3.5 Toxic Substances

During the course of the study, a toxicological assay was conducted to determine the presence of substances that could be toxic to aquatic life forms. Sediment from each of six water quality sampling locations representing all five sub-basins, was analyzed using a standardized toxicological assay. Analysis of these samples determined that toxins are not collecting in the sediments of the streambed. This is not to say that they are not present in the water column, merely that they are not collecting in the sediments. Possible reasons for this are: 1) that the sediments are primarily coarse grained, and as such are more difficult for various chemicals to adhere to, and 2) that the extreme hydrologic fluctuations do not provide stable areas within the streambed where toxin-laden sediments can deposit. However, in areas where water is detained for longer periods of time, such as wetlands, the assay revealed extremely elevated levels of unspecified toxins. Further analysis of these areas is recommended, especially considering that the areas revealing elevated toxicity levels are located in the manufacturing and industrial portions of the watershed. Additional information related to this area of study can be found in A Technical Supplement to the York Creek Watershed Project Watershed Management Plan.