FLOOD08206

• County: Statewide
• Community: All
• Stream Name: All
• Basin: Statewide
• Title: Colorado State Hazard Mitigation Grant Program
• Date: 9/1/1997
• Prepared For: CWCB
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

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PIONEER DRAINAGE DITCH

According to the COE, bridges that require minor channel improvements under the existing deck are as
follows;

. At the fil.rm road approximately 2,600 feet downstream ofHWY 14
. Franklin Street and North Seventh Avenue
. Sidney Avenue

For the purpose of this report, soil cement erosion protection is also proposed at these bridge locations.

In addition to the' bridge improvements noted above, thc COE also identified several channel reaches
which require improvements. The proposed channel improvements typically involve widening the
channel bottom and re-garding the channel siqeslopes. In addition, the banks of the Pioneer Ditch will
need to be raised in some locations by benDing to contain the 10-year flows. A realignment of a
portion of the Pioneer Ditch is recommended! to permit a steeper grade. The channel would be
realigned through a vacant field beginning at the southwest comer of Franklin Street and Seventh
Avenue, The new channel will continue to the southwest for approximately 3,800 feet having a bottom
width of 20 feet and 3:1 sideslopes. Approximately 1,200 feet of berms are required on both sides of
the channel upstream of the bridge at North Seventh Avenue and Franklin Street to contain the IO-year
flows. The berms will be about 2 feet in height on average.

Finally, a detention facility is proposed on the north side of Division Avenue and Filmore Street to
relieve flooding of the channel downstream. This detention facility is described in detail in the COE
1995 Report. The facility would have a side-channel weir 75 feet in width to spill stomlwater from
Pioneer Ditch into the pond. The pond would have a capacity of 129.4 acre-feet and would reduce the
10-year peak discharge from 1,040 cfs to 300 cfs. Stonnwater would drain out of the pond and back
into the Pioneer Ditch via a 54 inch diameter outlet pipe. Again a 2 foot tall berm is required between
the pond and the Pioneer Ditch to confme stonnwater to the ditch,

Cost Estimates

Conceptual designs were prepared for tJie proposed improvements in sufficient detail to determine and
document construction quantities and, subseq~ntly, a planning cost estimate. Topographic mapping at
a scale of 1"=500' was used as base mapping for conceptual designs. Criteria used for preparing
quantities were as follows; I

. Channel Sections
.. Trapezoidal .",clion
.. Sized using normal depth or HEC-2
.. Sideslopes for the major channel improvements are 3:1

· Drop Stnlctures
.. Based on details in the COE 199.5 report

· Standard Berms
.. 10 feet top width
.. 3:1 sideslopes
.. Minimum I foot of freeboard

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