The Watershed Approach
Watersheds are defined by topographic and hydrologic boundaries and represent the most natural and logical basis for assessing and managing the physical, chemical, and biological resources within an aquatic environment. This approach allows for the consideration of the cumulative effects of all pollutant sources within a watershed, which provides a broader and more complete picture of conditions present and allows for an assessment of the relative importance of the individual sources or groups of sources which contribute to impacts. This all leads to more effective problem solving.
Total maximum daily loads (TMDLs) are required to be developed by the Federal Clean Water Act to address long-standing, major contamination issues in waterbodies. Prior to the development of the WATAR program, TMDLs for polychlorinated biphenyls (PCBs) were not watershed-specific, but represented PCB accumulation across multiple tributaries. The new approach provides more-defined geographic focus and a better way to track improvements over time.
In the same way that people can be identified by their fingerprints, many sources of contamination can be identified in the environment by certain characteristics. Through sampling and transport modeling, scientists can determine by chemical properties and signatures where pollutants originate, which enables them to cut off the source and remediate the impacted areas. This is highly specialized, cutting-edge science that reduces the time it takes to finish projects and restore the waterways to a healthy condition.
Previous methods used to determine the presence of PCBs were only able to identify the contaminants if they existed in a particular form. However, certain conditions in the environment can cause changes in characteristics associated with the PCBs over time, which makes them less detectable but not less harmful. When scientific data revealed that the earlier method was insufficient in detecting some of these changes in the contaminants, it resulted in a change in policy to strengthen standard sampling methods. Current methods can detect a wider array of PCB chemical properties and allow for detection at lower concentrations to increase the accuracy of sample analysis and better protect human health and the environment.
DNREC has many pollutants that it is required to monitor and implements various management practices directly or through permitting action in an effort to keep those pollutants from reaching elevated concentrations. However, there are many contaminants that do not have regulatory enforcement to ensure that their concentrations do not exceed unsafe levels. The Environmental Protection Agency (EPA) issues advisories for pollutants which may be found in drinking water and has some requirements for monitoring. This is how emerging contaminants are discovered. DNREC has adopted EPA drinking water lifetime health advisories for certain contaminants that are considered persistent, bioaccumulative, and toxic compounds. DNREC is taking an active role in detection and information sharing to protect and alert the public to contaminants that may be widespread in the environment and with the potential for irreversible health effects.
Page reviewed 3/6/19