PROJ00318

• Contract/PO #: C153618
• Contractor Name: Greeley, City of
• Contract Type: Loan
• Water District: 3
• County: Larimer
• Bill Number: SB 87-15
• Loan Projects - Doc Type: Feasibility Study

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

1.4 Service Spillway

The servi ce spill Wi!y consi sts of a 36-i nch di ameter rei nforced concrete pi pe;
that tapers to 24-inches in diameter 74 feet downstream of the inlet;
installed along the left groin of the dam. The inlet is a semicircular
concrete wei r drop structure protected by a trash rack. The control wei r is
at e1 evati on 951 O. Di scharge capacity of the servi ce spi 1 1 way is shown on
Figure V.6. The service spillway was added during the 1972 repairs; The
inside of the service spillway conduit was not inspected, but from what could
be observed at both the upstream an<l downstream ends the spillway appears to
be in excellent condition.

1.5 Auxiliary Spillway

The auxiliary spillway was also constructed during the 1972 modifications. It
is located in a low sadd1 e in the northeastern corner of the reservoi rand
consl sts of a ri prap-armored earthfi 11 overflow section 12 feet wi de and 350
feet long at elevation 9511. It is flanked by an earthfill dike 500 feet
long, with a crest elevation of 9517 and a width of 12 feet. The upstream
slope is 2H to lV and the downstream slope 3H to 1V. The overflow section has
a one-foot wi de three-foot deep concrete beam runni ng its enti re 1 ength for
precise overflow control. Inspection of the auxiliary spillway and dike
revealed it to be in good condition, There is doubt, however, in regard to
the adequacy of the ri prap on the cl'est and downstream slope of the overflow
secti on to resi st erosi on duri ng overtoppi ng. The riprap adjacent to the
concrete beam is hard and angul ar, but only about si x inches to 12 inches in
diameter. The 3H to lV downstream slope is also steeper than is generally
recommended for thi s type of overflow structure. A1 though the reservoi r was
drained at the time of the inspections and no standing water was observed,
seepage at the downstream toe of the auxiliary spillway dike was evidenced by
the thick growth of grass in that area.

1.6 Summary of Deficiencies

This section summarizes the technici\l deficiencies at Peterson lake Dam; as
noted duri ng the on-si te i nspectl ons and revi ew of project records; The

-41-