APT
MA* 49Wm
».*. Bim«ftl|MMTAL
ra*TBCTI*l| A€BM«V
-------
SUMMARY
DRAFT
ENVIRONMENTAL IMPACT STATEMENT
on
MANAGEMENT PLAN FOR WASTEWATER SLUDGE
BY METROPOLITAN DENVER SEWAGE DISPOSAL DISTRICT NO. 1
DENVER, COLORADO
by
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION VIII, DENVER
May 1976
Approved by: John A. Green
Regional Administrator
Q£s&-
CONTENTS
Page
Why This E.I.S.? 1
The Problem and the Plan 3
The Analysis in this E.I.S. 9
The Alternatives 11
Potential Impacts, Mitigative Measures, 15
Unavoidable Effects and Long-Term Implications
The Important Issues 20
-------
1601
WHY THIS E.I.S.?
In 1969 a law of far-reaching significance for Federal agencies
was passed by Congress. This law, called-the National Environmental
Policy Act (and referred to as NEPA), requires a Federal agency to
take account of and make known the environmental impacts of any ma-
jor action it is about to undertake. The agency must decide whether
a given action is a major one that will have a significant effect on
the environment. The document that a Federal agency must prepare
on such a major action is called an environmental impact statement
(the EIS).
EPA and NEPA—the difference
The Environmental Protection Agency (EPA) is responsible for
seeing to it that many of the environmental laws passed by Congress
are put into effect; however, it is also one among many Federal
agencies which must also comply with NEPA in its own actions. The
action EPA could take in this case is the approval of a plan by the
Metropolitan Denver Sewage Disposal District No. 1 or 'Met™1 to de-
sign and construct a sludge processing and disposal system in Adams
County.
Under the Federal Water Pollution Control Act Amendments of
1972 (Public Law 92-500), EPA is responsible for approving such
plans for water pollution control improvements of municipal sewage
treatment systems. As part of this law, Congress set aside $18
billion for design and construction of facilities, which EPA has
the responsibility for distributing. Should this plan be approved
for funding, 75 percent of the eligible portion of the project
could be paid for with a Federal grant.
-------
EPA decided that the proposed Metro project involved signifi-
cant environmental impacts, and therefore has written this environ-
mental impact statement. The National Environmental Policy Act re-
quires a thorough review of the EIS by other Federal agencies,
State agencies, local governments and interested citizens. The
idea is to get the benefit of expertise both of other agencies and
of citizens, as well as tQ inform the public of what is about to
take place. The EPA must carefully weigh the comments it receives
before any final action can be taken.
This version of the EIS is a draft for your consideration; a
final EIS will be prepared and circulated after comments have been
received on the draft. No action will be taken in approving this
facility plan until thirty days following the release of the final
EIS.
The Draft EIS
The EIS outlines in detail the proposed design of the project.
This includes the location, alternatives to the project as a whole
or to parts of the project, and the environmental effects of what
is planned, as well as the likely impacts of alternative options to
the plan.
The discussion of environmental impacts includes both direct
and indirect impacts to the extent that they can be predicted.
NEPA requires disclosure of impacts of an irreversible or long-
lasting nature. A very important feature of the impact statement
is its attempt to propose ways to lessen the negative impacts
identified. These methods are known as "Mitigative Measures."
NERA
It should be made clear that the term "environment," as used
-------
in the National Environmental Policy Act, is very broad; it applies
to people and social institutions as well as the biological and
physical world.
The Facilities Plan
Because of problems with its present sludge disposal system,
the Metro District has developed a plan to dispose of its sludge by
recycling it to the land. Formally, the plan is called a facilities
plan under Public Law 92-500. A mechanism for parcelling grant mon-
ies was developed whereby an applicant such as Metro, after having
been given priority standing by the State, would develop and submit
a facilities plan. This is known as STEP I. This plan must meet
State water quality goals as well as the Congressionally ordered
goals (viz., wherever possible, the nation's streams would become
fishable and swimmable, maximum recycling of resources, etc.). EPA
has also developed, in its construction grant regulations, a fairly
lengthy list of what other information must be presented in a facil-
ities plan. Among these requirements is an environmental assessment
that helps EPA to decide upon the environmental importance of the
project. It is only after EPA has fulfilled its obligation under
the National Environmental Policy Act that STEP II funds can be
awarded for design. After the State has approved these design
plans, a STEP III construction grant can be made.
THE PROBLEM AND THE PLAN
Metropolitan Denver Sewage Disposal District No. 1 (Metro) pro-
vides sewage treatment for most of the Denver metropolitan area.
It is a District with 52 member sanitation districts in and around
Denver. The main treatment plant is located on the South Platte
River at Commerce City, as shown on Figure A.
What is Sludge?
The Metro's (wastewater treatment) facility must dispose of on
the average over 100 dry tons of sludge per day. Sludge is the
mixture of water and solid materials found in sewage that is re-
moved from wastewater in the process of purifying it. Sludge con-
tains water, the organic matter of human wastes, paper, some oils
and grease, traces of heavy metals and other elements, and some
salts. Sludge also contains those critical nutrients—nitrogen,
phosphate and potassium—in quantities similar to commercial fer-
tilizers. Table A below indicates the relative amounts of these
three constituents in Metro sludge, other natural fertilizer
sources and commercial fertilizer.
-------
,r-
I 2
TYT *°^
KIL'C
_»AJJ
,o^
V
k. E
leaf
I
/r
!^^
•a^S^iS
Ridge'
- 5dgewo
*l
H
ROUT!
East Colfa?
Tower
x-^UptMt'
CE/T
' ^'.^1
A ^. .VcOl
>F EASt
L^
WAL
rr y^j
:_j-M_y
'T
, CWrjy Cr^gk.Dajn
SJlill
2
rv-
^^ >
C,
tf-KV
i-
^,
65O
i
A
^
!^H
^4—
T?i't.
"Z^
/tv
^i
~<^ <
SltO
(N.ri - if i
ft-
Farm.
