PT15 Contaminated Harbour and River Sediment
Exhibit Hall
8:00 AM - Tuesday
(PT256) Weight-of-Evidence Ecological Assessment of an Urbanized River.
Bleiler, J1, Davis, R2, Archer, C.1, Mitchell, D.1, Mead, Helen3, 1 ENSR, Westford, MA, USA2 U.S. Army Corps of Engineers, New England Division, Concord, MA, USA3 US Army Corps of Engineers, Omaha, NB, USA
ABSTRACT- An extensive investigation of an urban riverine system in southern New England was recently completed to determine whether or not releases from a former defense facility posed a potential risk to ecological receptors. Due to the lack of a definitive chemical signature from the site, it was not possible to assign site attribution to specific constituents found in sediments. For this reason, the risk assessment relied on a weight-of-evidence (WOE) evaluation of the total site risks in each of four sampling reaches evaluated to infer whether or not the site could potentially have contributed to the potential for ecological risks in the system. Six benthic macroinvertebrate, three fish, and one protection of vertebrate wildlife consumers measurement endpoints were considered in the WOE evaluation. At project team meetings, an overall WOE weighting factors matrix was developed and approved by all parties, including the potentially responsible party, state and federal agencies, and natural resource trustees. Weighting factors were assigned for each endpoint, and the potential for risks was evaluated in four discrete categories, with decision rules identified for each category. The results of this WOE evaluation indicate that: (1) there are elevated levels of many constituents present in the river adjacent to, downstream, and upstream of the facility; (2) that the majority of these compounds are present at concentrations consistent with upstream reference conditions; and (3) there is a potential for ecological risk from exposure to these constituents upstream of, adjacent to, and downstream of the site. In general, the potential for ecological risk to benthic invertebrates was found to be low to moderate, with an even lower potential risk to finfish and vertebrate wildlife, respectively. The WOE results suggest that the incremental risks contributed by the former facility are indistinguishable from the anthropogenic, urban background conditions that characterize the river basin.
Key words: Ecological Risk Assessment, Sediment, Weight of Evidence, River