Trinity Oaks and Thousand Oaks are residential subdivisions located in Pasco County, Florida which were constructed between 1990 and 2003. Both areas experienced recurrent flooding of streets and residential property as a result of accumulated rainfall or single large rainfall events. Detention ponds within the Trinity Oaks neighborhood, intended to provide attenuation and storage of local runoff from residential lots and roadways, frequently overflow their banks and flood adjacent property.
DES staff performed hydraulic modeling support for design of structural improvements to allow for temporary draw down of water levels in wetlands that receive drainage flows from Trinity Oaks, providing increased storage for flood waters prior to large storms. The drainage improvements provide for temporary bypass of surface water stored in wetlands upstream of Mitchell Boulevard to the Anclote River, in preparation for predicted rainfall events. This, in turn, improves performance of detention ponds serving the residential subdivisions.
DES was contracted by Pasco County to provide modeling services, and collaborated with Atkins, Inc. to develop the design improvements.
BMP 1A consists of construction of two 36–inch culverts extending from Mitchell Road to Seven Springs Boulevard. A manually operated gate is installed at the downstream point of discharge to an existing sump. The gate will be included in an automated control system in the future. Construction of the culverts and operable gates resulted in minimal temporary impact to forested wetlands in and around the site.
The bypass structures are closed upon the onset of rainfall, so as to return the regional stormwater management system to its normal operating condition, only with some additional available storage having been created by the temporary operation of BMP 1A.