Underground chamber storage is a popular solution to meet LID, detention, and water quality requirements in urban settings; however, little is known about the long-term viability of geotextiles used as filter fabric to remove stormwater-borne pollutants. Nationally recognized performance testing programs such as the Washington State TAPE and the New Jersey Department of Environmental Protection (NJDEP) certification program do not recognize buried filter fabric as an approved treatment solution due to maintenance and access concerns. Questions around clogging, biofouling, and operations and maintenance are not wholly understood or resolved. Still, these practices are widely used across Virginia and in other parts of the country.

This presentation will address 2 recent research projects that examine the long-term water quality performance and maintenance needs of underground chamber storage systems utilizing filter fabric as a treatment mechanism. In the first study, pollutant removal trials conducted in a laboratory setting demonstrated that the addition of organics and hydrocarbons, which are typical constituents within urban stormwater runoff, can clog the filter fabric faster and be a better predictor of the long-term, in-situ filter fabric response. The second study, also conducted in the laboratory setting, evaluated the ultimate location and recoverability of captured sediment in these systems and determined that significant amounts are retained in the stone underneath the buried chambers. This finding suggests that these systems can be more challenging to maintain than previously understood, especially if the typical recovery methods of jetting or vacuuming cannot reach captured sediment in the underlying stone. Ultimately, the results from both studies contradict the limited existing literature data and necessitates a deeper understanding from designers and regulators regarding how these systems function. Drawing on the experience gained from these studies, recommendations intended to improve future testing and utilization of fabric wrapped chamber systems will be shared.