"1
"~c:
r§lTE Br2
—+-
V-t
0!
i—^
^s
AKn
^
£ta=
^M
F^
^tiSSMtem^
DISPOSAL OPERATION;
AT LOW«Y epMBINGL^RA
n-v s
.Bepnetl^T. J-
r^r
'^Jl
fr^^f^r^
iTowiiir^ ^ /
-, ~^- t^=O"
// ^i
u\
r^pv
,,/i
^ ,>v
4/
aj'
i r.
/t-.
^ c-
T
METRO DENVER
EXISTING AND PROPOSED
^^ SLUDGE MANAGEMENT FACILITIES
-------
Table A. CONCENTRATIONS OF MAJOR PLANT NUTRIENTS IN SLUDGE
AND OTHER FERTILIZER SOURCES
(percent of dry weight)
Total nitro- Total phosphoric Acid-soluble po-
Fertilizer gen (N) acid (P20s) tassium (K20)
Metro digested
sludge
Ammonium sulfate
Anhydrous ammonia
Urea
Farm manure
Chicken manure
Cottonseed meal
3.0 to 4.0
20.5
82.0
38.0
1.2
4.1
7.0
2.3 to 3.4
-
1.2
3.7
2.5
0.7 to 1.4
-
1.2
2.3
1.5
Source: Metro Denver District Sludge Management, Volume III,
Table 7-2.
Sludge produced in the course of the wastewater treatment pro-
cesses is collected in primary and secondary settling tanks (clari-
fiers). At the present time, Metro sludge is a mixture of primary
sludge (30 percent of the total) and secondary, waste-activated
sludge (58 percent of the total) from the Central Plant plus pri-
mary digested sludge (12 percent of the total) from the City of
Denver's North Side plant. Thus, the currently produced sludge is
composed of 88 percent undigested sludge.
Raw primary sludge is that sludge which settles out when sew-
age is first brought into settling tanks at the Central Plant.
Waste-activated sludge is produced when the sewage is brought into
contact with air and microorganisms. Much of the original material
in the sewage is converted into a living cell mass by this process.
These two types of sludge are highly odorous and have a high energy
content. In both types of sludge it is extremely difficult to sepa-
rate the solid matter from the water in the sludge.
Anaerobically digested sludge is produced in large, covered
tanks using self-sustaining, slow microbial combustion process that
reduces the energy content of primary and secondary waste-activated
sludge, as well as to break down the more complex, odorous com-
pounds in the sludge. What is left is a relatively inert, dark
-------
material, rich in nitrogen, phosphate, and trace elements. Anaer-
obic digestion generally performs in short time the natural break-
down of complicated organic material that is continually occurring
in nature.
Metro's Current Sludge Operation
The District now handles the sludge produced at the two plants
by first chemically treating it to reduce possible harmful bacteria
and other organisms and to make it possible to remove greater
amounts of water from the sludge. The sludge is "de-watered" and
then hauled by truck to a part of the Lowry Bombing Range area that
is leased by the City and County of Denver for solid waste dispos-
al, shown on Figure A. There, it is spread over the surface of
the land and disc-plowed into the topsoil after some air drying has
taken place.
Although this method of disposal has shown some positive bene-
fits (such as improved forage for cattle), there are a number of
outstanding problems with the present system:
First, the present sludge mixture is not of the proper type
for land recycling. Metro must use large doses of lime and ferric
chloride to disinfect the raw and primary sludge, to control odors,
and to dewater the sludge. This is expensive and adds large
amounts of chemicals (up to 30 percent of the dry weight of the
sludge) to the soil, with no benefit. Furthermore, odors from
these sludges are difficult to control.
Second, the amounts of sludge now spread on the Lowry Bombing
Range are great enough to cause concern about eventual effects on
the groundwater. The loading rates are excessive for the purpose
of using the sludge's nutrients on this kind of land in Denver's
semi-arid climate, given the limited area where sludge can now be
spread.
Third, Metro's existing sludge treatment and disposal system
is nearing its capacity in some units. Funds will have to be
granted either to expand the present system or to find another
alternative.
Finally, the system is expensive and highly energy-consuming.
Metro would like to cut operating costs while at the same time try-
ing to find a way to use the nutrients and soil-building potential
of the sludge.
-------
Metro's Sludge Recycling Plans
With the above problems in mind, Metro began searching for a
method of disposing of its sludge in a way that it could be of use
on agricultural lands. Metro originally proposed a system of
spraying sludge on dryland fanning areas to the northeast of Denver
in Adams County. The lands would have either been owned outright
and farmed by Metro or leased back to local farmers. This system,
however, was highly criticized by the local farming community be-
cause of the high loading rates suggested for dryland farming.
Farmers were also not happy with the prospect of having Metro as
a governmental competitor in the farming business. Fears were also
expressed about odors and the loss of land values around the site.
The Metro District then reviewed its original plans with its
engineering consultant, Cornell, Howland, Hayes, and Merryfield
and Hill (CH2M-Hill for short), and came up with a more flexible
plan for recycling sludge to the land. Instead of getting into
the farming business itself, Metro now proposes in their facilities
plan to build a drying, storage and distributing center in the same
general area it had proposed for the spraying/farming operation.
After the sludge has been pumped and dried at the site, the sludge
could then be sold at some reasonable charge to metropolitan area
users. The system would take advantage of plentiful solar heat to
dry the sludge.
Features of the Metro Proposal —
Anaerobic Digesters—At the Metro Central Plant, the system
would make use of new anaerobic digesters. These digesters are an
essential part of any land application plan for sludge. They allow
sewage solid material to be fermented in an air-free environment
for a period of 22 days on the average, resulting in a stabilized,
and relatively odor-free sludge.
This product then, is the material that would be pumped some
22 miles by pipeline to the drying/storage site. At this time,
the only operating digesters in the Metro system are at the Denver
Northside Plant about a mile upstream of the Central Plant. Its
sludge accounts for only a small percentage of Metro's total
sludge to be disposed of. Metro is responsible for further pro-
cessing and disposal of this sludge. It may be of interest to
note that at present, Metro is dewatering this sludge separately
from the rest of Metro's sludge. The Denver Parks Department
wishes to use this sludge on parklands, and Metro is storing and
drying this sludge in a small area of the Lowry Bombing Range for
use by the Parks Department.
