USGS Compiles Data Set for National Assessment of VOCs in Ground Water

Answering questions about the occurrence, status and distribution of volatile organic compounds (VOCs) in ground water at regional or national scales often is difficult if not impossible. Many local and State agencies have high-quality data sets to help answer such questions at the local and State levels; however, a national data set currently does not exist to address questions of regional or national concern. The U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program has compiled such a data set. The data set contains existing data from State and other ambient monitoring programs compiled by NAWQA Study Units in cooperation with local and State agencies, as well as data collected from sampling by the NAWQA Program.

VOC data are suitable for inclusion in the data set if criteria for well-network design and well construction are met and if the collection of the VOC data meet specific criteria. The well network for each aquifer or part of each aquifer should provided a generally unbiased, random, equal- area distribution of sampling sites throughout the aquifer, or part of the aquifer, of interest. Well-construction information must be sufficient to ensure that the water level measured in the well represents the water level in the aquifer being studied and that the sample water collected is from that aquifer. In addition, the well construction and pumping equipment in the well ideally should not affect concentrations of VOCs in the water sample. VOC data are suitable for inclusion in the data set if: (1) the sample was collected from untreated (raw) water at or near the well head before being held in a pressure tank or holding take; (2) nationally accepted methods for collection and analysis were used; (3) analysis was done by a laboratory certified by the U.S. Environmental Protection Agency; and (4) the quantitation levels for the VOC analytes are known and are less than about 5 micrograms per liter.

Published:

1997, Ground Water Monitoring & Remediation, v. 17, no. 4, p. 147-157.