United States
Environmental Protection
Agency
Region 8
1860 Lincoln Street
Denver, Colorado 80295
EPA-908/3-79-002
FOOTHILLS PROJECT:
Comments on Inadequacies,
Environmental Impact Analyses
and
Evaluation of Alternative Actions
March 1979

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EPA-908/3-79-002
FOOTHILLS PROJECT: COMMENTS ON
INADEQUACIES, ENVIRONMENTAL IMPACT
ANALYSES AND EVALUATION OF ALTERNATIVE
ACTIONS
by
Jack A. Stanford, Ph.D.
Department of Biological Sciences
North Texas State University
Denton, Texas 76203
817-788-2157
and
Director, Flathead Research Group
University of Montana Biological Station
Bigfork, Montana 59911
406-982-3201
Ronald M. Eddy
U.S. Environmental Protection Agency
Water Division
I860 Lincoln Street
Denver, Colorado 80295
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON D.C. 20460

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DISCLAIMER
This report has been reviewed by Region VIII, U.S.
Environmental Protection Agency, and approved for pub-
lication. Mention of trade names or commercial products
does not constitute endorsement or recommendation for
use.
DISTRIBUTION
Document is available to the public through the National
Technical Information Service, Springfield, Virginia 22161.

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ABSTRACT
Important scientific literature (Ward 1974; 1975; 1976), which
describe the limnology of the existing riverine environment, were over-
looked in the preparation of statements concerning environmental impacts
of the proposed action. The river in Waterton Canyon will be profoundly
affected by construction of the Strontia Springs Dam. Downstream from the
dam the riverine environment will be characterized by compacted substrata
(due to sluicing effect of discharge), luxurant growths of benthic algae
(due to lack of sediment scour and presence of adequate growth nutrients),
and depressed thermal regime (due to thermal stratification in the reservoir
and hypolimnial release from the dam). Although a fishery may be sustained
in the reservoir tailwaters, these changes should be considered as negative
impacts in terms of the existing environment. More environmentally sound
sites (i.e. Canyon Mouth and Chatfield Alternatives) for water diversion
are located at or downstream from the mouth of Waterton Canyon.

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CONTENTS
Abstract 		1
1.	Introduction	1
2.	Analysis of Stream Regulation 		2
Strontia Springs Alternative 		3
Chatfield and Canyon Mouth Alternatives 		4
Transmountain Diversion 		5
3.	Conclusions 		6
References			7
Bibliography 		8
Appendices
A. Schematic representation of proposed dams and
diversions that may be utilized to supply
raw water to the Foothills treatment system 	 12

