HomeMy WebLinkAbout851237.tiff -$T0p
r `" '*A>k% DEPARTMENT OF THE ARMY
2 OMAHA DISTRICT CORPS OF ENGINEERS
p, n 6014 U.S. POST OFFICE AND COURTHOUSE
y, OMAHA. NEBRASKA BB102
REPLY TO
ATTENTION OF April 10, 1985
Planning Division WELD COUNTY CO#M!SS!ONER5
APR 1 81985
GRLELEY. COLO.
METROPOLITAN DENVER WATER SUPPLY EIS
Copies of the Supplemental Work Plan No. 1, Site-Specific
Work Scope, and Supplemental Plan No. 2, Systemwide
Modifications, are enclosed for your information. Additional
copies are available upon request £rom Engineering-Science, Inc.,
10 Lakeside Lane, Denver, Colorado 80212.
Enclosures Richard B. Gorton
Chief, Environmental
Analysis Branch
U.S. Army Corps of Engineers
Omaha District
851237
adri;rc, 4.22-es
SYSTEMWIDE/SITE-SPECIFIC EIS
,r.. METROPOLITAN DENVER WATER SUPPLY
SUPPLEMENTAL WORK PLAN NO. 1
(CONTRACT DOCUMENT)
TABLE OF CONTENTS
SECTION PAGE
1. INTRODUCTION 1-1
2. BACKGROUND 2-1
Systemwide/Site—Specific EIS 2-1
Systemwide Alternative Scenarios 2-2
No Federal Action Alternative 2-2
Federal Action Alternative 2-5
Site-Specific Alternatives 2-6
Upper South Platte River Basin 2-6
Williams Fork Basin 2-8
3. NO FEDERAL ACTION ALTERNATIVE 3-1
Proposed Scope 3-1
Development and Evaluation of Water Sources
That Require No Federal Action 3-2
Conservation 3-2
Ground Water Development within Municipal
Boundaries 3-6
Nonpotable Reuse of Water 3-9
Sewage Exchange 3-11
Acquisition of Agricultural Rights 3-15
4. SITE SPECIFIC ALTERNATIVES 4-1
Introduction 4-1
Review and Analysis of Project Engineering 4-1
Introduction 4-1
Level of Detail 4-2
Engineering for Dams and Reservoirs 4-3
Project-Specific Analyses 4-8
Technical Report 4-13
Review and Analysis of Hydrologic Yields
and Impacts 4-15
Introduction 4-15
Yield and Operational Effects Analysis 4-19
Technical Report 4-24
Environmental Impact Analyses 4-26
Introduction 4-26
Physiography, Topography, and Geology 4-28
Soils 4-36
p'^ Water Quality 4-43
Channel Stability 4-52
PAGE
Vegetation 4-55
Wildlife 4-60
Aquatic Life 4-67
Threatened and Endangered Species 4-73
Wetlands 4-82
Socioeconomics 4-99
Transportation 4-107
Recreation 4-112
Visual Resources 4-119
Cultural Resources 4-123
Institutional Issues 4-131
APPENDIX A PRELIMINARY OUTLINE FOR SYSTEMWIDE/SITE-SPECIFIC EIS
APPENDIX B EVALUATION CRITERIA
LIST OF FIGURES
Number Title Page
2.1 Flow Diagram - Systemwide/Site Specific EIS 2-3
2.2 Systemwide/Site-Specific EIS Program Schedule 2-4
3.1 Activity Schedule for No Federal Action Water
Sources 3-19
4.1 Activity Schedule for Engineering/Cost Data 4-14
4.2 Activity Schedule for Hydrology 4-25
4.3 Work Groups 4-27
4.4 Activity Schedule for Physiography, Topography,
and Geology 4-35
4.5 Activity Schedule for Soils 4-40
4.6 Proposed Limits on Water Quality Study Areas 4-44
4.7 Activity Schedule for Water Quality 4-50
4.8 Activity Schedule for Channel Stability 4-54
4.9 Activity Schedule for Vegetation 4-58
4.10 Activity Schedule for Wildlife 4-66
4.11 Proposed Limits on Aquatic Life Study Areas 4-69
4.12 Activity Schedule for Aquatic Life 4-71
4.13 Activity Schedule for Threatened and
Endangered Species 4-80
4.14 Proposed Limits on Wetland Study Areas 4-84
4.15 Williams Fork-Wetlands/Hydrology Sites 4-90
4.16 Activity Schedule for Wetlands 4-97
Number Title Page
4.17 Activity Schedule for Socioeconomics 4-106
4.18 Activity Schedule for Transportation 4-111
4.19 Activity Schedule for Recreation 4-117
4.20 Activity Schedule for Visual Resources 4-121
4.21 Activity Schedule for Cultural Resources 4-130
4.22 Activity Schedule for Institutional Analyses 4-134
LIST OF TABLES
4.1 Water Quality Data Station Requirements and
Existing Stations 4-46
r
SECTION 1
INTRODUCTION
Supplemental Work Plan No. 1 describes the efforts required to
perform evaluations of site—specific water source alternatives for
inclusion in the Systemwide/Site—Specific Environmental Impact Statement
(S/SSEIS). The contents of the Work Plan are:
Section 2 - background information on work scope expansion with a
summary of site-specific alternatives;
Section 3 - additional work efforts required to refine the No
Federal Action alternative;
Section 4 - work efforts required to perform the detailed review
and analysis of project engineering and the environ-
mental impact analyses for the site-specific alterna-
tives.
The purpose of the S/SSEIS is to conduct site—specific analysis of
South Platte storage projects and the extension of the Williams Fork
Collection System. The analysis of South Platte storage projects will
be conducted as though permit application has been made for the con-
struction and operation of the Two Forks Dam and Reservoir. The analy-
sis of extension of the Williams Fork Collection System will be conduct-
ed as though a permit application has been made for the construction and
operation of the Williams Fork Gravity Collection System. Alternatives
to these two water sources will be evaluated at a site-specific level of
detail for comparative purpose.
This document, also, reflects the scope, schedule, and assignments
of work negotiated between the Corps of Engineers and Engineering-
Science during December 1984 and January 1985.
1-1
SECTION 2
BACKGROUND
SYSTEMWIDE/SITE-SPECIFIC EIS (S/SSEIS)
The Work Plan for the preparation of the Metropolitan Denver Water
Supply Systemwide Environmental Impact Statement (SEIS) was issued in
February 1983. In the fall of 1983 the Omaha District, U.S. Army Corps
of Engineers (COE) , conducted a midterm assessment of the progress of
work on the SEIS. Some of the major concerns raised by several inter-
est groups during this evaluation were:
(1) the time and money expended on the SEIS would result in a
product of limited utility in terms of providing a basis for
review of early action alternatives;
(2) there was not sufficient opportunity for public involvement;
(3) certain levels of analyses were insufficient; and
(4) some agencies, groups, and interested parties were apathetic
towards their involvement in the SEIS process.
The COE discussed these concerns with the Metropolitan Water Roundtable
EIS Task Force. It was agreed that an EIS Coordinating Committee would
be formed to work with the COE and its contractor to resolve the above
concerns and that the Committee would consist of two representatives
from each of the following principal interest groups:
(1) the West Slope;
(2) the Environmental Caucus;
(3) the Metropolitan Water Providers (Providers) ; and
(4) the Denver Water Department (DWD).
The EIS Coordinating Committee decided in January 1984 to request
that the SEIS process be expanded to include site-specific alternatives
that were candidates for implementation within the next 15 to 25 years.
In February 1984, the Denver Board of Water Commissioners (DWB) for-
mally notified the COE of this request in a letter of intent. Specifi-
cally, the DWB indicated the desire to have the SEIS expanded to
include site—specific analysis of the Upper South Platte River Basin
Alternatives (with emphasis on the Two Forks Storage Reservoir) and the
Williams Fork Basin Alternatives (with emphasis on the Williams Fork
Gravity System).
2-1
The COE recently expanded the SEIS effort to incorporate the above
requested work. Thus, the expanded report (Systemwide/Site—Specific
EIS, or S/SSEIS) will include the impact analyses of the systemwide
water development scenarios and the impact analyses of the site-specif-
ic alternatives.
The SEIS task diagram is expanded in figure 2. 1 to include site-
specific tasks and information flows. The results of Task 4 will now
contain detailed information on site-specific water sources. This
detailed information will be used in Task 5. Additional and more
detailed information will be developed for the No Federal Action
alternative.
The program schedule for the production of the draft S/SSEIS by
March 1986 is shown in figure 2.2. The additional work due to the
rescoping of the SEIS to include the site—specific projects is not
anticipated to alter the expected draft S/SSEIS completion date.
The S/SSEIS will provide sufficient detail on site—specific
alternatives to serve as the National Environmental Policy Act (NEPA)
document required for all Federal permitting decisions. The S/SSEIS
concept was presented to the Metropolitan Water Roundtable and has
since been endorsed by Governor Richard Lamm, Denver Mayor Federico
Pena, several suburban mayors and city councils, the Environmental
Caucus, the West Slope representatives, the DWB, and the Providers. It
is expected that project proponents will submit formal permit appli-
cations prior to the distribution of the draft S/SSEIS.
The preliminary outline for the S/SSEIS is presented in appendix
A. Information and analyses pertinent to the site-specific alterna-
tives will be included in various sections of the EIS.
SYSTEMWIDE ALTERNATIVE SCENARIOS
In addition to the No Federal Action alternative, three to five
systemwide alternative scenarios, which emphasize the contrast between
possible courses of water development, will be presented and evaluated
in the S/SSEIS. The common goal of each alternative scenario is to
meet the water supply requirements of the Denver metropolitan area
supplied by the DWB and the Providers for the next 50 years, that is
until 2035. The development and analysis of alternative scenarios will
be presented in technical appendix 5 and summarized in the S/SSEIS.
NO FEDERAL ACTION ALTERNATIVE
The No Federal Action alternative will address the sequence of
water source developments that do not require Federal agency approval
to meet the future water demands of the Denver metropolitan area.
2-2
FIGURE 2.1
FLOW DIAGRAM
SYSTEMWIDE / SITE-SPECIFIC EIS
TASK 1
PROJECT INITIATION
TASK 2 TASK 3
WATER DEMAND EXISTING YIELDS
11,
50 Year—PURPOSE AND NEED —Within 20 Years
TASK 4
POTENTIAL WATER SOURCES
Systemwide Site-Specific
Detail Detail
SPECIAL<
WORK
PLAN
TASK 5 NO FEDERAL
ALTERNATIVE ACTION _
SCENARIOS ALTERNATIVE
DRAFT SYSTEMWIDE
SCENARIO ANALYSIS . .
TASK 6
PUBLIC COMMENT 1J FINAL SYSTEMWIDE - -DRAFT SYSTEMWIDE /
ANALYSIS SITE-SPECIFIC EIS
TASK 7
PUBLIC COMMENT
4
i-. TASK 8
FINAL SYSTEMWIDE /
SITE-SPECIFIC EIS
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These would be the projects most likely implemented by the DWB and
Providers. Water sources that may be used in the development of the No
Federal Action alternative are:
' (1) Conservation (such as metering, voluntary retrofit, outdoor
water use limitation, leak detection, and pricing);
(2) Ground Water (such as within municipal boundaries) ;
(3) Sewage Exchange
(4) Potable Reuse
(5) Nonpotable Reuse
(6) Acquisition of Agricultural Water Rights
FEDERAL ACTION ALTERNATIVE
The systemwide analysis of alternative scenarios will address the
sequence of water source developments , including those requiring
Federal action, that are technically feasible programs for meeting the
future water demands of the Denver metropolitan area. Water sources
listed as alternatives to Upper South Platte River Storage and Williams
Fork Basin will be evaluated in site-specific detail.
Water sources that are expected to be the basis for the develop-
ment of the Federal Action scenarios include those listed above under
the No Federal Action alternative and the following candidates:
Upper South Platte River Storage
(1) Two Forks Reservoir
(2) Estabrook Reservoir
(3) Ferndale Reservoir
(4) New Cheesman Reservoir with Tunnel
(5) Chatfield Lake with Operational Changes
Williams Fork Basin
(6) Williams Fork Gravity Collection System
(7) Williams Fork Reservoir, Pumping, and Gravity System
(8) Gross Reservoir Enlargement
Other Sources
(9) East Gore
(10) Eagle-Piney/Eagle-Colorado
(11) Green Mountain Exchange
(12) Straight Creek
(13) Joint Use Reservoir
(14) Joint Use of Existing Systems
2-5
(15) Bear Creek Lake Operational Changes
Some of the above sources may not be used in the formulation of
scenarios.
SITE-SPECIFIC ALTERNATIVES
The expansion of the SEIS is to include site-specific analysis of
Two Forks and alternatives to it in the upper South Platte River basin
and completion of the Williams Fork gravity system and its alterna-
tives. Site-specific detail will provide sufficient information on
each source to allow Federal agencies to make decisions relative to
permits and rights-of-way, if an application is filed. Detailed
information on costs, yields, operational hydrology, resource impacts,
institutional constraints , and mitigation potential will also be
developed.
UPPER SOUTH PLATTE RIVER BASIN
Seven water storage projects were identified as candidates for
site-specific analysis in the upper South Platte River basin: Two
Forks, Estabrook, Ferndale, Highline with Tunnel, New Cheesman with
Tunnel, Wildcat, and Chatfield Lake Operational Changes.
Two Forks, New Cheesman with Tunnel, and Chatfield Lake Opera-
tional Changes will be evaluated in site-specific detail.
Presently, both Estabrook and Ferndale are being analyzed in
site-specific detail. However, as more specific information is devel-
oped on costs, yields, and geology, one of these projects may be
eliminated from further analysis.
Highline Reservoir with Tunnel and Wildcat Reservoir were elimin-
ated as potential near-term projects for the Denver metropolitan water
supply and will not be evaluated in site-specific detail. Highline
Reservoir with Tunnel does not appear to represent any comparative
advantage or disadvantage over New Cheesman and Two Forks to warrant
site-specific study at this time. The Highline Reservoir basically
will affect the same resources as Two Forks. Depending on the water
rights and sources of water, storage on the North Fork could have a
higher yield per unit of storage capacity than storage on the main stem
and, for this reason, some groups prefer the development of this water.
Storage of North Fork water could be accomplished either with a reser-
voir on the North Fork or a large reservoir on the main stem with a
pipeline or tunnel to the North Fork. Wildcat Reservoir would be a
relatively small reservoir which could only store South Platte main
stem water. Wildcat Reservoir will be available for use in the system-
wide development of alternative scenarios; for example, it could he a
future component of a scenario which included a North Fork reservoir.
2-6
r
WILLIAMS FORK BASIN
Three water sources were identified as candidates for site-speci-
fic analysis under this category: Williams Fork Gravity, Williams Fork
Pumping, and Gross Reservoir Enlargement. All three will be evaluated
in site-specific detail.
2-7
SECTION 3
NO FEDERAL ACTION ALTERNATIVE
PROPOSED SCOPE
The No Federal Action alternative from the Corps of Engineers'
guidelines for implementing NEPA is a description of conditions that are
expected to occur if Federal actions are not taken on the pending
permits.
This definition will be used in the S/SSEIS, recognizing two
assumptions. First, there is not always a clear distinction between
Federal and non-Federal actions in the development and approval of a
plan to supply water to a major metropolitan area, such as Denver and
neighboring cities. Most proposals to achieve this planning goal will
involve some direct or indirect Federal action. For the purposes of
this study, Federal action is defined as the issuance of a permit or
authorization by a Federal agency for the construction and operation of
a major water storage or conveyance facility. Second, if one of the
water storage or conveyance facilities is not permitted, then the Denver
Water Board and the Metropolitan Water Providers will pursue a variety
of actions , jointly and/or independently, to continue to meet the water
demands of their service areas. It is assumed that in most cases
cooperation among water suppliers will be limited, because excess water
supplies will be negligible.
It would be speculative to develop a full description of the No
Federal Action alternative for the 50-year planning period of the pro-
jects for each water supplier. Presently, no information exists on the
likely sequence or extent of these actions and such information will not
be developed within the timeframe for the preparation of the S/SSEIS.
Further, the expected actions by the individual water providers cannot
be initially proposed by the Federal government, because these actions
are generally beyond the Federal government 's jurisdiction.
Given the above problem in the development of a realistic No
Federal Action alternative, the following two—part approach will be
used.
First, under present conditions, there are certain water sources
that could be developed without a permit. One or more of these sources
could be incorporated into the individual and/or joint actions of the
water providers to meet their future water demands. Without addressing
the character of the action, the eligible water sources could be
described in terms of yield and costs and the potential environmental
consequences of development could be outlined. This would be the basis
for disclosing in the S/SSEIS the main components of the expected No
3-1
Federal Action alternative as they might exist for the next 10 to 20
years. If water shortfalls would potentially occur in this near—term
timeframe, their effects also will be discussed.
