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
Sedgwick
In February 1998, Tuttle-Applegate, Inc. completed a report on the Sedgwick
Reservoir located 3 miles east of Sedgwick, Colorado, about 15 miles upstream of the
' Nebraska State line along the Lower South Platte River. The land for the proposed
reservoir site is privately owned and is currently under cultivation. A small west to
' east flowing intermittent drainage flows through the site. The site contains wetlands
based on USFWS wetland delineation mapping. The reservoir would have a capacity
of 2,230 acre-feet with a maximum normal pool at Elevation 3566. The reservoir
' could be filled by the Peterson Ditch or by wells. The contributing drainage area
above the site is estimated to be 7.5 mi2; however, the reservoir will be impounded
above ground. The only uncontrolled water reaching the reservoir would be
' precipitation on the reservoir surface. The dam would be a zoned embankment dam
with a height of 15 feet and a crest length of 15,000 feet. The total cost to build the
reservoir would be $2,850,000, or$1,280 per acre-foot of storage.
LSP Sites
A study was conducted in the spring of 1995 by RBD of three reservoir alternatives
on the south side of the Lower South Platte River near the towns of Ovid and
' Sedgwick, Colorado. They are off-channel reservoirs that would store alluvial
groundwater and benefit a wide variety of water users. Off-season yields from high-
capacity wells owned by GASP would be stored, then released to satisfy irrigation
priorities on the river during Compact periods. These sites are part of the Lower
South Platte Sustainment Project, which has been termed LSP in this study. Site"A"
' (LSPA) was selected as the preferred site, while sites `B"and"C"were not evaluated
because they would not meet project needs. Site"A"is located about 17 miles
upstream of the Nebraska State line along the river and 1.8 miles southeast of
' Sedgwick, Colorado. The site is privately owned and there would be no need for
relocation of buildings or roads for construction of the reservoir. The site can be
described as having steep abutments, an incised valley bottom, occasional outcrops
with slightly cemented siltstone and an assumed shallow depth to bedrock. No
known streams run through the site although it does contain wetlands based on
' USFWS mapping. The reservoir would have a storage capacity of 1,580 acre-feet
with a maximum normal pool at Elevation 3650. The dam would have a crest length
of 1,800 feet and a height of 40 feet and would be a zoned embankment dam. The
' reservoir could be filled by three existing groundwater wells that are located north of
the proposed reservoir site. The contributing drainage area to the site is 2.8 mi2. The
' total cost of the project would be $4,020,000, which is $2,540 per acre-foot of storage
capacity.
GEI Consultants, Inc. 4-5 01002 Dec 2001 Lower South Platte River Study