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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previously, materials in the upper nine feet of the pit were loose to
moderately dense and corresponded to Zone II! fill on the "as-built" drawings
from the early 1970's. Materials in the bottom four feet of the pit were
dense and corresponded to Zone I! fill. Standard Proctor compaction tests
performed on each of these soils produced virtually the same maximum dry
density and optimum moisture content, 128 lb/ft3 and 10 percent,
respecti ve1y. Fall i ng head permeabi 1 ity tests were conducted on both the
upper and lower materials from the pit. The upper soil (Zone III) was
remol ded to 86 percent of the maximum dry density to represent the loose to
moderately dense in place condition. A permeability of 4 x 10-5 cm/sec was
computed. The lower materi a1 (Zone II) was remo1 ded to 94 percent of the
maximum dry density to simulate the denser in place condition. For all
practical purposes, the permeability was the same, 2 x 10-5 cm/sec.

Bulk samples from test pit BMP-3 and an unlogged pit on the crest of the dam
in the vicinity of BMP-3 were tested as potential aggregate for conventional
and roller compacted concrete (RCC). Because the reservoir was nearly full,
the material s were taken from the dam under the assumption that whatever
reservoi r borrow area was used to rai se the dam in 1972-1973 woul d agai n be
avail abl e for aggregate when the reservoi r is lowered. Aggregate qual i ty
tests indicated the material would be adequate for conventional concrete
(processed) or RCC, with high specific gravity, low absorption, and fair
durability as measured by L.A. abrasion and sodium sulfate soundness tests. A
set of six RCC test cy1 inders were cast using unprocessed material s and a
cement content of 175 1b/cy. Compressive strength tests were scheduled at 7,
28, and 56 days. Average compressive strength results .at 7 and 28 days of 480
psi and 660 psi, respectively, are considered low for the given cement content
when compared to similar mixes tested by MKE on past projects. The reason for
the low strengths is apparently due to the plastic nature of the fine fraction
( #200 sieve) which comprises over 11 percent of the material gradation.

Si nce the primary requi rement of the RCC wou1 d be durabil ity, and durabil ity
is directly related to compressive strength, it is MKE's opinion that the
local aggregate is unsuitable for use in RCC for the spillway.

1231 H

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