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

cobbles, and occasional boulders. Auger refusal at' 22 feet necessitated
switching to core drilling. The NX core penetrated cobbles and boulders in a
sandy gravel matrix to a depth of 38 feet, at which point auger drill ing was
again employed. Only small rock fragments were recovered by the coring, as
the sand and gravel infilling was probably washed out by the drill water. The
auger was carried down to 44 feet where a gray, moist to wet, soft, silty sand
was encountered. The foundation contact was penetrated at a depth of 51
feet. Thi s contact was marked by a 6~i nch layer of soft, organi c materi a1.
At 54 feet, material similar to that encountered at 44 feet was recovered.
Below 61.5 feet, the presence of cobbles and boulders again required the use
of NX core drill ing. The hole was carried to a depth of 100 feet, with
minimal recovery. Two slotted PVC stanapipe piezometers were installed in the
hole. Piezometer No.1 was isolated at the bottom between 95 and 100 feet in
the foundation. A bentonite plug was formed above the sanded interval.
Pi ezometer No. 2 was set between 35 and 40 feet in the lower part of the
embankment.

Bore hole BM-2 was auger drilled from the dam crest at Station 2+16,
approximately half way between the left abutment and the outlet works. From
the crest to a depth of 35 feet, the auger encountered light brown, moist,
dense, silty sand with gravel and occasional cobbles. From 35 to 39 feet, a
layer of gray, wet, soft, silty sand was penetrated. The foundation contact
was interpreted to be at 38 feet. Silty sand with gravel, simil ar to the
upper 35 feet only gray in color, was penetrated from 39 to 41 feet. The hole
was bottomed out on top of a boulder at 41 feet. A slotted PVC standpipe
piezometer was installed in the bottom of the hole between 36 and 41 feet. A
7-foot depth of sandpack was pl aced around the pi ezometer before formi ng a
bentonite seal to isolate the 5-foot slotted interval.

A third bore hole, BM-3, was drilled from the crest at Station 7+83,
approximately half way between the outlet conduit and the right abutment. As
with bore hole BM-2, this hole encount~red a light brown, moist, dense, silty
sand with gravel and occasional cobbles to a depth of 29 feet. At this point,
a 6-inch layer of black to dark brown, moist, soft, sandy clay with organics
marked the foundation contact. From 34 feet to the bottom of the hole at 40

1231 H

-48-