BOARD01841

• Board Meeting Date: 1/26/2000
• Description: CF Section - New Loans - Weld County Tri-Area Sanitation District - Stormwater Detention Facility
• Board Meetings - Doc Type: Memo

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The four communities have experienced severe flooding problems over the years due to
storm water runoff from the surrounding area. All four communities are partially located
in the 100-year floodplain as defined by the Federal Emergency Management Agency.

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The Weld County Tri-Area Sanitation District provides drainage services for Evanston,
Firestone and Frederick. (Drainage services for Dacono are provided by the City of
Dacono). In the last year, the District has participated in'a master drainage plan for the
Tri-Town basin and for a neighboring drainage basin. That study recommended a
regional detention pond near Frederick as a needed improvement for the Tri- Town Basin.

The Sear-Brown Group of Fort Collins subIl1itted a feasibility study for the project in
January of this year. Rocky Mountain Consl1ltants of Longmont provided the preliminary
design and cost estimate for the detention pond.

Proiect SDonsor

The WCTASD was established in 1956 to provide wastewater collection and treatment
facilities for Evanston, Firestone and Frederick. The District owns and operates a
wastewater collection and treatment system with an asset value of about $1.8 million.
Since the mid-1980's, the District has also assumed the responsibility for storm water
control within the District service area. A storm water enterprise fund was established in
1999. Some selected characteristics of the District are presented in Table I.

Table 1. WCTASD, Selected Characteristics

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Service Area Population . 3,555
Number of Taps 1,185
Monthly wastewater service charge $9.00
Mill levy 0.144 mills
Monthly storm water service charge $4.00
Estimated 1990 median household income $31,685

ProDosed Proiect

The purpose ofthe regional detention pond project is to reduce the peak historic flows in
the Tri- Town Drainageway downstream of the pond and thereby reduce the extent of
flooding in the three communities ofthe District. The pond would be located on 60 acres
of agricultural land immediately south of Frederick as shown on the attached map.

The detention pond will have the capacity to store 146 acre-feet during the 100-year
storm event. Maximum inflow to the pond during the 100-year storm event will be about
2,000 cubic feet per second (cfs) and the pond will be designed for a maximum release
rate of 567 cfs thus providing significant attenuation of the peak discharge. The Town of
Frederick will increase the capacity of the existing drainage channel to 567 cfs from the
pond outlet to 151 Street.

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