Dear Mr. Alcamo:

As requested by the U.S. Environmental Protection Agency (EPA), Tetra Tech EM Inc. (Tetra Tech) arranged to have laboratory performance evaluation (PE) samples submitted to its subcontracted laboratory, TriMatrix Laboratories, Inc. (TriMatrix), of Grand Rapids, Michigan, for the above-referenced work assignment. The PE samples were purchased from an independent vendor, Environmental Resource Associates (ERA) of Arvada, Colorado, which shipped them directly to TriMatrix for analysis. The purpose of the PE sample analysis was to verify that (1) TriMatrix is following standard EPA protocols for polychlorinated biphenyl (PCB) analysis of water and soil and (2) TriMatrix analytical data provided to Tetra Tech for the work assignment is acceptable according to industry standards. Tetra Tech has received and reviewed TriMatrix's PE sample analytical results. Tetra Tech's findings are summarized below.

A total of three PE samples (two water samples and one soil sample) were analyzed for PCBs by TriMatrix. ERA shipped the samples to TriMatrix on September 25, 2001, as "blind" samples; TriMatrix was not informed of the particular Aroclor present in the samples but was notified of the concentration ranges of 1 to 20 micrograms per liter (pg/L) and 1 to 20 milligrams per kilogram (mg/kg) for the water and soil samples, respectively. In addition, all three samples were labeled with an ERA project number that TriMatrix was to use when reporting its PE sample analytical results to Tetra Tech. Tetra Tech received the PE sample data certification forms from ERA and used them to evaluate TriMatrix's results.

As requested by Tetra Tech, the PE samples contained varying PCB concentrations and Aroclors. Specific PE sample information, including the sample matrix, PCB Aroclor, certified concentration value, and performance acceptance limits within the 95 percent confidence interval for each sample, is presented in the table below. In addition, TriMatrix's sample analytical results are shown in the table for comparison.

Note:

font size="-2">¹The performance acceptance limits are listed as guidelines for identifying acceptable analytical results generated by EPA methodologies commonly used to analyze for the parameters involved and closely approximate the 95 percent confidence intervals. The values are based on analytical verification data generated by ERA; independent referee laboratory results; data from EPA methods; and data from water pollution (wastewater), water supply (drinking water), and Contract Laboratory Program interlaboratory studies.

Tetra Tech has evaluated TriMatrix's PE sample analytical data and finds the results reported to be acceptable. Based on this evaluation, Tetra Tech can assure EPA that the subcontracted laboratory for the work assignment is performing PCB analyses in accordance with EPA protocols. For your reference, Enclosure I contains ERA's data certification forms for the laboratory PE samples (information for the relevant samples is shaded), and Enclosure 2 contains TriMatrix's PE sample analytical results.

If you have any questions regarding TriMatrix's performance, please call me at (847) 818-7189.

Sincerely,