Resources Division has evidence of a fault in
the bedrock formation near the 95th Street site and suspects there
is a commingling of waters from the alluvial zone with the deeper
groundwater (Reference D-23). The possible contamination of the deeper
siltstone aquifer was the reason for eliminating this site in the
original investigation for the facilities plan. The State Engineers
have installed a series of wells to determine volumes of groundwater
entering the siltstone aquifer. Since this area is not well under-
stood, damage would be difficult to assess, if contamination were
to occur. The Water Resources Division is interested in protecting
the vested water rights for each aquifer zone.
The postponement of gravel mining may constitute a short-term
loss to the economy of the region. The future value and quality
of gravels on the proposed site is uncertain, and present availability
of comparable gravels is also not known.
The existing heron rookery adjacent to the proposed site is
considered a critical wildlife habitat which both the City and
County of Boulder wish to preserve. Similar experiences with other
heron rookeries in the past have exhibited varying impacts. In one
case, a heron rookery was unaffected by the construction of a highway
closeby, and in other cases, herons have abandoned their nesting
spots (Reference D-24). Construction and operation of the I/P basins
near the heron rookery should be coordinated with the state and county
wildlife authorities to maintain the long-term productivity of the
rookery.
D-30
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AGRICULTURAL REUSE PROGRAM
The facilities plan put forth a beneficial reuse system as a
long-range program that could be used in conjunction with the con-
ventional wastewater treatment alternatives. Effluent reuse for
crop application would not only renovate the wastewater, but also
meet the 1985 zero discharge goal of P. L. #92-500. Under this
alternative evaluation, consideration will be given to the development
of a reuse system as the main treatment system to be implemented
within the present planning period.
Under this land-based treatment system, secondary effluent would
be distributed through existing irrigation ditches to privately-
owned farmland. The effluent would be applied by surface irrigation—
predominantly furrows—during the growing season. The nutrients in
the effluent would be used by crops, while the effluent would be
further cleansed through the soil column and ultimately recharge the
groundwater table. During the winter, effluent would be delivered
directly to a storage reservoir where it will be held until late spring
to supply peak irrigation demands. Approximately 10,000-12,000 acres for
irrigation and a 10,000 acre-foot storage reservoir(s) would be re-
quired.
The irrigation ditches and all irrigated land would remain under
private ownership, with the ditch company maintaining management and
operation of the system. This contrasts with the high-rate irrigation
alternative (G) in the EIS where a municipal corporation purchases
the required land and essentially enters into the farming business.
Massive local government land purchases would be relatively costly
and less acceptable to the public. However, the long-term success
of this program would require fixed land areas to utilize the waste-
water effluent and a long-term contract between the city and the
ditch company. The city could be required to purchase development
rights on the application sites and provide restitution for additional
costs incurred such as: increased maintenance, increased reservoir
capacity, control of return flows from canals and irrigated farms,
and correction of drainage problems developed as a result of increased
water supplies.
Agricultural Alternatives
Two alternative agricultural reuse systems for the City of
Boulder have been studied. Both envision piping of effluent from the
75th Street wastewater treatment plant to irrigation ditches and
reservoirs for placement on the land. Reservoir storage of winter
effluent for later use during the irrigation season is required for
both alternatives, along with substantial replacement water which
must be released to the stream to compensate out-of-priority deple-
tions.
D-31
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The first alternative for agricultural reuse was studied by
the facilities planner in 1974 (Reference D-16). The plan con-
sidered the Boulder and White Rocks, Boulder and Left Hand, Leggett,
Howell, and Godding Daily and Plum Ditches and the Six-Mile,
Panama No. 1 and Leggett Reservoirs. In the 1974 study, the ditch
and reservoir companies were not contacted, and their reaction to a
program involving the exchange of treated effluent for direct
irrigation water was not determined.
The current investigation includes a review of the 1975 plan
and a study of an alternative ditch and reservoir system for inclusion
in the exchange program. The concept of an exchange program for
land treatment of the city's effluent by exchanging water with
irrigation ditches has been discussed with representatives of two
Boulder Creek ditch companies. One of these companies, the Boulder
and White Rocks Ditch, was included in the 1975 study. The second
company contacted was the Lower Boulder Ditch Company, which has
been selected for study in this report. The reaction of the ditch
companies to an exchange program was cooperative but not enthusias-
tic. The companies were reluctant to discuss details without
additional information and expressed reservations relative to any
long-term agreement with the city which would limit the use or
sale of their water rights.
The second alternative for an agricultural reuse system focuses
on the Lower Boulder Ditch Company. This ditch company was selected
for the current study because it has the physical capacity to accept
the City of Boulder's effluent at design flow, is the number one
water right on the stream, and has sufficient land under irrigation
to absorb the effluent. A meeting was held with the Lower Boulder
Ditch Company president and engineering consultant in August 1978 and
included representatives of EPA, City of Boulder and the EIS consul-
tant. The ditch company showed some interest in an exchange plan
but requested additional information before considering a possible
agreement. It appeared doubtful that any exchange program could be
designed to the satisfaction of the ditch company. The primary
concerns were the effect of a long-term agreement between the city
and the ditch company and the restrictions that may be placed on
truck farming under the ditch. In addition, public health concerns
were expressed regarding use of ditch water for domestic purposes
by the Town of Frederick.
The problems of regulation of effluent application, limitation
of application to forage crops only, prohibition from domestic use
and long-term commitments of water and development rights would
require extensive negotiations and contractual agreements. Under
these conditions, EPA^ concluded" thaF a comprehensive and.workable
reuse plan could not be achieved at this time without considerable
difficulty and expense.
D-32
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The following section reviews the basic requisites for an agri-
cultural reuse system in Boulder County and the design parameters
that must be considered. A description of the potential problems
and issues associated with this system is also presented.
Agricultural Reuse for Boulder—
Any program involving the exchange of municipal wastewater eff-
luent with agricultural irrigation water must be accomplished in
accordance with the laws of the State of Colorado and water rights
administration under the priority system. A comprehensive review
of water rights law and administration is beyond the scope of this
report. For an analysis of water rights and land treatment alterna-
tives in Colorado, reference is made to the 1974 CH2M-Hill report,
"Comparative Study of Wastewater Treatment, City of Boulder",
(Reference D-16 ) . Appendix B of that report titled, "Water Rights
Aspects of Boulder's Proposed Land Treatment Sewage Effluent" con-
tains a thorough description of Colorado water rights administration
and analysis of a land treatment program.
