Assessment of Clogging Dynamics in Permeable Pavement Systems with Time Domain Reflectometers

Abstract

Infiltration is a primary functional mechanism in green infrastructure storm water controls. This study used time domain reflectometers (TDRs) to measure spatial infiltration and assess clogging dynamics of permeable pavement systems in Edison, New Jersey, and Louisville, Kentucky. In 2009, the U.S. Environmental Protection Agency constructed a 0.4-ha parking lot surfaced with three permeable pavement types (permeable interlocking concrete pavers, pervious concrete, and porous asphalt). Paired TDRs were installed at two locations in each permeable pavement type and at a depth of 0.4 m below the driving surface. The relative volumetric water content (RVWC) prior to an event had a significant negative correlation to antecedent dry period, and the peak RVWC during an event had a significant positive correlation to the peak 5-min rainfall intensity. The TDRs measured a significantly different response when water was presumably infiltrating as direct rainfall compared to rainfall combined with runoff from a contributing drainage area. The results indicated clogging progressed from the upgradient edge. Based on the lessons learned at Edison, TDRs were installed in permeable pavement strips in Louisville, Kentucky, during December 2011. The TDR placement strategy was selected to understand the spatial infiltration of runoff and to document clogging and infiltration dynamics. As contributing drainage area size and condition impacts incoming sediment load, and the runoff infiltrates along the upgradient edge of the permeable pavement surface, the ratio of drainage area to working width of permeable surface is an important design parameter to predict the rate of clogging. At Edison, the design ratio of contributing drainage area to permeable pavement width at the upgradient edge was 7.62 m2/m. In Louisville, the ratio was about 3,829 m2/m. Because of the much larger ratio, clogging was expected to occur rapidly at the Louisville site. Responses from rainfall events during the first three months at Louisville supports the hypotheses related to surface clogging mechanisms. This paper highlights evaluation techniques, placement locations, and techniques to use TDRs to remotely monitor surface clogging, which can be used to provide guidance for maintenance scheduling.