Infiltration trenches have been shown to effectively manage stormwater runoff but are reported to have a high risk of clogging when implemented without pretreatment. This study assessed the performance of an infiltration trench (IT) stormwater control measure (SCM) equipped with an R-Tank modular stormwater tank system and a pretreatment surface filtration system (Contech Jellyfish). The IT replaced an older IT without pretreatment that experienced diminished performance after only 1 year of operation due to sediment accumulation. The pretreatment filter system was installed upstream of the IT to minimize the accumulation of sediments that caused the previous IT to fail. The results presented herein document the performance of the filtration system to pretreat stormwater runoff from 541 m2 of an elevated parking deck over the first 29 months of operation with respect to total suspended solids (TSS) removal, as well as the removal of other water quality constituents. Even though the average TSS concentration entering the pretreatment system was relatively low (12.0±11.3 mg/L, n=31), the pretreatment system decreased the TSS concentration by 59.7%±39.7% (n=15) where influent TSS concentrations were above the minimum reporting limit. In addition, removal percentages of suspended copper (59.7%±21.1%, n=15), dissolved copper (53.1%±27.1%, n=5), and suspended zinc (59.8%±18.8%, n=12) concentrations were comparable to the TSS removal. Total Kjeldahl nitrogen (56.6%±29.3%, n=9) and total phosphorus (39.8%±27.8%, n=7) removal was also observed, and these losses were attributed to particulate organic N and P removal by the filters. Sediment accumulated on the filters at a rate of 20 mg/d/m2 of the parking deck surface area and had a medium particle size (53.3 μm) and organic content (30.1%±6.2%, n=3) that was comparable to the medium particle size and organic content of sediment that accumulated inside the old IT that failed within 1 year of operation. Recession rates of the IT retrofit were greater than the old IT prior to failure demonstrating that, after removal of the failed infiltration system, the subgrade infiltration function was still viable. No decrease in recession rates was observed in the IT retrofitted with pretreatment filters during the first 29 months of operation. These results indicate that surface filtration pretreatment to remove fine-grain stormwater sediment can play a role in extending IT operation, while also serving to remove pollutants from the watershed.
Komlos et al. (Sat,) studied this question.