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SECTION 1
INTRODUCTION
People of Denver and sister cities have been fortunate to have a very
high quality and almost unlimited muncipal water supply. Only during the
recent low water year, 1977, have water shortages of any consequence occured.
All figures Indicate that without conservation programs the present treatment
facilities cannot supply demand, even though raw water supplies exist. An
additional 100 mgd delivery to users will be needed by 1988 (BLM, 1978).
The Denver Water Board (DWB) has developed available East Slope raw
water supplies (e.g., South Platte Reservoirs) and augmented these with
transmountaln diversions from the West Slope. Most of this water is delivered
via the South Platte River. Diversion via low dams and conduits from the
Waterton Canyon area of the river facilitate gravity feed to the treatment
plants and much of the city. This has been a major feature in the existing
water supply network.
The low diversion dams in Waterton Canyon impound sediments which are
periodically sluiced downriver. This procedure, along with severe dewatering
in the lower canyon, has severely stressed the riverine habitat. Although
nearly all of the river system is regulated by dams or diversions, the areas
above Platte Canyon intake sustain a notable trout fishery. Scenery in the
canyon 1s also a valuable resource, especially because of its proximity to
the metropolitan area.
In order to supply additional treated waters to Denver, the DWB is
proceeding with plans to Impound a portion of Waterton Canyon. The 240 foot
high Strontia Springs Dam will be used to divert raw water through a new
tunnel to a new treatment facility, called Foothills Treatment Plant. These
plans exert major environmental consequences on the South Platte River and
areas on the west slope that will be used to develop additonal water sources
to supply the 500 mgd Foothills Plant.
The proposed project and viable alternatives along with associated
environmental Impacts were described in an Environmental Impact Statement
(BLM, 1978) and subsequent documents (U. S. Army Corps Engln., 1978).
However, a variety of environmental problems were either overlooked or not
properly addressed. The purpose of this report is to identify and discuss
particular points that have significant bearing on what course of action should
be taken to minimize further environmental degradation that may be caused
by the project alternatives.
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SECTION 2
ANALYSIS OF STREAM REGULATION
EXISTING REIVERINE ENVIRONMENT
The South Platte River is a regulated stream and only headwaters are
unaffected by augmented flow via transmountain diversions (i.e., Dilloq
Reservoir - Roberts Tunnel) or discharges from on-channel impoundments*
(i.e., Antero, Eleven-Mile, Cheesman, and Chatfield Reservoirs). Low diversion
dams in Waterton Canyon (i.e., Aurora and Platte Canyon) have been used since
the early 1900's to supply municipal waters to Denver. Artificial regulation
of flow has profoundly altered the lotic environment of the river by changing
physical regima (e.g., temperature, turbidity, bed loading, dissolved solids,
etc.) that would otherwise be characteristic of a Front Range stream. Biota
have been negatively affected by regulation; populations of indigenous species
have been eliminated or reduced. Virtually no portion of the South Platte
persists in a "natural" or "pristine" state. However, predictable responses
to existing conditions of stream regulation have been documented, but were not
considered in the EIS (BLM, 1978).
Ward: (1974, 1975, 1976 ) quantified the downstream effects of hypolimnial
discharges from Cheesman Reservoir. He found that regulation had profound
effects in Cheesman Canyon, but that discharges from the North Fork tended to
dilute these effects in Waterton Canyon. In the stretch of river between
Cheesman Reservoir and the North Fork confluence, hypolimnion discharges have
armored the river bottom by successive clear-water sluicing. Since turbidity
and bed loading associated with spring runoff is retained in the reservoir,
no redisposition of substrata is possible in the tail waters. This armoring
effect is accompanied by unchecked growth of attached algae; in unregulated
rivers periphyton is periodically scoured from the river bottom by the sand-
blasting effect of turbid discharges during spate or spring runoff events.
Also, since Cheesman Reservoir is sufficiently deep to stratify thermally,
hypolimnial releases are comparatively colder in summer and warmer in winter than
would be normally observed. Ward (1976, Fig. 3) showed that the thermal regime
in Cheesman Canyon was considerably dampened and delayed over that in Waterton
Canyon. Benthic community structure (i.e., numbers of species present) is
considerably less complex in Cheesman Canyon than in Waterton Canyon, due to the
effects of regulated releases from the bottom of Chessman Reservoir. Certain
Ephemeroptera (e.g., Baetis sp. and Ephemerella inermis), Chironomidae, and
Gammarus lacustrus are common benthic residents below the dam; 1n Waterton Canyon
Plecoptera, Trichoptera, and other Ephemeropta predominate, and Ward's (1976)
species list compares favorably with that reported for the Cache la Poudre River,
an un-regulated stream in the Front Range (see Stanford, 1971). However, biomass
is much greater in areas influenced by reservoir discharge (see Ward 1976, Fig. 4).
Almost identical consequences of hypolimnial releases on benthic ecology of
tail waters have been documented on the South Fork of Flathead River in Montana (see
Stanford and Potter, 1976) and elsewhere (see BIBLIOGRAPHY).
2

