WSP13020 ‎(2)‎

• File Number: 8430.500.60
• Description: Denver Water
• State: CO
• Basin: South Platte
• Date: 9/15/2003
• Author: USACOE/Denver Water
• Title: MOFFAT Tunnel System Project Information Document / EIS
• Water Supply Pro - Doc Type: Publication

~ Moffat Collection System Project Alternatives

The three alternatives described below, or a combination of these alternatives, are
reasonable options to address the problems defined earlier given the water rights,
property and facilities owned by Denver Water that could be used to provide new supply
to the Moffat Treatment Plant. As stated previously, Denver Water has not selected a
project and fully expects additional alternatives will be brought forth during NEP A
Scoping that could also address the problems. The NEP A environmental analysis will
provide a thorough, comprehensive disclosure of impacts associated with these three
alternatives, and other reasonable alternatives that are identified during the NEP A
process. The following discussion describes some of the potential environmental issues
associated with the presently identified alternatives,

Gross Reservoir Enlargement

Located 35 miles northeast of Denver in the Rocky Mountain Front Range, Gross
Reservoir is the work horse of Denver Water's Moffat Collection System. The
41,811 acre-foot reservoir was constructed in 1955, The predominant source of inflow to
Gross Reservoir is water diverted from the Williams Fork and Fraser rivers in the Upper
Colorado River basin, which is conveyed to South Boulder Creek through the Moffat
Tunnel.

Gross Reservoir occupies U.s. Forest Service and Denver Water lands. The landscape
surrounding the reservoir is characterized by primarily Ponderosa PinelDouglas-fir forest
and to a much lesser extent, mountain grasslands (Figure 6). The immediate vicinity of
Gross Reservoir is undeveloped although there is dispersed residential development and
several state, county, and city open space parks located nearby.

In March 2001, the Federal Energy Regulatory Commission (FERC) issued a new license
(Project No, 2035-006) for Gross Reservoir authorizing the continued use ofthe reservoir
for water supply purposes and construction and operation of a 5-megawatt hydropower
facility. The license recognizes that power generation is ancillary to the primary
operation and use of Gross Reservoir as a municipal water supply, License conditions
include a recreation management plan for the reservoir, development and implementation
of an erosion and sediment control plan for social trails and roads, implementation of a
weed management plan, implementation of a dissolved oxygen monitoring plan,
implementation of a ramping rate plan to control the allowable rate of flow changes to
minimize impacts to the fisheries, and implementation of a power-line raptor protection
plan and sensitive species surveys, The license is being amended to allow for an increase
in capacity and relocation of the powerhouse.

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