9/12/2014 Texas Floodplain Managers Association Fall Seminar September 4, 2014 Samantha Martin, CFM Water Resources EIT, CDM Smith Damien J Herrera, PE Senior Project Manager, CDM Smith Edgar A Munoz, PE Project Manager, CDM Smith Shiva Sandrana, PE, PH Project Manager, Bexar County • • • • • • The Problems Potential Solutions & Costs Constraints Recommended Plan More Constraints Cost Avoidance 1 9/12/2014 Project extent is approximately 6 miles from its confluence with the San Antonio River to upstream of I-35. The existing trapezoidal channel is concrete-lined upstream of Roosevelt Avenue and natural to its engineered outfall. More than 100 homes and 9 road crossings are at risk of flooding. The original South Flores Street Bridge overtopped frequently and by as much as 9 feet in the 1 percent flood. 2 9/12/2014 1 Clamp Avenue 2 Garnett Avenue Commercial Avenue Shemya Avenue Dorsey Street Moursund Boulevard • Primarily flood conveyance capacity with three reaches exhibiting overbank flooding due to undersized bridges and channels. • 304 parcels & 200 structures in the floodplain. West Baetz Boulevard West Baetz Boulevard 3 East Ansley Road 3 9/12/2014 South Flores St. Deck El. = 567.1 1% Ult. WSE = 576.95 Depth = 9.85 ft Roosevelt Rd. Deck El. = 573.38 1% Ult WSE= 575.88 Depth = 2.50 ft • • • • Alternative 1 – Increase Flood Storage Alternative 2 – Flood Storage with Channel Improvement Alternative 3 – Channel Improvements/Bridge Replacements Alternative 4 – Only Raise South Flores (Buyouts and Floodproofing) Note: Raising the South Flores Bridge was included in all of the Options 4 9/12/2014 Alternative Option Cost Estimate 1. Increase Flood Storage FSA 2 and FSA6 $27.7 Million 2. Increase Flood Storage & Channel Improvements FSA2 & FSA6, CCR1,CCR2, & CCR4 $55.7 Million 3. 1 Channel Improvements & Bridge Replacements CCR1, CCR2, CCR2 Bridge Replacements, CCR3, Roosevelt Bridge Replacement, and CCR4 $44.5 Million 3.2 Channel Improvements & Bridge CCR3 and CCR4 Replacements $29.6 Million 3.3 Channel Improvements & Bridge CCR3 and CCR4 Truncated Replacements $25.1 Million 3.4 Channel Improvements & Bridge CCR3 and CCR4 (From h-pile wall to Replacements conventional wall) $19 Million 4. Only Raise South Flores; Buyouts & Floodproofing $33.2 Million Only Raise South Flores; Buyouts & Floodproofing Ultimately, there was enough conveyance in the final channel design that no flood storage areas were necessary. 5 9/12/2014 • Solution must protect for 1% Chance Future Flows • Use Existing Right of Way (ROW) – Had to use retaining wall in limited ROW spaces • Utility crossings • Provisions of the San Antonio UDC – Freeboard (1ft channel; 1.5ft bridges) – Flow Velocity (Max 15 ft/s) – No downstream water surface elevation rise or increase in velocities 6 9/12/2014 7 9/12/2014 • • • • 7000ft of Channel Improvements 1 Bridge Replacement – Roosevelt South Flores Bridge Replacement (Completed 2011) Final Project Construction Cost $18.7 Million ($11.2 Million CCR3, $7.5 Million CCR4) • One 3-ft drop structure between Roosevelt and South Flores Bridges • CCR3 Transition Under Design • • • • • Stage increases downstream of project Channel transition downstream of project Geotechnical constraints New survey data didn’t align with previous data Cost 8 9/12/2014 • Streamlined Design: – – – – – Minimized number of drop structures from 5 to 1 Took online/offline storage options out of design Reduced the variation in cross section dimensions Removed CCR1 and CCR2 Proposing to Truncate upper part of the original design. Will potentially save $2 million. • Design – Saved over $3M on retaining wall costs by using cast-in-place instead of h-pile and pre-cast panels. 9 9/12/2014 Contact Information Samantha Martin [email protected] Shiva Sandrana [email protected] 10