2010-04-20_REVISION - M1977300 ‎(5)‎

• Permit No: M1977300
• IBM Index Class Name: REVISION
• Doc Date: 4/20/2010
• Doc Name: EPP- AR#1, Groundwater Information
• From: Whetstone Associates
• To: DRMS
• Type & Sequence: TR11
• Media Type: D
• Archive: No

Environmental Protection Plan, Schwartzwalder Mine 8-5
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Figure 8-1. Average Flow Rates in Ralston Creek vs. Monthly Mean Precipitation
•
(i).2 Ralston Reservoir
Ralston Reservoir is part of Denver Water Board's Moffat Tunnel Collection System, one of three major
water collection systems that include diversion, collection and transmission facilities that store and
distribute raw water prior to treatment. The Moffat Tunnel Collection System captures water from the
Williams Fork River, the Fraser River, South Boulder Creek and Ralston Creek, and subsequently delivers
this water for use in the Denver area (Figure 8-2). Ralston Reservoir is classified as a "terminal reservoir"
because the water stored in the reservoir is fed directly to the Moffat water treatment plant.
Water from Ralston Reservoir supplies most of metropolitan Denver's northern suburbs and is also sent to
Clear Creek to replace downstream flows that Denver Water withdraws from the Upper South Platte River.
The source of water to Ralston Reservoir includes flows from the Ralston Creek drainage combined with
water from the western slope and the South Boulder Creek watershed (Figure 8-2). Rainfall and snow melt
from the western slope collect through natural channels and flow toward the Winter Park/Fraser area. From
Winter Park and Fraser, the water flows through the Moffat Tunnel under the continental divide. After
exiting the tunnel on the east side of the continental divide it continues through South Boulder Creek,
where it is stored in Gross Reservoir. Water released from Gross Reservoir travels by gravity through
natural streams and man-made canals to Ralston Reservoir.
Ralston Reservoir has a capacity of 10,749 acre-ft (3,502.6 million gallons [MG]) which is approximately
one-fourth the capacity of Gross Reservoir (41,811 acre-ft, 13,624.2 MG) (Denver Water, 2009). Denver
Water allows no public access or recreational activities on Ralston Reservoir. The reservoir site and the
area immediately surrounding it are fenced to limit access, and on-site caretakers discourage people from
violating these rules and provide timely response to any security breaches.
• Water that exits Ralston Reservoir is delivered to the Moffat water treatment plant via Denver Water's
Conduits 16 and 22. The water is treated at the Moffat plant distributed to Denver Water customers.
4109C.100419 Whetstone Associates 6
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