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Enhancements of Nonpoint-Source Monitoring Programs to Assess Volatile Organic Compounds in the Nation's Ground Water

Wayne W. Lapham, Michael J. Moran, and John S. Zogorski

U.S. Geologcial Survey, 12201 Sunrise Valley Dr., Reston, VA, 20192
Phone (703) 648-5805 email

The U.S. Geological Survey (USGS) has compiled a national retrospective data set of analyses of volatile organic compounds (VOCs) in ground water of the United States. The data are from Federal, State, and local nonpoint-source monitoring programs and were collected during 1985-95. This data set will be used to augment data collected by the USGS National Water-Quality Assessment (NAWQA) Program for assessment of the occurrence of VOCs in ground water nationwide.

Eight attributes of the retrospective data set were evaluated to determine the suitability of the data to augment NAWQA data in answering occurrence questions of varying complexity. The attributes include: the VOCs analyzed for and the associated reporting levels, water use, well-casing material, well depth, depth from land surface to the water level in the well, aquifer lithology, and distribution of sampling points. The data set generally lacks documentation of some characteristics of each well sampled, such as casing material and depth from land surface to the water level in the well. Only about 20 percent of the wells have associated documentation of aquifer lithology.

More than 90 percent of the VOC data are suitable for use in addressing simple occurrence questions relative to some current drinking-water regulations of about 5 micrograms per liter (ug/L). However, only about 15 percent of the data are suitable for addressing these simple occurrence questions at a much lower assessment level of 0.2 ug/L. Enhancing monitoring-program data bases would greatly increase the usefulness of these data in addressing complex occurrence questions, such as those that seek to explain the reasons for VOC occurrence and nonoccurrence in the Nation's ground water. The three most important enhancements to the data set would be: an expanded VOC analyte list, recording the reporting level for each analyte for every analysis, and recording key ancillary information about each well.


National Monitoring Conference, July 7-9, 1998, Reno, Nev., [Proceedings]: National Water-Quality Monitoring Council, 1998, p. III-371-III-381.

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