Owner: City of Austin, Watershed Protection Development & Review Dept.
Contact: Mr. Johnnie Price, P.E.
Title of person named above: Project Manager
Address of person named above: 505 Barton Springs Rd, Austin, 78704
Phone number: ( 512) 974-3393
Completion Date: 2010
Cost: $165,000 (Fee)

Project Description:
The purpose of this project is to add flow capacity to the existing drainage structure for a tributary of Williamson Creek where it crosses beneath Covered Bridge Drive. The proposed improvements will add capacity to the existing 2-10'x9' box culverts, by either adding additional culverts or replacing the existing drainage structure with a new free span bridge. Covered Bridge Drive is located in southwest Austin, in the Williamson Creek watershed; a tributary to Onion Creek.

Services Provided:
CAS Consulting and Services, Inc. was retained, as part of the 2006-2008 Watershed Protection Engineering Rotation List, to perform preliminary design, final design, and bid and construction phase services. Based on watershed modeling results, Conceptual Designs have been prepared for several alternatives. At this moment, we are working diligently with Watershed Protection staff to select the best option in order to proceed with Final Design. The Final Design will meet the following requirements:

• Provide improved flood-flow conveyance capacity under Covered Bridge Dr. to limit the amount of overtopping of the bridge to less than six inches during the ultimate development condition 100-year peak flow, and no overtopping in the ultimate development condition 25-year peak flow
• Relocate existing 16-inch water main and 12-inch PVC sanitary sewer to accommodate the expanded stormwater conveyance improvements
• Adjust roadway elevations to minimize costs of conveyance improvements while taking full advantage of the effects of the improvements.
• Mitigate erosion problems upstream and downstream of Covered Bridge Dr. that may arise from widening the channel and increasing conveyance through the crossing.