-------
Recently, EPA gave the Metro District a construction grant to
build enough anaerobic digesters to handle all of Metro's present
and projected sludge loads to 1985. The grant was given with the
understanding that EPA would not be committed to approval of any
final method of disposal of the sludge. It was expected that the
anaerobic digesters would be-beneficial to the Metro system no mat-
ter what type of final disposal was selected. Some disposal alter-
natives (such as incineration) might operate better without diges-
tion, but enough options would still remain available for disposal
to permit such a grant. Thus, for all practical purposes, anaero-
bic digestion of sludge must be considered a part of any future
sludge handling plans.
Sludge Transport—The liquid digested sludge would be pumped
from the Central Plant through two pipelines, using two pumping
stations (at the Plant and midway), to the sludge drying, storage
and distribution center 22 miles east of the Central Plant in
Adams County.
Sludge Drying, Storage and Distribution—Metro's proposed sys-
tem calls for a site in western Adams County in Range 64 West,
Township 2 South, comprising Sections 16 and 21 and the western
halves of Sections 15 and 22. This site is known as B-2, as shown
on Figure A. Sludge would be air dried in unlined earthen basins
for about six months. Then it would be scraped and stockpiled for
another six months prior to shipment for reuse.
The site would include 600 acres of drying basins within its
total 2,000-acre area. Two impoundments are planned for capturing
all surface runoff from the site. A smaller area would be used to
stockpile the dried sludge on the land surface. A variety of re-
search and demonstration plots would surround the drying area, as
shown on Figure 3 in the body of the EIS. Metro also plans to use the
site for emergency disposal of the dried or liquid sludge, if neces-
sary.
Land Application of Sludge—The heart of the proposal is to
provide Metro dried sludge to willing users in the entire metropoli-
tan area. Metro has indicated that potential areas of use include
irrigated farms, dryland farms, sod farms, Denver parks and other
metropolitan parks, and mine spoil areas. Metro has also received
a considerable number of letters from individual home owners who
would like to use the sludge on home gardens and lawns. Other pos-
sible candidates include a company interested in bagging and market-
ing dried sludge fortified with additional fertilizer nutrients.
Another company proposes to utilize sludge and garbage as a fuel
source for a coal gasification plant. To a great extent, the suc-
cess of Metro's proposal will depend on the ability to develop a
market for the sludge.
-------
AREA IN FOREGROUND RECEIVED SLUDGE
THE ANALYSIS IN THIS E.I.S,
The National Environmental Policy Act requires that an EIS
evaluate the following five items: (1) the environmental impact of
the action, (2) alternatives, (3) adverse impacts that cannot be
mitigated, (4) irreversible and irretrievable committments and (5)
short-range versus long-term resource tradeoffs. Because EPA has
been given the responsibility by Congress to develop overall pol-
lution control approaches to wastewater treatment (including
sludge treatment and disposal), EPA is also very much interested
in seeing that the best possible methods are incorporated into
sludge processing and disposal projects. EPA has generally en-
dorsed the idea of recycling waste materials wherever it is cost-
effective and environmentally suitable. This includes making
use of the nutrient and soil-building benefits in municipal
sludge.
EPA is also aware of the myriad problem areas in applying this
general concept to a particular situation. Denver's case, for ex-
ample, requires a close look at the peculiarities of climate, soils,
water availability, the groundwater situation, health effects, sys-
tem design and a host of other factors. All environmental areas--
biological, cultural and physical—must be considered and protected
-------
in evaluating such a proposed system. EPA considers impacts occur-
ring "offsite," that is, where the sludge will ultimately be applied,
to be of critical importance. Factors such as loading rates, the
condition of the sludge, what the uses of the land are and how well
control will be exercised over areas receiving the sludge are im-
portant in deciding the overall merit of the proposal. The EIS is
EPA'S tool for evaluating these areas of concern on a site-specific
level.
In preparing this draft environmental impact statement, EPA
hired an environmental consultant to help evaluate the project.
The work of the consultant, Engineering-Science, was closely man-
aged by the EPA Region VIII staff in the preparation of the EIS.
The consultant was charged with the following tasks: (1) to review
and evaluate the work done by the Metro District and its engineer-
ing consultant, CH2M-Hill, (2) to evaluate Metro's tentative pro-
posals for use of the sludge in six areas—irrigated farms, dry-
land farms, sod farms, mine-spoil areas, parklands and home gar-
dens and (3) to develop its recommendations for any measures it
felt were needed to protect any and all environmental areas. The
environmental consultant evaluated the costs of 17 different sludge
treatment and disposal systems and compared them for environmental
and engineering tradeoffs.
EPA specifically asked the consultant to evaluate the two
most likely alternatives to Metro's proposal: continuation of
the existing system at Lowry and the combination of Metro's sludge
10
-------
with a Denver solid waste recycling system under study by the Denver
Regional Council of Governments (DRCOG). The latter involved pos-
sible use of sludge with solid waste in the Denver area for sup-
plementary fuel or for production of synthetic gas.
THE ALTERNATIVES
The EIS considers both entirely new sludge treatment and dis-
posal systems as well as options within the basic Metro plan, as
alternatives. These subsystem options include changes in site
location, sizing, and drying-basin design.
n
-------
Alternatives to the Overall Metro Plan
EPA first reviewed the work that had been done by others in de-
veloping overall system alternatives. Metro had considered three
basic options in its 1972 Predesign Study: the present disposal
system at Lowry, incineration, and a form of land recycling using
sludge spraying equipment. CH2M-Hill performed a more detailed
evaulation of sludge processing and disposal alternatives in Volume
II of the facilities plan. Eight systems were selected for detailed
comparison, including the present system, the proposed drying/distri-
bution method, composting, the use of heat treatment technology and
incineration. Engineering-Science was asked to evaluate combined
solid waste-sludge systems, the eight facilities plan alternatives
and additional feasible systems.
The solid waste-sludge combination seemed promising at first,
but the recent defeat in the State legislature of a bill to provide
funding for such a system has made this option much less realistic.
