Hydrologic Performance of a Permeable Pavement and Stormwater Harvesting Treatment Train Stormwater Control Measure

Abstract

Stormwater runoff from urban development causes undesired impacts to surface waters, including discharge of pollutants, stream erosion, and loss of in-stream habitat. Stormwater control measures (SCMs), such as ponds, wetlands, bioretention cells, and permeable pavements, are employed to ameliorate these impacts. A treatment train SCM was constructed and monitored in the parking lot at Old Woman Creek National Estuarine Research Reserve in Huron, Ohio. Native soils beneath this parking lot were heavy clay with measured average infiltration rates of 0.046 mm/h. The treatment train consisted of permeable interlocking concrete pavement (PICP) parking stalls that provided pretreatment for an underground stormwater harvesting system. The treatment train was intensively monitored for 13 months to quantify the water balance. The average postconstruction drawdown rate was 0.064 mm/h from the scarified soil beneath the permeable pavement, suggesting that if soil compaction imparted during construction is broken up, preconstruction soil testing provides representative estimates of postconstruction infiltration performance for permeable pavement. While stormwater stored in the cistern was never harvested during the monitoring period, total runoff volume was reduced significantly by 27% through infiltration into the underlying soils. Peak outflow rates were significantly reduced by 93.8%±10%. This was primarily related to slow exfiltration from the scarified soil underlying the permeable pavement. Additional (minor) exfiltration occurred due to an unintentional leak in the cistern, creating storage for follow-on events. These results suggest that scarifying the subsoil beneath permeable pavement without an internal water storage zone can lead to a modest amount of storage for stormwater in the subgrade (perhaps 2.5–5 cm below the underdrain invert), which would provide otherwise unrealized opportunities for exfiltration during inter-event periods. This treatment train SCM appears promising for reducing runoff volume and peak flow rate, particularly if a dedicated, year-round water use could be provided to drain the cistern between wet-weather events.