A common approach to pretreating subsurface infiltration galleries comprised of plastic chambers is to wrap filter fabric around one or more segregated chambers at the inlet. Stormwater runoff that enters this section of the chamber array is filtered through the fabric and stone prior to passing into the remainder of the chamber array. Sediment that is captured in the wrapped chamber section is periodically jetted and vacuumed out to refresh fabric permeability. To assess the long-term viability of such systems, laboratory tests using silica-based sediment were conducted on a full scale wrapped chamber following the NJDEP protocol for media filtration. In addition to head loss and removal efficiency monitoring, the location and recoverability of trapped sediment was assessed. The results suggest that while 80% TSS removal is achievable between the inlet and outlet of the system, a significant portion of the trapped sediment passes through the fabric barrier and is retained in the stone surrounding the chambers. This sediment is not recoverable via jetting and vacuuming. The long-term implications of sediment accumulating in the stone beneath the system are estimated for soils of varying permeability. Particle size distribution of sediment captured by the fabric and captured within the stone bed are also assessed and compared. Recommendations for future testing of fabric wrapped chamber systems to better characterize performance and longevity will be made drawing on the practical experience gained in this laboratory testing campaign.
.jpg "Craig Fairbaugh, A.M. ASCE (he/him/his) photo")