as an indicator of potential sources of cross contamination. All QC data should be submitted

to the Agency with the ground water monitoring sample results. Chapter One of SW 846

provides guidance for laboratory QA/QC programs.

7.9

Evaluation of the Quality of Ground Water Data

A ground water sampling and analysis program produces a variety of hydrogeological,

geophysical, and ground water analytical data. This section pertains primarily to the

evaluation of analytical data. These data are required by the Subpart F regulations to be

evaluated using the statistical tests outlined in  264.97(h). The results of these tests provide

the fundamental evidence used to determine whether the facility is contaminating the ground

water. Details regarding the specific protocols of these procedures are discussed in

"Statistical Analysis of Ground Water Monitoring Data at RCRA Facilities," Interim Final

Guidance (USEPA, 1989a) and any subsequent addenda to this guidance. The analytical data

may be presented to the owner or operator via electronic transmittal or on reporting sheets.

These data then should be compiled and statistically analyzed by the owner/operator prior to

submission to the state or to EPA. If data are to be transmitted electronically, the

owner/operator should discuss the procedures with EPA regional or state staff to ensure that

all software and hardware being used are compatible.

The following guidelines should help to ensure that units of measure associated with

data values are reported consistently and unambiguously:

The units of measure should accompany each target analyte. Laboratory data

sheets that include the statement "values are reported in ppm unless otherwise

noted" are discouraged, and at least should be examined in detail by the

technical reviewer. It is common to find errors in the units of measure on this

type of data reporting sheet, especially when the reporting sheets have been

prepared manually.

The units of measure for a given target analyte should be consistent throughout

the report.

Owner/operators should ensure that during chemical analysis, laboratory reporting,

computer automation, and report preparation, data are generated and processed to avoid

mistakes, and that data are complete and fully documented. Analytical data submitted to the

Agency should contain the date/time the sample was collected, the date/time the sample was

received by the laboratory, the date/time the sample was extracted, and the date/time the

sample was analyzed.

November 1992

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