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High biomass of forage organisms per unit area and availability of
refugia in deep pools behind large boulders characterize the South Platte
River below Cheesman Reservoir. This may largely account for the productive
trout fishery that presently exists in this stretch of the river. The fishery
is also apparently successful in the North Fork and Waterton Canyon, at least
to the Aurora diversion dam. This structure and the Platte Canyon diversion
dam accumulate sediments that are periodically sluiced downstream. The
resulting turbidity continues to impact unfavorably on benthos and fish by
clogging and abrasive actions, especially downstream from Platte Canyon intake
(BLM, 1978; James V. Ward, personal communication). The lower portion of Waterton
Canyon has a history of low flow due to upstream diversion, which coupled with
sediment deposition, has severly impacted the fishery (BLM, 1978).
Although Ward's work indicates that the riverine environment of the North
Fork and Waterton Canyon is much less altered that the South Fork in Cheesman
Canyon, little is known about the effects of transmountain diversions via the
Roberts Tunnel. During Ward's one year study of the Waterton Canyon section,
west-slope water was discharged only on two days. This source has been utilized
to a greater extent recently and will be even more of an influence if the proposed
project is completed. Associated impacts on fish and invertebrates have not
been investigated, but, since the river channel is so narrow, sustained high
flows would not likely be advantageous to fish and invertebrates.
STRONTIA SPRINGS ALTERNATIVE
Construction of the Stront^a Springs diversion dam is apparently the
preferred action from the viewpoint of DWB, because construction of access
roads and staging area at Stephen's Gulch is underway. Also, this action
provides gravity-flow to the treatment plant, eliminates ice problems at the
diversion site, and provides re-regulat1on capability and precedence for the
proposed Two Forks storage reservoir to be located upstream. The EIS (BLM,
1978) was woefully incomplete in accessing the impacts of the Strontia Springs
Dam on the riverine environment. The conclusion the river will return to near
"normal" conditions after construction (i.e. dam will have no downstream
effects) (BLM, 1978, pg. 3-73; similar conclusion reached by U.S. Army Corps
Engin., 1978a, pgs. 16-17) is entirely false.
The reservoir will likely stratify thermally. DWB plans to operate the
system so that detention time (theoretical, tdt) is > 20 days, except during
short periods of high water use in summer (see 12/Nov/78 letter from R. Weir,
DWD, to C. Garvey, Corps Eng.). Actually, 20 days is probably a fairly
conservative figure based on uncertainties about quantity and timing of trans-
mountain diversions. Pool elevation will remain relatively stable (BLM, 1978)
and incoming water masses will reach 15-17? C in late summer and 0-1° C during
the winter months. The reservoir will be 243 ft. deep and protected from wind-
mixing by steep canyon walls. Stratification will almost certainly occur
and since the diversion intake is near the surface to reduce sediment loading,
it is likely that warm, less-dense water masses coming into the reservoir during
3

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the sunnier wi11 merely overflow colder, more-dense subsurface waters to the
diversion gates. As the dam is presently to be constructed, any water
discharged downstream will constitute cold, hypolimnial releases.
The resulting riverine environment downstream from the dam may be compared
to that presently existing below Cheesman Dam: the river will not freeze due
to discharge of 4.0° C water during the winter; the river bottom will stabilize
and become coated with growths of Cladophora and Ulothrix algae; present
macrobenthos will be replaced by forms similar to those found downstream of
Cheesman (e.g., Chironomidae and Gammarus); and invertebrate biomass per unit
area may increase in comparison to pre-impoundment levels.
It is reasonable to assume that a trout fishery would develop below the
Strontia Springs Dam, since similar conditions produced viable fishery in
Cheesman Canyon. However, the downstream thermal regime may be more profoundly
depressed because Strontia Springs Reservoir will be much deeper than Cheesman
Reservoir. Thermal shock could be a problem during high flow periods (i.e., due
to flooding) when the dam was over-topped. Also, sustained cold water discharge
is not conducive to rapid growth of fish. These problems could easily be alle-
viated by construction of multiple level outlets for thermal management. Also,
1t is important to remember that substrate structure in Waterton Canyon is less
suitable for trout than in Cheesman Canyon, where sluicing around large boulders
has created deep pools. Implantation of gabions or other refugia below
Stontia Springs would be desirable.
The question of instream flow requirements below Strontia Springs has
been addressed as well as possible in light of the paucity of knowledge on the
subject 1n general. Thirty to sixty cfs probably would be sufficient (and is
apparently available) to sustain riverine biota, especially since dewatering
due to ice formation will likely not occur. The presence of the structure
does in itself pose two ultimate problems for management of riverine biota
that does establish downstream from the dam: 1) the river could be dewatered
completely by diversion, 1f for any reason it is deemed necessary to do so
(e.g., drought, mechanical problems in outlet gates, etc.) and 2) sediments
will fill the reservoir basin completely within 75-100 years and disposal
without destruction of the downstream habitat will be difficult if not impossible.
CHATFIELD AND CANYON MOUTH ALTERNATIVES
Although other alternatives to the proposed action were presented, only
Chatfield and Canyon Mouth proposals merit much consideration. These could
be utilized without continued operation of the existing diversion structures
at the Aurora and PlatteCanyonintakes,which should be eliminated to prevent
sedimentation problems. The riverine habitat in lower Waterton Canyon cannot
be expected to improve if sediments are sluiced from low diversion dams during
periods of low flow. Continued operation of the diversion dams might be possible
if sluicing operations were limited to periods of spring runoff, when the river
is turbid anyway; however, additional study of this matter would be required.
The Chatfield alternative is the most environmentally sound action, if the
objective is to minimize the loss of "natural" qualities of Waterton Canyon.
Water and sediments would be stored outside -the confines of the canyon, thus
eliminating all problems associated with a deep diversion/storage reservoir
within the canyon. The existing riverine environment in the canyon could be
enhanced by sustained flows from transmountain diversion and Cheesman Reser-
4