Second, the character of the No Federal Action alternative 20 to 50
years from now is unpredictable. For this timeframe, the description of
the No Federal Action alternative will be, of necessity, more general—
ized in terms of its yield, costs, and potential environmental conse—
quences.
DEVELOPMENT AND EVALUATION OF WATER SOURCES THAT REQUIRE NO FEDERAL
ACTION
Before a description of the No Federal Action alternative can be
completed, additional data and analyses are required for water sources
that can be developed without formal approval by the Federal agencies.
The scope of the additional work is presented below for each water
source.
CONSERVATION
Conservation measures could be utilized under the No Federal Action
and the Federal Action scenarios. All conservation analyses will be
conducted by ES with assistance from the Work Group.
Under the Federal Action scenario, the conservation measures could
be utilized to bridge the gap until the next major water supply project
is completed or to delay the need for future projects. Under the Feder-
al Action scenario, some of the conservation measures, that would be
implemented under No Federal Action, are not expected to he implemented
because certain water utilities would have no need or short-term incen-
tive to use them.
Conservation measures to be considered for development under the No
Federal Action alternative are:
(1) metering of 96,850 unmetered homes in the city and county of
Denver and adjacent suburban areas;
(2) retrofitting homes which do not have water-conserving fixtures
(such as toilets, low-flow shower heads);
(3) restrictions on the area of lawns and/or encouraging the use
of landscape vegetation having low-water requirements;
(4) implementation of a leak detection program;
(5) modification of the price of water; and
3-2
(6) education and public information.
Each level of conservation will represent different linkages of
specific measures and various institutional conditions that would affect
the implementation of a program.
The following describes the various conservation considerations in
the S/SSEIS analyses.
Metering
The cost of metering includes consideration of capital, installa—
tion, maintenance, and treated water costs. Yield will be determined
based on system losses and a comparison of metered and unmetered homes.
The effects will include a description of various affected groups rela—
tive to "who pays," "who benefits," socioeconomic consequences, and
institutional considerations. The analysis will be consistent with the
Institute of Water Resources (IWR) methodology for analyzing conserva-
tion.
Retrofitting
The analysis will consider the applicability of retrofitting
existing single-family metered homes, single-family flat rate homes,
multifamily units, public facilities, and commercial facilities. The
focus on housing units will be low-water-using shower and toilet units
and consider voluntary and mandatory programs. Under a voluntary
program, no more than 542,000 housing units will be considered. Under a
mandatory program, the analysis will also consider changes in building
codes and ordinances.
Commercial/public sector retrofitting will consider such items as
flow-reducing devices in toilets and automatic shut-off faucets.
Costs will include consideration of capital cost, installation (as
appropriate), program administration, and treated water costs. Yield
will be determined based on reported savings in the literature. The
effects will include a description of the hydraulic consequences of
reduced flows, efficiency of conversion, evaluation of continued saving,
effects on treatment requirements, and institutional problems of imple-
mentation. The analysis will be consistent with the IWR methodology for
analyzing conservation.
Reducing Outdoor Water Use
This includes both low water use landscaping, lawn size limit-
ations, and prohibition of outdoor water use. These measures will be
analyzed two ways: (1) new construction only and (2) new construction
and existing residences. These would be mandatory programs. The
analysis will also include consideration of changes in building codes
and ordinances.
3-3
The cost of the programs will consider the incremental difference
in sod versus alternative landscaping, the value effect on new homes
with smaller lots, administrative costs, and treated water costs. Yield
will be developed based on water not applied to turf areas. Water
savings will be based on the replacement of turf with nonirrigated
material and replacement with low water use landscaping.
The effects will consider the demand for administrative staffing
needs, financial and life style effects on the homeowner for alternative
landscaping, social acceptability, and institutional problems of imple-
mentation. The analysis will be consistent with the IWR methodology for
analyzing conservation.
Leak Detection Program
This program excludes the DWD service area because it has an
ongoing program. The target water providers will be those which have an
unaccounted water use which is greater than 15 percent. The objective
will be to reduce unaccounted water use to between 6 and 10 percent.
Costs will be based on costs of the DWD program and will include
capital for equipment, repair, and administration. Yield will be esti-
mated based on reducing water providers' unaccounted for water to 6 and
10 percent. Effects on administration and staffing of such a program
will be described and any institutional problems identified. The
analysis will be consistent with the IWR methodology for analyzing
conservation.
Modification of the Price of Water
This program will consider the effects of an increase in the margi-
nal price of water for a single-family metered household. The effect of
this marginal price on water demand will be determined using the disag-
gregated water use water demand model, review of case studies, the
household user survey, and an analysis of existing economic patterns
related to use. The pricing of water and the yield that it could pro-
duce become interactive features of several other conservation measures,
particularly metering, retrofitting, and reducing outdoor water use.
This interaction and water yield will be described.
The effects of this program will include discussion of the eco-
nomic and social acceptability effects on different income levels in the
community and institutional consideration, including the issue of
producing excess revenues.
Education and Public Information
This analysis will consider the effectiveness of existing programs,
their applicability to the entire metropolitan area, and the potential
for expanding and changing them to increase their effectiveness.
3-4
Components of the program that will be considered include: paid commer-
cial announcements; the evapotranspiration (E.T. ) program; distribution
of placards, fliers, and stickers; labeling of nursery stock; school
programs; and demonstration projects.
Data Collection
Identification of Data Gaps. Existing data collected and developed
for the SETS have been assembled by ES and presented to the COE, coop-
erating agencies, and the Coordinating Committee for review and comment.
Upon receipt of comments, ES and the Work Group will identify any
supplemental data needs. The existing data base will be reviewed to
update its adequacy to continue with completion of the conservation
analysis at the site-specific level of detail.
Studies Required to Fill Data Gaps. ES will review the assembled
data base and update the material. The update will be based on incor-
poration of data not available in 1983 when the existing data base was
assembled. In addition, ES will contact the Denver Water Department,
Aurora, Thornton, Littleton, and Golden to acquire additional inform-
ation on changes in municipal conservation programs in the last 18
months.
Analysis To Be Conducted
An initial activity of this resource analysis will be the formation
of a Work Group. The formation will be inititated by the COE with
assistance from ES. The technical Work Group will review and comment on
work products and participate in the formation of impact assessments.
The conservation plans under No Federal Action will be developed by
ES, based on information provided by the Providers, published litera-
ture, and information developed in Task 2, Future Water Demands. It is
assumed that the implementation of conservation plans will not occur as
a result of permit stipulations but will be motivated by a local desire
to avoid shortages and reduce water supply costs.
Possible modifications to the implementation plans of proposed
conservation measures will be developed by ES. In addition, other
conservation measures such as penalty pricing and more restrictive lawn
and landscape irrigation regulations will be considered. Costs and
yields associated with the newly applied conservation measures will be
developed and institutional constraints identified. Data from the
experience of other communities implementing conservation measures will
be collected and used to analyze effects of potential changes on life—
style, quality of life, and the urban environment.
ES will develop four or five water conservation scenarios as
assisted by the EIS Coordinating Committee. These would include:
3-5
conservation with No Federal Action on a permit application, the most
cost-effective conservation plan, and the maximum potential for conser-
vation. One or two additional conservation scenarios may be developed
for the EIS Coordinating Committee or alternative implementation plans
may be considered for any of the three scenarios defined above. The
scenarios, except for the No Federal Action, will be evaluated at 10-,
20-, and 50-year intervals to determine the cumulative scenario impact.
The evaluation will be based on the sequence of implementation of the
individual conservation measures in a scenario. The No Federal Action
conservation scenario will be evaluated only at 10- and 20-year inter-
vals. It is assumed that during the 50-year planning period, some
Federal action will be taken.
With the expanded description of the conservation components, the
environmental impact will focus on: implementation procedures, social
acceptability, socioeconomic effects, water cost, and water yield. In
addition, ES will identify and describe any impacts on natural environ—
mental resources. The resources which will be focused on will include
aquatic life, surface water quality, and recreation.
Report Preparation
ES will prepare a report on the conservation analysis. This report
will present and document the methodologies utilized, the data base, the
impact analysis, costs and yields, and any mitigation for implementation
of the conservation measure or measures. The report will include
descriptions of the individual conservation measures as well as the four
or five conservation scenarios. The No Federal Action conservation
scenario developed for use in the S/SSEIS will be one of these.
GROUND WATER DEVELOPMENT UNDER MUNICIPAL BOUNDARIES
Identification of Data Gaps
Under the No Federal Action alternative, some municipalities will
pursue the development of nontributary ground water underneath their
land as well as within their legal boundaries. This action may include
annexation of adjacent land that is suitable for well field development.
The objectives of the effort are: to define the feasibility of
this potential water source; to verify the amount and costs of safe
annual yield which could be derived from ground water; and to define
changes in streamflow regimes and ground water depletions which may have
environmental or socioeconomic impacts.
Most of the data required for the ground water studies for the
conceptual development of this water supply possibilty are available.
Data on aquifer boundaries, saturated thickness of aquifers , present
level of development of aquifers, and aquifer characteristics will be
used to determine the amount of potential yield. Existing data include
3-6
U.S. Geological Survey (USGS) and State Engineer's Office published
reports on the four Denver basin aquifers, selected well logs, existing
reports of aquifers coefficients, permits and decrees of existing wells,
and geologic and potentiometric maps. Many of the basic analyses and
tabulations of water quality, aquifer characteristics, and potential
well yields have already been done by ES as part of the SETS studies.
There is legal uncertainity about the right of a municipality to
develop nontributary ground water under private lands within the munic—
ipal boundaries. Although Federal Heights has successfully used the
"implied consent" concept , other Denver area municipalities such as
Lakewood are encountering trouble implementing this concept in their
jurisdictions. Additional information will be needed to analyze and
evaluate the current and expected future status of this institutional
issue.
Required Studies
Resource studies of expanded ground water development will be
performed for areas within municipal boundaries. Costs will be devel—
oped and conflicts with existing land use plans or patterns will be
described.
ES will use the existing and newly acquired data as the basis for
developing the following:
1. Describe Ground Water Source Alternatives.
a. Tributary (Alluvial) Ground Water. Tributary ground water
shall be described as a potential water source. Tributary ground water
rights could be purchased and condemned just as agricultural rights.
The SEIS work will be enhanced by ES to more fully determine the feasi—
bility of this source.
b. Nontributary Ground Water. The development of nontributary
ground water under municipal boundaries will be studied as an alterna-
tive.
2. Describe Operations Options for Development Under Municipal
Boundaries. The operations options as listed below shall be described.
a. Dry Year
b. Continuous Pumping
3. Safe Annual Yield Determinations. The safe annual yield
derived from the ground water alternatives will be defined and cuanti-
fied. The alternatives to be analyzed for safe annual yield determin-
ation are described as follows:
3-7
(1) Tributary Ground Water. The tributary water in the
South Platte River alluvium downstream of Denver shall be analyzed.
(2) Nontributary Ground Water
(a) (Development Under Municipal Boundaries).
(1) Dry Year
(2) Continuous Pumping
(b) Aquifer Recharge. The feasibility of aquifer
recharge was addressed in the SEIS studies. Additional information
shall be provided by ES to fully evaluate its feasibility.
4. Cost Determinations. The average cost per acre—foot of safe
annual yield will be estimated by ES for the above described alterna—
tives.
5. Impacts Support Analysis.
a. Tributary Ground Water.
(1) Describe Potential Impact on Downstream Users.
b. Nontributary Ground Water. The following tasks shall be
performed for each of the nontributary ground water alternatives and
operational schemes.
(1) Describe Potential Impacts on South Platte River
Downstream Users. The increased use of nontributary ground water would
increase flows downstream of Denver, if not fully reused, thus poten-
tially resulting in socioeconomic impacts. These impacts will be
evaluated if full reuse is not possible by ES.
(2) Identify Ground Water Depletion Levels. For each
alternative, drawdown levels will be shown to the extent possible on
exhibits which will portray regional impacts.
(3) Describe the Potential for Subsidence and Discuss
Associated Impacts. The potential for subsidence and associated impacts
will be discussed.
(4) Describe Advantages and Disadvantages of the Aquifer
Recharge Alternative. The impacts resulting from ground water deple-
tions would be reduced with the aquifer recharge alternative. The
potential for storage of treated water in the aquifer shall also be
addressed.
3-8
6. Institutional Constraints. The institutional issues analysis
in the SEIS did not discuss Senate Bills 213 and 439. This section
shall be modified to do so. The "implied consent" concept used by
Federal Heights to utilize ground water beneath municipal boundaries
shall be further discussed.
Report Preparation
ES will prepare a separate technical appendix on ground water which
will include the analyses of the potential development of ground water
sources under municipal boundaries. This report will present and
document the method used, the data base, the engineering and environ—
mental impact analyses, and costs and yields for the implementation of
ground water development. ES will also enhance the SEIS reports on
tributary ground water development and aquifer recharge.
NONPOTABLE REUSE OF WATER
Only water obtained through transmountain diversion, from nontribu-
tary ground water, or the portion of agricultural water designated for
consumptive use can be routed to nonpotable reuse. Work to date for the
SEIS has considered the various options and yields for reuse. However,
/a some additional work will be necessary to estimate the potential safe
yields derived from additional transmountain diversion or nontributary
ground water withdrawal. The potential for additional reuse for new
urban growth must be considered. ES will perform the additional work
except for the hydrologic analysis which, if required, will be performed
by the DWD.
1. Describe Nonpotable Water Reuse Alternatives and Implementation
Procedures. The following nonpotable water reuse alternatives will be
described and implementation procedures as necessary defined.
a. Transmountain Water
b. Nontributary Ground Water
c. Consumptive portion of agricultural water
2. Describe Demand Potential and Limitations.
The demand potential and limitations for the nonpotable reuse
alternatives will be defined and, to the extent possible, quantified.
The rationale for the assumptions regarding demand in the SEIS draft
technical appendix 4 will be fully described. The supporting documen-
tation from which engineering and reasonableness judgments were made
concerning demands and distribution costs will be presented in exhibits.
These above-described tasks will be performed for the following demand
area:
3-9
a. Industrial Reuse
b. Urban Public/Commercial Reuse
c. Agricultural Reuse
3. Safe Annual Yield Determinations.
a. Existing Transmountain Diversions (and Nontributary Ground
Water Withdrawals and Consumptive Portion of Agricultural Water).
( 1) Define Additional Yield Potential From Existing
Transmountain and Nontributary Ground Water Withdrawals and Consumptive
Portion of Agricultural Water. The potential for safe annual yield
additions to be derived from nonpotable reuse of existing transmountain
water, nontributary ground water withdrawals , and the consumptive
portion of agricultural water shall be defined and quantified for:
(a) Reuse under existing urban development conditions
(b) Reuse for new urban growth areas
b. Future Transmountain Diversions and Nontributary Ground
Water Withdrawals. The potential safe annual yield which can be derived
from the reuse of nonpotable water shall be described and estimated for:
(1) Potential additions to safe annual yields derived from
additional transmountain diversions, nontributary ground water with-
drawals, and consumptive portion of agricultural water for the same two
conditions as in the previous sections.
4. Cost Determinations. The annualized cost per acre-foot of safe
annual yield that would be necessary to develop the yield potential from
existing and future transmountain diversions, nontributary ground water
withdrawals, and consumptive portion of agricultural water is required
for the following alternatives:
a. Implementation of Industrial Reuse
b. Implementation of Urban Reuse
Cost estimates are required for each scheme.
5. Impacts Support Analysis. The purpose of the impacts support
analysis is to define changes in flow regimes that would result from the
reuse of nonpotable water which may have environmental or socioeconomic
impacts. The following analyses are required.
3-10
a. Quantify Flow Regimes in Study Area. To quantify the
changes in flow regime in the study area, monthly and annual flow dura-
tion curves may be needed. If needed, they will be prepared by the DWD
for conditions assuming full implementation of reuse of: (1) existing
transmountain diversions, nontributary ground water withdrawals, and
consumptive portion of agricultural water; and (2) future potential for
implementation of these same three water scenarios. The existing flow
regime flow-duration curves will also be presented for comparison
purposes, if needed.
b. Estimate Consumptive Use of Reused Water. The consumptive
use of reused nonpotable water must be estimated to complete the above-
described flow/duration curves. This information is required to revise
the Wetlands and Riparian Areas, the Socioeconomics, Water Quality, and
Hydrology impacts sections of Task 4 reports.
c. Quantify Impacts on Downstream Users. The potential
impacts, both positive and negative, on downstream users shall be
discussed. The impacts should include the environmental, economic, and
sociological issues.
6. Institutional Constraints. The 1940 Consolidated Ditches
Agreement, the Blue River Decree, dominion requirements, the Thornton
Senate Bill on exchange, Colorado water law, institutional constraints
on storage and other known institutional constraints shall be discussed.
7. Report Preparation. ES will prepare a report on the analyses
of the potential for nonpotable reuse. This document will describe the
reuse alternatives, discuss yields, and identify costs and impacts.
