FLOOD09590

• County: Arapahoe
• Community: Aurora
• Stream Name: Cherry Creek Lake
• Basin: South Platte
• Title: Hydrologic Improvement Assessment Cherry Creek Lake
• Date: 9/1/1993
• Prepared For: State of Colorado
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Project

reservoir. The Colorado State Engineer then requested authority to retain this
water. The following year. the Governor of Colorado formally requested that the
Corps allow the Colorado Fish and Game Depart:ment to store 10.000 acre - feet of
water in the conservation pool for recreatioll',l use by the general public in the
Denver area. In 1960. the State requested an addi tlonal increase in the
conservation storage of 5,000 acre-feet to a total of 15,000 acre-feet. Approval
\o1as given and an elevation of 5550 feet m. s. 1. was set as the base of the flood
control zone. The highest pool level recorded at Cherry Creek Dam was 5565,8
feet m.s.l.. on 3 July 1973. and the maximum regulated release through the outlet
works was 560 c.f.s. in August 1965,

EMBANKMENT

The embankment is a rolled zoned earthfUl approximately 14.300 feet long

with a crest width of 30 feet and a maximum height of the .embankment is about 140

feet. The embankment crest was designed for .~n elevation of 5645 feet m.s.l.

The most recent survey indicated the low point of the crest was at 5644,5 feet

m. s .1, Plates 3 and 4 show the embankment plan. and t:ypical embankment cross

sections are shown on plates 5 through 9, The embankment contains approximately

14.000,000 cubic yards of fill which includes about 1.000.000 cubic yards used

for the cutoff trench. Embankment zoning includes an inclined impervious core

flanked on the upstream side by pervious fill and on t:he downstre;llIl side by

random fill with a 10-foot-thick pervious horizontal blanket at: the base of the

zone for through seepage. The horizontal pervious fill at the downst.ream shell

is drained by a 12- inch diameter collector system. This system is also connected

to a 30-inch-diameter collector pipe for fourteen 6-inch-diameter relief wells

a,t the downstream toe of the embankment. The foundation bedrock for the dam is

the Denver formation which is overlain to variable depths by overburden

consisting primarily of sands and gravels "ith some clay layers, A cut:off trench

backfilled with impervious material was incorporated in the dam for the entire

length. but the cutoff does not extend to bedrock in reaches of deep alluvium,

M:aximum depth of the cutoff is about 50 fe.~t. whereas maximum depth of the

alluvium is about 100 feet, Pressure relief wells have been installed at the

downstream toe to intercept flows through this gap in the cutoff, The collector

pipe for the relief wells discharges below the outlet works stilling basin. The

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