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storm train Master PlanPhase 2 j RFP No. 16-02 G)JI Task 2A.2 Expected Value (EV) Hydrology Michael Baker will modify the approved hydrology (10-, 25- and 100-year high confidence) models developed previously in the 2015 SDMP. The Advanced Engineering Software (AES) add -on program will be utilized to globally change all soil types to B and all rainfall data for the respective storm event in accordance with the Orange County Hydrology Manual. The AMC for each model cannot be changed globally; therefore, each individual file will be updated manually. The locations and watersheds for alternative drainage improvements identified in Task 1 will use this EV hydrology for facility sizing. Similar to the process performed in the 2015 SDMP, the rational method hydrology will be converted to small area hydrograph. Michael Baker will test one area as agreed to with the City, to determine if expected value analysis is worthwhile. Once the area has been tested, the results will be discussed with the City prior to commencing all the expected value modeling. Task 2A.3 SD Alternative Formulation/ Feasibility Analysis Based on the expected value hydrology from Task 2A.2, Michael Baker will develop preliminary alternatives formulation for storm drain hydraulics. Michael Baker will perform a system optimization study, focusing on a "watershed solution", not just multiple local solutions. The EV hydrology (Task 2A.2) is anticipated to produce less discharge than the High Confidence (HC) hydrology used in the 2015 SDMP Phase 1. The evaluation will utilize the 2-dimensional surface flow coupled with the 1-dimensional storm drain model in XP-SWMM to fully analyze the potential for reductions in proposed pipe sizes from the master plan. The existing condition hydraulics will be updated with the revised expected value discharges and will be used as a baseline to build the proposed alternative improvements. The fee estimated for this task is based on updating the hydraulics for all watersheds in the baseline (existing) and proposed conditions. The proposed conceptual improvements will focus on either: (1) increasing the hydraulic capacity through enlarged drainage facilities or storm drain extension, (2) constructing a diversion system, or (3) constructing detention storage for flow reduction and water quality benefits (Task 2A.3). All "diversions" will be local, not regional. Potential concept alternatives will be proposed so as to not divert flows from one watershed to another, unless approved by the County. Michael Baker will perform a hydraulic analysis of the conveyance "capacity" of the existing City backbone storm drain and proposed facility systems including subsurface storm drains identified in the 2015 SDMP. Preliminary horizontal and vertical alignments will be developed for the recommended facilities. The lengths and elevation data will be used for detailed hydraulic analysis and cost estimating purposes. The water surface data and hydraulic information will be summarized in tabular format for each reach or element of the facility to allow easy use and review. A technical memorandum will be prepared that summarizes the results of the alternatives analysis. The memorandum will serve to reference the methodology, design assumptions, guidelines, and criteria developed for the identification and evaluations of the drainage alternatives. Task 2A.3 Cost Estimate Page 1 10 I N T E NN AT I0N AL 20C-24