FLOOD01374

• Designation Number: 521
• County: Weld
• Community: Erie, Firestone, Dacono
• Stream Name: Tri-town drainageway, Godding Hollow Basin
• Title: South Weld I-25 Corridor Master Drainage Plan
• Date: 9/8/1999
• Prepared For: Weld County
• Prepared By: Anderson Consulting Engineers, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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construction of an improved outlet structure. Construction of this pond will also
require the relocation of an existing irrigation lateral.

The pond located south of WCR 22 will require the acquisition of 28 acres of land
which will provide 139 acre-feet of detention storage. An outlet structure will also
be required.

2. WCR 22 Crossing Replace the existing 3'H x 5'W arch CMP crossing of WCR
22 with a structure with a minimum opening of 6.5'H x 30'W. Transitions from
the existing channel to the bridge crossing are required along with placement of
stabilization measures to control the potential erosion in the vicinity of the crossing.
In conjunction with replacement of the crossing structure, approximately 500 feet
of roadway should be raised a maximum of 2 feet.

5.2.13 Tri-Town Basin Reach T3: WCR 20/WCR III

The improvements in Reach T3 are focused on: (a) replacement of existing crossings at
WCR 20 and WCR 18; (b) construction of channel improvements near Milavec Reservoir; and (c)
construction of a regional detention pond. The specific improvements to Reach T3 are presented
below and also in Figure 5.14.

1. WCR 20 Crossing. Replace the existing 2.5'H x 3.5'W arch CMP crossing of
WCR 20 with a structure that incorporates a minimum opening that is 5'H x 50'W.
Transitions from the existing channel to the bridge crossing are required along with
placement of stabilization measures to control the potential erosion in the vicinity
of the crossing. In conjunction with replacement of the crossing structure,
approximately 720 feet of roadway should be raised a maximum of 3 feet.

2. Channel Improvements This improvement consists of the construction associated
with a conveyance channel along the east side of Milavec Reservoir and extending
through the crossings of WCR 18 and WCR 13. Approximately 2,800 feet of
channel improvements will be required. The channel improvements should include
a compound channel configuration, i.e., a low flow channel along with an overbank
area to convey flood flows. In addition, the channel incorporates a grass lining,
bottom width of 20 feet (low flow channel), maximum top width of 90 feet,
sideslopes of 4H:IV, and design depth of 4 feet. It should be noted that the Town
of Frederick is proposing to replace an existing access road crossing to Milavec
Reservoir which will cross the channel improvements.

3. WCR ]8 Crossing Replace the existing 17.5-foot bridge structure at WCR 18
with a structure that incorporates a minimum opening that is 5.5'H x 30'W.
Transitions from the existing channel to the bridge crossing are required along with

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5.27

September 8, J 999