Res 2013-124/Approving an agreement between the City and Espey Consultants, Inc. in connection with the Comprehensive Watershed Master Plan

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City of San Marcos - Drainage Master Plan Halff Associates Study Type Categories Type / Name Available Information outside DMP Scope Proposed DMP Scope Type A Streams - GBRA Survey: Survey will be performed under the GBRA scope to meet or exceed FEhLA requirements. No additional effort. Field Reconnaissance: Field photos of each structure will be performed under the GBRA scope to meet or exceed FE \dA requirements. No additional effort. Hydrology: Hydrologic analysis will be performed under the GBRA scope using Sn dens UH approach. No additional effort. Hydraulic analysis will be performed under the GBRA scope using limited detail and detailed methodologies. Most study designations match FEMA Hydraulics: designations and are therefore FFMA compliant. There are 3 exceptions that may not be FENiA compliant and may require additional survey and hydraulic modeling. n%illow Springs Creek (1.54 mi), Purgatory Creek (7.53 nhi), and Sink Creek (4.3 mi ) No additional effort. Frequency Events: Existing and 20 -yr Future Conditions 2 -, 5-, 10-, 25-, 50,100, 250-, 500- •r events No additional effort. Floodplain Mapping: Existing Condition 10- and 25 -year events Existin Condition 100- ear only and 20- •r Future Conditions 10-, 25-, and 100-year events Floodplain Mitigation Analysis: Stream regional flood control alternatives. No additional effort. Conceptual Concepts: Each proposed floodplain mitigation alternative will include a conceptual plan. Minimal effort to match San Marcos DMP standards. (7 Projects) Benefit Cost Estimations: Each Proposed floodplain mitigation alternative will include a basic cost estimation. \Minimal effort to match San Marcos DMP standards. (5 Projects) Structure Inventory and Inventory structure information that list the frequency and depth of 'Mitigation Ranking overtopping and ADT if available. A ranking of priorities is based on this information. No additional effort. Report: Tl1•DB Flood Protection Planning Report that outlines all tasks above. No additional effort. Type B Streams - 2007 FPP Survey: No new surveys will be necessary as long as structures have not been Surveyed in 2005 improved since date of last survey. Field Reconnaissance: No new surveys will be necessary as long as structures have not been Field photos of each structure were performed in 2005 improved since date of last survey. Hydrologic update would utilize GBRA hydrologic analysis on majority of Hydrology: streams with die exception of Cottonwood Creek. Cottonwood Creek is outside the scope of the GBRA study and therefore will require new Hydrologic analysis was performed in 2007 using NRCS UH approach. h drolo& analysis. Update of existing hydraulic models. 2007 geospatial XS will be re -cut on Hydraulics: the new 2006 -2009 LiDAR. Coded structures will not be revised unless necessary. New GBRA and Cottonwood Creek flow rates will also be Hydraulic analysis was performed in 3007 using 2003 LiDAR supplemented incorporated into the HEC -R\S models. Minor model adjustments may be with necessa • with the addition of new topo a by and flow rates. Frequency Events: Existing and 20 -yr Future Conditions Existing and 20 -yr Future Conditions (From GBRA study) 2-,10-, 25-, 50-, 100-, 500 -yc events 2 -, 5 -, 10-, 25-, 50-,100-, 250-, 500 - r events Floodplain \Lapping: Existing Condition and 20 -yr Future Conditions Existing and Ultimate Condition 100 -year 10-, 25-, and 100 -year events Update ofexisting floodplain mitigation analysis using new hydraulic Floodplain 'Mitigation Analysis: models. This will just be a validation that the 2007 mitigation alternative is Floodplain miti ation analysis was performed in 2007. valid with the updated hydraulic model. (8 projects) Conceptual Concepts: Update conceptual concepts using new hydraulic models. This effort will Limited conceptual concepts were performed in 2007. include slight revisions to the 2007 conce tual alternatives. (4 projects) Benefit Cost Estimations: Update benefit cost using new hydraulic models. This effort will include Limited cost estimations were performed in 2007. slight recisions to the 2007 costs.(4 projects) Structure Inventory and Inventory structure information that list the frequency and depth of Mitigation Ranking overtopping and ADT if available. A ranking of priorities is based on this This was not part of die 2007 study. information. Report: A report for the 2007 study was prepared in 2007. Fronde an amendment document for the 2007 report. Type C Streams - FENIA Survey: None 4 structures, 3 SS Field Reconnaissance: done 4 Zone AE structures and 1 Zone A structure Hydrology: Hydrologic analysis will be performed under the GBRA scope using Snyder's UH approach. No additional effort. Hydraulics: :lone Detailed: PC -1 & Willow Springs Creek; Limited Detail: LINT to PC Frequency Events: Existing and 20 -yr Future Conditions 2-,5-, 10-, 25-, 50-, 100-, 250-, 500 -yr events No additional effort. Floodpla n [app tag Existing Condition and 20 -yr Future Conditions None 10-, 25-, and 100 -year events Floodplain 'Mitigation Analysis: .lone Stream flood control alternatives. (3 projects) Conceptual Concepts: Each proposed floodplain mitigation alternative will include a conceptual None plan. (1 Project) Benefit Cost Estimations: Each proposed floodplain mitigation alternative will include a basic cost None estimation. (I Project) Structure Inventory and Inventory structure information that list the frequency and depth of Mitigation Ranking - overtopping and ADT if available. A ranking of priorities is based on this None information. Report: None Provide a report detailing methodologies and results. Now In order to submit this infinnariun to FE-MA for a ntap updtte, addiyoaml work is necessary. Additional tasks may include additional surmy and hydraulic modeling along identified Type A'- GBRA streams, generation of base flood elevations, delineation of the 500 -year floodptuns, floods ay analysts or ordinance adoption of freiloency event for flooduray regulation, generation of FE\LA profiles and Flood Insurance Study (FIS) information, and generation of necessary Fr—\L1 fomts and documentation for a letter o0lap Change.