SEWAGE EXCHANGE
Identification of Data Gaps
Sewage exchange involves exchanging the DWD's treated wastewater
for raw water at Denver's intakes. Only effluent obtained from trans—
mountain diverted water and nontributary ground water can be exchanged,
since Colorado water law prevents exchange or reuse of in—basin flows.
This analysis will focus on the effects of increased diversions at the
Denver intake on the South Platte River downstream. No separate on—
stream storage project to optimize this water source will be considered
because it would likely require a Federal permitting action and because
the maximum yield potential may be achievable without storage.
The magnitude of potential yield through sewage exchange is limited
mainly by the volume of South Platte River water available for exchange,
and not by the volume of sewage effluent. Thus, the yield will be
appraised as an overall yield to the Denver metropolitan area as if
operated by DWD, which has the senior exchange rights.
3-11
The actual analysis of potential yield will be done using the DWD
model, and the correctness of analysis will be verified by the COE and
its consultants.
The existing physical data base is sufficient for the study. The
required physical data include:
1. South Platte River gaging station records
2. South Platte River water rights records
3. Projected exchangable effluent volumes
Required Studies. Using the developed data base, the following
analyses will be performed. The DWD will perform all hydrologic analy-
ses, with assistance from the COE. ES will perform all impact analyses.
1. Safe Annual Yield Determinations. The safe annual yield
derived from sewage exchange will be defined for both existing West
Slope diversions (under No Federal Action) and estimated for potential --
future West Slope diversions (for systemwide studies). Each sewage
exchange alternative will be fully described and implementation proce-
dures defined. The work tasks required to accomplish this effort are as
follows:
a. Existing West Slope Diversions. A bar chart exhibit will
be prepared for the described alternatives which displays annual water
supply yields for the period of 1947 to 1974. The safe annual yield and
the average annual yield resulting from sewage exchange shall be identi-
fied on these exhibits.
(1) Quantify Exchange Yields Contributing to the Existing
Water Supply of 295,000 Acre-feet.
(a) Quantify Yields From Reservoir Evaporation Re-
placement. The amount of yield derived from reservoir evaporation
replacement that contributes to the existing safe yield of 295,000
acre-feet annually will be defined and quantified. Each reservoir
contributing to safe annual yield will be identified in a table and
yields quantified. Evaporation rates used and yield computation methods
will be presented.
(b) Quantify Yields From Other Exchanges. The amount
of yield derived from other exchanges such as the Burlington Ditch
interference call that contributes to the existing safe yield of 295,000
acre-feet annually will be defined and quantified. The computations
from which the yield is based will be presented.
3-12
(2) Define Yield Potential From Existing Transmountain Di-
versions. The potential safe annual yield derived from exchanging
existing transmountain diversions from both the north and south systems
will be defined and quantified as follows:
(a) Without New Storage. The potential safe annual
yield which can be derived from exchanging existing transmountain
diversions without utilizing storage shall be defined and quantified.
The costs associated with administering this alternative shall be
estimated by ES.
(b) With Downstream Effluent Storage. The potential
safe annual yield which can be derived from exchanging existing trans-
mountain diversions while utilizing downstream effluent storage shall be
quantified and briefly addressed. It should be noted that this alterna—
tive may require Federal action and this will be used to enhance the
sewage exchange analysis as a systemwide source. This work will be
performed by ES under the original systemwide contract.
(c) With New Upstream Storage. The potential safe
annual yield which can be derived from exchanging existing transmountain
diversions while utilizing upstream storage shall be defined and quanti—
fied. The DWD will furnish the hydrologic analysis. It should be noted
that this alternative may require Federal action and this should be
addressed in the description of the alternative. The results of this
analysis will be included in the South Platte storage technical appen-
dixes and in the Task 5 scenarios evaluation.
b. Future West Slope Diversions. The potential safe annual
yield which can be derived from exchanging future transmountain diver-
sions will be estimated in connection with Task 5 scenario evaluations.
This will be performed by ES under the existing SEIS contract.
c. Consumptive Use Estimates. The preliminary draft of the
sewage exchange technical appendix makes an issue of the lack of a
mechanism for tracking treated water in the distribution system. It is
stated further that "the DWD must maintain dominion over the transmoun—
tain waters throughout their passage from the point of diversion on the
West Slope to the point of discharge from a wastewater treatment plant
as sewage effluent." This statement will be expanded upon by ES to
address the following items:
(1) Possible use of a consumptive use factor to account
for West Slope water;
(2) Whether the dominion issue has ever been tested in
court and, if so, what the findings were will be described;
3-13
(3) How the transmountain water is tracked through the
system for the existing Burlington Ditch exchange;
(4) What facilities would be required for tracking the
West Slope water through the distribution system.
2. Impacts Support Analysis. The purpose of the impacts support
analysis is to define changes in flow regimes that would result from
sewage exchange which may have environmental or socioeconomic impacts.
The potential impact areas shall be described by ES. The known impact
areas are Barr Lake State Park and the South Platte River downstream
from Chatfield Dam in the Denver metropolitan area. The following
described analyses are required to define impacts:
a. Quantify Flow Regimes in the Study Area. To quantify the
changes in flow regimes in the study area, monthly and annual flow
duration curves may be required for current flow conditions and for
developing full exchange potential from existing transmountain diver-
sions. If required to properly evaluate impacts, this information will
be provided by the DWD. The effects of future transmountain diversions
or flow regimes shall be discussed by ES but not quantified. The
following reaches shall be analyzed as discussed above.
(1) Intake to Chatfield,
(2) Chatfield to Bear Creek,
(3) Bear Creek to MDSDD #1 ,
(4) MDSDD #1 to Clear Creek confluence,
(5) Clear Creek confluence to Henderson,
(6) Henderson to Fort Lupton.
It is not anticipated that there will be any impacts to the last three
reaches listed above; however, the analyses will be performed to examine
this assumption.
b. Quantify Potential Impact on Barr Lake State Park Water
Use. The effluent volumes that are diverted to Barr Lake for current
flow conditions and for developing full exchange potential from existing
transmountain diversions shall be quantified by COE. The environmental
and other effects of future transmountain diversions on effluent volumes
diverted to Barr Lake shall be discussed by ES but not quantified.
3-14
c. Quantify Impacts on Downstream Users. The impacts on
downstream users shall be quantified by ES for developing full exchange
potential from existing transmountain diversions.
3. Cost Determinations. The costs associated with sewage exchange
presented in the SEIS draft technical appendix 4 were inadequate. ES
will estimate these costs for various exchange situations as previously
described in this scope of work.
4. Institutional Constraints. The 1940 Consolidated Ditches
Agreement, dominion requirements, the Thornton Senate Bill on exchange,
institutional constraints on storage, and other known institutional
constraints will be discussed. The agreements between the DWD and the
Burlington Ditch and Barr Lake shall be discussed. Any other limita-
tions on sewage exchange will also be addressed.
5. Report Preparation. The sewage exchange technical appendix
will be prepared by ES. The appendix will include a description of the
various sewage exchange alternatives, yields, costs, impact evaluations,
and institutional constraints.
ACQUISITION OF AGRICULTURAL RIGHTS
Identification of Data Gaps
In the event that no structural water source projects are permit—
ted, municipalities and other water providers would likely pursue the
purchase, lease, and/or condemnation of agricultural rights. The
analysis of this source needs to focus on the senior agricultural water
right holders in the South Platte River basin and headwaters of the
Colorado River basin. The analysis also needs to consider water poten—
tially available and the loss of agricultural productivity due to
development of this water source, including socioeconomic impacts.
The general value of and potential for the conversion of agricul—
tural water rights to Denver—area municipal use was evaluated in the
SEIS. It was noted that only senior agricultural water rights that
would deliver significant volumes of water during a drought period would
be of importance without additional carry-over storage. This further
study for the S/SSEIS needs to focus on the identification of specific
senior agricultural water rights in the South Platte, Blue, Fraser and
Williams Fork River basins above and below the metropolitan Denver
diversion points.
These water rights need to identified to the extent possible from
the State Engineer's records, the Water Commissioners' personal know-
ledge, and information from the Denver area water providers. The rights
needs to be catalogued by priority. The water available for change of
point of diversion for municipal use will be estimated from the reported
areas and crops irrigated. The potential safe yield of these rights
3-15
will be determined by comparison to similar rights modeled in the DWD
system. Only those water rights that are not included in the reported
safe yield of the Providers needs to be evaluated.
The potential for acquiring agricultural water rights on the South
Platte River downstream from Denver to the mouth of the Cache La Poudre
River and transferring the water upstream to a Denver municipality
intake needs to be evaluated. The competition for available water in
the river needs to be considered; both the transfer of agricultural
water and exchange of sewage effluent compete for the same water and the
most efficient use will be identified and quantified. The potential for
acquiring agricultural water rights on the South Platte River downstream
of Denver and delivering the yield of these rights to the Metropolitan
Water Providers by pipeline and pumping will be evaluated. The water
quality aspects and the cost of treatment will be considered. The new
systemwide water source involving pumpback from the proposed Narrows Dam
site, as discussed in the revised systemwide work plan, will provide
supplemental information on the use of agricultural water downstream
from Denver.
The following studies will be performed by ES.
1. Describe Water Rights Condemnation Alternatives and Implementa—
tion Procedures. The following water rights condemnation alternatives
will be fully described and implementation procedures defined.
a. Acquisition of Water Rights.
b. Dry Year Crop Damage Lease. These water rights would
generally be used to increase safe yield during the 3—year span of low
supply for the modeled period from 1947 to 1974.
c. Elimination of Interference Calls.
2. Safe Annual Yield Determinations. The safe annual yield
derived from the water rights alternatives described above will be
defined and quantified. A bar chart exhibit will be prepared for each
alternative which displays annual water supply yields for the period of
1947 to 1974. The safe annual yield and the average annual yield
additions shall be identified on these exhibits.
These analyses shall include:
(a) Denver's Existing Supply (295,000).
(b) The Providers' Systems. The various providers shall
be identified and corresponding yields listed in tabular form.
3-16
3. Cost Determinations.
a. Dry Year Crop Damage. The costs of paying for crop damages
during the 3-year dry period shall be estimated and an average cost per
acre-foot of safe annual yield calculated.
b. From Direct Flow and from Elimination of Interference
Cells. The average cost per acre-foot of safe annual yield derived from
senior water rights with no new storage shall be calculated for these
two conditions.
c. With New Upstream Storage. Although not part of the No
Federal Action alternative, the effect of new upstream storage on yield
and cost of senior water rights will be calculated. This analysis will
be performed by the COE and included by ES as part of the South Platte
storage alternatives analysis.
4. Impacts Support Analysis. The purpose of the impacts support
analysis is to define changes in flow regimes that would result from the
use of agricultural rights, which may have environmental or socioeconom—
ic impacts. The following analyses are required.
a. Quantify Flow Regimes in Study Area. To quantify the
changes in flow regimes in the study area, monthly and annual flow
duration curves may be required for conditions assuming full utilization
of senior rights. The existing flow regime flow duration curves would
also be presented. If this information is required to evaluate impacts ,
it will be furnished by DWD.
b. Quantify Impacts on Downstream Users. The potential
impacts, both positive and negative on downstream uses shall be dis—
cussed. These impacts shall include economic, environmental, and
sociological issues.
5. Institutional Constraints. An institutional constraints
section shall be prepared and will include the following:
a. The implementation procedures for condemnation of agricul-
tural water rights.
b. Quotations of Colorado law relative to the condemnation of
agricultural rights will be included and explained. The legality of
condemnation of agricultural rights will be addressed.
c. The problem of losing yield as a result of transferring
water rights will be addressed. The track record of municipalities who
have previously purchased significant amounts of agricultural rights
will be used as a baseline.
3-17
d. The effect of DWD's 3,000 c.f.s. water right for exchange
will be addressed relative to its effects on yields from the purchase of
agricultural rights.
e. All other known institutional constraints will be dis-
cussed.
6. Report Preparation. ES will prepare a report on the potential
water yields that could be realized through acquisition or condemnation
of agricultural water rights. All pertinent methods, baseline data,
analysis, and evaluations will be presented in this report. Impacts
will be identified. Also, institutional constraints will be identified.
ACTIVITIES SCHEDULE
The activities and schedule for the efforts identified in the above
scope of work for the evaluation of the non—structural alternatives are
provided in figure 3. 1.
3-18
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SECTION 4
SITE-SPECIFIC ALTERNATIVES
INTRODUCTION
The work described in section 4 focuses on:
(1) Efforts required to perform the detailed review and analysis of
project engineering for the site-specific structural alterna-
tives, in order to provide a detailed description of each
source, an accurate cost, and a judgment of engineering feas-
ibility;
(2) Efforts required to perform the detailed impact analyses of the
site-specific structural and No Federal Action alternatives in
order to meet the requirements of NEPA.
REVIEW AND ANALYSIS OF PROJECT ENGINEERING
INTRODUCTION
Engineering studies and drawings will be required for each struc-
tural alternative to be evaluated in the S/SSEIS. The studies will
reflect the general plan for each alternative project and will be in
sufficient scope and detail to satisfy NEPA requirements for project
evaluations.
All studies and designs will be prepared by the DWD in conjunction
with its consultants and the Providers. These technical data will be
furnished to the COE. The COE will perform a detailed evaluation for
completeness, adequacy, and adherence to accepted engineering standards
and criteria. The COE also will make reconnaissance visits to each site
for the purpose of familiarization and data verification. The COE will
furnish ES with complete engineering write-ups for the new Task 4 Site
Specific technical appendicies.
The projects to be evaluated in site-specific detail include five
storage facilities in the upper South Platte River basin and three
alternative collection and/or storage systems for water from the
Williams Fork basin.
The alternative storage reservoirs in the upper South Platte River
basin are:
Dam and Reservoir Location
. Two Forks At confluence of the South Platte River
with the North Fork of the South Platte
• Ferndale On North Fork about 5 miles upstream from
confluence
4-1
. Estabrook On North Fork about 12 miles upstream from
confluence
. New Cheesman with Vicinity of existing Cheesman Lake
Tunnel
. Chatfield Existing dam and reservoir
The alternative systems for water from the Williams Fork basin are:
. Williams Fork Gravity Collection System
. South Fork Reservoir, Pumping, and Gravity System
. Enlarged Gross Reservoir
LEVEL OF DETAIL
The degree and amount of engineering studies performed to date vary
significantly from project to project. The Two Forks Dam and Reservoir
has a feasibility level study and engineering drawings are available.
Three alternatives, Ferndale, Estabrook, and New Cheesman, have only
received an appraisal level of study and require a significant amount of
investigation and design. The Chatfield alternative, which would
utilize an existing reservoir, involves reallocation of space and
relocation of recreational facilities has been studied at the feas-
ibility level.
All engineering work that has been prepared to the appropriate
level of detail on the site-specific alternatives will be reviewed to
determine its conformance with standard engineering practice and to
ensure that no major flaws are present. Should the review reveal any
problems or questionable study results, consultations will be arranged
with the DWD and its consultants to reach a common understanding of the
problem and a mutually acceptable solution.
Whereas the cost estimates in the SEIS were of appraisal level
only, the estimates for the comparison of projects in the site—specific
study will be in greater detail. To arrive at that level of detail will
require that the engineering drawings and calculations be such that
quantities can be measured for major items of construction. It is
anticipated that from 20 to 30 pay items will be quantified and unit
costs applied. The DWD has completed, or is in the process of pre—
paring, feasibility designs on the alternatives which should be suffici—
ent for the purpose.
The implementation schedule will be used to calculate interest
during construction (IDC). For storage projects, IDC will be computed
to the time at which the first yield is realized. First yield for
storage projects will be determined by the filling studies as described
under the hydrology section of this work plan. For collection systems
which will come online over a period of years, IDC will be calculated
4-2
for each discrete segment until the first yield is gained from that
segment.
Total annual costs of projects will be computed by amortizing at 8
percent over the assumed life of the project; the sum of the construc-
tion costs; the costs of engineering and permitting; IDC; annual opera-
tion, maintenance, and replacement; rights-of-way; and mitigation. For
cost analysis, 100 years are used as the life of tunnels and dams, 50
years for most other structural features, and average lives for
mechanical items.
The cost analysis will also present the annual cost of a project
by determining the project 's costs at the point of first yield ,
amortizing the cost over the project's period of adequacy, and adding
this annualized cost to the annual operating costs.
In addition, for use in cost estimating, the design drawings, data,
and calculations will be analyzed to verify the safety, reliability, and
constructibility of the proposed project. Structural stability analysis
calculations will be reviewed and possibly checked by different methods.
Where engineering drawings indicate problems which would occur during
construction, changes in design or procedures will be suggested.
Engineering comparisons of alternative water sources will examine
the suitability of each alternative in fulfilling the function desired,
and the unit cost of water yield. In this study, the annualized cost of
the facility as described above, less any secondary benefits derived,
will be divided by the safe annual yield to arrive at a comparable unit
cost of water developed by each structure.
