HydroQual provides a unique service to our clients who are in need of having an Ecological Risk Assessment completed. This arises from our recognized expertise in the development of techniques for assessing organic chemical and metal bioavailability in both water and sediment systems. These methods have typically been developed in studies conducted in cooperation with EPA. They have gained broad acceptance by regulatory and industry groups alike, in both the United States and abroad. The basic idea is that the total concentration of a stressor in an environmental media is not necessarily indicative of the potential for toxic effects. That is, equivalent concentrations of a stressor may exhibit markedly different effects as a result of the physical-chemical characteristics of the media (soil, sediment or water). Consideration of bioavailability provides a way to account for these differences and to make an informed and technically defensible decision with regard to the extent of remediation that is warranted at a site. These bioavailability-based methods provide a way to direct limited financial resources at problem areas that will yield the greatest environmental return on investment. At the same time they may lead to the identification and protection of a valuable ecological resource that may have been incorrectly viewed as being adversely impacted.