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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5.2.11 Tri-Town Basin Reach Tl: WCR 24

The improvements in the Tri-Town Basin begin in Reach Tl and are focused on: (aY the
transition of flows from the major drainageway into the improvements associated with the Godding
Hollow Basin; (b) channel improvements upstream and downstream of WCR 24; and (c)
installation of a crossing structure beneath WCR 24. The specific improvements to Reach Tl are
presented below and also in Figure S .12.

I. Transition to Godding Hollow Drainageway In the vicinity of the northern lake
associated with The Shores Development, the major drainageway for the Tri- Town
Basin will transition from an improved channel into the lake. Stabilization
measures will be required at this location.

2. Channel Improvements This improvement consists of the construction associated
with a conveyance channel from the transition into the lake to a proposed regional
pond located downstream of WCR 22. Approximately 7.600 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: 1 V, and design depth that varies from 4 to 6 feet. At the
upstream end of the channel improvements, a transition structure is required to
stabilize the outflow from the proposed regional pond.

3. WCR 24 Crossing Structure In conjunction with the conveyance channel, a
crossing of WCR 24 will be required. This crossing will consist of a structure with
a minimum opening that is 4'H x SO'W. A drop structure is also required in the
vicinity of this crossing to ensure that stormwater runoff will be conveyed beneath
WCR 24.

5.2.12 Tri-Town Basin Reach T2: WCR 22

The improvements in Reach T2 are focused on: (a) construction of two regional detention
ponds; and (b) replacement of an existing crossing of WCR 22. The specific improvements to
Reach T2 are presented below and also in Figure S .13.

I. Regional Detention Ponds To reduce the peak flows within the major
drainageway, two regional detention ponds are proposed north and south of WCR
22. For the pond located north of WCR 22, 10S acre-feet of storage is required
which will necessitate the acquisition of approximately 38 acres along with the

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5.26

September 8, 1999