ENGINEERING FOR DAMS AND RESERVOIRS
The engineering studies and designs needed for the analysis of each
dam and reservoir alternative are essentially the same. They include
all the basic hydrologic, geologic, and design studies together with the
recommended designs, cost estimates, and operating criteria for the
principal structure and related features. The data to be received for
the dams and reservoirs and the procedures and methods by which they
will be reviewed are described below.
Reservoir and Dam Site Topography
The reservoir topography will be reviewed for adequacy in construc—
ting the area—capacity curve for the reservoir and for satisfying
infrastructure needs. Dam site topography must be adequate to be used
in the decision on dam type and to permit design and quantity takeoffs
in the detail required.
4-3
Geotechnics
Areal geology in the vicinity of the site and geologic mapping and
subsurface exploration of the dam sites and the reservoir area will be
examined and interpreted. The reservoir mapping will be used to deter-
mine whether any features are present which would affect the water-
holding capacity or integrity of the reservoir. Such features as shear
zones, faults, or other pervious units will be examined and their
effects estimated. Slope stability or the potential of landslides in
the reservoir area will be evaluated. Economic mineral deposits or
mining activities would also be noted and evaluated.
Data for geologic descriptions and interpretations will be obtained
largely from USGS and Colorado Geological Survey reports and maps and
from reports of the DWD on specific sites. Aerial photographs will be
examined; significant geologic features will be depicted upon the
photos.
Detailed mapping and drilling on the dam site will be evaluated to
determine rock types and structures that determine foundation conditions
and the need and magnitude of foundation treatment. That review will
include the estimated depth of excavation into the foundation and the
methods of excavation anticipated to be required. Mapping of joint
patterns and shear zones in the abutment will reveal information to
estimate the need for, and quantity of, grouting which might be re-
quired, either for consolidation or to control seepage. Such data will
also be assessed to estimate structural strength of abutments for arch
dams.
Exploration for construction materials will be reviewed and exam-
ined. Test pits, borings, and geologic mapping will be used to verify
the location and quantities of embankment materials, concrete aggregate,
riprap, road surfacing materials, and general borrow areas. If labora-
tory tests are available, those data will be reviewed for suitability.
Where ground water appears to be a factor in construction or
stability, geohydrologic data will be reviewed.
Design Hydrologic Studies
Flood Hydrographs. Information necessary for development of flood
hydrographs including precipitation amounts and patterns; snowmelt; unit
hydrographs, either real or synthetic; and infiltration and loss charac-
teristics such as ground cover, soil type, and slope will be reviewed
for accuracy. The most recent references for precipitation data will be
consulted, including hydrometeorologic reports and atlases published by
NOAA, as well as DWD studies conducted in the South Platte basin east of
the Continental Divide but west of the 105th meridian. Historic floods
will be noted and where appropriate, frequency analyses will be made as
4-4
a check on the order of magnitude of flood peaks and volumes for various
return periods.
The choice of design floods for reservoir spillway sizing and
diversion dam will be reviewed based on safety considerations and
observed behavior of the stream. The length of time necessary for any
temporary diversions will be evaluated. The probable maximum flood
(PMF) will be evaluated as the inflow design flood for major structures.
The PMF could result from several different situations, depending upon
the size and location of the basin, and the amount and type of upstream
storage. These situations will be checked to ensure that the most
appropriate flood has been selected as the PMF.
Flood routing procedures will be reviewed based upon accepted
area-capacity information and spillway and outlet works rating curves.
Floods of different return intervals will be routed, probably using the
HEC-1 computer program, to verify outflow estimates.
Tailwater Curves. Using variable discharges and cross sections of
the river, water surface elevations at selected locations below the dams
will be checked. It is likely that the HEC-2 computer program will be
used to derive the water surface profiles. The resulting tailwater
curve will delineate the water surface elevations below the structures.
This tailwater information will then be used to evaluate the designs of
the spillway and outlet works under various levels of discharge. The
information will also be used in stability analyses of concrete dams to
determine the effect of uplift.
Dam Type
The type of dam selected for a particular site is influenced by a
number of factors including intended use, site topography, site geology,
spillway requirement, and availability of construction materials. All
of these factors taken together will be analyzed to verify that an
economical structure has been proposed which will perform the function
intended in a safe and efficient manner.
Reservoir Sizing and Design Operation Requirements
The factors in determining the ultimate size of each storage
reservoir and appurtenant works will be examined including the space
needed for sediment storage, active storage, and flood storage, as well
as the surcharge above the maximum controlled level. The sediment
storage requirement will be evaluated based on the location of the
stream and the assumed useful life of the project. The mode of project
operation will be reviewed for the purposes of examining such items as
engineering design parameters, dam safety, and reservoir slope stabili-
ty. Flood control storage will be reviewed with the Corps of Engineers
and checked against flood storage requirements in the basin. Design
flood storage will be checked against the reservoir operations of the
4-5
design flood and the potential operation of the spillways and outlet
works. The economics of passing versus storing the design flood will be
evaluated by DWD and provide for review. Adequacy of surcharge for the
type, size, and design of the facility will be checked.
The reservoir capacities allocated to each of the functions will be
compared to the desired function of the reservoirs and the unit cost of
additional yield. Capacities which optimize cost per unit of yield will
be determined. At some point, evaporation losses or operational factors
will define the maximum practical size.
All of these factors will be reviewed and the economics examined at
various sizes. The effects of various size facilities on other parts of
the system will also be examined.
Preliminary Dam Drawings
The preliminary drawing produced by the DWD and its consultant will
be analyzed for completeness and adequacy. The plans and sections of
various facilities will be checked to ensure that they provide a repre-
sentative portrayal of the required feature and adherence to the state-
of-the-art for the type of structure designed.
Design criteria such as anticipated wave action, ice problems,
backwater curves, and sedimentation will be reviewed.
Area-capacity curves for the reservoirs derived from the topo-
graphic maps of the reservoir area will be reviewed. Incremental
volumes allocated to various storage pools will be checked against those
obtained from the area-capacity curves.
Volumes of embankment and materials quantities will be checked.
The volumes will be approximated using typical sections and incremental
lengths between stations, and by adjusting the sections for abrupt
changes in configuration.
Seismicity Evaluation. The DWD has an ongoing study of the seismic
activity in the South Platte Valley. Data and conclusions from that
study will be reviewed for adequacy. Regional seismic events will be
researched. From these data, the seismic criteria applied in the
designs will be evaluated. These criteria may vary from site to site,
depending upon the type of dam, the foundation conditions, and the
hazard rating. Experience in seismic design in the Rocky Mountain
region, as well as in California and overseas seismic areas, will be
used in the analysis.
Breach Analysis and Hazard Evaluation. Assumptions regarding
breach size and shape and the time required for failure to occur will be
determined based on the size and type of dam. The assumptions will be
4-6
derived from details of historic dam failures. The DAMBRK computer
program or similar analysis will be used to perform the breach analysis.
DAMBRK is an unsteady flow model which allows for tailwater constraints.
The flood damage potential from a dam breach will be evaluated based
upon the inundation levels downstream. Cross sections of the channel
and floodplain will be used to estimate flood levels.
Stability Analysis. For each dam, the method of stability analysis
will be reviewed in detail. The computation process along with the
loading conditions will be examined for each loading case. The criteria
for acceptable factors of safety will be reviewed for each loading case
which shall cover at least the following cases: 1) normal, 2) unusual
(high water during the design flood), and 3) extreme (loads during high
reservoir levels with seismic loads) . The stability analysis requires
assigning material and foundation strength parameters. Those parameters
will be reviewed and evaluated for reasonableness, with consideration of
the tests or assumptions made to obtain the values used. In some
instances, alternative computations may be required to indicate the
sensitivity to material strengths and to indicate the range of safety
factors for each loading condition. If the stability is judged inade-
quate, measures will be recommended to modify the designs.
River Diversion Plans
For all dams located at "onstream" sites, the general design must
include a plan for handling the streamflow during construction. The
sizing of such river diversion facilities depends on factors such as the
duration of construction, normal streamflow variations, flood damage and
risks, and potential for diversion works to be later incorporated into
the final outlet works. The proposed diversion plans will be evaluated
for location, constructibility, sizing, and potential for dual function.
Hydrology of flood frequency and risk potentials will be checked as well
as the hydraulics and capacity of the facility.
Lands and Rights-of-Way
Land acquisition and easements for each dam and reservoir and
appurtenant works will be checked for adequacy and completeness. Land
costs based on use, present productivity, and location will be evalua-
ted. A comparison of land costs between each project alternative will
be made to ensure reliable comparison of costs.
Access and Relocations
The need for, and the designs of, access roads and relocation of
utilities and other facilities will be evaluated. Cost estimates will
be checked based on current experienced costs and evaluated for compari-
tiveness with other alternatives.
4-7
Construction Schedule
The proposed schedule of construction will be analyzed for reason-
ableness considering work force required, weather constraints, and plant
requirements. The schedule can have a significant influence on the cost
estimates. Assumptions made regarding construction staff requirements,
housing, and transportation will be appraised for impact analysis.
Staged Construction Potential
Some projects may be conducive to staged construction. The poten-
tial will be examined and the advantages and drawbacks enumerated.
Operation and Maintenance Plans
The operation of each alternative will be checked against project
objectives and the facility's capability to provide its intended ser-
vices. Operation procedures for the structure, the reservoir, and the
principal items of equipment will be analyzed. Annual costs will be
checked based on experienced cost of similar facilities.
Periodic maintenance and replacement programs will be examined and
evaluated for the projected life of the facility. Cost estimates for
both maintenance and replacement will be checked and converted to an
annual basis.
Project Cost Estimates
Cost estimates for the site-specific alternatives will be checked
based on quantities and unit costs. The quantity takeoffs will be
checked for accuracy and unit costs checked by comparison to presently
experienced construction costs. The cost estimates are anticipated to
consist of from 20 to 30 pay items, with no more than 15 percent un-
listed items, and 25 percent contingencies. Engineering will be esti-
mated at 15 percent of field costs. Interest during construction will
be calculated at 8 percent of annual expenditures .made from initiation
of construction to the time of filling to minimum pool. Total project
costs will then be estimated by adding to the dam cost the costs of
lands, rights-of-way, permitting, etc. The total costs will then be
annualized using 8 percent compound interest for the 100-year life of
the dam. Curves showing the relationship of size and cost to incre-
mental yield will be developed.
PROJECT-SPECIFIC ANALYSES
In addition to the above information on the dams and reservoir,
other project—specific information and data will be examined as follows:
North Fork Reservoirs
More than one type of dam construction may be feasible at these
sites. The various types will be reviewed to verify the optimization of
the design proposed. A particular effort will be made to compare the
two alternative sites suggested from an engineering point of view.
4-8
New Cheesman Dam and Tunnel
Sizing Criteria for Diversion Structure. The size of the works for
diversion from the North Fork into the tunnel will depend to a large
degree on the operating criteria used. If it is found that regulation
is essential on the North Fork, a relatively high dam will be required.
If no regulation is necessary, a low overflow weir will suffice.
Operation plans for the dam, Dillon Reservoir, Roberts Tunnel, and the
North Fork will be provided by DWD for review and analysis.
Site Geology for Diversion Structure. Geologic mapping will be
analyzed to verify the foundation conditions as in the other dam
alternatives.
Engineering Drawings for Diversion Structure. The drawings and
calculations will be reviewed to verify the suitability of the structure
to satisfy the function, to verify the safety of the structure, and to
check the quantity takeoffs for cost estimates.
Relocation Requirements and Concepts Along the North Fork. The
necessity of extensive relocation of infrastructure along the North Fork
will be tied closely to the size of the diversion structure. If
extensive road relocation is required, the proposed location and
drawings will be examined for engineering feasibility and cost.
Colorado Department of Highways criteria will be used in the analysis
and corridor level of detail utilized.
Sizing Criteria for Tunnel. Sizing and cost of the tunnel, which
will be provided by DWD, will be reviewed.
Geology Along Tunnel Alignment. It is not expected that adequate
drilling data will be available along the tunnel route. However, it is
anticipated that extension of surface data will be sufficient to predict
construction conditions and costs sufficiently for the level of this
study. Existing geologic maps and aerial photographs will be used in
the study.
Tunnel Drawings. Drawings to be reviewed include plan and profile
typical sections, intake and outlet structures, and support and/or
lining details. These will be reviewed for hydraulic analysis and
construction cost details.
Williams Fork Gravity Collection System
This is the only structural site—specific study that does not
include a storage structure. Features include pipelines, two tunnels,
access roads, and hydraulic structures. Items to be reviewed include
the following:
4-9
Geotechnics. Geologic mapping along the pipeline alignments, the
tunnel alignment, and along the access corridor from Kinney Creek to the
pipeline will be reviewed. The most significant data to be reviewed
will be those pertaining to slope stability and degree of rock excava-
tion required. Drilling data along the tunnel will be examined to
determine excavation problems and support needed.
Pipeline. Pipeline engineering drawings will be reviewed in
conjunction with pipe sizes and inlet designs to verify the capability
of the system to collect and convey the anticipated volume of water.
Adequacy of air valves , blowoffs , and cleaning facilities will be
checked. Drawings of inlet structures will be scrutinized for assurance
of proper operation which, considering the remoteness of the system,
must be as nearly maintenance-free as posssible. Depth of cover to
ensure against freezing will be examined. Planned pipe materials and
coupling designs will be analyzed to assist in evaluating construction
problems. If steel pipe is described, the cathodic protection plans
will be reviewed.
Tunnel Drawings. The alignment, grade, and size of the tunnels
will be examined to verify that the structure will function as required
and to allow checking of the cost estimates. Details of the transitions
at the portals will be analyzed to ensure ability to function properly.
Quantities and types of spoil will be checked to determine whether all
can be used in road construction or whether other disposal methods will
be required. Lining requirements will be examined.
Access Alignments. Four general access features will be reviewed -
the pioneer and maintenance road on the pipeline, the Kinney Creek new
access road, extension of South Fork road, and rehabilitation of the
Jones Pass road.
The road along the pipeline route will be used initially for
construction and later for maintenance. The alignment will be, to the
extent possible, that of the pipeline. The drawings and type and amount
of surfacing will be checked for stability, constructibility, and
utility. Structures will be assessed for stability, utility, and cost.
Construction staging areas along the road will be reviewed for adequacy
and for impact analysis.
The Jones Pass Road rehabilitation plans will be assessed for
stability, constructibility, and the ability to accommodate the con-
struction traffic expected.
Construction Procedures and Schedule. Construction of the project
will be difficult because of access, space, topography, geology, and
mobilization for the short construction season. While the construction
4-10
procedures and probably even selection of pipe materials will undoubt-
edly be left to the contractor, some procedures will be assumed in the
design, the construction schedule, and the cost estimates . Those
procedures will be examined for constructibility and reasonableness and
to appraise the cost estimates. Scheduling will be analyzed both for
construction ease and satisfaction of water demand. Assumptions made
regarding construction staff requirements, housing, and transportation
will be appraised for impact analysis.
Operation and Maintenance. The operation and maintenance program
will be appraised for adequacy, probability of performance, plant and
personnel requirements, and cost. The operation and maintenance
experience on the existing Williams Fork system will be used as a model.
Project Cost Estimates. The cost estimates will be examined for
adequacy of quantities and unit costs, taking into account the diffi-
culties of construction and the schedule proposed. IDC will be computed
from initiation of construction of each segment until that segment
contributes to the water yield. The annual unit cost of safe yield will
be obtained by amortizing the total construction cost at 8 percent over
50 years, adding the annual operation and maintenance costs , and
dividing by the safe annual yield.
Williams Fork Pumping System
Williams Fork Pumping System includes both a gravity pipeline
collection system and a reservoir-pressure pipeline-pumping plant to
supplement the gravity system. The information needed for the dam and
reservoir is discussed under Engineering For Dams and Reservoirs ;
following are other requirements.
Pipeline and Tunnel Geology. Drilling has been carried out on the
alignment of the tunnel from the reservoir to the pumping plant. Data
from that drilling will be analyzed to verify the degree and difficulty
of rock excavation, the probable support requirements, and the need for
permanent lining or support. Drilling data will be correlated with the
surface geology (also already mapped) to extend core information along
the line of the tunnel. Drilling and surface geology data will also be
interpreted to define the degree of surface stability, particularly at
the portals.
Geologic data along the pressure pipeline will be examined to
estimate the difficulty of excavation for both the pipeline and the
access road from the pumping station to the gravity pipeline.
Tunnel. The engineering drawings of the tunnel will be examined to
evaluate the size, alignment, excavation difficulty, support antici-
pated, and the inlet and control structures. The operating mechanisms
r of the inlet structure will be particularly examined in conjunction with
4-11
the fluctuating reservoir levels to analyze the magnitude of head
variations in the pumping plant. Disposal areas of spoil will be noted
for impact analysis.