Agricultural reuse of Boulder's wastewater effluent will require
construction of one or two storage reservoirs and related pumping and
transmission facilities. At design flow the Boulder plant will have
an average discharge of 17.6 mgd or 20,000 acre-feet per year.
Because the effluent can be used for irrigation only during the four-
or five-month irrigation season, winter effluent must be stored.
During the irrigation season all of the effluent will be pumped from
the storage reservoir to the ditch. In addition to storing winter
effluent, the storage reservoir will allow regulation of the flow
diverted to the ditch. In exchange for the effluent supplied to the
ditch, the ditch company will not divert water under its water
rights.
The winter storage of effluent that historically returned to
Boulder Creek will deplete the stream and lessen the amount of
water available to downstream users. To offset these depletions,
the city must provide replacement water in an amount equal to the
effluent being stored. Replacement water can come from a number
of sources, including storage rights that can be released to the
stream instead of being stored and the construction of a second
reservoir for storage of water rights during the irrigation season.
The replacement water, whether it is decreed winter water or
stored irrigation water, must be released at locations and times that
will not interfere with winter appropriations. Evaporation losses from
the winter effluent reservoir and the replacement reservoir must also
be replaced by water rights owned or to be acquired by the city.
To operate an agricultural reuse system, the city will require a
long-term agreement with the ditch company. The agreement must
encompass the continued use of water for agricultural purposes and
D-33
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ensure that land is available for irrigation. This agreement is
essential because the city will require that the entire annual supply
of effluent be placed on land for treatment purposes. This type of
agreement could take three forms: (1) an outright purchase of water and
land rights under the ditch company with a leaseback arrangement,
(2) an outright exchange of water rights with a provision that water
and land under the ditch will be retained in irrigation, or (3) a
"first right of refusal" in which the effluent is exchanged for water
in the ditch and the city has the first option to purchase the right
should an irrigator wish to sell his water right.
Land Treatment Issues—
Both alternatives for land treatment of Boulder's WWTP effluent
involve the delivery of effluent to an irrigation ditch for applica-
tion to the land, storage of winter effluent, and replacement of out-
of-priority depletions. Operation of such a program will be depen-
dent on an agreement between the city and the ditch company and
compliance with all applicable state and federal laws and regula-
tions, including those governing water rights administration and
water quality.
Discussions with representatives of two Boulder Creek ditch
companies raised the following issues:
1. Agreement - The ditch companies were not interested in a
long-term agreement with the city that would restrict the
use and sale of water from the ditch. The ditch companies
stated that they wanted flexibility in the use of their
water to allow them to sell either water or land at a
future date. It is doubtful that the City of Boulder would
enter into an agreement that would offer this flexibility.
2. Truck Farming - There are approximately 500 to 1000 acres
of truck farms under the ditches studied in the two alter-
natives. Under current guidelines prepared by the
Colorado Department of Health, secondary treated effluent
cannot be applied to vegetables that may be eaten raw. For
a land treatment plan to operate under either alternative,
truck farming cannot be permitted.
3. Domestic Water - While there is no domestic use of water
under the land treatment scheme using the Boulder and White
Rocks and other ditches proposed by CH2M-Hill, there is
domestic water in the Lower Boulder Ditch Company. The
Town of Frederick diverts water from the ditch into a small
reservoir and uses the water in its municipal system.
Replacement water for this domestic use will have to be
found to make this alternative feasible.
D-34
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Because of the above issues, a land treatment alternative for
the City of Boulder could not be completed within the time frame
of this report. An agreement between the City of Boulder and the
ditch company would require lengthy negotiations and EPA is pessi-
mistic that such an agreement can be worked out. For these reasons,
EPA does not recommend this system for Boulder.
Recommendations for Future Reuse Systems—
Though the particular set of circumstances involved in the Boulder
situation do not lend themselves to the institution of an agricultural
reuse program, EPA continues to believe that such systems have much
merit and should be encouraged. For this reason, the following recom-
mendations are offered so that other cities or wastewater agencies
interested in land treatment can benefit from the results of this
investigation. To lessen the time and the cost required to implement
a land treatment plan, it is recommended that future agricultural
reuse studies consider the following factors:
1. The amount of effluent to be treated by land application
should be less than the ditch's total flow. By offering
to replace only part of the ditch company's water with
secondary-treated effluent, the ditch company has flexi-
bility in that not all of the water is committed to agri-
cultural use. Ditch water not committed to replacement may be
sold or transferred outside the system. In addition, it
is possible that the exchange part of the ditch's decreed
water may be accomplished by a vote of the Board of
Directors whereas commitment of all of the water often
requires a vote by the stockholders.
2. There should be no truck farming or domestic water use under a
ditch receiving wastewater effluent. A plan can be
developed to purchase replacement water for truck farmers
or domestic users but would increase the cost of using
that particular ditch.
3. The minimum yield of a ditch company msut be determined to
ensure that the effluent will be treated in a dry year.
The amount of effluent exchanged should be limited to the
dry year yield of the ditch. The dry year yield in many
ditch companies is less than average yearly yield. An
exception to this generalization occurs for ditches with
very senior rights which usually get their full supply in
every year.
4. Only the most senior rights in an over-appropriated stream
basin should be considered for exchange of water. It is
important that water be available for exchange on a
continuous basis. The use of moderately senior or junior
water rights in an exchange plan increases the possibility
that effluent will have to be pumped directly into the
stream to meet downstream calls.
5. A physical site for a reservoir must be available within a
short distance of the waste treatment plant. Effluent can
D-35
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be piped considerable distances from a treatment plant and
piped back to a ditch company, but this increases the cost of
using the ditch involved.
6. A single ditch company with existing reservoirs is preferable
to a group of separate ditches. The use of a single ditch
company minimizes the administrative requirements of
transporting effluent from a waste treatment plant to a
ditch. If more than one ditch is involved, not only would
there be problems associated with transporting different
amounts of water to each ditch, but also, the ability of
the ditch to receive certain amounts of effluent may be
limited during parts of the year. To ensure that all
ditches can receive the same amount of water year in and
year out would require that the city purchase additional
replacement water which increases the cost. If a single
ditch company has existing reservoirs with sufficient
storage, the cost of land treatment alternative is consider-
ably lessened.
