The State of Hawaii Department of Transportation, Highways Division’s (DOT-HWYS) is engaged in ongoing efforts to reduce pollution from storm water runoff through the implementation of the Action Plan for Retrofitting Structural BMPs and the Trash Reduction Plan. Both plans prescribe storm water Best Management Practice (BMP) improvements of DOT-HWYS Municipal Separate Storm Sewer System (MS4). Storm water BMPs are currently in design and construction at several of DOT-HWYS maintenance baseyards on Oahu. The goal of storm water BMPs is to improve the quality of storm water from baseyards and other paved areas that typically drain through a network of pipes (the Municipal Separate Storm Sewer System, or “MS4”) to outfall locations in stream channels, or drain directly to the ocean. Prior to implementing these BMPs, storm water runoff may contain trash, oils and greases, and unnaturally high nutrients that can have negative impacts on streams and the ocean.
DOT-HWYS most recently completed construction at the Windward Baseyard in Kaneohe. Improvements included repairing and repaving old, damaged asphalt and rerouting storm water drainage to reduce the potential for contact with pollution sources and to allow for more accurate storm water quality monitoring. Storm water treatment improvements also included the construction of a vegetated swale, installation of storm drain inlet filter baskets, and the installation of two automated storm water sampling stations to monitor the quality of storm water leaving the baseyard. This project was managed by DOT-HWYS Lower Halawa Field Office and was completed in June 2019. Be sure to check back next month for details about storm water BMP improvements currently under construction at DOT-HWYS Waianae Baseyard!