Pumping Plant Layout. The pumping plant site has been drilled; the
data from that drilling will be inspected and analyzed to verify
foundation conditions relative to plant design. The layout of equipment
and the size, number, and type of pumps and drivers will be analyzed for
adherence to the ability to perform the functions assumed in the
operation studies of the reservoir. Operation facilities, whether
manual or automatic, will be examined and staff requirements estimated.
Facilities to handle hydraulic transients upon shutdown will be care-
fully analyzed, as the protection of the plant will be critical.
The pumping plant will be operated in very different fashions at
various times. Criteria for that sporadic pattern will be examined
closely to verify that unnecessary pumping will not occur and that the
equipment can be operated in the pattern indicated by the operation
studies. The number and size of units proposed to allow the variable
pumping schedule will be analyzed. Operation and maintenance costs will
be examined to ensure inclusion of the effects of variable periods of
use.
Powerline Source and Alignment. The proposed voltage, route of the
transmission corridor, and the number of transmission circuits will be
reviewed for adequacy, and to supply impact information to others. The
engineering drawings and method of construction of transmission lines
will also be reviewed to determine possible impacts and to assist in
verifying costs.
Pipeline. Whereas the nonpressurized portion of the pipeline will
be on the same alignment as in the gravity system, the size will be
different due to the pumped volume. Sizing will be checked to ensure
adequacy for operation as both the gravity collection system and as
conveyance from the pressure pipeline.
The pressure pipeline will be checked to verify size, pressure
rating, hydraulics, depth of cover, and mechanical design.
Road Corridors. The access road corridors and engineering drawings
to the pumping plant and to the gravity pipeline will be checked for
adequacy and to estimate the difficulty of construction and cost. The
geology along the route will be examined to ascertain both slope
stability and volume of rock excavation. The Jones Pass Road require-
ment will be the same as in the gravity system.
Cost Estimates. Estimates for the gravity and pressure pipelines,
the pumping plant , tunnel, and access road will be checked using
4-12
measured quantities and unit costs derived from similar construction
adjusted to account for the construction difficulties perceived.
Pumping costs will be estimated based on the operation studies.
Chatfield Reservoir
The structural aspects of this source are primarily in the reloca-
tion of recreational facilities. Only additional riprap and instrumen-
tation are proposed for the dam structure. The COE will provide an
operation plan, constraints on use, and other pertinent data.
Reallocation of Storage Space. The COE analysis which concluded
that reallocation of storage space could be made from flood control to
water supply storage will be reviewed to appraise the reasons for, and
adequacy of, the reallocation. Effects of municipal storage on the
flood control ability of the reservoir will be appraised. Adequacy of
the space for use as a municipal water supply will also be discussed.
Relocation Details. The facilities to be relocated will be
examined for necessity and completeness. The effects of anticipated
reservoir level fluctuation will be appraised. The proposed construe-
., tion schedule, the sources of construction material, the estimated
construction staff, and the effects of relocation on the recreation area
will be examined for impact analysis.
Project Cost Estimates. The COE has made very preliminary esti-
mates of the cost and procedures required to transfer the space to
municipal storage use. Those estimates and the basis for them will be
reviewed for accuracy. Operation and maintenance costs are to be an
allocation of the total reservoir operation and maintenance costs. That
amount will be ascertained and analyzed.
TECHNICAL REPORT
Each project evaluation by the COE will be the subject of a
separate narrative that will describe the location and function of the
project, its structural features, construction characteristics, imple-
mentation costs, and the relationship of the project to the rest of the
system. Drawings of the major project components will be presented,
such as plans and sections of dams, pipeline and tunnel profiles, and
major relocation requirements. Cost estimates will be displayed in
tabular form. Where pertinent, curves will be prepared to describe
relationships of cost, yield, and size.
The schedule of the engineering activities necessary to conduct and
complete the scope of work is shown in figure 4.1
4-13
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REVIEW AND ANALYSIS OF HYDROLOGIC YIELDS AND IMPACTS
INTRODUCTION
The objectives of the hydrologic analysis are to identify the safe
yield of each project and to identify the operation effects of the
projects on the entire DWD system. The data will be provided by the
following studies:
. Yield Studies - Including studies of each project to the Denver
system, and combination of projects, resulting in size/yield curves.
. Operational Effect Studies - Including studies of the inter-
actions of each project with various other planned projects to determine
preferential sizes of the site-specific projects. These would include
impact studies to determine the effect of each project on streamflows,
reservoir levels, and on the following resources:
Water Quality
Vegetation
Wildlife
Soils
Aquatic Life
Wetlands
Threatened and Endangered Species
Recreation
Visual Resources
Cultural Resources
The hydrologic studies will generally be prepared by the DWD. The
basic data, methodology, and results will be evaluated. The evaluation
will consider completeness, adequacy, and adherence to accepted stand—
ards and criteria. External calculations will be made, as necessary, to
verify critical results.
Hydrologic studies of some site—specific projects have already been
completed in satisfactory detail by the DWD, but further studies will be
necessary to complete the work plan described below.
The South Platte Storage alternatives and the Williams Fork Collec—
tion System alternatives will all require the same general type of
analysis with certain differences relating to the individual project.
The COE will verify all analyses and results.
Required Level of Detail
The level of detail of the hydrologic studies must be sufficient to
determine the yield of each project to approximately the same accuracy
as studies of the existing yield of the DWD system are determined. The
4-15
degree of consistency in accuracy among the computed yields must be
sufficient to provide meaningful cost/yield curve comparisons.
In the South Platte River and the Colorado River systems, monthly
records will be used for all studies. In the Williams Fork and Fraser
River basins, monthly average data can also be used for valid analyses.
The detail necessary for impact analysis is that necessary to
determine realistic effects on wildlife, the riparian environment, and
socioeconomic factors, and to permit valid comparisons of projects.
Data Base
The data base will include the following:
. Gaging station records from USGS;
. Record extension studies to relate gage station data to points
not gaged;
. Climatologic evaporation records for evaporation determinations
and flood and runoff projections;
. Exchanges and agreements affecting DWD water yield;
• Water rights and call records as recorded by the State Engi-
neer's Office and the courts;
. Previous model studies by the DWD, Bureau of Reclamation, and
various other parties that may be applicable.
Flow and Reservoir Water Level Data. Flow and reservoir water level
data requirements differ for yield studies and environmental impact
assessments. The data are required for the period of model simulation,
1947 to 1974 . In all cases for yield studies , flow data are from
historical records, or are derived from historical records by adjust-
ments or extensions to compensate for changed hydrologic conditions or
for locations different from the historical gaging station locations .
For impact studies, flow data are from model simulations or calcula-
tions.
Yield Study Data Requirements
Data Points. Within the South Platte River basin and other river
basins, the flows must be known at the dam sites and diversion points
for yield studies. For dams and diversions which are not close to an
established gaging station, flows will be determined by area and alti-
tude adjustments to records of existing gaging stations.
4-16
Reservoirs which are to store West Slope water delivered into the
North Fork of the South Platte River through the Roberts Tunnel are
dependent on the yield of the Blue River for much of their yield. Thus
the flows into Dillon Reservoir will be required, as will be the incre-
mental flows between Dillon and Green Mountain Reservoirs and the flows
in the Colorado River at the Dotsero and Cameo gages. Some of the
planned diversions from the Blue River will be out-of-priority diver-
sions made possible by exchange of water from Williams Fork Reservoir.
The requirements for exchange water and the ability of Williams Fork
Reservoir to supply it will be determined from the flows and diversions
in the Williams Fork and Fraser River basins, downstream Colorado River
flows, and the operation of Green Mountain Reservoir under the current
Bureau of Reclamation operating policies.
Average monthly water level elevations will be required for the
various reservoir simulated in the yield studies for evaporation deter-
minations.
Water Rights Inventory. An inventory will be made of the water
rights that determine the yield of each project. These rights will be
classified in three categories: DWD rights that will yield water to the
project; rights of other metro-Denver-area water providers that could
yield additional water to the project; and representative competing
rights of other water users that are more senior in priority than the
foregoing categories and so prohibit or restrict yield to the project.
Water Rights Evaluation. The status of water rights appropriate to
each project will be evaluated to determine if they are applicable to
the project without change or if the rights must be changed in point of
diversion or some other feature.
Of the South Platte Storage projects, only Two Forks Reservoir has
existing adjudicated water rights that would contribute yield without
transfer or modification. Even these rights are relatively junior on
the South Platte River and so are in priority only during some spring
runoff periods. Much of the yield of Two Forks or an alternative
reservoir would come from storage of West Slope water diverted under
Blue River water rights. The determination of yield of these rights
will be made by a simulated operation of these rights in the Colorado
water rights priority system as described below.
All of the other South Platte Storage Alternatives would either
operate with new, very junior water rights or would transfer the Two
Forks rights to the alternative storage site. A discussion will be
presented as to whether the Two Fork rights can be transferred, the
conditions likely to be attached to such a transfer, and the possible
impact of such conditions on yields. The yields of the alternative
4-17
South Platte Storage projects may be somewhat indeterminate until
conditions of a transfer are actually specified.
The Gross Reservoir Enlargement and Williams Fork Gravity Collec-
tion System have existing adjudicated rights. The change of rights
required for the Williams Fork Pumping Collection System will be dis-
cussed.
Operational Effects Data Requirements
Streamflow data and reservoir water levels will be determined for
each site-specific project operating as the next structural project
added to the DWD system.
Data Points. Streamflow data are required at the following points:
. South Platte River
North Fork near Grant
Downstream from the simulated reservoir site
South Platte River at South Platte
Downstream from Chatfield Lake
Henderson gage
Julesburg
Overton gage
. Blue River
Roberts Tunnel
Downstream from Dillon Reservoir
Downstream from Green Mountain Reservoir
. Colorado River
Kremmling
Dotsero
Cameo
State line
. Williams Fork River
Leal gage
Downstream from Williams Fork Reservoir
South Fork gage
. Fraser River
Granby
Moffat Tunnel
. South Boulder Creek
Upstream from Gross Reservoir
Downstream from Gross Reservoir
4-18
Preproject Flows. Historical flows adjusted to preproject, full
development (295,000 acre-feet per year safe yield) conditions are
required at the above listed points. The flows will be determined for
wet, dry, and average year conditions using monthly average flows.
Postproject Flows. Simulated flows will be determined at post-
project, full-utilization conditions as described above for preproject
flows.
Reservoir Water Levels. Annual maximum and minimum water level
elevations, mean water level with and without conservation pool, and
annual April and September water levels are required for the following
reservoirs:
. Each simulated reservoir
. Antero Reservoir
. Elevenmile Reservoir
. Cheesman Lake
. Chatfield Lake
. Dillon Reservoir
�-. Green Mountain Reservoir
. Williams Fork Reservoir
. Gross Reservoir
The water level elevations will be derived by model simulations for
postproject, full-utilization conditions.
YIELD AND OPERATIONAL EFFECTS ANALYSIS
The basic operation of each project will be evaluated; the yield
will be quantified; and the interactions with other projects will be
considered. Project yield will be determined through computer model
studies.
DWD Model
The DWD model used to determine the yield of the existing DWD water
supply system will be the basic tool to determine site-specific project
yields under various conditions. Many of the projects have already been
modeled. Existing model runs will be evaluated for input data, assump-
tions, and model logic. Model runs will not be repeated if existing
runs are suitable. Suitability will be determined by the COE.
Other Models
Other models have been used by many persons and entities to deter-
mine project yields in various areas. Some of these may be available
and may be used for checking or determining yields of various projects.
4-19
DWD Model Verification
The COE will review the basic manipulations of hydrologic data
performed by the DWD to generate flows at diversion points and will
perform their own check calculations as necessary. All assumptions,
operations, and input data not previously analyzed and used in the model
studies to determine the yield of each site specific project will be
thoroughly examined and critiqued. Where significant discrepancies are
noted, model runs will be repeated with changed parameters or adjusted
without rerun if this is sufficient for accurate results.
Basic Operation
The basic operation of each project as the next DWD structural
project will be evaluated for yield and operational hydrology. Basic
operation for storage projects will comprise filling and storing water
when South Platte rights are in priority, storing diversions from the
West Slope, storing exchanged water when advantageous, and releasing as
needed for the Denver metropolitan system. Basic operation for diver-
sion projects will comprise diversions in priority and by exchange and
delivery to storage or to the Denver metropolitan system. Source and
requirements of exchange water will be evaluated. The increased yield
to the system will be determined.
Yield/Volume Curves
The model runs to determine yield for each alternative storage
project will be repeated for a range of practical reservoir sizes for
each individual site. From the results, yield/ volume curves will be
developed to guide decision-making in respect to optimum reservoir
sizes.
To be consistent with the hydrologic and engineering work already
done, and considering the degree of precision in determining costs in
relation to size and yield, the analysis of the specific sizes for each
reservoir for which cost/size curves will be developed will use the
engineering data that have already been prepared. The sizes of reser-
voirs which will be modeled to provide data on yield/volume curves are
as follows:
. Two Forks - 200,000; 300,000; 400,000; 1,100,000
acre-feet
. Ferndale - 200,000; 400,000 acre-feet
. Estabrook - 200,000; 400,000 acre-feet
. New Cheesman - 600,000; to 1,000,000 acre-feet
. Chatfield Storage - 23,000 acre-feet
. Gross Enlargement - 113,000 acre-feet
4-20
The yield/volume data will be chosen and combined with cost/volume data
to derive cost/yield curves. These will be used to determine optimum
reservoir sizes and to compare the cost efficiency of alternative
projects.
Evaluation of Variations
The effect of potential variations on yield will be determined in
those cases where these variations could significantly affect the choice
of an alternative or the viability of a project.
Yield Variations Resulting from Operational Changes
Changes in by-pass and maintenance flows at dams and diversions
will affect the yield of a project. Another potential factor, closely
connected with the above, would be a general change of emphasis from
operational priorities to maximize yield to environmental priorities,
usually at the expense of maximum yield. In either case, if such
changes are believed to be potential considerations, the effect on yield
will be evaluated by calculations or by model runs, if necessary.
Interaction with Other Projects
Existing. This analysis will consist of the joint operation of a
storage project of relatively large size with various existing water
supplies and reservoirs of the DWD, or possibly those of other water
providers, which might result in a greater yield than that of the new
project operating alone on its own rights. The yield of both the Moffat
Tunnel and Roberts Tunnel diversions would increase (since water spilled
from diversions on the West Slope with the current system would be
captured and stored on the East Slope) as would the yield of the DWD
South Platte rights. This enhanced yield and its operational effects
will be investigated by the basic analysis. As a part of the analysis,
increased diversions from all sources will be identified and quantified.
The effects on the individual yields of the various components of
the DWD system will be determined and resulting changes in streamflow
patterns and reservoir levels will be presented.
The effect on the yield of the project being studied of the :Lncor-
poration of unused or under-utilized water rights of other water provi-
ders, such as agricultural rights in the South Park area, will be
evaluated. In addition, the potential for increased yield of projects
owned by other Denver metropolitan area water providers, such as Spinney
Reservoir, will be considered and evaluated.
Alternatives. An analysis similar to the above will be made for
enhanced yields through joint operation of a basic project in the
existing DWD system with specific planned projects. Examples of these
packages of planned projects are:
4-21
North Fork Two Forks
Storage Storage
(acre-feet) (acre-feet)
Diversion or 200 to
Storage Project 200,000 400,000 300,000 400,000 1,100,000
Eagle-Piney and
East Gore X X X X X
Green Mountain
Exchange X X X X X
Gross Enlargement X X X X X
Williams Fork
Collection
(Gravity and
Pumping) X X X X X
Williams Fork and
Gross Reservoir X X X X X
The analysis of the yields of the storage projects will define the
increase in yield from both the South Platte River basin and the West
Slope basins developed by increasing the size of a South Platte River
storage facility. This will, in turn, show the impact of increasing
reservoir size on both East Slope and West Slope diversions. The yield
studies of all of the grouped projects assessed in conjunction with the
yield studies of the individual projects will provide part of the
background necessary to compare projects.
As a specific example of the analysis of the source and require-
ments of exchange water allocated to specific projects, the potential
yield of exchange water from the Williams Fork Reservoir will be eval-
uated in conjunction with the requirements of exchange water for the
expanded Williams Fork Collection System, Gross Reservoir Enlargement,
increased Dillon Reservoir exchange, and other projects which will
benefit from the use of exchange water. Model studies and computations
will be done for this purpose.
The purpose is to evaluate the independent versus dependent utility
of the site-specific projects. The analyses of grouped projects for the
site-specific study will consider the conjunctive yields of groups of
specific potential structural projects for the purpose of identifying
4-22
advantages and disadvantages of certain factors such as reservoir size.
The only conjunctive environmental impacts that will be defined will be
the magnitudes of diversions from the various river basins supplying the
project packages. The studies will consider only the conditions of full
development and utilization of each package of projects. There will be
no evaluation of phasing projects in a time sequence to meet growing
demand as in the Task 5 alternative scenarios.