To a great extent, the compatibility of the two wastes would depend
on the system eventually selected by DRCOG. For example, sludge
would not fit well with the use of solid wastes for supplemental
fuel; however, a combination composting system could use sludge
fairly well.
CH2M-Hill and Engineering-Science both concluded that the
Metro overall proposal was probably the most economical for Metro
and likely the best overall system. Engineering-Science's cost
evaluation is found in Appendix A of the EIS.
EPA prepared its own general comparative evaluation, using
environmental, engineering and economic criteria, for this EIS.
This evaluation, presented in Section II and summarized in Table 2,
includes general sludge disposal options; EPA feels that the ulti-
mate disposal choice in the overall sludge processing system has
the most important environmental implications. EPA likewise con-
cludes from an overall standpoint that the land recycling approach
is generally preferable to other alternatives, for the Metro
situation.
EPA decided that two basic alternatives should be considered
further and evaluated in detail: Metro's proposed system and the
existing Lowry system. The latter must be considered further be-
cause it is an ongoing system, and future changes to the system
might make it more economical and environmentally less damaging.
At present, there are no Federal funds available for construction
of the proposed Metro system. Therefore, Metro might have to con-
tinue to use the Lowry area for a number of years.
12
-------
Alternatives to Portions of the Metro Plan
The EIS evaluates possible alternatives within these two sys-
tems. In the Metro proposal, alternative sites for the sludge dry-
ing and distribution center were evaluated. EPA reviewed the com-
parisons of 11 sites in a 1973 study developing the agricultural
reuse program. EPA also reviewed the evaluation of three sites se-
lected by Metro for more intensive consideration in the facilities
plan. In Section II, a discussion of other suggested sites is pre-
sented, including areas at the Lowry Bombing Range, the Rocky Moun-
tain Arsenal and areas to the north of the South Platte River.
Part of the assignment of Engineering-Science was to evaluate the
site location from the standpoint of costs and energy requirements
for hauling sludge by truck to possible sludge reuse areas.
It appears that the proposed site B-2 shown in Figure A is a
reasonable choice for a sludge drying and distribution center. No
one site appears to be completely favorable when all factors (such
as nearness to markets, elevation, soils, nearness of human habi-
tation, land values, etc.) are considered. It is perhaps more im-
portant, from an environmental viewpoint, to design correctly for
the site-specific conditions, whatever the site chosen. It is
somewhat distressing, however, that little soils and groundwater
information is available for proper evaluation of site differences
and impacts.
Other subsystem alternatives considered for the Metro system
are: digestion, conditioning, transportation of the sludge, drying
basin design, controls at land application sites and the sizing of
the system. Anaerobic, mesophilic digestion appears to be the only
realistic conditioning alternative at this point. Furthermore,
there appears to be little problem with the choice of pipeline
route or pipeline design selected.
Design of the drying basins may need to be changed if a danger
to groundwater quality exists. The design could also be modified
if salts are a problem or if longer drying times are needed. Metro
will have to demonstrate that there will be no groundwater problem
with its proposal.
In order to control the amounts of some heavy metals in the
sludge, Metro might be required to institute some control over dis-
charges into the sewer system. The most critical need for control
would likely involve discharges of cadmium into the system.
The question of who should be allowed to use the sludge will be
an important one from a public health standpoint. Either restric-
tions could be placed on the types of users, "or the system design
13
-------
could be changed to produce a sludge so benign as to allow for the
whole range of possible users, without any potential health hazard.
System Capacity--
EPA considered a change in the design capacity of the project.
The project was originally designed for a growth rate considerably
greater than the present rate. Furthermore, the sizing appears to
be out of line with DRCOG desirable population growth limits for the
metropolitan Denver region. However, EPA has decided not to require
a change in the system capacity at this point, for two reasons:
(1) the greater capacity would be useful for a longer period of time
and might be needed if longer drying and storage times became neces-
sary for pathogen reduction, and (2) the effect on secondary impacts
(air pollution and land use from new populations) is only very dis-
tantly related to sludge handling subsystems. A more definite con-
trol can be put on the wastewater treatment facilities in their
drainage basin population sizing.
Lowry Disposal System Modification
Alternatives to the present Lowry system are described in the
EIS. Metro's new anaerobic digesters will change the type of sludge
being applied to the Bombing Range. Some form of composting/drying
and storage could be instituted at Lowry to allow eventual reuse of
some or all of the sludge. It is possible that more land could be
acquired at the Bombing Range to improve the soils and vegetation
without accumulating excess metals in the soils or nitrates in the
groundwater reservoir.
SLUDGE APPLIED TO LOWRY BOMBING RANGE
14
-------
POTENTIAL IMPACTS, MITIGATING MEASURES,
UNAVOIDABLE EFFECTS AND LONG-TERM IMPLICATIONS
The evaluation of environmental impacts is carried out in this
EIS in the following way. A description of potential positive and
negative impacts from the proposed Metro system is provided. Wher-
ever possible, impacts are quantified with reasonable basic assump-
tions regarding the system and prevailing conditions. Where quanti-
fication is difficult due to lack of basic data or an imprecise
state of knowledge, ranges of possible impacts or qualitative state-
ments of impacts are made. In all cases, thresholds of significance
for impacts are determined from the experience of the professionals
on the environmental team and from knowledge of local conditions.
Mitigative measures are developed for reducing the severity of
impacts. Section VII is devoted to a listing of negative or adverse
effects that cannot be avoided and of the long-term implications of
the proposal.
The EIS looks at three basic areas in analyzing the environmen-
tal impacts: Metro's proposed system, including digesters, pipeline,
site and drying/processing/storage facilities; off-site areas where
the sludge is likely to be applied; and the part of the Lowry Bomb-
ing Range containing the existing Metro sludge processing system.
Schematic representations of impacts In these three basic areas of
concern are presented in Figures 16, 17 and 18 in the main text.
Table B provides a rough summary of the major impacts expected
from the proposed Metro system and the existing Lowry operation, di-
vided into the same three basic areas. This table also summarizes
possible mitigating measures and those adverse effects that cannot
be lessened.
