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
Harmony Ditch West
The Harmony Ditch West Reservoir would be located approximately 28 miles
upstream of the Colorado-Nebraska State line along the Lower South Platte River,
3.5 miles northeast of Crook, Colorado. The land at this reservoir site is primarily
privately held, while a small portion of the site appears to be in state ownership. The
' dam site has gentle sloping abutments. There is a cemented sandstone remnant high
spot at a turn point in the axis alignment. Brule Formation bedrock is exposed in a
ft of axis alignment.h Jonson Draw This rucann
directly through the proposed site based on USGS mapping. The site also contains
wetlands, as delineated on USFWS mapping. Field observations suggest that the
' defined channel and wetlands are tributary to the Harmony Ditch and, therefore,
could be non jurisdictional due to lack of connection to waters of the U.S. A paved
county road crosses the reservoir basin and would need to be relocated. Several
' buildings are located within the reservoir basin. The reservoir would have a storage
capacity of 10,000 acre-feet and a normal maximum pool at Elevation 3760. The
' dam would be a zoned embankment with a height of 50 feet and a crest length of
4,400 feet. The reservoir could be filled by gravity from the North Sterling Outlet
Canal,by pumping from the Harmony Ditch, or by pumping from wells or a
diversion on the South Platte River. The contributing drainage area to the reservoir
is estimated to be 7.1 square miles. The total cost to construct the reservoir would be
$8,420,000, a cost of$840 per acre-foot of storage.
Hawk Springs
The proposed Hawk Springs Reservoir site is located about 30 miles upstream of the
Nebraska State line along the Lower South Platte River, 2.6 miles north of Crook,
' Colorado. The dam site has moderately steep abutments, Brule bedrock outcrops
exposed near the proposed axis and cemented sandstone erosional remnants
' downstream. The bedrock is believed to be at a shallow depth at the axis. There is a
small land surface slump feature in the downstream right abutment area. The
reservoir would inundate portions of Duck Creek and two of its tributaries and small
areas of wetlands delineated by the USFWS. Several relocations of paved county
roads are likely to be needed for construction of the reservoir, and several buildings
are located near the proposed site. The reservoir would have a capacity of 3,500
acre-feet with a normal maximum pool at Elevation 3760. The dam would be a
zoned embankment dam with a height of 50 feet and a crest length of 2,300 feet.
' Hawk Springs Reservoir could be filled by gravity from the North Sterling Outlet
Canal or by pumping water from Harmony Ditch. The contributing drainage area of
Duck Creek above the dam site is 12 square miles. The total cost to build the dam is
estimated to be$4,230,000, or$1,210 per acre-foot of storage.
GEI Consultants, Inc. 4-13 01002 Dec 2001 Lower South Platte River Study