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0,,,,,, „,..,„-z, 6° LAFIIMLR - WELD REGIONAL COUNCIL OF GOVERNMENTS
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701 EAST 4th STREET
fvf LOVELAND, COLORADO 80537
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December 2 , 1976 G<r
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TO: Don Brandes , Weld County Planning Department : �Ccr'�'sio4
Dr. Franklin Yoder, Director, Weld County \-c::::...,/,,_:1 ,i „�
Health Department _ 4�
FROM: Terrence L. Trembly -
Asst . Director, 208 Areawide Planning
SUBJ: Review of "Lower South Platte Facility Plan -
Phase I Report" for Metro Denver Sewage Disposal
District No. 1
Pursuant to your request, attached is our review of the
above referenced study . COG staff and our 208 water quality
consultant met with engineers from the Metro District to
discuss the report on November 3 . We have outlined specific
areas of concern to the region and in particular, potential
impacts to communities in Weld County. If you have further
questions , please call upon us.
TLT:psj
Enc.
4 LAI 11MF_IR WEL_O F1EOIONAL COUNCIL OF GOVERNMENTS
1 d no 7 RI IONE (303) 66/-3288
moojr
+ f2OOM 201
201 EAST 4th S1 REET
.yf_,Pdr tt,• LOVELAND, COLORADO 80537
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REVIEW OF "LOWER SOUTH PLATTE FACILITY PLAN -
PHASE ] REPORT" FOR METROPOLITAN DENVER SEWAGE
DISPOSAL ])TSTRTC'1' NO. 1
SUMMARY
The specific alternative selected by Metro Denver is of little
concern to the Larimer-Weld region. However , it apnears that the
alternative will result in_ the discharge of an estimated 26 , 800
tons of salts annually and on undetermined quantity of nitrates and
heavy metals to the South Platte River just upstream of the Weld
County line by the year 2000 . A number of communities in Weld
County are totally dependent on the alluvial aquifers of the South
Platte Basin for water supply. In addition , a considerable amount
of irrigated acreage is dependent on groundwater. Historical
data indicates that the alluvial aquifers of the lower South Platte
already exhibit excess salinity , particularly with regards to
drinking water standards . A number of communities are suffering
from excess nitrates in their drinking water. Furthermore , it
would appear that there is a possibility that the Denver Metro dis-
�•' charge would use up the entire wasteload allocation of the lower
South Platte River for ammonia. If this occurs , communities such
as Fort Lupton would become located in a water quality limited seg-
ment and ammonia removal would be required in the future. This
would greatly increase the cost of wastewater treatment to Fort
Lupton and possibly other communities .
As a result of the review of the Facilities Plan , we have
identified matters of concern to the Larimer-Weld region. These
concerns are :
1 . The impact of increased salinity , heavy metals , and
nitrate loading on the groundwater quality which will
affect the ability of communities in the region to
meet drinking water standards imposed under the Safe
Drinking Water Act;
2. The impact of increased salinity loading on future
agricultural production ;
3 . The impacts of degrading water quality and including
dischargers at Weld County and water quality limited
segments , thus increasing their cost of treatment;
4. The impact of the alternative on air quality , including
indirect impact such as promoted growth resulting from
the implementation of an alternative.
These critical consideration; have not been addressed in Lhe
Denver Metro Facility Plan .
Reivew of Facility Plan , Page Two
COMMENTS
No comments are offered on the first three sections of the
report which are entitled " Introduction , " Existing Facilities , "
and "Population Wastewater Flows . "
SECTION 4 - EFFLUENT LIMITATIONS
Under the heading of "DRCOG Water Quality Management Plan , "
it is stated that , "The modeling (by DROOL) identifies three
potential problems which impact aesthetics and secondary contact
recreation in the South Platte River. The three parameters of
concern are phosphorous (P) , total nitrogen content (Total-N) ,
and fecal coliforms (soli) . " This is followed by a rather standard
section which describes the impact of BOD, suspended and soluble
solids , dissolved oxygen , -chlorine , fecal coliform, nitrogen, and
phosphorus on beneficial uses . The report then jumps to the
concluding section entitled "Proposed Effluent Quality. " No rela-
tionship is established between beneficial uses in the South Platte
below the proposed point of discharge , i .e . , near Brighton , and
effluent qualities proposed in the report.
The report , which was prepared by CI-i2M-IIill , does state that
the results of the "DRCOG Modeling Program have been discussed with
both DRCOG staff as well as the technical consultant to DRCOG in
an effort to establish the required effluent qualities for discharge
to the South Platte River. " It should be noted that the DRCOG
Technical Consul tant is CII2M-hIill .
In the section under "Proposed Effluent Quality , " the _state-
ment is made as follows : "At present the State Discharge Control
System does not account for the dilution effect of the water in the
receiving stream. As a result , the State is now studying the stream
classifications with the objectiveof establishing in-stream water
quality standards for municipal discharges . " This report, which
was published in September of 1976 does not recognize the fact that
waste load allocations were conducted in the initial DRCOG 3-C
Water. Quality Management Program, and in the Water Quality Management
Plan for the South Platte River Basin. Both of these plans were
adopted by the Water Quality Control Commission in November 1974 .