By-pass and Maintenance Flows. The yield of each project will be
determined with appropriate minimum flows bypassed at storage and
diversion structures for maintenance of wildlife and riparian environ-
ment. Minimum bypass flows studied will be CDOW-recommended minimum
instream flows, filings by the Colorado Water Conservation Board, flows
specified by agreements or right-of-way stipulations, or in the absence
of such information, 30 percent of long-term average flows.
Evaporation Losses. Evaporation losses will be computed for
various reservoir levels and such losses will be included in the yield
studies. Computations will be based on adjusted pan evaporation and
surface areas at various water levels or on mass balance calculations.
!-` Reservoir Filling Studies
Initial Fill. Each site-specific reservoir will be modeled during
its simulated initial fill period. Initial conditions will be with the
reservoir empty and the system demand at the 295,000 acre-feet per year
level. The operation will be simulated through model studies based on
historic flows of 1947 through 1974. When the demand reaches the safe
yield of the system including the new storage project, demand will be
held at that constant level through the remainder of the modeled period.
Monthly simulated water levels will be determined and tabulated.
Pool Level Graphs . The reservoir water level data from both
"initial fill" and "safe yield operation" studies will be presented.
Initial fill graphs will portray end-of-year contents during the fill
period. Site-yield graphs will depict monthly operation in a dry, wet,
and average year.
Pool Duration Curves. The reservoir water level data from both the
"initial fill" and "safe yield operation" studies will be presented in
the form of pool duration curves showing the percentage of time the pool
level is at each elevation between minimum and maximum during the model
simulations.
Hydrologic Effect Analysis. The hydrology analysis is designed to
provide the flow regime comparisons necessary for the impact analysis by
the various EIS disciplines. The primary disciplines include aquatic
life, wildlife, wetlands, recreation, and water quality. The hydrologic
i-. analyses will include monthly average pre and postproject discharge at
4-23
the various project-related points of concern. The analysis will be
conducted for an average condition and a representative drought condi-
tion. Both tabular and graphic analyses will be prepared. Graphic
analysis will include stage relationship curves. An example of the
tabular analysis follows.
Average Discharge
Year (thousand acre-feet)
1947
through Project Project Post- Remaining
1974 Preproject Depletion Increase project Discharge
(percent)
January 1.2 0.2 0.0 1.0 83
February 1.0 0.1 0.0 0.9 90
March 1.1 0.1 0.0 1.0 91
April 1.9 0.3 0.0 1.6 84
May 9.0 3.1 0.0 5.9 65
June 23.2 9.0 0.0 14.2 61
July 10.6 4.6 0.0 6.0 57
August 3.8 1.5 0.0 2.3 61 ^
September 2.2 0.7 0.0 1.5 68
October 2.0 0.6 0.0 1.4 70
November 1.6 0.3 0.0 1.3 81
December 1.4 0.2 0.0 1.3 86
Totals 59.0 20.7 0.0 38.5 65
TECHNICAL REPORT
The hydrologic evaluation of each project by the COE and DWD will
be the subject of a separate narrative.
The new yield of the DWD system with the project incorporated as
the next structural project, the sources of the additional yield, and
the impacts of the augmented DWD system on each affected stream basin
will be identified. The data will be presented in tabular form, where
appropriate, and curves showing operational reservoir water levels and
the relationships of volume and yield will be included for each storage
project. In addition, the results of operating certain site-specific
projects (such as large and small South Platte storage) in conjunction
with packages of planned projects (such as West Slope gravity projects)
will be presented for comparison of the potential value of various site-
specific projects and the source of the water that could ultimately be
diverted to provide the yield of the studied packages of projects.
Figure 4.2 is a schedule of the hydrologic activities necessary to ^
conduct and complete the above scope of work.
4-24
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ENVIRONMENTAL IMPACT ANALYSES
INTRODUCTION
Portions of the environmental data base and the impact analyses
prepared for the SEIS will be used in the evaluation of the site—
specific alternatives for the S/SSEIS. However, in order to conduct
the site-specific impact analyses in sufficient detail to satisfy NEPA
requirements, additional data and work are needed.
The scope of the additional work in the environmental disciplines
is presented under four headings in a common format:
1. Objectives;
2. Data collection;
3. Analyses to be conducted; and
4. Report preparation.
The development of the additional work scope included two import-
ant considerations:
1. The significant issues concerning the site-specific alterna-
tives are likely to be potential impacts to water quality, wetlands,
wildlife, threatened and endangered species, infrastructure, trans-
portation systems, recreation, visual resources, and non-developed
recreational use and
2. The specific criteria developed in the SEIS process (appendix
B) are used as an initial framework for determining additional data
needs. (The additional data needs will be reviewed during the respec-
tive Work Group meetings.)
Technical Work Groups, comprised of representatives of Federal and
State agencies which have permitting or authorizing responsibilities,
DWD, and the COE's consultant will be established for each discipline
(figure 4.3). The purpose of each Work Group is to review data and
technical products, monitor field studies, and provide technical
quality control.
4-26
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PHYSIOGRAPHY, TOPOGRAPHY, AND GEOLOGY
Objectives
This analysis will be conducted to determine how the construction
and/or operation of a project could potentially affect local physi-
ography, topography, and geology. Key issues are faults, unstable
slopes, highly permeable bedrock formations, flash flood zones, mineral
resources, and percent slopes, because these features could be altered,
activated, or made unavailable by implementation of the water supply
projects.
The analyses of the physiographic, topographic, and geologic
impacts will be sufficiently detailed to fulfill the requirements of
NEPA regarding the description of the affected environment.
Data Collection
Identification of Data Gaps. The following data deficiencies have
been identified for the topographic, physiographic, and geologic
sections of the S/SSEIS. Categorized by project, they are:
Two Forks Reservoir.
1. To assess the nature, permeability and strength of materials
occurring in the inferred fault zone, more field verification of the
Kennedy Gulch Fault in the vicinity of Two Forks Dam is required.
Also, the potential for seismicity at the site will be determined.
2. A determination of the extent of weathered, sheared, and
fractured rock which must be excavated and removed from the left dam
abutment will be made. Potential waste rock stockpiling areas will be
identified.
Estabrook Reservoir.
1. The potential activity, permeability, and stability of the
Shawnee Fault where it passes within 0.5 mile of the proposed dam site
and near the saddle dikes will be assessed. The potential for
seismicity at the site will be determined.
2. A fatal-flaw level evaluation will be performed for faulted
low areas a mile upstream from the dam on the right reservoir rim and
for the fault through the saddle behind the right dam abutment. Both
of these faulted areas will be addressed for potential seepage path-
ways.
3. Fatal flaw evaluations will be completed for a sheared zone
on the lower right dam abutment.
4-28
• Ferndale Reservoir.
I. An assessment of potential activity of the Kennedy Gulch
Fault and general seismicity within the area is required.
2. The site-specific geologic needs will be determined once the
exact location of the dam is provided.
▪ New Cheesman Reservoir.
1. Subsurface investigations are required to determine the
lateral and vertical extent and condition of decomposed granite zones
near the new dam site.
2. Joints in the immediate vicinity of the diversion dam site
will be evaluated for strength and permeability.
3. The faulted zone along portions of the right reservoir rim
will be investigated for potential slope instability and potential
seepage pathways.
4. Rock conditions in faulted zones crossed by the diversion
tunnel will be evaluated.
5. The potential for seismicity at the site will be determined.
• Chatfield Lake.
Extensive geologic testing and analysis was done prior to the
construction of Chatfield Lake. For the purpose of the S/SSEIS, no
data gaps were identified and it is not anticipated that any additional
data will be required.
• Williams Fork Gravity/Pumping.
1. Avalanche chutes will be identified and their potential for
activity will be determined.
2. Bedrock fracture patterns in the vicinity of the proposed dam
site will be evaluated. A relationship between fracture patterns and
permeability will be established and related to seepage pathways
beneath the dam foundation and abutments.
3. The potential for seismicity in the upper Williams Fork basin
will be determined.
4. The slope stability during the construction and operational
phases of both projects will be analyzed. Areas of concern include the
dam site, slopes along the collection system alignments, and borrow and
waste rock storage sites.
4-29
Gross Reservoir.
1. The potential for seismicity at the site will be determined.
Studies Required to Fill Data Gaps. The DWD will be responsible
for data collection to fill the identified data gaps.
• Two Forks, Estabrook, Ferndale, New Cheesman Reservoirs. The
information required to fill data gaps for these reservoirs will be
sufficiently detailed to perform fatal—flaw analyses for seismicity and
to develop cost estimates for the dam based on faulting, seismicity,
and the presence of weathered rock. This information will be available
°from geologic and seismic studies being conducted on the site by the
DWD.
▪ Chatfield Lake.
No additional data are required.
▪ Williams Fork Gravity and Pumping.
1. Avalanche tracks will be identified by the DWD from aerial
photographs. The potential for activity of each chute will be esti—
mated, based on the successional stage and maturity of vegetation
within the chute.
2. Sufficiently detailed information to perform a fatal—flaw
analysis on the dam site will be collected by DWD.
3. Knowledgeable personnel with the Colorado Geological Survey
will be contacted to determine the potential for seismicity in the
upper Williams Fork basin.
4. Potential slope failure areas in the upper Williams Fork basin
have been mapped by the Arapaho National Forest. No slope failure
areas have been identified in the vicinity of the dam site. When the
final alignment of the collection system and locations of borrow and
rock storage sites have been determined, the geologist who prepared the
Arapahoe National Forest slope stability maps will be contacted by the
DWD to determine the potential for slope failure in these areas and the
potential hazard to construction workers and project facilities.
• Gross Reservoir. Seismic data developed for the site will be
collected by the DWD.
Analyses to be Conducted
Many of the analyses for this task were originally performed for
the SEIS Task 4 technical appendices. ES is responsible for updating
these analyses and producing new analyses for Estabrook, Ferndale, and
New Cheesman, using the DWD furnished data as described in the previous
section and herein. The topography of sloping areas can be directly
4-30
affected by project construction. Effects include cuts and fills for
roads, dams, conduits, and other project features. In addition, the
topography of disturbed areas affects other resources, such as soil
erosion and revegetation potential. Slopes between 0 and 30 percent
generally have a slight to moderate soil erosion hazard, very good to
fair revegetation success, and few engineering constraints. Slopes of
30 to 50 percent have a moderate to critical soil erosion hazard, fair
to poor revegetation success, and construction complications due to
slope and/or instability. Slopes greater than 50 percent usually have
critical to severe soil erosion hazard, poor to improbable revegetation
success, and construction complications due to slope and/or instability
(Bureau of Land Management and U.S. Geological Survey, 1977). There-
fore, the linear footage of the project features which intersect slopes
between 30 and 50 percent and slopes greater than 50 percent will be
calculated by ES and used to assess the potential for successful
revegetation, slope erosion, and slope stability on land disturbed by
project activities.
An analysis of site geology will be conducted by the DWD: (1) to
determine how construction and/or operation of a project could poten-
tially affect site geology; (2) to evaluate dam safety; and (3) to
review the potential cost items.
To characterize the regional geology, analysis will be conducted
of the geologic formations, formation rock types, bedrock structure,
and any major faults which occur within a 10-mile radius of the study
area. The 10-mile criterion represents the outer limit of effects of
adjacent fault systems and accounts for regional seismic and tectonic
influences. Whether a fault system is classified "active" or "inac-
tive" will be examined.
Geologic data needed by ES to describe the regional geology are
available from reports previously prepared for the DWD and from reports
published by the USGS and the Colorado Geologic Survey. Information
pertaining to local and regional seismicity will be available from a
comprehensive seismic investigation currently being performed by the
DWD.
The geologic discussions concerning site geology prepared by ES
will focus on issues of (1) bedrock geology, (2) surficial geology, (3)
seismicity, (4) bedrock perviousness, (5) slope failure, (6) flash
flood zones, (7) construction material borrow sites, and (8) mineral
resources in the project areas. Each of these issues is discussed
below.
Bedrock Geology. Bedrock in the vicinity of project features will
be evaluated for lithology, rock strength, foliation trends, fractur-
ing, and shear zones. Bedrock strength will be evaluated for potential
4-31
weak zones caused by weathering or tectonic movement that could poten-
tially affect slope stability and dam safety during project construc-
tion or operation. Foliation trends, fracturing, and shear zones will
be investigated as indicators of potential seepage pathways which could
lead to slope instability problems or affect local and/or regional
ground water regimes. Geologic data sources for this section will
include reports prepared by Harza Engineering Company (1983), CH2M Hill
(1974 to 1976), and previous drafts of technical appendices prepared
for the SETS. ES is responsible for incorporation of these data.
Surficial Geology. The surface preparation required for construc-
tion of project features will depend on the depositional nature,
material type, and depth of overburden materials. Careful review will
be made of potential impacts caused by the excavation and stockpiling
of overburden material. Slope stability, erosion, and potential
geochemical interactions will be assessed for areas of overburden
disturbance. The references cited above will be utilized by ES in this
assessment.
Seismicity. A fault is defined as a fracture or fracture zone
i-- along which there has been displacement of the sides relative to one
another and parallel to the fracture. Seismicity can be induced along
faults by the construction and filling of reservoirs. Reservoir-
induced seismicity is usually associated with deep (greater than 300
feet) or very large reservoirs and active faults are associated with
most, if not all, reservoirs that have induced earthquakes of magnitude
5 or greater (Kirkham and Rogers, 1981) . Faults within 1 mile of
reservoir sites with horizontal continuity greater than 1 mile in
length will be investigated by the DWD for susceptibility to reservoir-
induced seismicity. In addition, fault systems consisting of several
proximal or interconnecting faults having lengths of less than 1 mile
will also be considered. Such faults may define a zone of potential
geologic movement. Localized fault sets have been identified at most
of the project sites by the DWD. Fault sets which have not been
identified will be investigated using available USGS geologic data. ES
will incorporate this information into the technical appendix 4 report
for each project.
Bedrock Perviousness. Extremely pervious units can affect water
storage or water collection systems because of the potentially high
water losses likely and/or the construction associated with such
formations. Alternatively, water projects can result in the structural
failure of pervious foundation formations. Potentially pervious
geologic units include beds of gypsum, anhydrite, salt, or Karstic
limestone. Heavily fractured rock formations may also constitute
extremely pervious rock. Such fractured rock may include deep and
sufficiently widespread interconnected fracture lines which could allow
high water losses through seepage. Pervious units are determined using
4-32
geologic maps available from the USGS and Colorado Geologic Survey.
Fractured rock has been mapped at each project site to different levels
of detail by the DWD. The evaluation criteria used in the SETS (appen-
dix B) will be supplemented with the following criterion to determine
the extent of pervious materials potentially affected by project
features:
Unit of
Criterion Measurement
Area of pervious geologic formations, square feet
including inherently pervious geologic
units or fractured rock formations, within
areas exposed to impounded waters.
ES will perform this analysis and include it in the technical
appendix 4 reports.
Slope Failure. Slope failure is the mass movement of earth
materials downslope and results when gravitational stress exceeds
cohesion and/or friction (Soule, 1977). Slope failure areas include
unstable slopes (including slumps, soil creep, minor earth flows, or
heavy erosional areas) , active or inactive landslides (including both
bedrock and debris slides), mud and earth flows, rockfalls, and debris
fans. These areas are examined because they could be activated by
facility construction and operation and because of potential con-
straints of slope failure on postconstruction restoration efforts.
Avalanches are considered along with slope failure because of the
potential of both of these geologic hazards to damage project features.
Geologic hazard maps prepared by the USGS, the USFS, or through House
Bill 1041 or other studies will be used to determine linear feet of
project features in areas with a moderate or greater potential for
slope failure or avalanche. If necessary, this information will be
supplemented with information from aerial photographs. ES will perform
these analyses and incorporate the results into the technical appendix
4 reports.
Construction Material Borrow Sites. Construction material borrow
sites located outside of proposed reservoir inundation areas will be
evaluated for local geologic impacts. Borrow sites are typically used
to supply materials such as sand and gravel, rock for riprap, and fine—
to coarse—grained material for cofferdams and roadway and pipeline base
material. Sand and gravel are necessary for concrete aggregate ,
roadfill, ramps, and cofferdam embankments (Harza, 1983) . Slope
stability and erosion control measures at each of these borrow sites
4-33
will be evaluated by ES for potential long-term impacts. The location
of suitable borrow site locations will be provided by the DWD.
Mineral Resources. Construction of a project within an area of
mineral resources represents a potential constraint on the future
economical recovery of resources. Some projects, such as collection
systems, may have little effect on future recovery. Other projects,
like new reservoir construction, could preclude economical recovery
within the near future because the resource would be inundated .
Although water development projects would not affect the integrity of
the resource, potential use conflicts could affect the attractiveness
of mineral resource recovery. Mineral resources of concern include
ferrous and non-ferrous metals, hydrocarbons (such as oil, gas, and
coal), geothermal resources, industrial minerals, and sand and gravel.