To make a land treatment exchange attractive to a ditch company,
the city or wastewater agency needs to be aware of its bargaining
position. The city/agency can make an exchange attractive to a
ditch company by providing water of good to excellent irrigation
quality, a firm yield of water rights, a single source of water
for the ditch company, and a bonus of additional water to make
more water available to users in the ditch company. Senior water
rights, particularly the first water right of a stream system, will
require more negotiations to reach an agreement because they
essentially have enough water and a firm supply of water. Less
senior water rights will be more interested in such a plan but
are subject to calls in dry years. Thus the city/agency will be
required to provide additional replacement water to ensure
downstream water rights.
D-36
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REFERENCES FOR APPENDIX D
D-l City of Boulder, Colorado Wastewater Utility Division and
CH M-Hill, Inc., "Wastewater Facilities Plans for Boulder,
Colorado", October 1975.
D-2 Secor, Dick, Plant Personnel, Lake George Sewage Treatment
Plant, Telephone Conversation, 21 August 1978.
D-3 Satterwhite, M. B. and Stewart, G. L., "Evaluation of an
Infiltration-Percolation System for Final Treatment of Primary
Sewage Effluent in a New England Environment" from Land as a
Waste Management Alternative, Lochr, Raymond (Ed.), Ann Arbor
Science Publishers, Inc., 1977, pp. 435-49.
D-4 Nellor, Margaret, Los Angeles County Sanitation District.
Telephone Conversation, 21 August 1978.
D-5 Tamburini, J. U., e± al., "Demonstration Plant Evaluation of
an Infiltration-Percolation System for Boulder, Colorado."
D-6 St. John, D. M. , "Seasonal and Climatic Effects on the
Performance of an Infiltration-Percolation System." Thesis.
D-7 Tamburini, J. U., "Comparative Hydraulic Performance of
Infiltration-Percolation Wastewater Treatment Systems." Thesis.
D-8 Miller, Steven G., Water Quality Monitor, City of Boulder,
Colorado, Letter. 26 July 1978.
D-9 CH?M Hill, Inc., "Wastewater Facilities Plan for Boulder,
Colorado, Supplement-Cost revisions to alternative wastewater
management plans." February 1977.
D-10 Colton, Roger B. and Harold R. Fitch, "Map showing potential
sources of gravel and crushed rock aggregate in the Boulder-
Ft. Collins-Greeley area, Front Range Urban Corridor, Colorado",
U. S. Geological Survey, Map I-855-D.
D-ll Zawistowski, Stan, 1978, personal conversation, State Engineer's
Office, Division of Water Resources, Denver, Colorado.
D-12 Culver, Donald M. , Boulder Valley Farm, Inc., Owner, Personal
Communication, 18 July 1978.
D-13 Flatiron Sand and Gravel Co., "Application for Mining Reclamation
Permit, Boulder Valley Farms Pit," (1978).
D-37
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D-14 Tate, Marcia, State Historic Preservation Office, Archaeological
Resources, Telephone Communication, 15 August 1978.
D-15 Boulder County Assessor's Office, 19 July 1978.
D-16 CH?M-Hill, Inc., "Comparative Study of Wastewater Treatment,"
July 1974.
D-17 Boulder County Comprehensive Plan, "Goals and Policies," March 1978.
D-18 Boulder County Comprehensive Plan, "Lefthand/Niwot/Boulder Creek
Subregion", March 1978.
D-19 Nelson, Donald M., "The Potential Impacts of Gravel Mining on the
Boulder Valley Farms Heron Rookery", National Audubon Society
Internship. 5 May 1978.
D-20 Hart, Michael, Flatiron Sand and Gravel Company, Personal
Communication, 20 July 1978.
D-21 Boulder Valley Comprehensive Plan, City of Boulder Planning
Department and Boulder County Land Use Department, August 1977-
D-22 Boulder County Comprehensive Plan, "Open Space", March 1978.
D-23 Zawistowski, Stan, Water Resources Division, State Engineer's
Office, Telephone Conversation, 21 July 1978.
D-24 Maxwell, Paul and Proctor, Tina, Boulder County Parks and Open
Space Department, Personal Communication, 19 July 1978.
D-38
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APPENDIX E
SHORT-TERM ENVIRONMENTAL IMPACTS
PHYSICAL ENVIRONMENT
Soils
Alternatives B and D would have a minor destructive impact
upon properties of soils at the construction site and along pipe-
line routes for sludge injection. These alternatives are gener-
ally confined within the existing treatment plant site; therefore,
the area affected would be limited.
Alternative A entails the construction of 13 ponds and their
associated conveyance and drainage pipelines. Installation of
underdrains requires the excavation of 8- to 10-ft deep trenches
while the larger gravity collection lines require trenches 10- to
30-ft deep. Conveyance lines would be constructed within the
earthen berms. Removal of several inches to several feet of the
topsoil would be required to prepare the basin surface. Construc-
tion of the basins would require large-scale earthmoving activity
to form the 4-ft-high, 55-ft-wide tapered berms. In addition,
clay soils would be imported to line the basin walls.
Alternative C requires the construction of seven polishing
ponds. The proposed pond areas fall within gravel mining sites
along Boulder Creek. The County is planning to extract gravel
from these area; the initial impact of gravel mining will have
a far greater effect than the secondary effects of formation of
polishing ponds from gravel pits. As in Alternative A, the basins
require construction of wide earthen berms and importation of clay
soils to line the entire basin.
Alternative G requires large-scale earthmoving to construct
the 8,800 ac-ft storage lagoon. Approximately 16,940^00 cu yd
excavated soil would be used to construct the perimeter berms,
but the remainder would probably be transported from the site.
Even though part of the disturbed soil mass would remain at the
site, soil profile characteristics, structure and other physical
properties would be so thoroughly destroyed or modified that an
agricultural substratum would no longer exist. Additional clay
soils would be imported to line the entire storage lagoon.
Alternatives A through D and Alternative G consider sludge
injection into nearby croplands. Construction of conveyance lines
would have a minor effect upon soils. Preparation of the fields
E-l
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for sludge injection requires only the installation of feeder
lines, at approximately 1,500 ft intervals.
Land Forms
Alternatives B and D would have a negligible effect on land
forms in the vicinity of Boulder Creek. These alternatives call
for the construction of specific facilities within the existing
treatment plant site. The addition of these structures to the
site would be almost unnoticeable due to the prominence of the
existing large, red-brick treatment plant.
