The typical approach to mapping groundwater contaminant plumes involves drawing plume contours out to each contaminant’s site-specific cleanup criterion. Cleanup criteria differ between contaminants, sites and U.S. states. For this reason, it is difficult to determine which monitoring wells, plumes and sites are most contaminated within a given area or region. For the same reason, it is also difficult to determine which individual contaminant is most concentrated within a single monitoring well.
The Contaminant Exceedance Rating System (CERS) was developed to address these issues by normalizing groundwater contaminant data against their site-specific cleanup criteria. Each contaminant’s laboratory analytical result is divided by its respective site-specific cleanup criterion and the result is a unitless ratio which is then compared against other CERS Values. The CERS Values are then ranked into a set of CERS Ranking Categories for data grouping purposes and ease of mapping.
The CERS was successfully implemented utilizing data from the Former Wurtsmith Air Force Base (WAFB) in Oscoda, Michigan (provided by the Air Force Center for Engineering and the Environment[AFCEE]). Basewide groundwater volatile organic compound (VOC) data from Summer/Fall 2009 was utilized. ESRI¿¿ ArcGIS Version
10.0 was used to map the resultant CERS Values, symbolized by their Ranking Categories. By implementing the CERS, the following were successfully determined for this data: the most concentrated contaminant in each sample, the most contaminated well(s) within each site, the most contaminated wells on the entire base, and the most contaminated plumes on the base.
It is recommended that the CERS be further implemented using additional temporal data from the Former WAFB. It is also recommended that the CERS be implemented using contaminant data from other Department of Defense (DoD) installations. The CERS could allow for comparison of maximum degree of contamination between entire installations, with the overall intent being to assist in the DoD-wide remedial funding prioritizing process. CERS Values could also be used to track remedial progress over time when implemented using temporal data. The CERS does not take into consideration such factors as toxicity or receptor analysis. This document serves as a manual for implementation of the CERS using contaminant data from other sites.