The ultimate fate of some treated transportation stormwater runoff from BMPs is groundwater. Groundwater is a precious resource. If groundwater quality has become degraded from transportation BMP stormwater runoff, the opportunities for the improvement of its water quality is extremely costly. Many beneficial uses of groundwater rely on high levels of water quality, which must be protected. BMPs of concern that could contribute to the degradation of groundwater quality include infiltration BMPs, swales, detention basins, and wetlands. Many state water pollution control regulatory agencies have nondegradation policies regarding groundwater quality. State DOTs need to know the potential extent and magnitude of groundwater quality degradation impacts from transportation BMPs.

The objective of the proposed research is to provide state DOTs with a procedure to estimate the potential extent and magnitude of groundwater quality degradation from transportation BMPs. The research project should include procedures to identify and evaluate current and potential uses of groundwater and water quality requirements that could be affected by transportation BMPs. The direction and flow movement in groundwater aquifers needs to be identified. Any pollutant plumes in aquifers must be evaluated, including direction of flow and concentrations. Treated stormwater quality from transportation BMPs that could infiltrate to groundwater should be identified in terms of flows, constituents, and concentrations. Soil characteristics between the BMPs and the groundwater must be described. The distance between BMP invert and the maximum groundwater elevation must be determined, as well as the rate of flow downward to the groundwater. The fate and transport of stormwater constituents from BMPs must be determined as the constituents move through the soil mantle and ultimately move through groundwater. Procedures should be developed to evaluate the extent and magnitude of any potential groundwater quality degradation from possible transportation BMPs.