Publication Summary

A prototype stormwater sediment trap was constructed and tested under actual field conditions at four sites in the vicinity of the city of Lacey (Washington State) between June 29 and October 4, 1995. Low flow conditions were present during the testing period with rainfall totaling 5.18 inches.

A prototype stormwater sediment trap was constructed and tested under actual field conditions at four sites in the vicinity of the city of Lacey (Washington State) between June 29 and October 4, 1995. Low flow conditions were present during the testing period with rainfall totaling 5.18 inches.

The sediment traps were able to collect sufficient material (8-164 grams, dry) at all sites to perform at least a portion of the planned physical/chemical analysis on the trapped particulates. Results of chemical analysis of the trap samples indicated that, for metals, the data collected were comparable to a particulate sample collected by continuous-flow centrifugation. Concentrations of polynuclear aromatic hydrocarbons in the trap samples most closely resembled bottom sediment concentrations after the data had been normalized to the total organic carbon content of the samples.

Data collected during the pilot study suggest that stormwater sediment traps have the potential to significantly lower monitoring costs for collection of particulate samples from stormwater discharges. Additional data on the performance of the stormwater sediment traps under actual field conditions (especially high flow) are needed before the traps are ready for routine application in a regulatory framework. Recommendations for follow-up work are provided.