Both of these plans established in-stream limitations on municipal
discharges in accordance with PL 92-500 wtatch was passed in 1972.
Also under the section entitled "Proposed Effluent Qualities , "
it is stated that "To achieve standards set by the Colorado Water
Quality Control Commission , any proposed facility in the South Platte
Basin will have to produce an effluent with less than 20 mg/1 of BOD
and suspended solids and less than 3 mg/1 of ammonia nitrogen . "
There is no known basis for stating that all proposed facilities in
the South Platte Basin will have to meet these standards . It should
be noted that these standards were , in some cases , established as
a result of wastelcad allocations conducted by DRCOG and the State
of Colorado in the development of the Water Quality Management Plan
for the South Platte. however, these are not dunera] rules . Dis-
charge standards may be more st, i-ngent or less stringent , clepcnding
on in-stream water quality impacts .
,
Review of Facility Plan Page Three
Although the initial statements indicate that nitrate is
recognized to be a problem, there are no limitations placed on
nitrates in Table 4 - "Proposed Effluent Quality for Discharge to
the South Platte River. " The report recognizes that nitrate con-
centrations in excess of 10 mg/1 (as nitrogen) in drinking waters
have been shown to cause methemoglobinemia in infants less than three
months old . The report does not recognize the fact that many
communities along the Platte River in Weld County , which are depen-
dent on groundwaLer for drinking supplies , suffer from excess con-
centrations of nitrates in those supplies . The only limitation
indicated is for ammonia nitrogen.
It can be anticipated that any of the discharge schemes for the
lower South Platte Basin will affect nitrate concentrations in both
the South Platte River and the alluvial aquifers of the South
Platte River in Weld County. No mitigative measures for this
increase in concentration are indicated in the report.
Regarding the limitation for ammonia nitrogen , a limit of
3 mg/1 or less is proposed. A 7-day , 10-year low flow at the
Henderson Gage is 46 cfs . The proposed effluent discharge for the
year 2O00 is 27 mgd , or 41 cfs . This almost 1 to 1 dillution would
result in ammonia nitrogen concentration in the stream of 1 . 5 mg/l ,
or slightly higher. This is the limit allowed by EPA and the
State due to the fact that concentrations of ammonia in excess of
1 . 5 mg/1 are generally accepted to be toxic to fish life .
Discharge by the proposed plant of 3 mg/1 would use up the
entire wasteload allocation of the ,lower South Platte area . Brighton
would not be affected by this plan since it is incorporated into
the discharge . However, Fort Lupton would be directly affected by
this in-stream limitation. If the discharge at Fort Lupton , which
is only a few miles downstream of the proposed discharge , resulted
in violation of the stream standard of 1 . 5 mg/l , both the Denver
Metro Plant and the Town of Fort Lupton would be in violation of
"in-stream" water quality standards. Under existing interpretations
of the definition of "water quality limited segments , " both Fort
Lupton and the Denver Metro Plant would be required to reduce dis-
charges of ammonia nitrogen to the stream. Addition of nitrification
facilities to the Town of Fort Lupton would creat tremendous addi-
tional expense for the construction and operation of their treatment
plant. . The major question that arises is who is responsible for this
expense , if it is incurred. '
In addition to the items mentioned above , it is quite possible
that in-stream standards for residual chlorine would not be met
with the proposed discharge limit at . 05 mg/l .
The State has already established in-stream ] imitations for
municipal dischargers in all streams in the State of Colorado. The
proposed effluent qualities of the Denver Metro discharge in the
Lower PlaLte river as reflected in the report do not reflect these
in-stream limitations .
Review of Facility Plan Page Four
SECTION 5= ALTERNATIVE WASTEWATER MANAGEMENT SYSTEMS
The report indicates that opportunities for industrial or
domestic reuse cannot be identified within the planning period.
If water rights limitations can be resolved , then urban irriga-
tion (parks , golf courses) become a possibility for reuse . . The
question of urban reuse is left hanging and no positive or negative
indication is provided.
On Lhe question of agricultural reuse , the report lists a
number of structural and non-structural_ factors (page 27) which
would influence the decision . It is concluded "because of the
estimated time constraints and the high cost , an agricultural reuse
system has not been considered any further in this facility elan. "
There are a number of things which have not •been considered,
including the fact that th.e in-stream limitations for the discharge
into the South Platte may call for much higher effluent qualities
than indicated in Sec _ion 4 of the report. If that is the case ,
overcoming problems associated with agricultural reuse may be much
cheaper than providing very advanced waste treatment techniques .
