WSP05425

• File Number: 8101
• Description: Arkansas River Basin Description
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 9/1/1962
• Author: High Plains SCD
• Title: Watershed Work Plan - Limon Watershed Protection Project - Elbert and Lincoln Counties - Colorado
• Water Supply Pro - Doc Type: Report/Study

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C=1757

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Structural Measures

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This work plan proposes the installation of three floodwater-
retarding structures (L-l, L-2, and L-3) on the three tributary
drainages which carry floodwaters into the Town of Limon, These
structures will be located approximately one-half mile north and
northwest of the corporate limits of Limon. They will consist of
rolled earth-fill darns with ungated concrete principal spillway tubes.
Emergency spillway will be provided by excavated earth sections.

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The locations of structures are shown on the Project Map, An
illustration of a typical floodwater-retarding structure is sho>m
on Figure 2.

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The reservoir areas behind these darns will have sufficient
capacity to provide storage for floodwater resulting fram storms
with a recurrence interval of 100 years. Additional storage will
be provided for the amount of sediment expected to accumulate over
a 50-year period, There will be no permanent storage of water,
and the reservoirs will be dry except during flood runoff.

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The total estimated cost of installing these three structures
is $209,544. The cost distribution is shown in Table 2, The
structures, as well as the reservoir areas above them, will be
located on rangelands under private ownership.

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The total storage capacity of the three structures will be
1,929 acre-feet, of which 1,778 acre-feet will be allocated to
flood detention and 151 acre-feet to sediment storage.

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The structures will control runoff from 13.33 square miles
or about 86 percent of the total watershed area. They will provide
floodwater detention storage for 2,50 inches/0f runoff from the
area controlled. The capacity equivalents 'of the sediment storage
are O.22-inch for structure L-1, a.21-inch for L-2, and O,20-inch
for L-3.

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The release rate of floodwater fram the structures through
the principal spillway tube varies with the water surface elevation
in the reservoir. The following table shows the maximum release
rates, average release rates, and time required to empty a full
reservoir.

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