15
-------
Table
Environmental
parameter
Soil/land
Groundwater
Water quantities
Air quality
Public health
Energy use
Nutrient resources
Food chain
Public health
Water quality
Soil productivity
Soil salinity
B. SUMMARY OF MAJOR POTENTIAL IMPACTS, MITIGATION MEASURES AND UNAVOIDABLE EFFECTS
lapact
Destruction of profile
Nitrate and salt con-
tamination
Removal from South Platte
Odor generation; particu-
lates
Pathogen survival and
vector proliferation;
airborne particles
beneficial
beneficial
Magnification of heavy
metals, especially
cadmium
Pathogen survival, es-
pecially Ascari*
Nitrate apd salt concen-
tration
beneficial
adverse
Icpor-
tance
moderate
high
minor
negligible
high
moderate
high
high
high
high
high
moderate
Severity Feasi-
of inp.ict bility
Sludge Dryins, Storage and Distribution Site
Confined to site, -
severe
Potentially severe +
moderate P
Negligible except P
with digester up-
set; particulars
in severe wind
Low, except with +
loss of control
NA
NA
Sludge Application Areas
Low under strict •*•
controls
Low on sod farms, +
high on hone jar-
dcns
Minor on drylands,
severe on others
NA
High on dryland
farms only
Mitigation3
Methods
NA
(1) Lino basins; (2) Renove
decant; (3) Collect drain-
age; '4) Promote anaerobic
conditions
(1) Avoid irrigation;
(2) Return water
(1) Bury sour digester con-
tents elsewhere; (2) Keep
stockpiles moist
(1) Medical attention;
(2) Insect control
NA
NA
(1) Limit sites, crops,
users, rates; (2) Control
heavy -i^tals at source
(1) Restrict use of sludge;
(2) Longer drying, storage;
(3) Medical attention
NA
NA
NA
Unavoidable
effects8
Elimination of agriculture
in the site; destruction of
wildlife habitat
Mitigation will increase
project cost
Minor odors on calm days;
sone particulate dispersal
in severe winds
none
NA
NA
Heavy metals contamination
in soils; exposure of bur-
rowing animals to toxic
elements
Possible mismanagement of
the sludge reuse
Long-term cumulative ef-
fect in entire region
NA
Long-term cumulative ef-
fect in dry farms
-------
Plant nutrition
Energy use
beneficial
Fuel requirement for
trucking
moderate
moderate
Lover than present
operations
NA NA
+ Develop markets in vicinity
of site
NA
Moderate fuel consumption
Lowry Bombing Range Existing Operations
Food chain
Public health
Soil productivity
Soil salinity
Domestic anlnals grazing
on sludge-amended fields
Exposure of people in
parks and hone gardens
to pathogens
beneficial
Salt buildup in root
zone
high
potentially severe
Groundwater quality Nitrate pollution, salt
increase
Air quality
Energy
Chemicals resources
Odors
Use of large amounts of
fuel for transport
Use of conditioning chem-
icals (ferric chloride
and line)
very high potentially severe
low
moderate
high
low
moderate
moderate
moderate
Low to potentially
severe
Low except with
digester upsets
high
high
NA
P
(1) Restrict grazing;
(2) Control heavy metals at
source
(1) Longer drying tine;
(2) Medical attention
NA
(1) Remove decant,
(2) Spread over larger
areas and lower the load-
ing rates
NA
(1) Source control of toxic
materials; (2) Optimal oper-
ation of digesters; (3) Bur-
ial of sour digester sludge
(1) Use of anaerobic sludge
reduces total load, produces
gas
Use of anaerobic digesters
Heavy metals accumulation
in soils
NA
Gradual salt buildup in
the region
Groundwater pollution In
irrigated farms
Complaints from neighbor-
ing areas
Loss of energy; resources
wasted
"The symbol + indicates totally feasible; - Indicates infeasible; P indicates feasible in part; NA indicates not applicable.
-------
Sludge Drying and Distribution Site
The most serious negative environmental impacts at the sludge
drying and distribution center are on soil properties, groundwater
quality and the public health through nitrate pollution of ground-
water and pathogen problems. Positive impacts are energy and re-
source conservation. Other impacts will occur to downstream water
users because of increased consumption of water; minor impacts will
also be felt from occasional odors. Very little mitigation of the
soil destruction is possible; groundwater effects and exposure of
the public to pathogens can be controlled with proper measures as
shown in Table B.
Land application Areas
Land application areas hold both the greatest promise for bene-
fits as well as the greatest amount of potential detrimental impact
from sludge application. On the positive side, the Metro proposal
would lessen overall energy use^-in comparison with commercial fer-
tilizers, which require energy for their production—by taking ad-
vantage of solar heat in the drying process. A beneficial effect
is expected on the soil structure and moisture-holding capacity of
the soil as a result of sludge application. Properly applied, the
nutrients in sludge can replace commercial fertilizers. Sludge ni-
trogen is also of the slow-release form that would be available to
plants over a number of years, somewhat in harmony with plant needs.
The principal negative features of the application of sludge
on farms and gardens are keyed to the specific kind of land use in-
volved. Dryland farms have different (lower) requirements for
amounts of nutrients and sludge from those of irrigated areas. Ex-
posure to pathogens will differ greatly, depending on whether sludge
is applied to farmland or to city parks and home gardens.
The principal areas of concern in applying sludge to lands on
which various kinds of crops for human use are grown would be: nu-
trient loadings, toxic or plant-inhibiting effects of heavy metals,
salt accumulation in the soil profile and food-chain effects (the
gradual buildup of trace elements in plants and animals or in humans
consuming the plants and specific organs of the animals). Other
concerns involve effects on groundwater and runoff effects on water
quality. The latter are not considered very significant overall be-
cause of the projected recommended loading rates considered for this
semi-arid area.
Each of the above problem areas can be mitigated to a large ex-
tent, either by controlling how much sludge is applied and where it
is applied or by source control of heavy metals and greater treat-
18
-------
ment at the Metro facility. Such measures will require greater man-
agerial control by the Metro District as to the final disposition of
sludge. Currently, legislation is pending in the State of Colorado
to remove sewage sludge from the category of solid waste and, pre-
sumably, to set up a new statute or bring sludge application into
closer harmony with existing public health laws. This, in turn,
would mean that the State Health Department could establish regula-
tions defining where and how sludge could be applied to the land.