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voir. At peak operation of 500 mgd at Foothills, plus Marston and Kassler
treatment plants in full operation, the South Platte would have to sustain
flow of 1,170 cfs. Although this volume is not likely before 2000, such
flows might prove to be deleterous due to excessive sluicing in the river
channel. If enough water were available, controlled releases from Chatfield
Reservoir could enhance water quality of the South Platte as It flows through
metropolitan Denver.
The Chatfield alternative is criticized 1n the EIS (BLM, 1978) on the
basis of greater productivity of algae which may produce treatment problems
due to tastes and odors. Certainly, water stored in Chatfield Reservoir will
be more productive than in a deep, cold reservoir like Strontia Springs,
but if I am to believethe phosphorus and nitrogen data (x PO^ = 0.05 ppm;
X N0Z = 0.08 ppm) presented in the EIS (BLM, 1978), algal growth may be a
significant problem in all of the alternatives. It is doubtful these data
are accurate. Regardless, such algae problems are easily handled by modern
water treatment processes.
The Canyon Mouth Alternative (see U. S. Army Corps Engin., 1978b), like
Chatfield, contains significant advantages over Strontia Springs: much of
the canyon section would remain free flowing and the riverine environment of
the lower section (except that to be impounded) would be improved by sustained
discharges; sediments would be retained near the canyon mouth; regulated
releases from the reservoir could vastly improve aquatic habitat downstream
to Chatfield. A significant advantage of Chatfield over Canyon Mouth is that
the former is already built.
TRANSMOUNTAIN DIVERSION
Under the proposed action a sustained discharge of approximately 1,176 cfs
would be required to maximize treatment capacity (assuming Marston and Kassler
plants were operating at capacity). Both additional west-slope water rights
and storage capacity (e.g., Two Forks and/or Eagle-Colorado Reservoirs, see
Appendix . B) will have to be adjudicated to suDply this volume of water.
The EIS (BLM, 1978) identified plans involving west-slope diversions that
significantly affect the Colorado River system. Very little quantitative
information exists pertaining to the environmental quality or ecology of the
various Colorado River tributaries that may be dewatered by diversions to
supply the ultimate demands of the Foothills Project. It is clear that impacts
on wilderness areas (Gore) and probably rare or endangered species are
involved in the plans, although such was not stated in the EIS. It is not
clear from the EIS that sufficient water is presently available to sustain even
125 mgd operation at the proposed plant. Therefore, discussions pertaining to
impacts and mitigation of habitat in Waterton Canyon seem rather inadequate in
light of west-slope alterations. I believe a detailed environmental assess-
ment of the situation is needed immediately; one in which all aspects of the
proposed action are modeled and studied precisely. This should be done before
any additional construction on the Foothills Project is undertaken.
5

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SECTION 3
CONCLUSIONS
1)	The present EIS (BLM, 1978) 1s very inadequate in terms of describing
impact of proposed Strontia Springs/Foothills Project because (1) available
literature on ecology of Waterton and Cheeseman Canyons was not considered,
(2) 1t is erroneously assumed that no long-term alteration of riverine
environment downstream from Strontia Springs will occur (i.e., river will
return to "normal" if 30 cfs minimum flow is established) and (3) Chatfield
and Canyon-Mouth alternatives were not presented in full light of their
reduced impact (compared to Strontia Springs) on the Canyon environment.
2)	The reservoir behind Strontia Springs Dam will stratify and the
downstream effects of hypollmnial release will manifest similarily to those
seen in the South Fork of South Platte below Cheesman Dam. The effects may
be more severe, however. The resultant thermal regime 1n Strontia Springs
tailwaters may be depressed compared to Cheesman because Strontia Springs is
much deeper and therefore stratification may be more profound (e.g., water
released from the bottom of the reservoir would be closer to 4° C year
around). Regardless, the riverine environment after construction will not
compare to the existing environment for virtually any ecological parameter.
3)	Since a productive fishery exists below Cheesman, it is reasonable
to assume a similar one might develop below Strontia Springs. This might be
maximized by sustained flows in excess of 30 cfs, accompanied by thermal
management via selective outlet portals in the dam and placement of rock-
gabions or other structures in the river channel to promote development of
pool refugia.
4)	From an environmental viewpoint the most logical alternative is to
locate the diversion structure as far downstream as possible. Impoundment
within the canyon will change the nature and quality of the riverine
environment and retain large volumes of sediments, that will ultimately have
to be sluiced or hauled. The most ecologically sound alternative would be to
use the existing Chatfield Reservoir as the diversion point; the only anthro-
pogencic impacts related to recruitment of waters for municipal use would
be due to changes on characteristics of flow regima from Cheesman and Dillon
Reservoirs. In addition, utilization of existing Chatfield impoundment
would ensure minimum flows throughout the entire reach of the canyon. Of the
remaining two alternatives, Strontia Springs and the Canyon Mouth, the Canyon
Mouth Dam would have the least adverse environmental impacts.
5)	The whole environmental picture is greatly confused by the relation-
ship of the proposed project to the overall (especially west-slope) impacts
of transmountain diversions to meet ultimate 500 mgd supply to Denver. A
complete assessment of the environmental consequences on both slopes should
be completed and debated before further construction of the Foothills Project
is warranted.
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Whitton, B.A. (ed.) 1975. River ecology. Studies in ecology, Vol. II.
Univ. Calif. Press, Los Angeles, 725 pp.
Young, W.C., D.H. Kent, and B.G. Whiteside. 1976. The influence of a
deep storage reservoir on the species diversity of benthic macro-
invertebrate communities of the Guadalupe River, Texas. Texas J.
Sci. 27: 213-224.
11