Additional expenses could be incurred when the State of Colorado
realizes that ammonia removal to protect fish life may not be
effective without pII control . Undoubtedly , the Denver Metro dis-
charge of the Lower South Platte unit will affect pit in the South
Platte River. At 20 degrees C. , toxicity of ammonia to fish at a
pH of 6 is 51 mg/l, and at a pH of 9 is . 0726 mg/l . Tn light of
`„✓ these considerations , it is quite possible that both the structural
and non-structural problems associated with agricultural reuse
could be overcome economically .
SECTION 6 - EVALUATION OF ALTERNATIVES
Section 6 indicates that Alternatives 9 , 10 , and 11 are the
most cost effective .
Effluent Quality
The report states that the total dissolved solids content of
wastewater i_s increased by about 10 percent in an infiltration/
percolation system. This implies that consumptive use of approximately
4 cfs for the year 20C0 flow, or 3 , 000-acre-feeL per year. The
report indicates that the acceptable limit for drinking water is
500 and/l. It is a fact that most of the communities served by ground-
water in South Weld County , and this includes practically all of the
small communities , arc presently in excess of the accepted drinking
water limits . No consideration i_s given in the report to the long-
term impacts of increased salinity resulting from the Denver Metro
discharge .
Legal
No consideration is given to the water rights implications
resulting from consumptive use of 3 ,000 acre-feeLper year by the
infiltration/percolation method . This ponderous question should be
considered durI ug the facil i ti_e.c planning stage before it is i aised
by downstream water users .
t. nev i ew n I I'ac i l.i Ly Plan Page Five
Groundwater
The report does not recognize the long--term implications of
increased salinity , heavy metals , and nitrate loading on the
alluvia] aquifer of the South Platte Basin . As mentioned above ,
this long- term impact will have an effect on drinking water supplies
in several communities . Proposed EPA drinking water standards
limit concentration of heavy metals in drinking water supplies .
No reference is made to the impact of heavy metals under the long-
term loading conditions proposed .
The report indicates that "the potential build-up of heavy
metals and salts in the soil profile of the infiltration/percola-
tion basins presents a possibility of leaching to the .groundwater. "
The report does not reflect that inevitably practically all the
heavy metals and salts di: charged by the Denver Metro Plant will
find their_ way into the alluvial groundwater basins of the South
Platte . This will occur either through the fact that at certain
times of the year. the South Platte replenishes alluvial groundwater
basins , or through the fact that at certain points on the Platte
during the irrigation season the river is dried up entirely by
diversions . These diversions are subsequently applied to the land
as irrigation water.
The proposed year 2000 discharge of 27 mgd will add 26 , 800
tons of salt annually to the Platte , and an undetermined quantity
of heavy metals .
We recognize that this extremely complex question has not been
addressed in facilities plans developed in Colorado to date. IIow-
ever, because of the magnitude of discharge and its potential
impact on a basin already experiencing excess salinity and nitrates ,
these problems should be considered by the Denver Metro District.
Vegetation/Wildlife
It is stated that no significant impacts on native flora are
anticipated . Thu reason for this is that the study area has
"supported extensive agricultural activity for approximately 100
years . " This proponderance of irrigated agriculture makes one
question why the agricultural reuse alternative was ( 1) eliminated
in the initial phase of planning , and ( 2) was the most expensive
alternative involved. It is possible that construction of a biolog-
ical treatment plant was anticipated as part of the agricultural reuse
system. If this is the case , the comparison between the agricultural
reuse system and the infiltration/percolation system is biased by
the fact that the infiltration/percolation system required only the
construct of aerated lagoons .
The intent_ of the paragraphf "Hydrology/Water Quality" is
unclear. The pai agrnph states that continued monitoring will be
conducted by numerous agencies , that DRCOC wL1 1 determine the most
practical program for insuring protection of surface and ground-
water resources , and that the e: i si ng average annual flow of the
South Platte River is approximately 55 percent Metro Denver e fluent
as measured at Henderson . No c. nuluslons are provided .
•
•
4' Review of 1'aci l i ty Plant Page Six
The water quality impact of the proposed 27 mgd discharge can
only be properly evaluated according to IPA regulations when
considered in the context of low flow conditions . Reference to
average annual flows are meaningless from a regulatory standpoint
in determining water quality impacts . Since the intent of PL 92-500
is to provide for fishable and swimmable waters were attainable ,
it would appear that a more intensive analysis of hydrology and
wa ter quality is called for be fore a decision can be made regarding
an alternative . In addition , there should be some analysis of the
attainability of the 1983 goals of PL 92-500 in this section of the
Platte before the alternative can be selected. This might have a
tremendous influence on the level of treatment required .
Alternative Comparison Summary
A scoreboard is presented -for the alternatives . in general , we wish
to offer no comment on the results of the scoreboard approach .
This approach is a simplistic quantification of subjective information.
We assume it was prepared to assist the lay person in understanding
of the best alternatives . However, we would hope that the report
or supplemental documents would document in detail the cost-effective
analysis traditionally used in addition to the subjective evaluations .
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