Groundwater Mounding at a Storm-Water Infiltration BMP

Abstract

This research presents an initial study of the impacts of storm-water infiltration on a shallow unconfined aquifer at a bioinfiltration best management practice (BMP) on the campus of Villanova University. The study site is a vegetated infiltration basin with a 0.52 ha drainage area consisting of parking areas and recreational fields and features approximately 35% directly connected impervious area. The research utilized continuous monitoring of precipitation, groundwater elevation, and groundwater temperature in conjunction with surface water hydrologic modeling to assess the duration, magnitude, and extent of groundwater mounding at a storm-water infiltration BMP. Results indicate that precipitation greater than 1.80 cm causes increased mounding at wells adjacent to the site. In addition, it was found that precipitation less than approximately 1.80 cm leads to larger increases in groundwater elevation at an upgradient control well located near the edge of a large grass field. The extent of groundwater mounding is observed to be localized to the BMP and does not extend a significant distance downgradient. In addition, the magnitude and duration of groundwater mounding is related to both infiltration rate and groundwater temperature, such that cooler temperatures correlate to increased mounding. This study demonstrates the utility of groundwater monitoring for the purpose of BMP hydraulic performance assessment, and recommends that additional research be conducted in the future and that groundwater monitoring be considered for site monitoring plans.