LID Treatment Train: Pervious Concrete with Subsurface Storage in Series with Bioretention and Care with Seasonal High Water Tables

Abstract

Two infiltrating low-impact development (LID) practices configured in-series, pervious concrete and bioretention (PC-B), were monitored for 17 months to examine the hydrologic and water quality response of this LID treatment train design. For the first LID practice, 0.53 ha of pervious concrete was installed to treat direct rainfall and run-on from 0.36 ha of asphalt parking lot. The pervious concrete was installed over a gravel subsurface storage basin, which was designed to store 25 mm (1 in.) of runoff from the parking lot before draining into the second LID practice, which was a 0.05 ha bioretention cell. The bioretention cell was conventionally drained, had a media depth of 0.5 m (1.6 ft), and was constructed at a location with a high water table. Outflow was only generated in 33 out of 80 monitored events, and over the course of the entire monitoring period, the total outflow volume reduction was 69%. The large outflow reduction subsequently led to high pollutant load reductions for total nitrogen (49%), total phosphorus (51%), and total suspended solids (89%). However, when the contribution of base flow was included in the calculation, the total nitrogen load discharged from the bioretention cell was 64% higher than that of the runoff load because of nitrite and nitrate,