Evaluation of BMP Effectiveness for the Removal of Contaminants Prior to Infiltration

Maine has taken an approach that is at once cautious and aggressive in managing storm water through recharge.  With the exception of sand and gravel aquifers, most soils in Maine have limited capacity to accept water at high rates. Most of the aquifers that are in areas requiring storm water management are utilized for public water supplies. These aquifers can benefit from clean, ‘virgin’ storm water or well-managed and treated storm water and similarly can be damaged by poorly designed and managed systems.Maine storm water regulations do not allow storm water infiltration in public water supply contributing areas unless the design is reviewed and approved by both the DEP and the Drinking Water Program. 

UNH Stormwater Center has been evaluating BMP pollutant removal, including seasonal effects of stormwater through several classes of stormwater systems.The facility is designed to provide a comparison of water quality treatment and water quantity management performance. A range of stormwater systems installed in a parallel yet separate configuration normalizes the variability inherent in stormwater contaminant loading and rainfall. Each system is uniformly sized to address runoff generated by one inch of rainfall off one acre of impervious surface. The facility contains three classes of stormwater treatment systems: conventional, structural systems such as swales and ponds; LID designs such as bioretention cells and subsurface gravel wetlands; and manufactured systems such as hydrodynamic separators and subsurface infiltration and filtration systems.  All systems are installed with an impermeable liner so that researchers   can provide a strict accounting of the runoff flowing through the systems, as well as the contaminants it contains.

This talk will compare pollutant removal and seasonal effects for several systems from each class, including LID systems