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Abstract:Stormwater best management practice (BMP) design must incorporate the expected long-term performance from both a water quantity and water quality perspective to sustainably mitigate hydrologic and water quality impacts of development. Infiltration trench structures are one of many infiltration BMPs that reduce runoff volume and capture pollutants. Research on the longevity of these structures is sparse, leading to concerns about their long-term value and impeding implementation. In the present study, an infiltration trench was monitored from its inception to determine its hydrologic performance over time and total suspended solids (TSS) capture efficiency. The infiltration trench was intentionally undersized to accelerate longevity-related processes. The infiltration trench provided a 36% TSS removal rate and displayed a distinct decrease in its ability to infiltrate stormwater runoff over the first three years of operation. Results indicate that infiltration through the bottom of the BMP became negligible, while infiltration through the sides of the BMP remained active over the 3-year study period. The results lead to recommendations for BMP design.

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Wadzuk, Bridget M., Matthew Rea, Gregg Woodruff, Kelly Flynn, and Robert G. Traver, 2010. Water‐Quality Performance of a Constructed Stormwater Wetland for All Flow Conditions. Journal of the American Water Resources Association (JAWRA) 46(2):385‐394. DOI: 10.1111/j.1752‐1688.2009.00408.x Abstract:  Results from a multiyear study demonstrate that a constructed stormwater wetland (CSW) improves urban stormwater runoff quality mitigating downstream impacts. Best management practices, such as CSWs, can comprehensively treat the various scales of stormwater runoff issues. Discrete sample analysis was used to investigate the CSW effect for storm events and base‐flow periods on water‐quality parameters [i.e., total suspended solids, total dissolved solids, total nitrogen, phosphorous (total and reactive), chloride, heavy metals (zinc, lead, and copper), and Escherichia coli]. The primary finding was that stormwater sediment load was removed through the CSW for all flow conditions during all seasons. The mechanisms responsible for the removal of suspended solids, including slower flow velocity, longer retention times, and vegetative contact, also reduced the mass of nutrients discharged downstream throughout the year. Exceedance probabilities were used to evaluate the expected pollutant reductions of nutrients and to incorporate the effect of natural flow variation on quality. Other findings included the observation that there was no significant difference in the performance of the CSW over two‐year‐long periods four years apart, indicating that a CSW is effective for an extended period.

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