In the present EIS, EPA has provided recommended measures for
minimizing the environmental impacts of the use of sludge on land
areas. A set of recommendations is presented in Section VI of the
EIS.
Disposal Operations at Lowry Bombing Range
The impacts associated with the continued use of the existing
system, including final disposal of sludge at the Lowry Bombing
Range, must be considered generally negative at this point. The
existing system uses considerably more energy and chemicals than
would be required with the Metro proposal. Little agricultural pro-
ductivity, except for grazing forage, is now derived from Lowry
rangelands. At the present rates of application, there could be
discernible effects on groundwater quality around the landspreading
area in the future, and heavy metals will accumulate in the soils.
Since cattle grazing is the chief use of Lowry lands, possible toxic
chemical buildup in cattle tissues will have to be monitored. A
study is underway at present, funded by the U.S. Food and Drug Admin-
istration, to determine what heavy metals buildups are taking place
in cattle now grazing on the sludge application areas. Cattle are
known to ingest a substantial amount of soil as part of their diet.
Mitigation of some of these impacts at Lowry could be achieved
by spreading the sludge over larger areas of the Bombing Range. The
use of anaerobic digesters could also produce a better sludge, which
could be stockpiled at Lowry and distributed to farmers, thus lessen-
ing the burden on the soil of the Bombing Range.
Long-Term Implications
The Metro proposal offers an opportunity to increase the use
of renewable resources as well as to lessen the use of non-renew-
able materials. The extensive use of chemicals can be eliminated.
The sludge drying and distribution proposal will lessen Metro's
consumption of dwindling fossil fuels; reuse of nutrients would also
lessen the amount of fossil fuel needed to produce these fertil-
izers. Soil productivity could be improved by recycling carbona-
ceous material to the soil. Solar energy would replace the fossil
19
-------
fuel energy needed to dry the sludge. Additional gas from the
anaerobic digestion process would also substitute for commercial
fuels at the Metro plant.
Long-term uses of heavy metals in sludge on soils are not ex-
pected to significantly deteriorate soil quality if the conserva-
tive application rates are followed. Some metals could be bene-
ficial as micro-nutrients to crops.
THE IMPORTANT ISSUES
This section of the Summary Document is an attempt to bring
into focus what EPA considers to be the most important issues sur-
rounding the Metro project at the time of the writing of the draft
EIS. Some of the issues have arisen from people's reactions to
the Metro agricultural reuse proposal; other issues were identified
in the course of the analytical process in the EIS. Some are tech-
nical issues while others represent potential value judgments in
the political process.
The EIS process has thus far served to sharpen the focus and
put into perspective the relative severity of impacts that give
rise to these issues. The Draft EIS points out where additional
basic data are needed and where the need for intensive monitoring
is most critical for continuous safeguarding of the environment.
The continuous need for specialized expertise in the various dis-
ciplines of soil science, entomology, public health medicine, en-
gineering, etc., in the proposed project cannot be overemphasized.
EPA expects to resolve these issues in the course of the EIS
process. The final EIS will make specific recommendations on the
following issues (or any other issues raised in public and agency
review and comment) that will become a part of the grant require-
ments. The issues below are listed as they appear in the evalua-
tion of environmental impacts; the order in which they are listed
does not necessarily reflect the importance of the issues.
Source Control of Trace Elements in Sludge
Will heavy metals affect crop growthf soil pro-
ductivity and/or the food chain? Should Metro insti-
tute source control of .cadmium, since ttie cadmium/zinc
concentration ratio is in excess of the recommended 0.01?
The general heavy metals effect at the recommended sludge ap-
plication rates for dryland and irrigated croplands is expected to
be small. A comprehensive discussion of this issue is provided in
Appendix D of the EIS.
20
-------
Cadmium has been identified as a special problem because of
its known toxic effects in humans (kidney damage and hypertension).
Although the absolute concentrations of cadmium are lower than in
many large metropolitan area municipal sludges, the Cd:Zn concen-
tration ratio is relatively high (0.017) compared with recommended
levels variously set at 0.005 and 0.01. The calcareous nature of
soils in the Denver region makes heavy metals less available for
plant uptake and may somewhat compensate for this high concentra-
tion ratio.
A very effective method of control of the heavy metals (cad-
mium in particular) would be for Metro and its member districts
to survey industrial sources of cadmium, such as electroplating
firms, and to impose pre-treatment requirements on their discharges.
Sludge Drying and Distribution Site Selection
Should Metro look for another site for its drying/
distribution site?
This is an extremely controversial issue that cannot be de-
cided solely upon technical grounds. CH2M-Hill has established
that the present site is a reasonable choice, although it is not
an optimum site by any means. Metro has stated that its overwhelm-
ing concern is to place the site as far away as possible from
human habitation. This site was selected even though it had ob-
vious disadvantages, one being its distance from potential irri-
gated farm markets and the Central Plant.
EPA has experienced in its construction grants program that
site locations are always controversial. All other things being
equal, no one wants a sewage treatment plant located close to them.
EPA further evaluated through its consultant the relative
benefits and costs of having the site located so far from its po-
tential markets. Using the nitrogen fertilizer value in the
sludge as a sole criterion, it appears that up to distances of
50 to 70 miles, the value of the nutrients in the sludge exceeds
the cost of truck-hauling the sludge. Whether a potential sludge
user would realize the same economics is another matter.
EPA has raised other site possibilities such as the Rocky
Mountain Arsenal or the Lowry Bombing Range, because some people
have expressed interest in knowing whether these sites would be
better. At this point in time, this issue is still unresolved.
21
-------
Lining of the Drying Basins
Will nitrate concentration and salt buildup in the
qroundwater below the drying site be a problem? Should
Metro be required to line the drying basins or use some
other technique to prevent groundwater contamination?
Indications are that a substantial part of the total nitrogen
available in the sludge may be converted to nitrate. In this
highly soluble form, nitrates could move easily toward the ground-
water.
