Evaluation of Surface Infiltration Testing Procedures in Permeable Pavement Systems

The ASTM method for measuring the infiltration rate of in-place pervious concrete provides limited guidance on how to select test locations and how results should be interpreted to assess surface condition and maintenance needs. The ASTM method is written specifically for pervious concrete, so additional research is needed to determine the applicability of this method to other permeable pavement types. In 2009, the U.S. Environmental Protection Agency constructed a 0.4-ha parking lot surfaced with permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA). Surface infiltration testing was conducted for almost three years, and two methods were used to select test locations: monthly testing at randomly selected locations and quarterly testing at fixed locations. Infiltration rates were significantly different for each pavement type. With almost three years of use, maintenance has yet to be required, although infiltration has decreased in areas immediately downgradient of impermeable asphalt driving lanes and to a greater extent where disturbed soil was present. The longevity was attributed to the clogging mechanism. Runoff transports solids to the upgradient edge of the permeable pavement surface where the solids are filtered and accumulate as runoff infiltrates. As surface clogging progresses from the upgradient edge, the method of selecting a random location across the entire area typically resulted in most locations being on an unaffected area. This did not produce a meaningful change in infiltration rate to suggest maintenance was needed for the entire surface. The results of this study indicate that the ASTM C1701 method may be applicable to PICP; however, for PA, further evaluation is needed. It is recommended that future infiltration testing should strategically select fixed test locations based on expected clogging patterns. Furthermore, less water can be used, enabling more tests to be conducted at strategic locations over the pavement surface area to better determine locations of clogging.