Hydrologic Performance of Four Permeable Pavement Systems Constructed over Low-Permeability Soils in Northeast Ohio

Permeable pavements benefit urban hydrology through detention of stormwater in the aggregate base and subsequent exfiltration to the underlying soil. The majority of previous research has focused on permeable pavements constructed in sandy soils and/or treating only direct rainfall. Four permeable pavements employing internal water storage (IWS) zones and situated over low-permeability soils were intensively monitored for their hydrologic performance in northern Ohio. Volume reduction varied from 16 to 53% for permeable pavements with low drawdown rates (<0.35 mm/h) and loading ratios (Watershed Area+ Permeable Pavement Area/Permeable Pavement Area) exceeding 5:1. Postconstruction drawdown rates were similar to saturated hydraulic conductivity (K-sat) measured during construction, suggesting that lateral exfiltration and evaporation were relatively minor contributors to volume reduction. Stormwater was completely captured (i.e.,no discharge from the permeable pavements) during 4-80% of observed storm events. Average depth of abstraction ranged from 3.0mm (site with highest loading ratio) to 25.2mm (site treating only direct rainfall). Substantial peak flow mitigation was observed for all rainfall events not producing surface runoff (i.e.,untreated bypass). Under these conditions, peak flow was diminished by more than 80% for seven events exceeding the 1-year, 5-min design rainfall intensity for Cleveland, Ohio. Lower loading ratios, reduced surface runoff, an IWS zone, and higher underlying soil K-sat directly impacted volume reduction and peak flow mitigation. Overall, permeable pavement mitigated negative hydrologic impacts of impervious surfaces even when sited over low-conductivity clay soils.