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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facilities that do exist along the major drainageways are not related to land development and can
be characterized as detention storage created by roadway embankments, Several additional
detention facilities, not located on the major drainageway, also exist and are effective in reducing
the peak discharge. These off-channel detention areas are also typically related to storage created
by existing embankments, Minor detention facilities also exist within the Godding Hollow and
Tri- Town Basins. These minor facilities provide for a reduction in peak flows locally, but offer
a limited significant reduction of peak flows along the major drainageway. Consequently, they
were not specifically inventoried during the master planning effort. These minor facilities were
included in the hydrologic analysis, however, to define existing conditions as discussed in Chapter
4.

3.1.1 (,y()dding Hollow Basin

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The existing detention facilities identified within the Godding Hollow Basin which were
effective in reducing the peak discharge in the major drainageway are described in the following
paragraphs and are presented on Sheet 1.
Slilte Highwa.y 52/CoaJridge Ditch Detention Pond. This detention pond is located in the
upper portion of the Godding Hollow Basin immediately south of Slilte Highway 52, The roadway
embankment associated with State Highway 52 is elevated approximately 14.5 feet above the invert
of the 8'H x 8'W RCB which releases runoff from the detention area, The canal embankment
associated with the CoaJridge Canal is located within the backwater created by the Slilte Highway
52 Detention Pond. This embankment is elevated approximately 14,1 feet above the invert of the
7'H x 7'W RCB which releases runoff from the detention area upstream of the canal, The two
detention areas fonn one pond during large events with water from the canal pond flowing directly
into the pond fonned by the State Highway 52 embankment. The volume provided behind the
roadway embankment prior to overtopping is 58 acre-feet with a corresponding release through
the existing box culvert of 1,000 cfs, The additional volume provided by the canal embankment
prior to overtopping is 32 acre-feet with a release rate of approximately 790 cfs, The 100-year
existing conditions discharge is estimated to be 4,010 cfs which corresponds to a combined storage
volume of 144 acre-feet and overtopping depths of approximately 1,9 feet for both State Highway
52 and the Coalridge Ditch embankments,
1-25/St.ate Hig)1way 52 Pond This detention facility is an existing pond located on the
major west tributary to the main Godding Hollow flow path, approximately 800 feet north of the
intersection of 1-25 and State Highway 52, The roadway embankment associated with 1-25 and
its frontage roads is elevated approximately 8 feet above the invert of the existing 36-inch siphon

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3.4

September 8, 1999