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

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Physical property tests on embankment samples classified the soils as silty
sand with gravel (SM), using the USC system. The soils are fairly well
graded, typically containing 20 to 30 percent gravel and 15 to 2S percent silt
fi nes. Natural moi sture contents of the embankment soi 1 s ranged from si x to
nine percent, generally being drier near the surface. In situ dry densities
of the dam material ranged from apprOXimately 110 to 120 lb/ft3. Based on
standard Proctor compaction tests conducted on typical embankment soil s from
test pit BMP-2, these dry densities corl'espond to between 85 and 95 percent of
the maximum dry density.

The dam foundation materials displayed a wider range of soil classifications
than the embankment dam, ranging from clayey sand to silty sand, to silty sand
with gravel, cobbles, and boulders. Materials for approximately 15 feet below
the foundation contact were classified as a silty sand. (SM) and typically
contained 40 to 45 percent nonp1astic to low plasticity silt fines and five to
15 percent gravel to one-half inch in size. The materials in the foundation
of the emergency spi 11 way exhi bi ted basi cally the same gradati on, but the
fines were moderately plastic, which resulted in a clay~y sand (SC)
cl assifi cati on. The remai nder of the foundati on was cl ass ifi ed as a si lty
sand (SM), but primarily consisted of gravel, cobbles, and boulders in a silty
sand matrix. Natural moisture contents and dry densities of the silty sand
wi thi n the top 15 feet of the foundati on were on the order of 18 to 20
/ 3 .
percent, and 101 to 108 lb ft , respect1vely.

Materials comprising the auxiliary spillway dikes and foundation were
classified as a silty sand (SM) and contained 25 to 30 percent silt fines and
about 20 percent gravel to one inch ill size. A standard Proctor compaction
test was conducted on a bul k soil samp1 e taken from test pit BMP-5 at the
auxiliary spillway. The maximum dry density was determined to be 135 lb/ft3
at an optimum moisture content of 6.6 percent. A falling head permeability
test was also conducted on a sample of this material remolded to 91 percent of
the maximum dry density. A permeability value of 10-6 cm/sec was obtained.

Bul k samp1 es were taken from test pit BMP-2 on the upstream face of the dam
for standard Proctor compacti on and l'emol ded permeabi 1 i ty tests. As noted

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