Mineral resources will be determined by ES using documents available
from governmental agencies, including the USGS and the Colorado Geo-
logical Survey. County planning agencies will be contacted by ES
concerning geologic resources within their jurisdictions.
Report Preparation
The physiography/topography analyses in technical appendix 4 will
by prepared by ES. These will include a description of physiographic
features and landforms within the study area. Slopes in the study area
will be mapped by ES for the ranges of 0 to 30 percent, 30 to 50
percent, and greater than 50 percent. The geological analysis produced
by ES will describe bedrock and surface geology as they relate to the
project, present a map of slope failure areas and avalanche tracks, and
identify mineral resources in the study area. Features of each project
will be evaluated by ES using the topographical and geologic evaluation
criteria to determine the quantitative impacts. A qualitative dis-
cussion of impacts will also be provided by ES.
The schedule for the above activities is presented in figure 4.4.
4-34
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SOILS
Objectives
Soils data are necessary for a comprehensive evaluation of the
potential impacts posed by a project to the soil resource and of
mitigation measures to lessen or counter the impacts. The important
aspects of soil resources that affect the environmental evaluation of a
project are erosion potential, watershed condition, permeability, soil
chemistry, particle size, distribution, revegetation potential on
denuded soils, and the loss or significant alteration of highly pro-
ductive agricultural soils . Disturbance of highly erosive soils
represents a potential hazard to local water quality through sediment-
ation, turbidity, and leaching of noxious minerals. Revegetation
efforts are constrained not only by severe erosion characteristics, but
by thin or extremely rocky soils and unfavorable soil temperature and
moisture. The inability to adequately revegetate large areas results
in long-term vegetation, wildlife, water quality, and scenic effects.
Soils information is required for S/SSEIS preparation as soils data is
a part of the overall description of the environment and impact assess-
ment for the entire project. Soils information should include a soil
survey with mapping unit descriptions, acreage, and percent composi-
tion. Specific mapping of soils in the transportation corridors will
be needed for permitting, but not for the above objectives.
Data Collection
Identification of Data Gaps.
• Two Forks Reservoir. Existing soils data consist of prelim—
inary USFS (Pike National Forest) soil maps of approximately 100
percent of the project area. The mapping intensity is an intensive
Order 2 and 3 survey (minimum delineation 10 to 20 acres) with mapping
units classified to the soil series level. Nine soil mapping units are
identified. Brief mapping unit descriptions and a listing of acreage
and percent composition are presented for each mapping unit . In
addition to soils mapping, physiochemical data have been recorded for
all soil units by the USFS as part of its soil survey. Available data
are adequate for impact assessment. The USFS will collect data on the
remaining areas for which soil surveys have not been conducted. This
represents less than 10 percent of the project area.
• Estabrook, Ferndale, New Cheesman Reservoirs. Needed data
for the preparation of the S/SSEIS include soil surveys, complete with
mapping unit descriptions, acreages, and percent composition for the
project areas. The USFS will conduct the necessary soil surveys and
provide these data and maps to ES.
• Chatfield Lake. Soil mapping and descriptions are adequate
for preparation of the S/SSEIS. The COE will furnish these to ES.
4-36
• Williams Fork Gravity/Pumping. Current data consist of
SCS-USFS (Grand County soil survey) soil maps which include the entire
project area. The mapping intensity is between Order 2 and 3 surveys
with mapping units classified to the soil series level. Eleven soil
mapping units are identified. Brief mapping unit descriptions and a
listing of acreage and percent composition are presented for each
mapping unit. Soil mapping and classifications are adequate for the
S/SSEIS.
▪ Gross Reservoir. Existing soils data consist of SCS (Boulder
County area) soil mapping (Order 2 survey) of approximately 47 percent
of the project area. Mapping units are classified to the soil series
level. Three soil mapping units are identified. Brief descriptions
and a listing of acreage and percent composition are presented for each
mapping unit. Needed data include a soil survey, complete with mapping
unit descriptions, acreages, and percent composition for the remaining
53 percent of the project area. The additional soil information will
be collected by the USFS and provided to ES for analysis in the
S/SSEIS.
Studies Required to Fill Data Gaps.
▪ Two Forks Reservoir. The USFS will conduct soil surveys,
mapping, and tabularization of data for any portions of the project
area for which soil mapping is still lacking. These areas will be
mapped at the same intensity as the previous USFS survey. The USFS
survey will be used as the basis for the development of mapping units.
Data for each soil series mapping unit will be provided and mapped
by the USFS. The USFS will compile the mapping units as part of the
soil survey for the project area. Information on rates of infiltration
is currently not available, but is of interest to the USFS and could be
obtained by USFS soil scientists.
▪ Estabrook, Ferndale, New Cheesman Reservoirs. The USFS has
indicated that most of the project areas (all USFS lands) were mapped
during the spring and summer of 1984. Any portions of the project area
for which soils mapping is lacking will be determined through consulta-
tions with the USFS. These areas should be mapped by the USFS at the
same intensity (Order 2) as the USFS survey. The USFS survey will
provide the basis for the development of mapping units.
In addition to soils mapping, physiochemical data have been
recorded for all soil units by USFS as part of their soil survey. Data
for each soil series mapping unit will be obtained from USFS by ES and
compiled as part of the soil survey for the project area. Information
on rates of infiltration is currently not available, but is of interest
to USFS and could be obtained by USFS soil scientists.
4-37
Williams Fork Gravity/Pumping. As part of an SCS-USFS soil
survey, physiochemical data have been recorded for all soil units.
Data for each soil series mapping unit will be obtained by ES from the
SCS-USFS and compiled as part of the soil survey for the project area.
The USFS will be consulted to determine what, if any, additional
physiochemical data will be obtained.
Gross Reservoir. The unmapped portions of the project area
will be mapped at the same intensity as the SCS survey (Order 2) by the
USFS. The SCS survey will provide the basis for the development of
mapping units. The new information will be compiled with the available
data by ES.
In addition to soil mapping by the USFS, physiochemical data have
been recorded for all soil units by the SCS as part of their soil
survey. These data for each soil series mapping unit will be obtained
from the SCS and compiled as part of the soil survey for the project
area. Information for any parameters which is currently not available,
but which will be required by the USFS, will be obtained by the USFS.
The USFS will be consulted to determine what , if any, additional
physiochemical data will be obtained.
Analyses to be Conducted
An initial activity of this resource analysis (figure 4.5) will be
the formation of a technical Soils Work Group by the COE. The Work
Group will review and comment on work products and participate in the
formation of impact assessments and development of mitigation alter-
natives. The plans for all project development, including construc-
tion, operations, and decommission of nonpermanent facilities, will be
reviewed by the Work Group along with the pertinent soils baseline
information. DWD will provide project summaries of feature maps and ES
will provide available baseline information.
The evaluation criteria developed for use in the SEIS will be
reviewed by the Work Group, edited as needed, and used by ES to make
the impact assessment. No more than three possible means of mitigating
impacts of nonpermanent disturbance will be identified by the Work
Group. Cost estimates for the mitigation programs will be supplied by
ES, following meetings with the Work Group to determine the extent of
mitigation to be considered and data requirements to develop the
potential mitigative measures.
Report Preparation
Technical appendix 4 of the S/SSEIS , as prepared by ES , will
include the following soil information: (1) a baseline soil survey of
the project area complete with mapping unit descriptions, (2) a review
of additional pertinent literature, (3) an assessment of project
•— impacts on soils, (4) plans for mitigating impacts of nonpermanent
4-38
disturbance developed by the Work Group, and (5) costs for implementing
mitigation as estimated by ES.
4-39
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WATER QUALITY
Objectives
The evaluations of the potential impacts of the proposed site-
specific projects on water quality will identify and evaluate the
significance of:
• Changes in predicted water quality levels of impacted streams
and reservoirs (figure 4.6), with reference to Colorado standards which
are determined applicable by the Work Group;
▪ Changes in the predicted eutrophication rates of existing and
new reservoirs impacted by project implementation, with reference to
eutrophication rates of existing reservoirs in the study areas; and
• Changes in predicted salinity of the Colorado River immed-
iately downstream from the proposed project areas and at the Inter-
national Border, as determined applicable by the Work Group.
The COE, Forest Service, EPA, and Colorado Department of Health
will require certain water quality data and information to perform the
analyses for their permit and authorization requirements. The infor-
mation base developed in meeting the above impact analysis objectives
(in combination with hydrologic, fisheries, and other data) will be
sufficient for these evaluations. Other objectives which have multi-
resource implications concern stream channel geomorphology, including
bank stability; sediment and bedload parameters; and other data related
to the determination of bypass flow requirements and water quality.
Data Collection
Identification of Data Gaps. In order to characterize and evalu-
ate the potential water quality changes due to project implementation,
the following technical information is needed:
1. Monthly average values for selected water quality parameters
at locations upstream and downstream from project-impacted waters. The
parameters selected as indicative of prevailing water quality con-
ditions are temperature, pH, specific conductance, total dissolved
solids, suspended solids, total and ortho-phosphate, nitrates, and
ammonia.
However, these parameters will be reviewed by the Work Group and
parameters may be added or deleted.
2. Seasonal data on inorganic forms of nitrogen and phosphorus
present in existing and potential inflows to project reservoirs, in
existing project reservoirs, and in areas downstream from existing
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reservoirs and proposed reservoirs. Also, concurrent information on
stream and reservoir hydrologic and hydraulic properties will be
required (such as, flow rates, lake volumes, lake fluctuations, and
turnover rates) . Finally, the vertical profile of temperature levels
in proposed reservoirs is needed to predict potential thermal impacts
on downstream water quality.
3. Background information on nutrient loading to, and trophic
status of, existing reservoirs in the study areas. Prediction models
for reservoir eutrophication will be based on nutrient loadings and
hydraulic features.
4. Average and low flow data (Q7_10) for all project-impacted
streams.
5. Salinity data for the Colorado River at locations just
downstream from the entrance of the Blue, Williams Fork, and Fraser
Rivers; at Dotsero; the Grand Valley at Imperial Dam; and near the
U.S.-Mexico border. The Bureau of Reclamation mass-balance method will
be used to project any project-related salinity changes.
Studies Required to Fill Data Gaps. The DWD conducted a prelim-
inary review of the frequency and type of water quality data available
for the 34 stations required in the site-specific evaluation of water
quality impacts (table 4.1) . Currently, data are available for 27 of
the 34 stations. Sampling frequency is usually quarterly and annually,
although monthly data are available for the State Department of Health
stations. The types of analyses performed on samples collected by the
DWD essentially match the data needs.
Concerning the acquisition of needed water quality data, the water
quality data now being collected by State and Federal agencies and the
DWD for the study should be adequate for the anticipated impact analy-
sis. This assumption will be reviewed by the Work Group during its
early meetings and possible needs for additional sampling will be
identified.
An extended analysis of the nutrients will be performed on water
quality samples collected for existing and potential reservoir inflow
and outflow sites. Specifically, these are stations 1, 2, 4, 5, 6, 7,
9, 10, 13, 14, 16, 17, 25, 26, 30, and 31 (table 4.1) . On a seasonal
basis, the water samples will be analyzed for:
1. Nitrogen forms
(a) total Kjeldahl
(b) nitrate
(c) nitrite
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(d) ammonia
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(f) particulate (suspended) organic nitrogen
2. Phosphorus forms
(a) total phosphorus
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(e) particulate (suspended) organic phosphorus
Additional parameters may be added by the Work Group.
Nutrient balance and eutrophication studies have been conducted
for Dillon Reservoir and Chatfield Lake by others. These efforts will
be reviewed and should provide sufficient background data for use in
evaluating potential changes in these reservoirs (nutrient dynamics or
trophic status) related to site-specific project implementation. The
Vollenweider Model, or a similar input/output model, will be used by ES
to predict trophic status of other reservoirs under alternative nutri-
ent loading rates. The Work Group will be involved in model selection,
based on prior Clean Lakes studies performed in study areas. No
additional work will be performed by ES on model development.
Given existing and anticipated information on stream hydrology and
total dissolved solids (TDS) concentrations in the study areas for
potentially project-impacted streams, there will be sufficient infor-
mation to estimate salinity changes in the Blue, Williams Fork, and
Fraser Rivers and at Dotsero and Grand Valley on the Colorado River.
Salinity values will be computed for low, average, and high flow
regimes in the project areas. Using these data as input, the equations
of the Colorado River Simulation System methodology (developed by the
U.S. Bureau of Reclamation) will be used by ES to estimate the magni-
tude of change in salinity in the Colorado River water at Imperial Dam
(Arizona—California) .
Analyses to be Conducted
The initial analysis by ES will address the potential water
quality impacts from a regulatory perspective. Any predicted changes
in the quality of existing streams and surface waters of reservoirs
will be evaluated by ES in terms of the Colorado Water Quality Stand—
ards. Also, the impacts of the proposed projects on the assimilation
capacity of downstream reaches will be determined by ES, based on
changes in discharge volumes. The Work Group will review the adequacy
of these analyses.
The second type of analysis performed by ES will predict the
trophic status of new reservoirs and the expected changes in the
trophic status of existing reservoirs that will be affected by the
4-48
site-specific projects. The background eutrophication rates for each
type of reservoir will be defined using the nutrient loading approach
(Vollenweider Model or similar). The analyses will focus on ident-
ifying and characterizing situations where changes in nutrient loading
may occur as a result of project construction or operation. Addition-
ally, existing nutrient information for other nonimpacted lakes in the
study area will be reviewed and used as a reference. The Clean Lake
Model for Dillon Reservoir will be used to forecast water quality under
postproject conditions. Finally, an explanation will be provided on
the expected sensitivity of impacted existing and new reservoirs to
additional (nonproject-related) changes in nutrient loadings.
Finally, water quality analyses will focus on the prediction of
salinity changes in the Colorado River at the previously mentioned
stations due to water diversions implemented by one or more site-
specific projects.
ES will participate with the Work Group in the development of any
mitigation plans. ES will prepare the cost estimates for any mitiga-
tion plans.
Activities necessary to accomplish the above analyses are ident-
ified and scheduled in figure 4.7.
Report Preparation
Technical appendix 4 as prepared by ES will contain narrative
discussions and graphic presentation of baseline data gathered by ES
and analyses of the water quality impacts of the site-specific projects
as performed by ES. Potential impacts will be characterized by ES for
each project in terms of the SEIS evaluation criteria (appendix B) .
4-49
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CHANNEL STABILITY
Objectives
The USFS has flow requirements that must be maintained in order to
maintain and to protect resources in the national forests. These
requirements are based primarily on the necessity to maintain the
hydrologic character of a stream or stream network. Other factors
incorporated into these requirements include aquatic resources,
aesthestics, and recreation. The minimum flow requirements for a
stream may or may not be equivalent to instream flow requirements
developed by the Colorado Water Conservation Board.
The evaluations of the potential impacts of the proposed site-
specific projects on channel stability will identify and evaluate the
significance of:
1. Possible changes in future stream discharge patterns as a
result of water diversions due to proposed projects and
2. Possible changes in future stream discharge patterns as a
result of water additions due to proposed projects.
Stream segments will have increased, decreased, or modified flow
patterns as a result of project operations. These can all affect
channel stability. In the Williams Fork basin, the streams downstream
from diversions will experience reduction in streamflow. The remaining
portions of the DWD Moffat Tunnel system will generally experience
increases in streamflow to Gross Reservoir. The North Fork system is
expected to experience increased streamflow as inflow to reservoirs
which outflow from the Estabrook, Ferndale, and New Cheesman Reservoirs
and may represent variations in historic flow that are neither con-
sistently increasing nor decreasing. The Blue River downstream from
Dillon Reservoir would experience a reduction in streamflow. These
general conditions will require further definition and classification
prior to conducting the channel stability analysis.
Major areas of evaluation will include:
1. Channel geomorphology,
2. Bank stability, and
3. Sediment and bedload parameters.
Data Collection
Identification of Data Gaps. Stream channel morphology impacts
will require analysis of the project hydrology and changes in stream
4-52
channel conditions. The necessary data base will include information
on stream hydrology, bank stability, character of bed and bank mater-
ials, channel pattern, sediment and bedload parameters, stream cross-
sections, velocity, water profile slope, channel and adjacent flood
plain roughness, and substrate characteristics.
Studies Required to Fill Data Gaps. Information on stream
stability and geomorphology has been collected as part of work done by
the DWD in the North Fork of the South Platte River and for South
Boulder Creek. The CDOW and DWD have collected some data in connection
with aquatic studies. A substantial amount of data on channel charac-
teristics for the main streams in the upper South Platte River system
has been collected by the USFS. Additionally, the U.S. Fish and
Wildlife Service (USFWS) has channel data for selected streams in the
site-specific study areas.
The above data base will be assembled and reviewed by the Work
Group to determine adequacy and completeness. Significant data gaps
will be filled by field work in the spring, summer, and possibly fall
of 1985. The USFS will collect these data under contract with the DWD.