Construction under Alternative A would lead to a series of
wide, 4-ft high earthen berms, visible at eye level. The bottom
of the ponds will be close to the existing grade, forming broad,
shallow basins. Viewed from the same elevation at 75th Street or
along Boulder Creek, the earthen berms would probably be no more
prominent than the basins themselves.
Alternatives C and G embody many of the final effects upon
land forms that would be experienced under Alternative A. The
polishing ponds and storage lagoon, however, would be 10 to 30
ft deep and would have steeper sides within the basins.
Preparation of the sites for sludge injection in all alter-
natives would have negligible effect on land forms.
Air Quality
All alternatives require earthmoving to some degree. Alter-
natives A, C and G require substantial grading activities during
construction. Depending upon seasonal conditions, the generation
of suspended particulate matter is unavoidable. Dust raised dur-
ing site preparation, and engine emissions from the construction
equipment—generally lacking in air pollution emission controls,
comprise the sources of air pollution during a maximum period of
two years. These activities will not have a severe or long-lasting
effect upon local air quality although they may cause a noticeable
nuisance effect.
Under normal conditions, dust picked up by the wind could
be expected to settle out within 300 ft from the site. In the
project area, winds typically are from the east during the day
and reverse to the west at night. As the areas are sparsely
populated, the magnitude of the impact is small. Under Alter-
native A, however, a small home situated at the eastern boundary
of the pond site between the creek and the railroad tracks would
experience blowing dust and particulate fallout. Control measures
E-2
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such as spraying water on the ground surface would reduce this
to some extent. Precautionary measures during construction should
also include scheduling of activities in a manner that will avoid
windy periods.
Vehicular emissions from diesel and gasoline engines would
be another source of air pollution during construction. Increased
traffic during the construction period would contribute a localized
deterioration in air quality which sould disperse gradually. How-
ever, under any alternative, the number of vehicles involved is
not large, and attendant effects upon air quality would have
only a minor impact.
Groundwater
Alternatives B and D are largely confined to the existing
treatment plant site and would have only minor impacts on the local
groundwater during construction. Within a limited area, the ground-
water table may be slightly depressed due to dewatering during con-
struction of building foundations.
In Alternative A, construction of the underdrains require de-
watering to a depth of 8 to 10 ft. To preclude groundwater flow
under the site during construction, an impermeable barrier—such
as a clay or plastic liner—would probably be placed around the
site's perimeter. This would tend to divert groundwater flow
around the basin site and depress the groundwater levels in the
immediate vicinity of the site. Groundwater flow to the pasture-
lands immediately east of the infiltration/percolation basin site
would also be reduced during the construction period, which may
last up to two years. Existing ground cover east of the basin
site would probably suffer from the diminished availability of
groundwater for subirrigation.
The pond sites for Alternative C will undergo an extensive
gravel-extraction process prior to preparation for land treatment
facilities. Gravel mining generally entails construction of
barriers to groundwater movement, excavation, dewatering, pro-
cessing, discharge of silt-laden waters and other such activities.
The impacts of gravel mining vary with the degree of environmental
protection incorporated into the mining process. However, the
main impacts on ground and surface waters will have occurred
during gravel mining prior to construction of the treatment
facilities for Alternative C. The existing plant site is sur-
rounded by open ground covered predominantly with weed species
and has few trees. Removal of ground cover would not represent
a significant loss.
E-3
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The aeration and polishing pond site under Alternative C would
initially be subject to gravel mining. Mixed pasture grasses and weed
species are found in this area and would be already greatly disturbed
or destroyed by the gravel mining process.
The construction of a large storage reservoir under Alternative G
would initially destroy 350 acres of cropland. The remainder of the
irrigation area would undergo crop preparation and planting procedures
similar to agricultural operations.
Alternatives A-D and G would require approximately 170 acres for
sludge injection. Some cottonwood trees may be removed to aid the
operational efficiency of the injection apparatus; however, the exist-
ing mixed pasture grasses and weeds would not be significantly different
from adjacent vegetation types. This area is presently under cultiva-
tion and would experience a type of land use essentially the same as
now exists.
Wildlife Patterns
Alternatives B and D are generally confined to the existing treat-
ment plant site. Construction effects would deter wildlife from the
immediate area but would generally have a short-term impact.
Alternatives A, C and G would disrupt approximately 225, 145 and
350 acres, respectively, of pasture/agricultural habitats. The removal
of ground cover and topsoil for basin preparation would destroy exist-
ing small-mammal habitat. Most greatly affected would be ground
squirrels, moles and gophers, which would lose a food source as well
as shelter. Dust, noise and vibrations during construction would also
depreciate the quality of neighboring riparian and pastureland/agri-
cultural habitats.
Concomitant with the loss of habitat, a cessation of the present
wildlife community in the proposed site would occur. The majority of
the ground-dwelling wildlife would necessarily be displaced to other
areas. The main animals displaced would be ground squirrels, mice and
jack rabbits. One might be tempted to dismiss this displacement, rea-
soning that the animals would migrate to neighboring areas. However,
since most biological systems operate at or near capacity, the displaced
animals would have difficulty in finding a niche in an already well-
established ecosystem. In reality, the overloading of animals in any
area will lead to mortality or migration. Thus, predatory birds and
animals will initially experience a surplus food supply from displaced
animals; later, as the population comes to equilibrium, they will find
the former concentration of small animals, but the area of habitation
will be smaller.
E-4
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Loss of space among territorial species will lead to migration
to more remote areas or to marginal habitats. For example, urban
development has destroyed red-winged blackbird habitats in some coun-
ties. As a result, some birds are now strutting and vocalizing their
territorial songs in unusual areas such as roadway border strips.
Similarly, invasions of squirrels and mice cause competition with other
species such as native harvest mice. The Norway rat, in particular,
has been very successful at invading other established ecosystems.
SOCIAL AND ECONOMIC ENVIRONMENT
Historical and Archaeological Resources—
The proposed alternative treatment systems will have no direct
impacts upon archaeological resources within the areas that were
visually examined for archaeological remains unless subsurface or
buried remains are encountered during project development or related
activities. This would also be an accurate assessment should there
be no archaeological resources in the areas which could not be examined,
Should there be any archaeological resources within those areas which
were not visually inspected, they could be damaged or destroyed by
project-related activities such as facility construction, pipeline
trenching and plowing for sludge injection.
