Field investigation of clogging in a permeable pavement system

Permeable pavements are commonly used around commercial and industrial buildings to reduce the environmental impact. Results are presented from a forensic investigation of a permeable interlocking concrete paving (PICP) system that has been in service for over eight years. The aims were to quantify the sediment accumulation processes that occurred in the different pavement layers and to improve understanding of the change in the pavement hydraulic conductivity due to the trapped sediments. The majority of the sediment (by mass) was retained in the 2-5 mm aggregate bedding layer, irrespective of the pavement blockage conditions. While geofabrics are efficient at retaining sediment particles less than 33 mm in diameter, a maximum of only 8.3% of the total sediment mass was retained in the geofabric layers. Over 90% of the sediments were trapped in the paving and bedding aggregate layers. The beneficial role of geofabric in filtering out sediments and protecting the integrity of the underlying basecourse may not be significant enough to warrant its inclusion in permeable pavement installations. The PICP system was very effective at filtering and retaining sediments from stormwater runoff. While this resulted in reduced permeability over time, the overall infiltration performance of the PICP system was still satisfactory after eight years of continuous service.