Analysis to be Conducted
Stream discharge data will be developed by the DWD with and
without the proposed project(s) for each of the potentially impacted
streams. Key points of evaluation will be magnitude and timing of
discharge peaks and depletion (or addition) of flow to the downslope of
the discharge hydrographs. The USFS will perform the impact analysis
using USFS methodologies. The USFS also will prepare mitigation plans
and cost estimates.
Report Preparation
Technical appendix 4 will be prepared by ES using information
provided by the USFS and the Work Group. It will contain narrative
discussions and graphic presentation of baseline data and impact
analyses conducted by the USFS for predicting the channel stability
changes caused by the site-specific projects. Figure 4.8 identifies
and schedules the activities necessary for the development and com-
pletion of the report.
4-53
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VEGETATION
Objectives
The amount and kind of vegetation change that occurs as the result
of reservoir or other water system construction has important implica-
tions to the local biological environment . Both terrestrial and
aquatic communities can be affected. Wildlife habitat, water quality,
productivity of aquatic biota, grazing capacity, and soil erosion are
all influenced by the general condition of the prevalent plant commun-
ities. Changes in the composition and abundance of local vegetation
can significantly affect these related concerns.
Vegetation data are necessary for a comprehensive evaluation of
potential impacts to vegetation and for development of mitigation
measures to lessen these impacts. The vegetation information will
include a 1:24,000 vegetation map with community mapping unit descrip-
tions.
Data Collection
Identification of Information Gaps.
Two Forks Reservoir. The available vegetation information
for the project is not sufficient for impact analysis in the S/SSEIS.
Available data include general plant community mapping (scale 1:24,000)
and descriptions developed from SCS county land use and natural com-
munity mapping by county (scale 1:126,720) and USFS cover mapping.
However, both mapping sources are general in intensity and are not
site-specific. The plant community descriptions comprised of percent
area composition, list of dominant and associated species, and an
estimate of herbage production have been developed from the literature.
Data which are lacking at the site-specific level include Work
Group-approved plant community maps and descriptions and quantitative
data on the timber resource for areas to be disturbed.
Estabrook, Ferndale, and New Cheesman Reservoirs, Chatfield
Lake. The available vegetation information for the project areas is
not sufficient for the preparation of the S/SSEIS. Data which are
lacking at the site-specific level are Work Group-approved plant
community maps, and quantitative data on the timber resource, if
present, for areas to be disturbed.
Williams Fork Gravity/Pumping. The currently available
vegetation information for the Williams Fork system is not sufficient
to prepare the S/SSEIS. Available data include general plant community
mapping (scale 1:24,000) and descriptions developed from SCS land use
and natural community maps (scale 1:126,720) and USFS cover maps.
.-. However, both mapping sources are general in intensity and are not
site-specific. The plant community descriptions, comprised of percent
4-55
area composition, list of dominant and associated species, and an
estimate of herbage production, have been developed from the litera-
ture. A species list and quantitative vegetation data (frequency,
cover) are presented for several proposed areas of disturbance (CH2M
Hill, 1976).
Data which are lacking at the site-specific level are Work Group-
approved plant community maps and descriptions and quantitative data on
the timber resource for areas to be disturbed.
Gross Reservoir Enlargement. The currently available vegeta-
tion information for the Gross Reservoir area will not allow prepar-
ation of the S/SSEIS. Existing data consist of general plant community
maps (scale 1:24,000) and descriptions developed from SCS land use and
natural community maps (scale 1:126,720) and USFS cover maps. However,
both mapping sources are general in intensity and are not site-
specific. The plant community descriptions, comprised of percent area
composition, list of dominant and associated species, and an estimate
of herbage production have been developed from the literature.
Data which are lacking at the site-specific level are Work Group-
approved plant community maps and descriptions and quantitative data on
the timber resource for areas to be disturbed.
Studies Required to Fill Data Gaps. To upgrade the vegetation
information to a level descriptive of the sites and of sufficient
detail to make site-specific evaluations, a more refined vegetation map
and field-verified plant community descriptions will be developed by
the DWD with Work Group concurrence. Plant community mapping will be
initiated on recent stereoscopic photography of the project area at a
scale of 1:24,000. A field reconnaissance survey of the project areas
by the USFS and the Work Group will follow to verify/amend map unit
boundaries and dominant and associated species list of plant commun-
ities. The collection of quantitative data for project area plant
communities will be done for the forest communities; however, meetings
with the permitting agencies will be conducted to finalize requirements
and approve the scope of work for the studies.
The USFS has indicated that a stage two forest inventory to
quantify the timber resource of the project area should be conducted
prior to any project-related disturbance. The Work Group will select a
representative stand for each forest community type in the project area
and quantitative data will be collected by the USFS and DWD to assess
canopy density and timber volumes.
Analyses to be Conducted
For all projects, plans for project development, including con-
struction, operations, and decommission (nonpermanent facilities) ,
4-56
e-.
vegetation baseline information for the project area, and detailed
vegetation information for the disturbance areas, will be provided by
the DWD. These will be used by the USFS to assess project impacts on
vegetation. Any changes in vegetation characteristics can be critical
changes in habitat for economically important wildlife species,
threatened and endangered species, and timber yields.
Utilizing the SEIS evaluation criteria (appendix B) , a complete
and final assessment will be made by ES, using the available data base
and additional literature review. No more than three impact mitigation
alternatives for adverse disturbance will be identified by the USFS and
the Work Group. Cost estimates for preparing mitigation programs will
be developed by ES as part of this work effort.
Report Preparation
After the studies have been completed (figure 4.9), technical
appendix 4, as prepared by ES, will include the following vegetation
information. The responsibility for producing each item of information
to be incorporated in the technical appendix 4 is noted.
1. Detailed vegetation mapping, including digitization, and plant
community descriptions for areas to be disturbed or eliminated by
project development (DWD with verification by USFS and Work Group);
2. A baseline vegetation survey of the project area (DWD/ES with
Work Group review);
3. A stage two forest inventory will be conducted by the USFS, if
required, for selected, representative stands of forest community types
(this will require identification of timber volumes of the project
areas and the valuation of forest products which will be harvested as a
result of project implementation);
4. A review of additional pertinent literature (ES and Work
Group);
5. An assessment of project impacts on vegetation (USFS with Work
Group review and digitization by the DWD);
6. A discussion of the availability of procedures and materials
to successfully revegetate nonpermanent areas of disturbance (USFS with
Work Group review);
7. Plans for mitigating impacts of nonpermanent disturbance (USES
with Work Group review); and
8. Costs for implementing mitigative procedures (ES with Work
Group review) .
4-57
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WILDLIFE
Objectives
Water resources development often involves substantial alteration
of wildlife resources through inundation of habitats, blockage of
migration corridors, fragmentation of habitat, and development of new
supporting habitats. The objectives of the wildlife analysis are to
evaluate potential effects on wildlife resource characteristics in
general and determine effects on special interest species and habitat
features. Determining changes in supporting habitats and changes to
aspects of the species' habitat which are essential for continued
welfare are the primary methods of evaluating impacts. This evaluation
approach will utilize a habitat-based impact methodology that will
satisfy Federal agency management requirements.
It is assumed that a habitat evaluation technique developed
recently by the USFS will be used as the primary method of analyzing
effects of proposed water development activities on wildlife resources.
This is a habitat-based system that can estimate existing habitat
quality, changes in the suitability of future habitat conditions,
and/or changes in population numbers for specific wildlife species
associated with forest ecosystems. The procedure was developed to
provide wildlife assessment capabilities for silvicultural practices.
However, it can be used to evaluate the effectiveness of different
forest habitat management approaches. It can be applied in nonforested
ecosystems, such as mountain meadows and sagebrush; however, modifica-
tions are required to develop species-specific habitat ratings.
The key underlying assumption of the evaluation procedure is that
wildlife habitat requirements in forested areas can be described
largely by combinations of five basic vegetation structural stages and
three canopy closure conditions. Changes in these characteristics in a
given area provide the means for determining the future habitat suit-
ability of that area for the wildlife species of interest.
The procedure relies on an individual data base for each of about
60 indicator wildlife species, which provides information on habitat
and other ecological requirements of the species. The data base is
called a species profile and contains both a narrative description of
its known habitat requirements and a series of habitat value matrices.
The habitat value matrices display the rank and relative value of each
vegetation structural and canopy closure category for each of the
different forest ecosystems the species is associated with. The
habitat values are determined by the capability of each forest struc—
tural stage (five choices) and canopy closure condition (three choices)
of each forested ecosystem type (nine choices) to provide the required
i-- rearing, feeding, cover, spatial, and any special habitat requirements
of each indicator species. Each species uses different combinations of
4-60
habitats and ecosystems. Provisions are incorporated to account for
seasonal habitat use differences, minimum habitat area requirements,
minimum viable population size, and differences in local habitat
values. The procedure does allow adjustments in the standard rankings
of habitat features to account for local conditions. The suitability
and use of each structural stage and canopy condition in each ecosystem
used by a species is rated with one of four category rankings, ranging
from no habitat value to optimum habitat value. The rankings are
standardized so that comparisons are possible among habitats and
ecosystems. The assignment of rating values provided in the matrices
is based on the combined use of existing scientific literature and
professional judgements of wildlife biologists.
The process of determining project-induced changes in wildlife
habitat availability, habitat quality, or population numbers of a
particular species consists of comparing existing, preproject to
modified, postproject habitat conditions. Existing habitat conditions
are determined for each indicator species by segregating the geograph-
ical area of interest into ecosystems and habitat types. The habitat
types are identified in terms of the structural and canopy closure
categories previously mentioned. The condition (quality) of each
habitat type is compared to the appropriate habitat rating value matrix
for the species in that particular ecosystem type. An individual
habitat type value is thus generated which, when combined with values
for other habitat types, provides an overall rating for the entire area
for that species. The process is repeated for each different species
of interest and for all ecosystems. Future habitat conditions with the
project are determined by reevaluating the same geographical area;
estimating the anticipated structural and canopy changes in each
habitat type; and the size (area) of each habitat type remaining.
The data requirements described below are necessary for a compre-
hensive evaluation of project impacts on wildlife resources. The
requirements for additional data differ by species and by project area
because the completeness of the existing information varies by project
area. The evaluation of wildlife impacts will be approached from both
a species-specific basis and a habitat-association perspective.
Species of special or high concern, such as big game, will be evaluated
on an individual basis, using both population- and habitat-related
information. Wildlife groups, such as songbirds, small mammals, and
fur-bearers, which have very diverse biological requirements, will be
evaluated in a more general sense, using habitat association/affinity
relationships.
The SETS criteria will be reviewed by the Work Group and the
selected criteria will be used to quantify the degree of potential
impacts and to provide a foundation for evaluating the amount of
4-61
mitigation required. This procedure will assist in calculating mitiga-
tion methods and criteria. Supplemental field studies are intended to
provide the basis for answering the following key questions:
1. Which important and/or key interest species are present, where
are they found, what is the current population status, and how is their
welfare linked to the project area?
2. What effects will project construction have?
3. What effects will project operation have?
4. What kind of project mitigation is needed, feasible, and how
much will it cost?
5. How much key wildlife habitat will be lost and/or permanently
degraded through direct and indirect project effects?
6. Have the concerns of all interested parties been incorporated
and addressed by the analyses?
Data Collection
Identification of Information Gaps. Data which will be required
to analyze project effects to wildlife in site-specific detail are
listed by project below:
Two Forks.
I. Average number of mule deer migrating between summer and
winter ranges;
2. Average number of deer using winter range and the areal extent
of each type of winter range in the project area;
3. Number of elk using winter ranges and the areal extent of each
type of winter range in the project area; and
4. A habitat quality analysis for species selected by the Work
Group.
. Estabrook, Ferndale, and New Cheesman Reservoirs.
1. A habitat quality analysis for deer, elk, songbird, duck, and
beaver/muskrat;
2. Location of big game winter ranges for mule deer, elk, and
bighorn sheep and an estimate of the approximate number of animals of
each species using the area;
.�+ 3. Location of areas used for calving, fawning, and lambing as
appropriate;
4-62
4. Location of big game migration corridors;
5. Location of waterfowl concentration areas;
6. Big game density (mule deer, elk, bighorn sheep, bear, lion)
for summer range and winter ranges (each species treated separately);
and
7. Estimates of habitat quality for each big game species.
▪ Chatfield Reservoir.
1. Location, description, and mapping of high value or concen-
tration areas for wildlife;
2. Location, description, and estimate of numbers of birds
annually using rookeries within the project area;
3. Location of feeding areas for wading birds using any rooker-
ies; and
4. Location and descriptions of waterfowl concentration areas.
. Williams Fork (Pumping and Gravity).
1. Location/routes of elk migration and Pumping/Gravity corridors
in upper basin;
2. Estimated numbers/percentages of individuals using each
migration corridor;
3. DWD annual elk monitoring data for 1983 and 1984; and
4. A habitat quality analysis for elk.
. Gross Reservoir.
1. A habitat quality analysis for species selected by the Work
Group.
. All Projects.
1. A proposed, detailed wildlife habitat restoration plan spe-
cific for each project site and correlated with the overall revegeta-
tion plan for each site.
Studies Required to Fill Data Gaps. Field measurements of habitat
parameters are required to evaluate wildlife models for selected
species for terrestrial habitat quality analysis. This analysis will
require Work Group meetings to select species for the evaluation.
Field work to collect habitat data will be necessary at each project
4-63
site. USFWS/CDOW will collect habitat data which will be necessary at
each project site.
Determination of elk migration pattern into/out of the Williams
Fork basin is being made by the DWD and will be reviewed by the Work
Group. Fall/winter elk movement patterns are probably too disrupted by
hunting activities and the tendency of elk to remain in dense timber
during this time of year must be determined. Migration data collected
by the DWD during spring 1984 may be suitable for this purpose. The
elk movement study for the Williams Fork drainage will provide data for
the evaluation of future project construction impacts on overall herd
movement, integrity, productivity, and use of alpine summer range.
Determination of mule deer and elk numbers using winter ranges
should be made using aerial surveys; at least three counts at 1-month
intervals are preferable. Project areas requiring counts are those for
Two Forks, Ferndale, Estabrook, and, possibly, New Cheesman Reservoirs.
These studies are being made by the DWD and will be reviewed by the
Work Group. The big game winter range surveys proposed for the Two
Forks, Estabrook, Ferndale, and, possibly, New Cheesman project areas
will quantify the current numbers of deer/elk/bighorn sheep that
currently use the winter ranges. The CDOW presently has rough esti-
mates of the number of animals dependent on the range.
Analyses to be Conducted
Literature and field data will be summarized by ES to provide
descriptions of the existing status of wildlife resources in each
project area. The data will be used to provide:
1. Maps and locations of high value habitats and resources,
2. Quantification of key species populations affected,
3. Characterizations of key species and wildlife assemblages
(such as songbirds) ,
4. Quantification of existing habitat conditions/quality, and
5. Inventory of key species.
The wildlife impact analysis to be conducted by the USFS is
expected to tabulate habitat losses for a key species as well as
groups, such as small mammals, songbirds, furbearers, waterfowl, and
raptors. The USFS is expected to make estimates of habitat quality
degradation and losses for deer, elk, bighorn sheep, bears, and lions
based on habitat requirements and tolerance to human presence. The
habitat quality analysis will quantify existing habitat conditions and
will project habitat losses under future project conditions. The
4-64
difference in pre- and postproject conditions will establish part of
the mitigation needs for wildlife. The impact analysis conducted by
the USFS will also consider potential large-scale effects of the
interruption and/or blockage of big game seasonal movement patterns.
The USFS wildlife impact analysis will then be incorporated into a FWCA
report by the USFWS.
Wildlife mitigation alternatives will be developed by the USFS,
with assistance from the Work Group, for each project area. The USFWS
mitigation policy, issued in 1980, will be employed as a guideline.
The associated costs of each alternative will be estimated by ES to the
extent permitted by planning details and regulatory comments.
In addition to the evaluation criteria used in technical appendix
4 to the SEIS (appendix B) , the following criteria are proposed for use
in evaluating project impacts on wildlife. ES will perform the
criteria analysis based on information furnished by the USFS.
Unit of
Criterion Measurement
Costs of wildlife habitat mitigation/
enhancement measures. dollars
Acres of waterfowl habitat lost/gained. acres
Average number of (deer/elk/bighorn sheep)
dependent on winter range. number
Acres of big game habitat degraded from
good and moderate quality to fair and poor
quality (each key species analyzed separately). acres
Number of net habitat units lost
for each terrestrial wildlife species selected
for analysis (each species analyzed separately) .
(Note: Recommend five species to cover big
game, nongame, furbearers, and waterfowl.) HUs
Report Preparation
The evaluations of the effects of each site-specific project on
wildlife resources will be described in detail in technical appendix 4
by ES. The activities identified for this evaluation are scheduled in
figure 4.10.
4-65
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