It does not appear that facilities construction will have any
direct impacts on historical resources. The Kolb house and out-build-
ings are adjacent to an area that would be utilized for sludge injec-
tion, and there would be no necessity for removing the structures. If,
however, it is determined for any reason that the Kolb buildings must
be altered or removed, steps recommended in the mitigation section
could be implemented.
Noise
Construction activities under all alternatives will increase
background ambient noise levels for a short period of time in
the vicinity of the site proposed. On some occasions, heavy
equipment will produce louder noise, audible at great distances
from the site. In Alternative G, where the construction site is
E-5
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removed from human habitation, noise at these levels will not be
felt by local residents. Under Alternatives A through D, however,
a significant degree of short-term annoyances will be experienced
by residents along 75th Street, Jay Road and Heatherwood Estates.
Odor
The primary construction activities will be grading, trenching,
excavation and compacting. These activities, involving soil move-
ments and water drainage, are not anticipated to cause significant
odor effects in the immediate area or its vicinity.
Traffic and Circulation
Alternatives A through D all depend upon 75th Street as a
main access route. This road is two lanes wide and currently
handles about 4,000 automobile trips per day. An addition of
50 to 100 automobile trips per day during construction would be
well within the capacity of this road. Some disruption of traf-
fic flow would occur if specific off-road parking areas reserved
for construction workers were not provided on the site. Traffic
circulation would also be impeded during delivery of materials
and transport of equipment to the site. This can be reduced by
providing the necessary access and turn-around space on the site.
The site for Alternative G is located in the eastern portion
of the county. The proposed effluent storage reservoir would be
reached mainly by North 107th Street or Mineral Road. These roads
presently handle a small to moderate traffic load and would be
able to accommodate the additional vehicle traffic generated dur-
ing construction.
Project Employment
It is estimated that an average construction workforce of
70 employees will be required for both phases of construction
for the various alternatives. Alternative G could.require a
larger workforce, but it is not expected to be more than 100
employees. Discussions with the local construction trade coun-
cil representative indicates that the Boulder labor market has
substantial unemployment in the skills required for the project
and will not be strained by project construction, but local
hiring will depend on the location of the contractor chosen
(Reference E-l).
According to the facilities planner, approximately 30 percent
of all capital costs other than land represents labor costs, in-
cluding payroll burden and all indirect labor such as mainte-
E-6
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Table E-l. ESTIMATED LAND, LABOR AND MATERIALS COST - FOR CONSTRUCTION OF EACH ALTERNATIVE
($1000)
Capital Costs^)
Less Land Costs ^a^
Cost of Improvements^3^
Labor Cost @ 30% of
Improvements (b)
Payroll Spent in Boulder
@ 70% of Labor Cost(c)
w
"-' Materials Cost,|,70% of
Improvements
Maximum Materials Purchased
in Boulder @ 50%
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nance and security. On this basis, payroll costs will range from
$2.2 million (Alternative C) to $7.7 million (Alternative G) for
both phases of construction.
Municipal Service Costs
It is not expected that construction of any of the alternatives
will create any measurable impacts on municipal services. The
only municipal cost attributable to the project is that of con-
struction itself. For a discussion of the financing of the alter-
natives see Section IV of the EIS under Long-Term Impacts-Loans,
Bonds and Subsidies. Project costs are discussed in Section III
of the EIS under Project Costs - Capital Costs and Project Costs -
Operation and Maintenance (O&M).
Direct Business Effects
Table E-l presents an estimated allocation of capital costs
for each alternative. It is estimated that capital costs less
land costs represent approximately 30 percent labor and 70 per-
cent materials. If a non-local (outside Boulder Valley) contractor
is used for construction, a minimum of 10 percent of materials
would be locally purchased. This represents a "worst case." The
maximum, or "best case" represents 50 percent of construction
materials purchased in Boulder.
Project payroll, including indirect labor (security and
maintenance), is expected to range from $1.4 million (Alternative
F) to $7.7 million (Alternative G) for both phases of construction.
Most of this payroll will probably be paid to Boulder residents.
Indirect Business Effects
Both phases of project construction will generate indirect
business effects in the Boulder economy, as the result of (1)
local spending by the contractor for materials and (2) local
spending by the construction workforce. This spending will create
additional jobs locally.
Assuming a "best case" example, 50% of construction materials
purchased in Boulder (Reference E-2), additional employment of
from 70 job-years (Alternative C) to 240 job-years (Alternative
G) would result locally. (See Table E-2 for details for each
alternative.) This assumes a Boulder-based firm would be awarded
the construction contract. Assuming a worst case example, only
10 percent of construction materials purchased locally (Reference
(E-l), additional employment of from 38 job-years (Alternative C)
E-8
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would result locally. Details of the assumptions used for the
best case and worst case examples can be found in the preceding
Direct Business Effects. Both examples assume that all construc-
tion manpower will be hired from the local Boulder labor market
(Reference E-3) . Since current unemployment in the Denver-Boulder
area stands at 45,300, projected employment would have a beneficial
effect upon the local labor resources.
This analysis assumes that 30 percent of construction costs
less land purchases represents labor and 70 percent represents
materials. Maximum and minimum job-years of local employment
generated by construction activities are projected in Table E-2
for each alternative including both phases of construction. De-
tails of the analysis discussed above can be found in Table E-3.
Table E-2. PROJECTED LOCAL EMPLOYMENT
BOULDER, COLORADO
Alternative Job-Years of Employment
Maximum Minimum
A
B
C
D
G
82
94
70
106
240
44
51
38
57
130
An update of the 1972 U. S. Department of Commerce Census of
Business suggests that $52,000 of retail spending will create one
job-year of employment in the Denver-Boulder area. It further
suggests that $65,000 of spending for building materials will
create one job-year of employment presented above. Retail sales
employment was applied to payroll spending and building materials
employment was applied to construction materials spending.
