WSP03196

• File Number: 8443.600
• Description: Narrows Unit - Studies
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 6/30/1975
• Author: Dames and Moore
• Title: Flood Study Narrows Dam South Platte River
• Water Supply Pro - Doc Type: Report/Study

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DAMES 8- MOORE

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Significant economies can be achieved by eliminating the service

spillway. For an IDF that is 75 percent of' theUSBR IDF, the additional

investment cost to add a service spillway is $19 million.

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, Conclusions on Risk of Damage .to Auxiliary' Spillw"Y

These facts lead us to the primary conclusion that p service

spillway is not justified; in effect, the combination of the large flood

control space and the large river outlet' capacity take the place of a

service spillway,

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The Narrows Project should be designed on the basis of a cal-

culated risk of damage to the auxiliary spillway, with protection against

damage at approximately the same level as,prS'vided by the USBR in its

feasibility drawing no. 553~D-22.

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In the event the District is held liable for a share of the cost
oLrepairs to the auxiliary spillway in the H,motechanee that significant,
damage occurs during the' repayment period, the District should take
appropriate steps to protect its cash flow position.

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It has been a pleasure serving you on this very interesting

"assignment. We will be pleased to answer any questions you may have,

regarding our report.

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Very truly yours,

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DAMES' 5< MOORE

~ [,U/:RJ

Erie Will
Associate

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Ene, Report

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