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<br />.....:J:J <br /> <br />Table 2 -- Analysis of Recreational Use Improvement Options <br /> <br />;ii~f <br />NOg" <br />R,2 <br /> <br /> <br />Enlarge RG <br />Reservoir capacity <br />by: <br />8) raising dam <br />crest, and/or <br />b} raising spillway <br />crest. <br /> <br />81 Raise top of dam 1 to 4 <br />feet by adding fill material to <br />top and side slopes of <br />existing dam or constructing <br />a parapet wall along the top <br />of the dam. Also raise <br />spillway crest. <br /> <br />b) Temporarily raise elevation <br />of spillway crest 1 to 2 feet <br />by placing stoplogs in <br />spillwav or installing a radial <br />gate. <br /> <br />'n, .. <br /> <br />Additional storage couk:t <br />be: <br />- 362 af from a 1 ft. <br />faise; <br />- 729 af from a 2 ft. <br />faise; <br />- t,482 af from a 4 ft. <br />raise; <br />but this wou\d depend <br />on how often the space <br />i. filled (i.e. the yieldl. <br />Thi. .p.ce would not fill <br />every year. <br /> <br />Additional storage of <br />362 af from a 1 ft. rai.e; <br />729 from a 2 ft. raise. <br /> <br /> <br />Safety of Dams <br />considerations <br />about liquefaction <br />possibility for the <br />dam foundation. <br />Additional detailed <br />studies required <br />to make 8 <br />determination. <br /> <br />- Spillway does <br />not currently pass <br />the PMF. <br />- Dam safety <br />guid~lines will not <br />allow without <br />raising the dam <br />crest <br /> <br />21 <br /> <br />. Using fill to raise the <br />dam 4 ft. would cost <br />about $4.296.000; <br />Annual cost - $336.000 <br />or $378 per af per year, <br />assuming space is filled 6 <br />out of 10 years (historical <br />average is 62%) <br /> <br />- Building a 4 ft. w.n on <br />top of the dam would <br />cost .bout $1.542.000. <br />Annu.' cost - $121.000 <br />or $1 36 per af per year <br />(assuming filled 6 of 10 <br />years), <br /> <br />Costs of modifications or <br />relocations of recreation <br />facilities were not <br />estimated. <br /> <br />Not estimated. <br /> <br />. Helps recreation only in years when <br />r858Noir spill5 {wet Y88rs)--help is needed <br />mainly in !!!:y years. Could be helpful if this <br />watar could be carried over to a following <br />dry year. <br />. Requires new water right to fill. <br />- ReqUires evaluation of statk: & dynamic <br />dam stability, &. analysis of foundation <br />liquefaction possibilities with larger pool. <br />- Requires new flood routing study. <br />. Requires meeting current stringent Federal <br />requirements; upgrades of other <br />appurtenant structures including the <br />spillway may also be required. Costs for <br />such improvements have not been included <br />in this estimate. <br />- Reservoir would have to be dewatered to <br />place fill material on upstream face. <br />. May have to extend inlet to outlet works, <br />relocate some other facilities (e.g. roads, & <br />do other mitigation. These costs are not <br />included. <br />. Dam design may not be conducive to a <br />raise <e.g. drains may not function <br />roperly). <br /> <br />- See considerations from R-2(a) above. <br />- Long term use of stoplogs or radial gate <br />would not be allowed due to safety <br />concerns - dam height and spillway were <br />designed with a maximum pool in mind. <br />. Safety concerns: would have to eV81uate <br />possibility of liquefaction of dam <br />foundation end flood routing. Risk of <br />overtopping may increase if stoplogs could <br />not easily be removed in face of high <br />runoff from upstream of dam. Break.eway <br />gates coutd be used, but e surge may <br />increase liability. <br />. Designers do not typicallV recommend <br />use of sta I s. <br />