Implementation of Low Impact Development (LID) Practices in the District of Columbia: Lessons Learned

Abstract

The District of Columbia storm water management regulations established in 1988 now require mitigation of storm water run off where construction and or 5000 sq/ ft of earth disturbance occurs. As in many municipalities in the Mid-Atlantic seeking to meet requirements of the Clean Water Act (CWA), and the Water Quality Amendment in 1987 to the CWA, the District of Columbia began employing Storm Water Best Management Practices (BMPs) for the treatment of storm water run-off. BMPs have typically been end of pipe proprietary devices, underground vaults, modified manholes or filtering practices for water quality treatment and even larger under ground vaults, reinforced concrete, and metal or plastic pipes for storm water quantity control. While the district was a pioneer in the use of underground sand filters for the treatment of storm water in ultra urban settings and continues to approve and install these devices, as well as other subterranean vault and manhole BMP, the city is turning to Low Impact Development (LID) practices which have began to gain more prominence in the development community. This paper investigates publicly financed and implemented LID projects in the District of Columbia and will discuss the types of problems that have occurred and the lessons learned. Biomass mortality, aesthetics and function, as well as hydraulics and maintenance are blamed for most problems. Two LID retrofits are included in the case study and analysis focusing on a bioretention cell (including cost and monitoring data), as well as a retrofit application of various types of pervious pavers.