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<br />Grace Le, Redwood City <br />Redwood Shores Levee Certification Proposal <br />September 15, 2009 <br />Page 3 <br /> <br />~~ <br /> <br />Based on the review of the operating records, BKF will assign a probability to pumps <br />not functioning or being available during a storm event. A Technical Memorandum will <br />be prepared that documents the combined probability of concurrent design storm event <br />and pump outage. <br /> <br />2) Interior Drainage Studies <br /> <br />The existing Redwood Shores hydrology and hydraulic reports will be reviewed to <br />determine interior storm drainage during a 1 DO-year event. BKF will verify the total <br />drainage area to each pump station, update percent impervious area based on existing <br />conditions, and available storage within the Lagoon and channel systems. The <br />percentage of impervious area anticipated during the design process will be compared <br />with current and proposed development. <br /> <br />BKF will review approximate pumping capacities by reviewing drawdown in pond levels <br />versus pumping time during dry weather conditions. As-built pump station discharge <br />rates will be compared with current conditions. <br /> <br />The initial Design Reports will be updated based on existing conditions. At this time, it <br />is anticipated that minimal change will be required and that the system will function as <br />designed during a 1 DO-year storm event. <br /> <br />Flow to the interior levee system is from the City of San Carlos Harbor Industrial <br />District Channel via Phelps Slough, off-site to San Carlos Airport, direct rainfall to San <br />Carlos Airport and direct rainfall to Redwood Shores. BKF will review the combined <br />pumping and storage capacity of the existing facilities to determine expected water <br />levels within the Redwood Shores Lagoons. <br /> <br />A Technical Memorandum will be prepared that documents the interior drainage <br />analyses including design parameters and study results. The document will reference <br />previous drainage reports. The document will be used as a part of certification <br />documents for Redwood Shores, San Carlos Airport and City of San Carlos. <br /> <br />3) Survey <br /> <br />Analyses of the interior drainage system will be based on the County L1DAR mapping. <br />GPS survey will be utilized to determine spot elevations at low points within Redwood <br />Shores as identified by the L1DAR mapping. These spot survey results will be utilized <br />to determine whether differential settlement has occurred that may affect the level of <br />protection provided by the interior drainage system. <br /> <br />BKF will provide benchmarks on the levee that will be used to establish borings <br />locations and to set levee crest elevations for monitoring of future settlement. <br /> <br />4) Levee Certification Documentation <br /> <br />BKF will assist with compilation of the Redwood Shores, San Carlos Airport and San <br />Carlos levee certification packages. BKF will provide a section for the operations <br />manual summarizing procedures that are used for operating the interior drainage pump <br />and Lagoon system. BKF will provide memoranda summarizing results specific to each <br />area, will review the submittal package for consistency and will attend up to 2 post- <br />submittal meetings to explain results to certifying agencies. <br /> <br />M:\2009 Proposals\09545 Redwood Shores Levee Certification\GLe_Scope_9-14-09.doc <br />