Potential for Existing Detention Basins to Comply with Updated Stormwater Rules: Case Study

Abstract

In 2004 the State of New Jersey updated its stormwater management regulations with stricter design standards for attenuating peak flow, improving water quality, and recharging groundwater. This case study modeled four properties in Middlesex County, New Jersey to examine the potential of basins built before 2004 to comply with the new design standards. None of the models meets all aspects of the 2004 regulations. The model of a 10-year-old residential site produces results within 10% of two of the peak flow reduction targets and provides 18% of the target groundwater recharge volume. The model of a 32-year-old basin does not meet any of the peak flow reduction targets, has a detention time of less than 1 h and infiltrates 1% of its target recharge volume. A hypothetical hydraulic conductivity of 5 cm/h was added to the models to explore the potential effects of a soil restoration technique such as deep tillage. With this rate, the groundwater recharge for the 10-, 21-, and 32-year-old models increases to 101, 21, and 22% of their target volumes.