Costello prepared a Conceptual Design Report, Plans, Specifications, and Estimates, and a Drainage Impact Study for improvements to the South Shaver Stormwater Detention Basin (C506-01-00) to provide a watershed analysis of the flood reduction benefits along Berry Bayou (C106-00-00). Three project alternatives were developed, analyzed, and a selection matrix developed to determine reduced flood elevations, construction costs, and community needs. Costello assisted in the preparation of data/information used for a Federal grant funding application.
Coordination efforts included meetings with Harris County Precinct 2 to review project benefits, desires of the Precinct, and to discuss overall construction costs. Within the limits of the project site, a City of Houston roadway, Witt Road, provides access to Pasadena Independent School District’s (PISD) Milstead Middle School. Coordination with the City of Houston was completed to allow for the abandonment of Witt Road to provide room for additional detention. The detention volume within the basin will also be provided for City of Houston CIP projects in the area. Coordination with PISD was also provided, and a new access road will be constructed to replace the access by Witt Road.

The 96-acre site will provide 551 acre-feet of stormwater storage volume in the preferred recommended alternative, reducing the existing 100-year base flood elevation by as much as 1.0’. Approximately 45 acres of downstream FEMA Zone AE floodplain and an estimated 449 structures (homes) will be removed from the current 100-year inundation area.

To complete the analysis, the FEMA effective hydrologic HEC-HMS model was updated. Due to the area’s flat terrain, a 2D unsteady state HEC-RAS model was prepared to help calibrate flow paths and hydrologic parameters, better defining drainage sub-watersheds. Unsteady state HEC-RAS was used to complete the hydraulic analysis.
Avoidance of environmentally sensitive areas, including Berry Bayou’s stream centerline/ordinary high-water mark and potential jurisdictional wetlands, helped minimize permitting requirements.

Stormwater Quality for the project will be provided in the form of Permanent Ponded Pool volume for the entire upstream tributary area.