The exact amount of nitrate reaching the groundwater must be
considered an unknown at this point. In an anaerobic environment
as could occur at the bottom of the drying basins, nitrate is
converted to nitrogen gas, which is itself harmless. Nitrate in
groundwater is a public health hazard, since high concentrations
of nitrate are linked to methemoglobinemia in infants.
Metro liquid sludge presently contains a high concentration
of soluble salts. Under present design conditions, a highly con-
centrated salt solution would move unrestrained toward the ground-
water table.
Mitigation for nitrates and other salts could easily be ac-
complished by lining the 600 acres of drying basins, but this
would be very expensive. A system of vacuum filtration and
decanting liquid from the pumped sludge could be installed at
the drying site that would also be very expensive. The decant
would have to be stored and treated. Metro has suggested pumping
the groundwater if a problem were discovered, but this will not
be a reliable way of handling the problem. The pumped water would
in turn need proper disposal.
For the present, EPA will require Metro to develop a research
site under conditions similar to the operation expected at the
site. Nitrate and other s.alts concentrations will then be mon-
itored to determine the seriousness of the problem. Only if Metro
can conclusively demonstrate that the nitrate has been converted
to nitrogen gas and that other salts do not pose a serious prob-
lem under all operating conditions will the original proposal be
approved.
22
-------
Reduction of Pathogenic Organisms
Should Metro dry and store the sludge for longer
periods of time (than the six months drying, one year
total storage now stipulated) to adequately overcome
pathogen survival?
Although many pathogenic organisms have fairly short life-
spans in dried sludge, some organisms such as Ascaris can live
for two years or more. To a great extent, this issue should be
decided by the type of land to which sludge is applied. If
individual homeowners are to be allowed to use the sludge, a
longer storage time (up to three years) may be needed.
Use Restriction of the Sludge
Should Metro place restrictions on the use of the
dried sludge, especially where parklands and individual
home users are concerned? What crops should be restricted?
This EIS argues that environmental impacts will be felt dif-
ferentially from the use of sludge at different application sites.
Given Metro's proposal for sludge drying and storage, pathogens
can be reduced but cannot be eliminated entirely. Home gardens
growing leafy vegetables will be particularly vulnerable to con-
tamination by pathogens. People eating these vegetables would
run the risk of disease. Direct contamination could occur in
parklands if people were to use grass areas that had been treated
with sludge.
Depending on the results of the study underway to determine
the amounts of heavy metals uptake by cattle at Lowry, it may
become advisable to restrict sludge applications or restrict
cattle grazing where sludge is applied. Certain crops are also
susceptible to heavy metal uptake. Swiss chard, lettuce, spinach
and sugar beets are among the most efficient accumulators of
heavy metals. By contrast, the use of sludge on sod farms and
certain irrigated and dry farm lands may pose fewer problems.
EPA feels that these differences should be taken into account
in developing markets for future use of the sludge. Eventually,
the State of Colorado will have to set such limits through its
regulations on sludge use. The final EIS will develop recommenda-
tions and require Metro to develop its own guidelines as to best
areas for sludge use as well as what areas should be restricted.
23
-------
Control and Surveillance over Sludge Users
Once sludge has been sold to the ultimate user,
should Metro or another responsible agency control
the manner and rate of appl ication?
Application of sludge to various soils and crops, under dif-
ferent management conditions, requires a sophistication of ap-
proach that is somewhat more than that required for use of com-
mercial fertilizers and farm manures. Furthermore, some of the
negative impacts transcend the boundaries of the farm area on
which the sludge is applied. Hence, land application of sludge
by individuals becomes a public concern and may need to be regu-
lated by appropriate public agencies, such as public health de-
partments. It may be necessary to obtain binding agreements with
users, delineating precise manners of use, annual rate limitations,
time of cessation of use, field re-entry periods, crop use limi-
tations in succeeding years, etc. Such agreement would best in-
clude provisions for field inspection, monitoring, additional
management practices and amendments, and termination conditions.
Present State of Colorado statutory and regulatory provisions
may not be adequate to ensure good control over the sludge applica-
tions. There are changes being proposed to the State Solid Waste
Act and new regulations being initiated dealing with sludge appli-
cations that may improve State control over this area.
Control of Salt Accumulation
Will soluble salt loadings from the sludge buildup
in the soil inhibit plant growth in the sludge applica-
tion areas?
Salt contamination of western soils is a common problem.
Gradual buildups of salts in the soil profile can inhibit plant
growth. Sensitivity to salts varies with the kind of crop grown.
Sugar beets and citrus crops are especially sensitive, corn mod-
erately so and grasses very salt-resistent.
Metro has reported that the salt content of the sludge was
measured at about 6,000 ppm. However, the most critical con-
stituents, sodium and chloride, accounted for only about five
percent of the total dissolved salts (IDS). Data on concentra-
tions of other cations and anions is lacking; however, it would
not be unreasonable to expect that much of the salts are of the
calcareous, alkaline earth kind, with some sulfate. These salts
are generally less of a problem than sodium and chloride. EPA
will require Metro to provide a more complete cetion and anion
analysis for the sludge stream expectec1 at the drying site.
24
-------
Mitigation would be best accomplished for soluble salt re-
moval by separating the decant from the heavier sludge, if
necessary. Irrigated land application of sludge might not be
a problem if sufficient water is applied to flush the salts through
the soil profile.
Air Pollution Abatement
Could airborne sludge from the sludge drying and
distribution center create health problems around the
site?
The possibility exists that pathogens could be transmitted
through the air. This statement is made mostly because of the
lack of any definite evidence to the contrary. The studies that
have been performed on workers at sewage treatment plants does
not indicate any greater health risk than for the general popula-
tion. Metro's sludge will also have undergone anaerobic digestion
that greatly reduces the number of pathogens in sludge. The distance
from human habitation is also a factor that would minimize this
problem. However, the exposed nature of the proposed stockpile
windrows makes aerosol and particulate matter blowing a problem
during the more severe windy conditions. Metro will be required
to develop a contingency plan to protect against fugitive dust
leaving the stockpile areas during high wind conditions.
Odor Problems and Land Values
Will the proposed Metro system of drying sludge at
Site B-2 create odor problems? What effect will it have
on the value of adjacent lands?
