Grant Award Year:
2014-2015
Principal Investigator:
Paul Mathisen
Civil & Environmental Engineering
Worcester Polytechnic Institute
Research Description:
Stormwater associated with runoff in urbanized areas and transportation corridors introduces a wide variety of
contaminants into water supplies. Best Management Practices (BMPs) are normally implemented to mitigate
the impacts of these contaminant loads. However, the processes governing the effectiveness of these systems
in treating stormwater are complex. Furthermore, the role of subsurface flow, a key feature of many of these
systems, is difficult to quantify. An understanding of the processes governing the transport and
transformations of these contaminants in BMPs is essential for protecting groundwater and surface water
resources. The proposed research is a collaborative effort between Worcester Polytechnic Institute (WPI) and
the Massachusetts Department of Conservation and Recreation (DCR) to address these processes. The project
will characterize transport and transformations of contaminants within and adjacent to biofiltration systems,
with specific consideration to the role subsurface processes in mitigating discharge of pollutants into water
supplies. The approach combines a field sampling and monitoring program with field data analysis, reactive
transport modeling, and design assessment. The field sampling program includes collection of field
parameters (dissolved oxygen, specific conductance, pH, and temperature) and samples for nutrients (nitrogen
and phosphorus compounds), additional cations and anions, suspended sediments, and bacteria. The
laboratory analyses will include use of Atomic Absorption Spectrophotometry and ion chromatography to
provide information on a broad range of cations and anions. Simulations will be developed using the
PHREEQC software package to simulate geochemical transport and transformation experienced by
stormwater in the infiltration bed and groundwater downstream of the basin. The reactive transport model will
include consideration of surface exchange reactions, sorption processes and rate-limited oxidation processes
(e.g. ammonium and carbon oxidation). The results are used to quantify the potential transformations that may
affect groundwater quality, and the distance over which these transformations would be expected to occur. By
comparing these results with conditions in an aquifer, the implications of transport in groundwater can be
assessed with respect to the requirements for protecting water supplies.