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APPENDIX A
Schematic representation of proposed dams
and diversions that may be utilized to supply
water to the Foothills treatment system.
12

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WILLIAMS
FORK
RESERYOi R
GREEN MTU RES.
YASQUEZ TUNNEL
CONTINENTAL DIVIDE
WILLIAMS FORK RIVER
GROSS RESERVOIR
BOULDER
HOFFAT TUNHEL ^
^ MOFFAT
TREATMENT
PLANT
SOUTH BOULDER CREE?
LONG LAKES ->
GUMLICK TUNNEL
		DILLON
RESERVOIR
PI MET LAKE
DENYER
O
SODA LAKES
HARRIHAH LAKE —
ROBERTS
TUNNEL
COLORADO
KASSLER
TREATMENT
PLANT
PLATTE CANTON RESERVOIR
STRONTIA SPRINGS RESERVOIR
DENYER
GRAND
JUNCTION
\	FOOTHILLS
TREATMEHT
PLANT
\ T*0 FORKS
GRANT
f~\ CASTLE ROCK
CONTINENTAL DIVIDE
^SPT" PUTT*
*ircK
ELEYEN MILE
RESERYOIR
lAHTER0 RESERYOIR
COLORADO SPRINGS
o
EXISTING
PROPOSED
WATER SUPPLY SYSTEM
DENVER WATER DEPARTMENT
SOURCE: RTO

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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. 2.
EPA-908/3-79^002
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Foothills Project: Comments on Inadequacies,
Environmental Impact Analyses and Evaluation
of Alternative Actions
5. REPORT DATE
March 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Jack A. Stanford
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Dept. of Biological Sciences
Morth Texas State University
Denton, Texas 76203
10. PROGRAM ELEMENT NO.
2BA653
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
Region VIII
i860 Lincoln Street
Denver, Colorado 80295
13. TYPE OF REPORT AND PERIOD COVERED
Pinal
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT	:
Important scientific literature (Ward 1974; 1975; 1976), which
describe the limnology of the existing reverine environment, were
overlooked In the preparation of statements concerning environmental
impacts of the proposed action. The river in Waterton Canyon will
be profoundly affected by construction of the Strontia Springs Dam.
Downstream from the dam riverine environment will be characterized'by
compacted substrata (due to sluicing effect of discharge), luxurant
growths of benthic algae (due to lack of sediment scour and presence
of adequate growth nutrients), and depressed thermal regime (due to
thermal stratification in the reservoir and hypolimnial release from
the dam). Although a fishery may be sustained in the reservoir
tailwaters, these changes should be considered as negative impacts
in terms of the existing environment. More environmentally sound
sites (i.e. Canyon Mouth and Chatfield Alternatives) for water
diversion are located at or downstream from the mouth of Waterton
Canyon.
		——					a
17.	KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
		—¦	-1
c. cosati Field/Group
Reserviors
Impoundment
Water supply
Environmental impact statements
Foothills
Water Supply - Denvei
Transmountain diver-
sion
j
18. DISTRIBUTION STATEMENT
Distribution Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES ' j
i
20. SECURITY CLASS (This page)
Unclassified
22. PRICE j
J
EPA Farm 2220-1 (Rav. 4-77) previous edition is obsolete

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