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Measuring Clogging with Pressure Transducers in Permeable Pavement Strips
Borst, M., R. Brown, J. Rivard, J. Gray, AND L. Kurtz. Measuring Clogging with Pressure Transducers in Permeable Pavement Strips. Presented at World Environmental & Water Resources Congress (EWRI 2013), Cincinnati, OH, May 19 - 23, 2013.
This abstract will highlight the results of using pressure transducers in permeable pavement strips at a field application in Louisville, KY, to measure clogging at the paver surface and at the underlying soil interface.
Two issues that have a negative affect on the long term hydrologic performance of permeable pavement systems are surface clogging and clogging at the interface with the underlying soil. Surface clogging limits infiltration capacity and results in bypass if runoff rate exceeds infiltration capacity. If the interface of the underlying soil clogs, the drain time of the storage layer increases, potentially creating conditions where the storage capacity might be insufficient to capture the next event. In December 2011, the Louisville and Jefferson County MSD installed two permeable pavement strips in parking lanes in the Butchertown section of the city. The surface is 2.4-m (8-ft) wide and either 16.8-m or 36.6-m (55-ft or 120-ft) long. The paver blocks are installed over a 0.6-m (2-ft) deep storage gallery. A 0.6-m (2-ft) wide by 3.0-m (10-ft) deep trench extends along the length of the control beneath the storage gallery. Piezometers were installed at roughly one-third and two-thirds of the length to measure the rise and fall of water. Combining continuous water level monitoring with known internal dimensions and estimated intra-event exfiltration as a function of water level depth, the event runoff volume captured was calculated. These volumes were compared against rainfall depth to determine surface clogging. All runoff was captured until the surface was clogged along the entire control length. Once surface clogging progressed along the entire length, only 25 to 30 percent of the runoff was captured with the remainder of runoff volume bypassing the control. In measuring the water level rise, a subsurface gradient was created from incoming runoff. As surface clogging progressed along the length, the gradient between piezometers reversed after the surface clogging approaches the downgradient piezometer. The exfiltration rate into the underlying soil decreased from the first event. One source of sediment is from the attached solids on the washed aggregate. About 1.7 to 1.8 percent of the mass of the aggregate was smaller than 75 um (silt and clay sized particles – AASHTO).