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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />~ <br /> <br /> <br />I <br />I <br />I <br />I <br />I <br />, <br />I <br />I <br /> <br />performed to veri fy that fact. A PI,IF was developed using NOAA IIydrometeoro- <br />logical Report Number 55, and allowing for Infiltration losses using the Green <br />and flmpt model. The computed runoff hydrographs for both the general and <br />local (thunderstorm) storms resulted In nearly Identical peak discharges of <br />19,300 cfs, with a volume of 1,300 acre-feet. The flood was routed through <br />the reservoir utll Izlng the IIEC-l computer program. It was found that the <br />existing spillways could, in fact, safely pass the PHF, but that there would <br />be zero freeboarrl. It would therefore be necessary to raise the main <br />embankment and auxiliary spillway dike one foot In order to provide the one <br />foot of net freeboard required by the SEO. <br /> <br />The hydraulics of the existing outlet . works were evaluated based on three <br />performance criterl a: III the capabll ity to release the maximum five feet of <br />reservoir storage at a rate of one foot per day, (2) the ability to maintain <br />water level s to comply with the current operating restriction, and (3) the <br />capability to safely pass normal flows. The release capability of the outlet <br />works was found to be adequate to meet these criteria. <br /> <br />Field work commenced with a site inspection by several I~KE personnel In <br />June 1906. At that time, a Phase I Inspection checklist was prepared, similar <br />to the form used by the SEO. Several other Inspections were made during the <br />course of the sturly, Including an Internal Inspection of the outlet works <br />conr!ul t. <br /> <br />lhe site Inspections <br />excellent condition. <br />erosion rivulets have <br /> <br />showed the dam crest and upstream slope to be In <br />The downstream slope appeared stabl e, but numerous <br />formed In the sparse grass slope protection. <br /> <br />Uncontrolled seepage Is one of the primary concerns of Peterson lake Dam that <br />has led to the present restriction. Seepage measurement weirs have been In <br />place for years and the City Inspects the dam, reads piezometers, and observes <br />seepage on a dally basis when the reservoir Is being operated. Because the <br />reservoir was drainer!, no seepage was observed during any of the Inspections, <br />although the lush grass cover on the lower one-third of the downstream slopes <br />Is evidence of Its occurrence. Review of previous Inspection reports and <br />piezometric data collected when the reservoir was storing water Indicates the <br /> <br />Ifl <br />