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Historic Analytical Data

On November 23, 1987, CSSA received a letter from the TDH Drinking Water Surveillance Program indicating that VOC monitoring of potable water sources was in the beginning stages of implementation. Based on program requirements, CSSA, which supplies water for less than 3,300 people, had to comply with the new standards by January 1, 1991. Prior to 1991, groundwater VOC data was not collected at CSSA.

Analytical laboratory data collected from CSSA since 1991 are from several different sampling periods, and have been analyzed using different methods and different laboratories. The EPA analytical methods chosen for analyzing samples collected from CSSA are described in Test Methods for Evaluating Solid Waste (EPA 1986; referred to as SW-846 Methods). The SW-846 Methods are appropriate for CSSA, since CSSA is not a Superfund site. (Superfund sites require that the EPA Contract Laboratory Program (CLP) be used instead). The SW-846 Methods are analytical procedures to test solid waste defined under RCRA. The methods include procedures for collecting solid waste samples and analyzing them. These methods are frequently updated, and during the course of CSSA’s sampling history, several procedures and analytical methods have been improved upon and altered.

Comparison of these resultant data over time involves evaluating data from different time periods and analytical methods to determine if concentrations are similar, or if changes have occurred between sampling periods. If the methods of analyzing the samples and the QA/QC procedures that were followed are similar, than the data may be combined for the purposes of quantitative characterization of a site. However, if the concentrations of analytes change significantly between sampling periods, the data may be kept separate and evaluated separately. Also, the most recent data may be used for quantitative purposes, and the older data may be used for qualitative purposes to see changes in concentrations over time. These guidelines may be found in the Interim Final Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation Manual (Part A), USEPA, December 1989.

The data collected at CSSA have been analyzed using similar methods for each analyte and QA/QC procedures. Sampling protocol, data validation and SW-846 methodology were similar in all of the data collected at CSSA after 1993; therefore, the data are compared for qualitative purposes. In the future, if data quantification is necessary for any reason, such as a risk assessment, then detailed quantitative comparisons can be made following the guidelines listed in the Guidance for Data Usability in Risk Assessment (Part A), USEPA, April 1992. Data quantification involves analyzing several criteria, including data sources, documentation, analytical methods and detection limits, data quality indicators, and data review. Currently at CSSA, clean-up goals for each analyte at the site (below background levels) indicate that any detection of an analyte from laboratory analysis could be considered viable data in qualitative analysis. Also, the qualitative comparison of data collected from each area has been used to determine the priority of each area. The areas have been assigned a priority of low, medium or high based on data collected at CSSA.