PROJ00400

• Contract/PO #: C153588
• Contractor Name: Greeley, City of
• Contract Type: Loan
• Water District: 3
• County: Larimer
• Bill Number: SB 89-85
• 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

feet, the auger penetrated a gray, wet, soft silty sand with gravel. A
slotted PVC standpipe piezometer was isolated in the bottom of the hole
between 35 and 40 feet.

Test pi t BMP-2 was excavated into the upstream face of the embankment at
Station 4+24. The riprap slope protection was noted to be approximately 2.5
feet thick. The backwa11 (downstream face) of the pit was about 13 feet deep,
while the frontwall (upstream face) was roughly five feet deep. The walls of
the test pit revealed a well-defined horizon, apparently marking the location
of the Zone II and II I fi 11 contact as constructed under the 1972-1973
rehabilitation. This horizon was observed 9 feet down in the backwa11 and 2.5
feet deep at the frontwa11, and was nearly horizontal. The Zone III fill was
dark brown and appeared to contai n a hi gher percentage of gravel and 1 ess
fi nes than the 1 i ght gray Zone 11 fi 11. Laboratory tests performed on bul k
samples collected from the test pit verified this observation. The Zone III
fill was also noticably less dense than that comprising Zone II. Both
materi al s were cl assi fi ed accordi ng to the Unifi ed Soi 1 Cl assifi cati on (USC)
system, as a silty sand with gravel (SM).

Test pit BMP-3. was excavated into the downstream face of the dam at Station
1 +98. The pi t was roughly four feet deep on the downslope si de and 13 feet
deep near the edge of the crest. At a depth of 7.5 feet, measured along the
backwa 11, a we ll-defi ned hori zon was observed between the fill used to ra i se
the dam in 1972-1973 and the ori gi na1 dam. The fi 11 compri si ng the rai sed
portion of the dam was a dark brown, loose to moderately dense, silty sand
with gravel and cobbles to 8 inches in size. This material contained
approximately 10 percent nonp1astic silt fines and 40 percent gravel (SM
classification). According to the existing "as-built" drawings, this material
should be Zone II fill. However, it contained considerably more gravel and
less fines than the Zone II material encountered in test pit BMP-2 on the
upstream face. The ori gi na 1 dam, below 7.5 feet, consi sted of 1 i ght gray,
moderately dense silty to clayey sand with occasional cobbles to six inches in
size. Approximately 20 to 30 percent silt and clay fines were noted in the
material.

1231 H

-49-