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Hydrology & Hydraulics <br />1.6.2 Establish Baseline (Existing) Conditions <br />a) Data Collection: obtain studies, models, terrain, surveys, plans (Dam #5), <br />historical rainfall & highwater marks. <br />b) Field Survey: accurately define existing channel along Purgatory Creek from <br />Wonder World to about 3,500 downstream. This includes 7 channel sections <br />about every 500', and 4 bounding sections at Hunter Road culverts, with <br />breaklines (flow lines and banks) defined every 250' between sections. In <br />addition 5 sections will be surveyed to define the "diversion 1" channel. . <br />c) Terrain: merge field survey with LiDAR for seamless terrain model <br />d) Hydrology: define methodology, delineate basin, determine parameters, correlate <br />to historical event (if data is available), conduct frequency analysis, corrdinate <br />with NRCS, estimate existing and future urbanized land use conditions. <br />e) Hydraulics: define cross sections (from terrain and surveys), input <br />bridge /culverts, analyze overflows /diversions, correlate to historical event (if data <br />is available), prepare frequency profiles, delineate frequency floodplains for the <br />10 -, 50 -, 100- and 500- year events. <br />1.6.2 Prepare Future Conditions (with project) <br />a) Design Criteria: establish design frequency for interim and future conditions <br />b) Channelization: develop a concept hydraulic model of future channel and bridge <br />improvements <br />c) Bridge Sizing: determine bridge size (with alternative for ConSpan), roadway <br />elevation guidance, and channelization limits for interim and future channel and <br />roadway conditions. <br />d) Project Impacts: analyze improvements to minimize potential rise in computed <br />100 -year flood elevations <br />e) Permitting: coordinate with agencies (Corps, TCEQ, F &W, FEMA, NRCS, <br />etc)and provide guidance for interim and future permitting requirements <br />1.6.3 Develop Concept Design <br />a) Plan Profile: prepare concept grading and plan/profile of proposed channel <br />improvements for interim and future conditions including: typical sections and <br />plan/profile to be included as an exhibit for the Drainage Design Report. <br />b) Bridge: prepare prelim plan of bridge improvements for ultimate and interim <br />conditions including: typical section depicting hydraulic requirements, erosion <br />protection, and roadway elevation guidance. <br />1.6.4 Deliverables will consist of two (2) copies and one (1) electronic copy of the Preliminary <br />Drainage Design Report summarizing H &H modeling and including exhibits described above <br />1.7 TASK 7 — GEOTECHNICAL INVESTIGATIONS <br />Kirnley -Horn — FM 2439 (Hunter Road) <br />15 <br />