Stormwater Gravel-Peat Infiltration Filter – An Ecohydrological Technology with Good Urban Design

Abstract

Urban stormwater flooding and pollution are severe issues due to connected impervious surfaces. Over recent decades, solutions to these issues have been towards stormwater source control measures. We developed an innovative cost-efficient stormwater infiltration filter, made of gravel-peat mixture and geotextile. Laboratory column tests were conducted to compare a range of volumetric ratios of gravel (limestone and silica) to peat regarding their heavy metal removal efficiency (RE). The tested heavy metals were cadmium, lead and zinc. All ratios had a high RE (95.9%-100%), despite very high initial metal concentrations. The 5LG:1P mixture (i.e., volumetric ratio of limestone gravel to peat was 5:1) had the highest RE (99.6%-100%) and is suggested as a good candidate for implementation. If a longer-term use is required, a 5SG:10LG:3P mixture (i.e., volumetric ratio of silica gravel, limestone gravel, and peat of 5:10:3) is recommended as it kept the high heavy metal RE with a lower clogging potential and lower cost than the 5LG:1P mixture. The most convenient but expensive filter material with high RE is limestone gravel alone. Finally, we proposed two field designs for implementing the infiltration filter, which incorporate concepts of “treatment train” and “good urban design”. We also provided some suggestions for the installation of gravel-peat infiltration filters.