This is a controversial issue that cannot be decided solely on
technical grounds. Sludge has been processed by anaerobic diges-
tion for most of this century and is known to be much less odorous
than raw or activated sludge from municipal treatment plants.
This is not to say that some persons might not find the odor un-
desirable. The B-2 site location offers a buffer from human habi-
tation that would make any odors difficult to detect. Calm in-
version conditions might occasionally allow odors to carry offsite,
but this would occur infrequently. Upset of the anaerobic di-
gesters that can happen occasionally would create a much more
odorous sludge. Metro will have to develop a contingency plan
before the final EIS is issued, showing how they will handle this
situation. A comparison is fortunately available from actually
operating digesters at the Denver Northside Plant that could tell
how often such a situation might occur and what is done under these
conditions. The Northside plant is an exceptionally good example
25
-------
because it receives the bulk of the industrial discharges in the
metropolitan Denver system. Slugs of heavy metal discharges are
generally the cause of disruption of the anaerobic digestion pro-
cess.
The effect on land values is unclear. Since the lands around
the B-2 site are mostly dryland farms, little or no change would
be expected in their present farm value. Such land would be less
valuable for sale for housing developments or other urban uses.
If County, Regional, local or state planners are interested in
preserving areas around the metropolitan region for open space,
this use would be quite compatible with such goals. Adams County
is considering the development of a regional airport in the future,
possibly located near the B-2 site in Range 65 West. The large
open space afforded by this drying site could be useful as a safe
"clear zone" for airplanes landing and taking off at such an airport.
Finally, if the Metro distribution center were to become a
financial success and if sludge application on dryland farms proves
feasible, nearness of such farms to the distribution center could
be an advantage.
Continuation of Landspreading of Sludge at Lowry
Could Metro use the existing sludge treatment
and disposal system at Lowry without having to de-
velop a new system?
EPA has presented briefly some possibilities for an improved
sludge disposal and perhaps utilization approach that could be de-
veloped at Lowry. This will depend on a number of very uncertain
factors: how the treatment system will operate with the new
anaerobic digesters, whether more land could be acquired at Lowry,
and whether Federal construction grant funds become available for
the proposed Metro project.
The EIS has tentatively concluded that the overall Lowry sys-
tem is not as environmentally desirable a system as the agricul-
tural reuse plan, especially as the Lowry system is now operated.
Whether it is worth the investment of some $18 to $22 million of
Federal funds to achieve this improvement is a difficult question
to answer, especially where Federal funding for water quality im-
provements is limited.
Metro will have to explore further other possible ways to
make use of the present Lowry-based system, at least for the near
future. The present system may be needed for a number of years
if Federal funds are not available, if litigation holds up the
funding process, or if EPA does not approve the proposal.
26
-------
Should EPA even consider approval of the Metro land
recycling proposal in the event that Metro is not able
to demonstrate that a users market will be available for
the dried sludge? Could Metro use site B-2 for disposal?
This is an extremely complex question to answer that depends
upon many factors. With a pioneering project of this kind, it may
not be completely possible to evaluate the full market potential
for the use of sludge until some time after the project has been
in existence. Strictly from an economic perspective, the value of
sludge will depend on how farmers and other potential users per-
ceive the value of the sludge, efforts by the Metro District to
familiarize and convince potential users about the benefits of the
sludge, and the rates Metro will charge for the product. State
regulations could also affect the extent to which various users
could apply the sludge. Research and demonstration efforts, which
can only be done over an extended period of time, may be necessary
to convince potential users about the value of sludge.
EPA recognizes that there is a certain amount of risk involved
in terms of the "success" of the project. The Agency can evaluate
the technical merits of the proposal as it has done in this EIS,
make recommendations, and see to it that certain procedures are
followed. It cannot, however, guarantee that the project will be
a success. Many other public institutions and private individuals
will have a hand in its success or failure.
It is possible for Metro to operate the drying/distribution
operation for some period of time before any distribution will be
required. The size of the proposed site offers a great deal of
flexibility in storing stockpiled sludge for greater amounts of
time than currently proposed (six months). Metro has indicated
in its facility plan that some sludge could be buried on-site if
necessary for disposal purposes. Metro could also itself haul
dried sludge to a landfill, if no other market were available for
recycling. The cost evaluations by both CH2M-Hill and Engineering-
Science considered the relative economics of the "worst-case" con-
dition of no market for the sludge and showed that even under this
condition the drying/distribution was competitive with other al-
ternatives.
It does not appear then, that the fact of an immediate lack
of a market for the sludge product would necessarily preclude EPA
from approval of the proposed project. EPA will require Metro to
become more specific about the most likely markets for sludge use
in the final EIS. In addition, Metro will have to spell out
exactly how the sludge would be disposed of .and where, both on-site
and off-site, in the eventuality that for at least the short-term,
no users market were available for the dried sludge.
27
-------
Regarding the second question, EPA would be strongly opposed
to having Metro use the drying/processing site for any ultimate
disposal of sludge other than for research and demonstration pur-
poses. The evaluation of sludge injection for a secondary disposal
system at site B-2 (page 166 of the EIS) indicates that severe ef-
fects on plant life, the soil profile, and groundwater would be
expected at the application rates proposed. The site is not large
enough to effectively dispose of the sludge either liquid or dried.
Therefore, as mentioned above, Metro will have to develop a con-
tingency plan of some form of off-site disposal to handle all ex-
cess sludge that cannot be marketed or used in the research and
demonstration plots, for the final EIS.
28
-------
Readers of this document and of the EIS it summarizes are re-
quested to comment with respect to contents, conclusions and the
project evaluated. All comments may be addressed to:
Regional Administrator
U.S. Environmental Protection Agency
Rocky Mountain-Prairie Region VIII
Suite 900
1860 Lincoln Street
Denver, Colorado 80203
Copies of the full EIS may be reviewed at public libraries and
the libraries of Colorado State University and the University of
Colorado as well as at the address shown above. A public hearing
will be held to receive additional written or oral comments from
the general public.
29
* U.S. Government Printing Office: 1976-678-852
------- |