<strong>Feasibility</strong> <strong>of</strong> <strong>Fish</strong> <strong>Passage</strong> <strong>at</strong> <strong>Alameda</strong> <strong>Creek</strong> <strong>Diversion</strong> <strong>Dam</strong>For the cost <strong>of</strong> w<strong>at</strong>er associ<strong>at</strong>ed with oper<strong>at</strong>ing the fish ladder design component, the estim<strong>at</strong>ed annualw<strong>at</strong>er cost assumes th<strong>at</strong> the SFPUC-proposed normal w<strong>at</strong>er year instream flows will be used when theyare available <strong>at</strong> ACDD during the adult immigr<strong>at</strong>ion period <strong>of</strong> December through April. Assuming th<strong>at</strong> aflow <strong>of</strong> 10 cfs is sufficient to oper<strong>at</strong>e the fish ladder, 12 opportunity costs would not be incurred when theSFPUC-proposed normal w<strong>at</strong>er year instream flows are bypassed between approxim<strong>at</strong>ely January 11 andApril 30. During this time period, the fish ladder flow (10 cfs) combined with the fish screen bypass flows(5 cfs) would be less than the SFPUC-proposed normal w<strong>at</strong>er year instream flows (Table 2-3). The w<strong>at</strong>erth<strong>at</strong> would be bypassed <strong>at</strong> ACDD and assumed to be available for oper<strong>at</strong>ion <strong>of</strong> screens and ladders withoutincurring additional cost, is shown in green on Figure 5-3.However, from December 1 to approxim<strong>at</strong>ely January 11, the SFPUC-proposed normal w<strong>at</strong>er yearinstream flows, along with WSIP Final PEIR mitig<strong>at</strong>ion flows <strong>of</strong> 10 cfs, are estim<strong>at</strong>ed to be insufficient tooper<strong>at</strong>e both a fish ladder and fish screen bypass. In th<strong>at</strong> case, the w<strong>at</strong>er cost estim<strong>at</strong>ed for oper<strong>at</strong>ion <strong>of</strong>screens and ladders includes the cost <strong>of</strong> these additional flows (shown in pink in Figure 5-3). The cost <strong>of</strong>the additional flows <strong>of</strong> up to 5 cfs th<strong>at</strong> would be required from December 1 through approxim<strong>at</strong>elyJanuary 11, when sufficient flows are available, are applied to the annual cost <strong>of</strong> oper<strong>at</strong>ing a fish ladder.Similar to the analysis <strong>of</strong> reduction in diversion capacity due to screening described in Section 5.2.1,predicted daily average flows from the model described in Appendix B were used to estim<strong>at</strong>eunimpaired flow for each day in the simul<strong>at</strong>ed period. These unimpaired flows were then used tocalcul<strong>at</strong>e the daily difference between SFPUC-proposed normal w<strong>at</strong>er year instream flows and flowsrequired for oper<strong>at</strong>ion <strong>of</strong> a fish screen bypass and fish ladder combined, for the period fromDecember 1 through approxim<strong>at</strong>ely January 11 when the proposed flows would not be sufficient foroper<strong>at</strong>ing these two design components. Based on this analysis, the additional volume <strong>of</strong> w<strong>at</strong>errequired to oper<strong>at</strong>e a fish ladder <strong>at</strong> ACDD (potentially required from December 1 throughapproxim<strong>at</strong>ely January 11, only when sufficient flows are available) during the simul<strong>at</strong>ed period <strong>of</strong>record (1969-1985 and 1996-2004) would range annually from 0 to 440 acre-feet. The estim<strong>at</strong>edvolume <strong>of</strong> w<strong>at</strong>er th<strong>at</strong> would be required to oper<strong>at</strong>e a fish ladder is illustr<strong>at</strong>ed in Figure 5-3 for both awet year and a dry year. The average annual volume <strong>of</strong> w<strong>at</strong>er required to oper<strong>at</strong>e a fish ladder, inexcess <strong>of</strong> the SFPUC-proposed normal w<strong>at</strong>er year instream flows, is approxim<strong>at</strong>ely 130 acre-feet.Based on the estim<strong>at</strong>ed 2016 w<strong>at</strong>er r<strong>at</strong>e <strong>of</strong> $1,500 per acre-foot, the average annual lost diversionopportunity cost associ<strong>at</strong>ed with oper<strong>at</strong>ion <strong>of</strong> a fish ladder to facilit<strong>at</strong>e steelhead immigr<strong>at</strong>ion isapproxim<strong>at</strong>ely $195,000. This w<strong>at</strong>er cost is added to the annualized fish ladder cost in Section 5.3.5.2.4 LIMITATIONS OF WATER DIVERSION ESTIMATIONSA number <strong>of</strong> limit<strong>at</strong>ions are associ<strong>at</strong>ed with the lost w<strong>at</strong>er diversion opportunity costs for both screensand fishways, some <strong>of</strong> which may affect the accuracy <strong>of</strong> the estim<strong>at</strong>es. Limit<strong>at</strong>ions with this analysisare listed below:■Daily averages were used to model flows in <strong>Alameda</strong> <strong>Creek</strong> because those d<strong>at</strong>a were available,but daily average flow does not accur<strong>at</strong>ely represent the flashy n<strong>at</strong>ure <strong>of</strong> flows in <strong>Alameda</strong> <strong>Creek</strong>.Because the daily average reduces the height <strong>of</strong> the short peaks th<strong>at</strong> occur in the hydrographimmedi<strong>at</strong>ely after precipit<strong>at</strong>ion events, use <strong>of</strong> these d<strong>at</strong>a underestim<strong>at</strong>es the quantity <strong>of</strong> w<strong>at</strong>er inexcess <strong>of</strong> the diversion capacity <strong>of</strong> the ACDT th<strong>at</strong> flows down <strong>Alameda</strong> <strong>Creek</strong> and over theACDD. Use <strong>of</strong> shorter time-step d<strong>at</strong>a, such as 15-minute interval real-time flow d<strong>at</strong>a, would12 This estim<strong>at</strong>e is based on a preliminary review <strong>of</strong> the <strong>Alameda</strong> <strong>Creek</strong> hydrograph and the Long <strong>Fish</strong>way described inSection 4.1. A more accur<strong>at</strong>e estim<strong>at</strong>e <strong>of</strong> flows through a fishway <strong>at</strong> ACDD would require a flow dur<strong>at</strong>ion analysis, astorm peaking analysis, design work, and a stage discharge evalu<strong>at</strong>ion.ACDD <strong>Passage</strong> June 2009 Page 5-8
50451998 Modeled Hydrology, Wet Year// // //Flow (cfs)403530252015105011/1 11/15 11/29 12/13 12/27 1/10 1/24 2/7 2/21 3/7 3/21 4/4 4/18 5/2D<strong>at</strong>e2002 Modeled Hydrology, Dry YearFlow (cfs)5045403530252015105//// // //011/1 11/15 11/29 12/13 12/27 1/10 1/24 2/7 2/21 3/7 3/21 4/4 4/18 5/2D<strong>at</strong>eSFPUC Proposed Instream FlowSchedule BWSIP PEIR Mitig<strong>at</strong>ion BypassPeriod <strong>of</strong> Ladder Oper<strong>at</strong>ionCombined Screen and Ladder FlowScreen Bypass Flow<strong>Alameda</strong> <strong>Creek</strong> Predicted FlowCurrently Proposed Flow (Schedule B) Assumed Available for Ladder and Screen Oper<strong>at</strong>ionAdditional Flow Required for Ladder and Screen Oper<strong>at</strong>ionW<strong>at</strong>er Potentially Required for a<strong>Fish</strong> Ladder and <strong>Fish</strong> Screen Bypass <strong>at</strong> ACDD<strong>Feasibility</strong> <strong>of</strong> <strong>Fish</strong> <strong>Passage</strong> <strong>at</strong> <strong>Alameda</strong> <strong>Creek</strong> <strong>Diversion</strong> <strong>Dam</strong>Technical MemorandumJune 2009 Figure 5-3
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