Public Fiscal Impacts
Construction of the wastewater treatment plant will generate
revenues to the City and County of Boulder. Retail spending by
the construction workers in Boulder will result in use tax reve-
nues collected by the City. Total collections for both phases
could range from $31,000 for Alternative C to $107,000 for Alter-
native G for both phases. (See Table E-4 for the details on all
alternatives). The City of Boulder collects a $0.2 tax on all
E-9
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Table E~3. INDIRECT JOBS CREATED BY LOCAL SPENDING FOR CONSTRUCTION OF EACH ALTERNATIVE
Alternatives
A
Payroll Spent in Boulder $1,824
($1,000) (a)
Job-Years of Employment 35
Created by Payroll
Spending (b)
Maximum Materials Purchased $3,039
in Boulder @ 50 percent
($1,000) (a)
Job-Years of Employment 47
Created by Spending (°)
Minimum Materials Purchased $ 608
in Boulder @ 10 percent
($1,000) (a)
Job-Years of Employment _9
Created by Spending 'c'
Maximum Job-Years of 82
Employment Created
Minimum Job-Years of 44
Employment Created
B
$2,094
AP.
$3,491
54
$ 698
II
ii
51
C D G
$1,554 $2,362 $5,361
30 .45 103
$2,590 $3,936 $8,935
AP_ .61 137
$ 518 $ 787 $1,787
1 M 27_
70_ 106 240
^8 51_ 130
(a) From Table E-2.
(b) Assumes $52,000 of retail sales represents one job-year of employment; from U.S. Department
of Commerce Census of Business.
(c) Assumes $65,000 of sales of building materials represents one job-year of employment; from
U.S. Department of Commerce Census of Business.
-------
retail transactions. These revenues were estimated by applying
this rate to the projected local purchases (70 percent of payroll).
Boulder County does not collect either a sales tax or a use
tax. The City collects its tax only if the ultimate delivery
point of the item is within the city limits. When the City re-
ceives its building permit from the County, that permit serves
to prove that materials purchased for the project are going to
be used outside city limits and that vendors do not collect the
tax. Therefore, no local agency will benefit from the sale of
construction materials. (Reference E-4).
The County of Boulder will receive from $8,000 for Alternative
C to $26,000 for Alternative G in revenues when the building permit
is issued. The permit fee is based on the total cost of labor and
materials estimated at the beginning of the project. A charge of
$887 is levied against the first $500,000 of construction costs,
plus an additional $1.00 for every $1,000 above that amount. For
details on all alternatives, see Table E-4. (Reference E-5).
E-ll
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w
I
Table E-4. PROJECTED REVENUES TO THE CITY AND COUNTY OF BOULDER DURING CONSTRUCTION
($1,000)
Payroll Spent on Taxable
Items (a)
Use Tax Collected by the
City of Boulder (b)
Capital Costs (Excluding
A
$1,824
$36
$8,683
B
$2,094
$42
$9,974
CD G
$1,554 $ 2,362 $ 5,361
$31 $47 $107
$7,400 $11,246 $25,527
Land)(c)
Building Permit Fee .. _9 10 8^ 12_
(Revenues to the
County of Boulder)
(a) From Table E-3, Indirect Business Effects.
(b) The City of Boulder collects a $0.2 use tax on every dollar of retail sales within the City.
(c) From Table E-3, Project Costs - Capital Costs.
(d) Building permit fees are charged on labor and materials as follows: $887 for the first
$500,000 and a dollar for every additional $1,000.
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REFERENCES FOR APPENDIX E
E-l Ulrich, Don, Economic Regional Planner, CH2M Hill,
Personal communication, March 1977
E-2 Draft Environmental Impact Statement on Management
Plan for Wastewater Sludge by Metropolitan Denver
Sewaqe Disposal Distract No. I, Denver, Colorado,
May 1976. Engineering-Science, Inc.
E-3 Westerberg, George, Business Representative, Colorado
Building and Construction Trades Council. Personal
communication, October 1976.
E-4 Manzanares, Dave, Sales Tax Administrator, City of
Boulder. Personal communication, October 1976.
E-5 Wages, John, Chief Building Inspector, County of
Boulder. Personal communication, March 1977.
E-13
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APPENDIX F
COLORADO WATER QUALITY
CONTROL COMMISSION
JUNE 6, 1978 GUIDELINES FOR
WASTEWATER DISCHARGE
ENFORCEMENT POLICIES
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COLORADO OBPMTMIIIT OF HEALTH
4210 EAST 11TH AVENUE DENVER, COLORADO 80220 F*GHE 32O-8333
Anthony Kotobins, M.O., M.P.A. BMcutiv* Director
WATER QUALITY CONTROL CCMCSSICN
SPECIAL
NOTICE
Pursuant to the provisions of C.R.S., 1973, 25-8-101, as amended,
NOTICE is hereby given that the Water Quality Control Conmission
adopted the attached guidelines as an enforcement policy to be
used in assuring water quality control for discharges of domestic
type vastewater.
The effective date of this policy is June 6, 1978.
Dated this 24th day of August, 1978, at Denver, Colorado.
Evan D. Dildine, P.E.
Technical Secretary
Water Quality Control Ccnmission
EDD:rr
Attachment
F-l
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COLORADO DEPARTMENT OF HEALTH
Water Quality Control Commission
4210 E. llth Avenue
Denver, Colorado 80220
Adopted: June 6, 1978
ENFORCEMENT
COMMISSION POLICY
Section 25-8-501(6) C.R.S. 1973 reads as follows; "Every permit issued
for a sewage treatment works shall contain such terms and conditions
as the division determines to be necessary or desirable to assure con-
tinuning compliance with applicable control regulations. Such terms and
conditions may require that whenever deemed necessary by the division
to assure such compliance the permittee shall:
(a) ...
(b) ...
(c) ....
(d) Initiate engineering and financial planning for expansion of
the sewage treatment works whenever throughput and treatment reaches
eighty percent of design capacity;
(e) Commence construction of such sewage treatment works expan-
sion whenever throughput and treatment reaches ninety-five percent of
design capacity or, in the case of a municipality, either commence
such construction or cease issuance of building permits within such
municipality until such construction is commenced, except that the
building permits may continue to be issued for any construction which
would not have the effect of increasing the input of sewage to the sew-
age treatment works of the municipality involved; ..."
When the municipality's self-monitoring or the division's monitoring
data indicates that a. sewage treatment works lias reached 80% of capacity
and the division determines that no action has been taken by the muni-
cipality to initiate engineering and financial planning for expansion
of the sewage treatment works, the division will notify the appropriate
municipal authorities by certified letter of the necessary action. The
municipality will also be notified that failure to proceed with planning
may cause the commission to cease any further action on site location
application for sewer extensions for that municipality until the necessary
planning is pursued.
