Lower South Platte River Study

• Contractor Name: Colorado Water Conservation Board
• Loan Projects - Doc Type: Feasibility Study

Lower South Platte River Study
Colorado Water Conservation Board
December 2001
' Hawk Springs Reservoir would inundate portions of the Duck Creek State Wildlife
Area. The CDOW was ready to proceed with implementation of a dam and reservoir
at this site in the mid-1980s. Plans and specifications were essentially completed
and the project was close to bidding for construction. As configured in the mid-
1980s, Hawk Springs Dam had a nominal height of 40 feet and storage volume of
' approximately 1,200 acre-feet. Significant subsurface investigations and design
analyses have been completed but would definitely need to be updated. The
embankment and outlet works configurations in the mid-1980s development plan are
' somewhat different than presented on Figures 4.2 and 4.3. However, the differences
are not significant enough to affect cost estimates at the present level of study. The
mid-1980s design configuration of the embankment tends to confirm assumptions on
' depth of excavation, dam slopes, and key trench made for the reconnaissance study.
Sterling Lateral East
The potential Sterling Lateral East Reservoir is located 2.5 miles north of Crook,
' Colorado, approximately 32 miles upstream of the Colorado-Nebraska State line
along the Lower South Platte River. The site has no distinct surficial geologic
features. The valley has broad, gentle slopes. A very small portion of the site is
' located within the boundaries of Duck Creek State Wildlife Area, with the majority
being privately owned. The relocation of paved county roads would be necessary for
' the construction of the reservoir, which also would impact ranch buildings. The
contributing drainage basin to the reservoir is 2.7 square miles. The reservoir could
be filled by the North Sterling Outlet Canal or by pumping water from Harmony
' Ditch. An intermittent stream runs through the site and wetlands are also present in
the reservoir basin area based on USFWS wetland mapping. The reservoir would
have a maximum normal pool at Elevation 3790 and a capacity of 4,900 acre-feet.
' The dam would be a zoned embankment with a height of 50 feet and a crest length
of 3,000 feet. The dam would cost an estimated $6,080,000 to build, or$1,240 per
' acre-foot of storage.
Sterling Lateral South
The proposed Sterling Lateral South Reservoir site is located about 31 miles
upstream of the state line along the Lower South Platte River, 1.5 miles north of
' Crook, Colorado. The land in the reservoir area is mainly privately owned, with a
small portion lying in the Duck Creek State Wildlife Area. The valley at the site has
broad, gentle slopes, but no distinct features. The contributing drainage area to the
' site, from an intermittent stream, is 6.8 square miles. The reservoir could be filled
by gravity from the North Sterling Outlet Canal or by pumping from the Harmony
' Ditch. It would be necessary to relocate a paved county road and several buildings
GEI Consultants, Inc. 4-14 01002 Dec 2001 Lower South Platte River Study