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Storm Dram Master Flan <br />G Phase 2 ( RFP No, 16-02 r; <br />Task 2A.2 Expected Value (EV) Hydrology <br />Michael Baker will modify the approved hydrology (10 -, 25- and 100 -year high confidence) models <br />developed previously in the 2015 SDMP. The Advanced Engineering Software (AES) add -on program <br />will be utilized to globally change all soil types to B and all rainfall data for the respective storm event in <br />accordance with the Orange County Hydrology Manual. The AMC for each model cannot be changed <br />globally; therefore, each individual file will be updated manually. The locations and watersheds for <br />alternative drainage improvements identified in Task 1 will use this EV hydrology for facility sizing. <br />Similar to the process performed in the 2015 SDMP, the rational method hydrology will be converted to <br />small area hydrograph. <br />Michael Baker will test one area as agreed to with the City, to determine if expected value analysis is <br />worthwhile. Once the area has been tested, the results will be discussed with the City prior to <br />commencing all the expected value modeling. <br />Task 2A.3 SD Alternative Formulation/ Feasibility Analysis <br />Based on the expected value hydrology from Task 2A.2, Michael Baker will develop preliminary <br />alternatives formulation for storm drain hydraulics. Michael Baker will perform a system optimization <br />study, focusing on a "watershed solution ", not just multiple local solutions. The EV hydrology (Task 2A.2) <br />is anticipated to produce less discharge than the High Confidence (HC) hydrology used in the 2015 SDMP <br />Phase 1. The evaluation will utilize the 2- dimensional surface flow coupled with the 1- dimensional storm <br />drain model in XP -SWMM to fully analyze the potential for reductions in proposed pipe sizes from the <br />master plan. The existing condition hydraulics will be updated with the revised expected value discharges <br />and will be used as a baseline to build the proposed alternative improvements. The fee estimated for this <br />task is based on updating the hydraulics for all watersheds in the baseline (existing) and proposed <br />conditions. <br />The proposed conceptual improvements will focus on either: (1) increasing the hydraulic capacity through <br />enlarged drainage facilities or storm drain extension, (2) constructing a diversion system, or (3) <br />constructing detention storage for flow reduction and water quality benefits (Task 2A.3). All "diversions" <br />will be local, not regional. Potential concept alternatives will be proposed so as to not divert flows from <br />one watershed to another, unless approved by the County. <br />Michael Baker will perform a hydraulic analysis of the conveyance "capacity" of the existing City backbone <br />storm drain and proposed facility systems including subsurface storm drains identified in the 2015 SDMP. <br />Preliminary horizontal and vertical alignments will be developed for the recommended facilities. The <br />lengths and elevation data will be used for detailed hydraulic analysis and cost estimating purposes. <br />The water surface data and hydraulic information will be summarized in tabular format for each reach or <br />element of the facility to allow easy use and review. <br />A technical memorandum will be prepared that summarizes the results of the alternatives analysis. The <br />memorandum will serve to reference the methodology, design assumptions, guidelines, and criteria <br />developed for the identification and evaluations of the drainage alternatives. <br />Task 2A.3 Cost Estimate <br />Page 1 10 <br />INTERNATIONAL <br />20C -24 <br />