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

Bore holes P-2 and P-3 were located 46 feet right and 37 feet left of P-1,
respectively, at the downstream edge of the crest. Both holes revealed
similar conditions, 10 to 14 feet of light brown, slightly sflty; sand and
gravel overlying about 20 feet of alternating thin layers of multicolored
coarse sand and gravel, gray silty sand, and dark gray to b1 ack, cl ayey sand
with brown spongy organic inclusions, such as roots and wood fibre. The holes
passed from the embankment dam di rectly into bedrock at a depth of 36; 5 feet
and 44.0 feet, respectively. The rock on both abutments was sound to slightly
weathered gray gneiss, lightly jointed with principal joints parallel to
foli ati on at N700E, 900 and N150W, 450 _600NE and N450W, 650 _850NL The core
was oriented based on ~he foliation measurements obtained from outcrops on the
abutments.

The maximum coefficient of penneability in the near surface foundation rock
was 4.6 x 10-5cm/second.

Bore hole P-4 was drilled from the upstream benn at approximately elevation
9490, sl i ghtly downstream and to the 1 eft of the drop i nl et structure: The
objective of this hole was to investigate the condition of the backfill around
the original timber crib structure. Previous repair work around the intake
had experienced high water and grout takes, indicating possible voids in the
embankment. The auger penetrated about 3.0 feet of riprap at the surface;
followed by 13.0 feet of poorly compacted medium size sand. The remainder of
the hole was cored through a nest of large boulders, up to 5 feet in diameter,
to bedrock at a depth of 38.5 feet. Total loss of circu1 ati on water was
registered at a depth of 22.0 feet. This boring hole indicates that the fill
surrounding the drop structure consists of large boulders, and that the
structure may also be founded on boulders.

Test pit PP-13 was excavated into the downstream face of the dam near the
right toe, perpendicular to the centerline. The trench revealed light brown,
slightly silty, sand and gravel, with cobbles to eight inches overlying a
layer of black organic topsoil and vegetation, one to two feet thick,
representing the downstream slope of the ori gi nal dam. The over1yi ng materi a1
fonned a wedge that gradually thi ck(lned up the slope to a maximum of 12 feet

-46-