Purpose: Contaminants in sediments endanger bottom-dwelling organisms like crayfish, and are threats to birds and other creatures that eat these organisms. To measure this risk accurately, BES and its contractor, Parametrix, need to predict how much contaminant goes into the water (where it affects the organisms) and how much remains on the sediment particles (where it may be harmless). OGIšs results are designed to provide the key information that has not yet been obtained.
Benefits to BES: BES wants to gain the greatest improvement in environmental quality for the least amount of money. The details about contaminant distribution provided by OGI will allow Parametrix to fine-tune its risk assessments for the city. This detailed risk analysis will help BES create a final cleanup plan that attacks the worst problems first, and avoid wasting resources on areas that present minimal risk to humans or the environment.
Purpose: Colloids are particles so small that they often appear to be dissolved in the water. Contaminants can adhere to colloids and thereby also seem dissolved in the water. Truly dissolved contaminants present a high risk to organisms, but colloid-bound contaminants may present little or no danger. Thus, BES and its contractors must be able to distinguish between contaminants adhered to these fine particles and the more dangerous fraction of contaminants in true solution.
Benefits to BES: Existing measurements of contaminants in sediment pore water are an important part of establishing the risk posed by these contaminants, and thus affect the direction of the cleanup. A recent scientific guidance document issued by the EPA suggests that conventional measurements of pore waters may overestimate this risk of contaminants by failing to distinguish between high-risk chemicals in solution and low-risk chemicals on colloids. The OGI results will help BES and Parametrix avoid potentially costly overestimates of risk by making this critical distinction possible.
Purpose: The risk posed by contaminants in sediments often depends on how quickly these compounds are released from the surface of the sediment particles, especially when the sediments are being washed along by the current or disrupted during a cleanup operation. It also is important to know how quickly sediment particles take up a contaminant that enters the slough. Virtually nothing is known about these critical rates in the Columbia Slough, so OGI will measure them for samples taken from the slough bottom.
Benefits to BES: BES needs to provide DEQ with accurate models of the movement of contaminated sediments in the slough. OGI's results will be an essential part of creating a suitable model for this purpose. Furthermore, BES needs to assess different strategies for cleaning up the worst of the contaminated sediments, such as dredging and land-disposal of spoils. The OGI rate data will be useful in selecting and justifying the most environmentally sound, yet cost-effective, cleanup options.
Purpose: "Fugacity" is a scientific term that refers to the tendency of a chemical to "flee" from one material to another (for example from sediments to water, or from water into fish tissues). Fugacity modeling is a valuable tool for understanding how contaminants migrate into fish tissues or escape into the air, and thus is helpful for both risk and transport assessments.
Benefits to BES: To accurately define the risk of contaminants for BES, Parametrix is developing and refining estimates of the distribution of contaminants among the important components of the slough system. Parametrix has recommended that these results could be made even more useful if they are put in a general fugacity- based model of contaminant behavior. Such a comprehensive model, as prepared by OGI, will allow BES to present the most coherent possible picture of contaminant behavior to DEQ and other regulators. A fugacity model also allows BES to construct valuable "what if" scenarios about the overall results of various cleanup options.