The provision of Section 25-8-501(6) has been inserted in each municipal
discharge permit and when the division determines that a municipality
has not started construction on the expansion of their waste treatment
works after the facility has reached 95% of its (designed) rated capacity,
F-2
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Commission Policy
Page 2
they will be notified by certified letter that if construction of the
sewage treatment works is not started and if a compliance schedule
satisfactory to the division for accomplishing the construction start
is not submitted within sixty days, the division may seek an injunction
prohibiting the issuance of any further building permits until such
time as construction of the sewage treatment facility expansion begins.
"Commencement of construction" means the actual physical effort to con-
struct the project, excluding engineering, architectural, legal, fiscal
and economic investigations and studies and surveys, and which would
include any expenditure of effort which would commit the contractor to
completion of the project or which if abandoned would cause significant
financial loss. Such efforts may include, but not be limited to, site
clearing, excavation, construction or moving an office, construction
building onto the site or obtaining a performance surety bond.
In order to provide support to the division in exercising these pro-
visions of the Act, the Water Quality Control Commission will cease
to take action on any site location applications in the municipal ser-
vice area in question during the time that the building permit moratorium
is in effect.
F-3
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Page of
Permit No.
OTHER REQUIREMENTS (continued)
LAND APPLICATION PROGRAM - Existing Sites
The permittee shall submit within sixty (60) days from the effective date
of this permit for existing land application sites, a design report on the
existing land application site to the permit issuing authority. The continuance
of this land application program will be subject to .approval of this design
report by the permit issuing authority.
This design report shall include any proposed and/or existing groundwater
monitoring program designed to monitor any movement of pollutants into the
groundwater in the area of the land application site. Monitoring wells should
be situated-soas to monitor groundwater quality inside the site, in each
dominant direction of groundwater movement away from the site, and background
water quality for groundwater entering the site. The design report shall
also contain the following information as a minimum:
1. A large scale topographic map of the land application site and
surrounding area. This map shall, show the location and estimated
water levels of the proposed and/or existing groundwater monitoring
points, including an estimate of the rate of groundwater movement and
the direction of the groundwater gradient.
2. A description of the proposed and/or existing monitoring wells including
casing size and the perforated zone of the casing and the method of
installation.
3. A description of the method of sampling and listing of the analyses
performed on the applied wastewater plus water removed from background
and down-gradient groundwater quality monitoring points. As a minimum, the
following analyses shall be performed on a basis and reported
on a basis for each monitoring point:
a) Nitrate and Ammonia Nitrogen, mg/1
b) Total Dissolved Solids, mg/1
c) COD, mg/1
d) Fecal Coliform, #/100 ml
e) Chlorides, mg/1
Before sampling, all monitoring wells must be pumped for a minimum of
ten minutes. Wells should be capped and locked when not sampling.
4. Groundwater uses in the area. Show location of all wells (domestic,
irrigation, etc.) in and within one-half mile (1/2 mile) of site.
5. Operating procedures, including as a minimum:
a) Type of irrigation used
b) Application rates
c) Available acreage & type of vegetation
d) Rotation schedule
F-4
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PART I I I
Page of
Permit No.
OTHER REQUIREMENTS (continued)
LAND APPLICATION PROGRAM - Existing Sites
6. SCS soil classification of surface layer and soil profile to a 10-foot
depth.
The first monitoring report shall be submitted within one hundred and twenty (120)
days from the date of approval of the design report by the permit issuing-author?ty
and on a basis thereafter. Each report shall contain, at a
minimum, the following information:
1. The required analyses and the date the sample was taken for each
monitoring point;
2. The average volume used per application day and quality of effluent during
the reporting period.
3. The static water level in each well.
In addition to the above information, the first monitoring report shall contain
the following:
1. Monitoring point location and number (consecutive numbering),
date completed, depth, surface elevation, depth to static water
level, date of measurement.
F-5
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rani I I I
Page of
Permit No.
OTHER REQUIREMENTS (continued)
LAND APPLICATION PROGRAM -Proposed Sites
The permittee shall submit within ninety (90) days prior to the planned
commencement date for proposed land application sites, a design report including
plans and specifications foe the proposed land application site to the permit
issuing authority. The commencement of this land application program will be
subject to approval of this design report by the permit issuing authority.
This design report shall include a proposed groundwater monitoring program
designed to monitor any movement of pollutants into the groundwater in the
area of the land application site. Monitoring wells shall be situated so as to
monitor groundwater quality inside the site, in each dominant direction of
groundwater movement away from the site, and background water quality for
groundwater entering the site. The design report shall also contain the following
information as a minimum:
1. A large scale topographic map of the land application site and surrounding
area. This map shall show the location and estimated water levels of the
proposed groundwater monitoring points, including an estimate of the rate
of groundwater movement and the direction of the groundwater gradient.
2. A description of the proposed monitoring wells including casing size
and the perforated zone of the casing and the method of installation.
3. A description of the method of sampling and a listing of the analyses
to be performed on the applied wastewater plus water removed from
background and down-gradient groundwater quality monitoring points.
As a minimum, the following analyses shall be performed on a
basis and reported on a basis for each monitoring point:
a) Nitrate and Ammonia Nitrogen, mg/1
b) Total Dissolved Solids, mg/1
c) COD, mg/1
d) Fecal Coliform, #/100 ml
e) Chlorides, mg/1
Before sampling, all monitoring wells must be pumped for a minimum of
ten minutes. Wells should be capped and locked when not sampling.
k. Groundwater uses in the area. Show location of all wells (domestic,
irrigation, etc.) in and within one-half (1/2 mile) of site.
5- Proposed operating procedures, including as a minimum:
a) Type of irrigation to be used
b) Application rates
c) Available acreage S type of vegetation
d) Rotation schedule
F-6
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PART I I I
Page of
Permit No.
OTHER REQUIREMENTS (continued)
LAND APPLICATION PROGRAM - Proposed Sites
6. SCS soil classification of surface layer and soil profile to a
10-foot depth.
The groundwater monitoring points shall be installed and the first monitoring
report shall be submitted within one hundred and twenty (120) days from the
date of approval of the design report by the permit issuing authority and on
a basis thereafter. Each report shall contain, at a
minimum, the following information:
1. The required analyses and the date the sample was taken for each
monitoring point.
2. The average volume used per application day and quality of effluent
during the reporting period.
