C150009 Project Completion Summary

• Contract/PO #: C150009
• Contractor Name: Boulder & Left Hand Irrigation Company, The
• Contract Type: Loan
• Water District: 5
• County: Boulder
• Bill Number: SPL
• Loan Projects - Doc Type: Report

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Approximately 150 cubic yards of weathered claystone were excavated and imported from the bottom
of the west lake and used to construct the top two feet of the dam embankment.

4.0 VEHICLE TURNAROUND CONSTRUCTION SUMMARY

A 30-foot by 40-foot vehicle turnaround was constructed to access the outlet works gate control and to
allow for maintenance operations to be performed at the outlet structure. Compacted pit run material
was placed on the upstream side of the dam embankment and around the sides of the spillway/outlet
structure. The pit run was covered by six inches of granular bedding material. An 18-inch thick layer
of riprap, with a 050 of 12 inches, was placed on the newly constructed embankment. A walkway
from the vehicle turnaround to the outlet structure was constructed through the riprap.

5.0 DAM CREST REGRADING SUMMARY

The dam crest was graded to gauge elevation 12.7 on the north, south, and east sides of the dam. The
western dam crest, along the Boulder and White Rock Ditch, was raised to gauge elevation 13.3.
Three inches of Class 6 road base was placed on the entire dam crest and the road was graded to
provide for drainage toward the reservoir. The downstream slope of the reconstructed dam crest was
covered with an erosion control blanket and was seeded.

6.0 PROBLEMS ENCOUNTERED AND SOLUTIONS

~ Excessive Leakaf!e Throuf!h the Sluice Gate: A one-inch gap between the sluice gate frame,
and the outlet structure wall was filled with non-shrink grout. After seepage testing, it was
determined that water was leaking through the interface between the grout and the machined
surface of the gate frame. Ram-Neck was placed into the gap to create a seal between the gate
frame and the grout. This provided a tight seal. When the gate was retested, a leakage rate of
less than 0.25 gal/min resulted.

~ Not Enough Dam Embankment Fill: During reconstruction of the dam it was found that the
previously excavated materials were not sufficient to raise the dam crest to the previous
elevation. Approximately 150 cubic yards of weathered claystone was scraped from the
bottom of the west lake and used to complete the dam embankment reconstruction. The
imported soil met all of the specifications for dam embankment fill material.

~ Upper brass seat on f!ate frame damaged: The gate frame was damaged during installation
due to the lower limiting nut on the stem being set too low at the factory. The gate was hauled
to California and gate repairs were completed by Waterman Industries Inc. An approximately
one week project delay resulted.

FINAL CONSTRUCTION REPORT - Davis No.1 Dam
Outlet Works and Spillway Rehabilitation

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May 2001
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