PROJ00151

• Contract/PO #: C153449
• Contractor Name: North Poudre Irrigation Company
• Contract Type: Loan
• Water District: 3
• County: Larimer
• Bill Number: HB 85-1042
• Loan Projects - Doc Type: Feasibility Study

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the center to the top of the dam with two 36" control gates; and
new energy dissipator, drop structure, and Parshall Flume downstream.

A preliminary sketch of this proposed outlet 1S included 1n Appendix

"Fl!.

EMBANKMENT

A Preliminary Stability Analysis was completed by Chen and Associates,
Inc. and is included in their report in Appendix D. Their analysis
consiuered an 18 foot top width, 3:1 upstream slope, anu 2:1
versus 2~:1 downstream slopes. The apparent factor of safety for
the existing 2:1 downstream slope was 1.35 compared to a recommended
factor of safety of 1.5. Therefore, an additional analysis of a
backs lope at 2~:1 was completed.

Due to high winds in this area and the excessive erosion of the
upstream face, several alternates are considered for the embankment
reconstruction. Alternate "A" considers an upstrcam sl.ope of 3:1;
Alternate "B" an upstream slope of 3~:1; and Alternate "C" an up-
stream slope of 4:1. All three of these were presented with 12"
of filter gravel and 30" of riprap with an amount to be added to
provide for 18" of filter gravel and 36" of riprap.

In order to flatten the backs lope to a slope of 2~:1, an item for
backs lope excavation is includcd.

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Ibe core excavation and core fill items are proposed as a means of
cutting-off seepage below the dam. If this item were eliminated,
front face fill would be foundcu on the natural overburden material.
The core item does not necessarily include only low and wet exca-
vations.

Breach excavation and fill is separated as an item required for con-
struction of a new outlet works. If an alternative of repairing the
existing outlet were selected, the breach earthwork would be eliminated.

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