PROJ00137

• Contract/PO #: C153467
• Contractor Name: Greeley, City of
• Contract Type: Loan
• Water District: 0
• County: Weld
• Bill Number: XB 99-999
• Loan Projects - Doc Type: Feasibility Study

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The study was initiated by reviewing available reference material on file at
the City of Greeley and the SED. A list of these references was compiled.

Background information on the City of Greeley's history, laws, physical
assets, and present and future fi nanci al status was gathered. The Ci ty' s
water exchange plan with the North Poudre Irrigation Company for Colorado-Big
Thompson (CBT) water was also researched. The City's water requirements were
assessed as a functi on of popul ati on projecti ons and per capi ta use rates.
The water supply and project yield were determined using the Twin lakes
storage right. The firm annual yield from Twin lakes Reservoir at the present
restricted level is zero acre-feet.

If the dam were rehabilitated and enlarged to store its full decreed volume
and the restriction removed, the firm annual yield would increase to 454
acre-feet. The sediment yield in the Twin lakes Reservoir drainage basin was
estimated at nine acre-feet, for a 100-year project 1 ife. Water quality of
the Cache la Poudre River was analyzed and was generally found to be excellent
for domestic, municipal, industrial, and agricultural purposes.

A hydrologic analysis of the drainage basin was performed. A probable maximum
flood (PMF) was developed USing NOAA Hydrometeorological Report Number 55, and
allowing for infiltration losses using the Green and Ampt model. The computed
runoff hydrograph resulting from the local probable maximum precipitation
stonn resulted in a peak discharge of 8,420 cfs, with a volume of 465
acre-feet. The flood was routed through the reservoi r util i zi ng the HEC-l
computer program in order to detennine the required capacity of the spillway
to safely pass the PMF as required by the SED.

Field work commenced with a site inspection by several MKE personnel in
June 1986. At that time, a Phase I inspection checklist was prepared similar
to the form used by the SED. Several other inspections were made during the
course of the study, including a review of a video tape made by remote
controlled video camera inspection of the outlet works.

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