3. The static water level in each well.
In addition to the above information, the first monitoring report shall
contain the following:
1. Monitoring point location and number (consecutive numbering),
date completed, depth, surface elevation, depth to static water
level, date of measurement.
2. The required analyses taken prior to the commencement of the land
application program.
F-7
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Page of
Permit NQ,
OTHER REQUIREMENTS (Continued)
GROUNDWATER DISCHARGES (Leach Fields, Exfiltration ponds, subsurface filtration, etc.)
The Colorado Water Quality Control Acts specifies that "state waters" include
groundwater for discharge permit requirements. However, wastewater treatment
facilities utilizing final unit processes such as stated above do not discharge
directly to subsurface waters- Therefore, the permittee is directed to install
a groundwater monitoring program to insure that groundwater degradation is not
occurring at the site.
Within sixty (60) days from the effective date of the permit, the permittee
shall submit a design report for this program to the Colorado Water Quality
Control Division.
This design report shall include any proposed and/or existing groundwater
monitoring program designed to monitor any movement of pollutants into the
groundwater in the area. Monitoring wells should be situated so as to monitor
in each dominant direction of groundwater movement away from the site, and
background water quality for groundwater entering the site. The design report
shall also contain the following information as a minimum:
1. A large scale topographic map of the treatment plant site and
surrounding area. This map shall show the location and estimated
water levels of the proposed and/or existing groundwater monitoring
points, including as estimate of the rate of groundwater movement and
the direction of the groundwater gradient.
2. A description of the proposed and/or existing monitoring wells
including casing size and the perforated zone of the casing and
the method of installation.
3. A description of the method of sampling and a listing of the analyses
performed on the applied wastewater plus water removed from background
and down-gradient groundwater quality monitoring points. As a
minimum, the following analyses shall be performed on a basis
and reported on a basis for eachmoni tor ing point:
a) Nitrate and Ammonia Nitrogen, mg/1
b) Total Dissolved Solids, mg/1
c) COD, mg/1
d) Fecal Coliform, #/100 ml
e) Chlorides, mg/1
Before sampling, all monitoring wells must be pumped for a minimum
of ten minutes. Wells should be capped and located when not sampling.
k. Groundwater uses in the area. Show location of all wells (domestic,
irrigation, etc.) in and within one-half mile (1/2. mile) of site.
F-8
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PART III
Page of
Permit No.
OTHER REQUIREMENTS (continued)
GROUNDWATER DISCHARGES (Continued)
5» SCS soil classification, of surface layer and soil profile to a 10-foot
depth.
The first monitoring report shall be submitted within one hundred and twenty (120)
days from the date of approval of the design report by the permit issuing authority
and on a basis thereafter. Each report shall contain, at a
minimum, the following information;
1. The required analyses and the date the sample was taken for each
monitoring point.
2. The static water level in each well.
In addition to the above information, the first monitoring report shall contain
the following:
1. Monitorrng point location and number (consecutive numbering),
date completed, depth, surface elevation, depth to static water
level, date of measurement.
F-9
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APPENDIX C
ENVIRONMENTAL TEAM
GENE TAYLOR, M.A., M.P.A.
*EMY CHAN
TARAS A. BURSZTYNSKY, M.S., P.E.
*SAMUAL B. EARNSHAW, B.S.
*BAHMAN SHEIKH-OL-ESLAMI, Ph.D,
P.E.
*WILLIAM BORGES, B.A.
JOYCE S. HSIAO, M.S.
*THOMAS T. JONES, M.S.
ALAN UDIN, M.S., P.E.
PHILIP N. STORRS, M.S., P.E.
ROBERT E. BROGDEN, M.S.
GUY LEONARD, B.S.
*GEORGE A. JOHNSON, M.B.A., M.S.
SHERRI CANN, M.I.M.
*JULE FISCH, M.A.
STEPHEN A. DIETZ, M.A.
JANE L. ANDERSON, M.A.
EPA Project Officer, Coordination
of Public Meetings and Notices
Project Manager, Alternatives
Evaluation, Biotic Communities,
Noise, Graphic Arts
Sanitary Engineering, Alterna-
tives Evaluation, Odor
Vegetation, Visual and Aesthetics
(Appendix C)
Soils, Sludge-Injection System
Geology, Soils, Climate, Surface
Water
Infiltration/Percolation Basins
Alternatives Evaluation
Project Cost Evaluation
Technical Direction
Agricultural Reuse, Water Rights
Groundwater, Water Rights
Economics, Project Costs,
Statutory Impacts
Economics, Public and Social
Services, Socio-Cultural
Impacts
Land Use
Archaeology and Historical
Resources
Archaeology and Historical
Resources
*Member of the Association of Environmental Professionals.
G-l
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
. REPORT NO.
_EPA-^Q8/5-78-QQ3
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
5. REPORT DATE
Boulder, Colorado Wastewater Treatment Facilities
Final Environmental Impact Statement.
a.NI Z A T I O N COOt
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Engineering-Science, Inc.
600 Bancroft Way
Berkeley, California 94710
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-01-3443
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
Region VIII
1860 Lincoln Street
Denver, Colorado 80295
13. TYPE OF RE PORT AND PERIOD COVERED
Final EIS
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This document describes the proposed EPA action regarding wastewater treat-
ment facilities for the City of Boulder, Colorado. Alternative facilities
involving advanced waste treatment techniques were considered to meet NPDES
permit requirements for Boulder Creek. Principal alternatives considered
include land treatment by infiltration/percolation, modified activated sludge/
trickling filters, chemical treatment, aeration/polishing ponds, and agri-
cultural reuse. A form of activated sludge followed by trickling filters was
chosen.
Environmental reports were assessed for this plan including effects on
water quality, groundwater levels, groundwater quality, odor generation,
fog or aerosol formation, increased energy demand, land use patterns, public
health problems, soil productivity and visual effects. Sludge treatment will
be the subject of a supplemental EIS.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Wastewater treatment; advanced wastewater
treatment; activated sludge; White Rocks;
Boulder Creek; groundwater quality; growth
impacts; percolation basins; agricultural
reuse
b.IDENTIFIERS/OPEN ENDED TERMS
Boulder, Colorado; final
EIS; 201 Facilities
Plan
COSATI 1'icld/Group
8. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report!
Unclassified
21. NO. OF PAGES
302
20 SECURITY CLASS (This page/
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
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