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DocuSign Envelope ID:Al FOD76C-8E37-4295-AO8C-9A99498B56F7 <br /> 0 111110 <br /> ■■■ haLff <br /> ■00000■ <br /> rod height information. Survey datums will be established and recorded for the ability to <br /> compare gage reading to hydraulic models. <br /> Task 3: Stormwater Problem Identification <br /> Halffwill compile an inventory of up to fifty (50) stormwater problem area"hot spots"identified based <br /> on the data collected in the previous task, prior master planning efforts,Citystaff input, rapid assessment <br /> analysis,and theairport assessment analysis.Flood and drainage issueswill be identified using the best <br /> available existing information, local drainage complaints,anclCityknown areas offlooding. The initial list <br /> of hot spots from Task 2b will be refined during the initial workshop with City staff to include <br /> improvements that have been implemented as well as locations identified since the 2018 SWMP was <br /> published. Specific tasks for stormwater problem identification include the following. <br /> a. Prepare Hydrologic and Hydraulic Models <br /> i. Since the City has existing hydrologic and hydraulic studies (FEMA — FIS) for all major <br /> waterways which define associated flood hazard boundary areas, additional riverine flood <br /> analyses will not be developed for this analysis. <br /> a. The best available models for the Blanco River will be utilized to assessthe Blanco <br /> Bypass mitigation project with the stormwater solutions considered for Task 4. <br /> ii. Ahigh-level HEC-RAS 2D hydraulic ana lysis rapid assessment will be performed to determine <br /> local "hot spot" locations within the city based on the 25- and 100-year return events with <br /> Atlas 14 rainfall,24-hour storm durations.The extents of the rapid assessment 2D hydraulic <br /> analysis will be as outlined in turquoise in the figure below. This analysis will focus on <br /> overland flow utilizing LiDAR and limited breakline features. The rapid assessment will not <br /> include detailed modeling of initial conditions or riverine flood risk.This rapid assessmentto <br /> identify local flooding areas will not include storm drain pipes, culverts, or other drainage <br /> infrastructure and is intended primarily to identify low lying areas with a probability of <br /> flooding based on existing watershed conditions. The initial flood risk areas will be further <br /> vetted in the next task. Halff shall obtain approval from the City Project Manager prior to <br /> beginning this analysis. <br /> 4 1 P <br />