THE OCCURRENCE OF APPENDIX-IX ORGANIC-CONSTITUENTS IN DISPOSAL SITE GROUND-WATER

Monitoring data from 479 disposal site investigations were used to provide an initial estimate of the occurrence and distribution of 208 Appendix IX organic constituents in ground water. The most prevalent class of contaminants were the volatile organic compounds, which accounted for 84 percent of all the detectable events in the composite data set involving Appendix IX organic constituents. The abundance of the remaining subsets of Appendix IX organic constituents decreased in the following order: base/neutral compounds (8.6 percent), acid extractable compounds (3.5 percent), pesticides (3.0 percent), RCRA pesticides (0.6 percent), and non-priority pollutants (0.25 percent). A total of 66 Appendix IX organic constituents, including one volatile compound, two pesticides, three base/neutral compounds, and 60 non-priority pollutant compounds were not detected in any of the waste disposal site ground water monitoring records that were reviewed. The current regulatory requirement to monitor for Appendix IX organic constituents is approximately four times more expensive than monitoring for conventional priority pollutants (volatile, base/neutral, acid extractable, and pesticide compounds). Because the non-priority pollutant compounds account for an estimated 76 percent of the Appendix IX analytical costs but only 0.25 percent of the detectable events in disposal site ground water, it has been recommended that this class of compounds be deleted from routine monitoring programs. A scaling back of the current requirement to the conventional priority pollutants would still target more than 99 percent of the Appendix IX organic constituent occurrences in ground water and result in an analytical cost savings of approximately $2750 per sample or an estimated $51 million a year without significantly reducing the volume of useful organic monitoring data that would be generated to assess ground water conditions in the vicinity of waste disposal sites.