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<br />November 17, 1975
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<br />Cache La Poudre Reservoir Co.
<br />708 8th St.
<br />Greeley,~olorado 806~1
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<br />RE:
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<br />Project 75-1-4-1505-2
<br />Evaluation of Alternate
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<br />Rep~iis to Existing Dams-
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<br />Gentlemen';
<br />
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<br />
<br />The accompanying engineer's evaluation of alternate repairs
<br />to the Cache La Poudre Reservoir is herewith submitted for
<br />your consideration and approval.
<br />
<br />The' evaluation details the possibility of 3 alternate repairs
<br />to the existing dams. The supporting data used in determinin~
<br />the conceptual designs was based on previous surveys of soil -
<br />materials and bedrock conditions, hydrologic data used to
<br />determine drainage basin storm runoff, and the ground.topog-
<br />raphy for the dam design.
<br />
<br />The alternate repairs detail both the complete cutoff and
<br />partial cutoff of subsoil pervious strata beneath the dams,
<br />but it appears that the dense sand layer beneath the main
<br />dam would complicate the installation of sheet piling in
<br />order to provide a positive cutoff. The construction of
<br />a partial earthen cutoff through the soft unstable organic
<br />sandy, silty clay layer in conjunction with the construction
<br />of a pervious downstream shell and toe drains would increase
<br />the stability of the upstream and downstream 'faces and would
<br />provide a repair that would be long lasting with economic'
<br />advantages.. The relative cost data submitted represent esti-
<br />mates on conceptual design only and do not represent a tabu-
<br />lated construction cost estimate based on final design.
<br />
<br />Al though the conclus ions sho\.[ that 'repair Al terna te
<br />appears to be the most ~conomical solution, careful
<br />
<br />No. 1
<br />thought
<br />
<br />GONSULilNG
<br />
<br />ENGINEERS f P:"ANNERS I LA.ND. SURVEYORS
<br />
<br />1035 COFFMAN STREET
<br />
<br />LONGMONT, COLORADO 80501
<br />
<br />PHONE 303 776,8610 I Metro 534-8822
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