June 12, 2003

Tetra Tech Em, Inc.

Mr. Thomas Alcamo
Work Assignment Manager
U.S. Environmental Protection Agency Region 5
77 West Jackson Boulevard
Chicago, IL 60604

Dear Mr. Alcamo:

Tetra Tech EM Inc. (Tetra Tech) is submitting analytical results for two surface water samples collected by Tetra Tech's subcontractor, Earth Tech, Inc., at the Illinois Central Spring (ICS) treatment facility near the above-referenced site on April 25, 2003, during storm (high-flow) conditions. Paradigm Analytical Laboratories, Inc. (Paradigm), of Wilmington, North Carolina, analyzed the samples for polychlorinated biphenyl (PCB) congeners using U.S. Environmental Protection Agency (EPA) Method 1668.

Tetra Tech reviewed Paradigm's analytical data to evaluate whether the data met the data quality objectives specified in the quality assurance project plan for the above-referenced work assignment. Tetra Tech's review was conducted in general accordance with procedures discussed in EPA's "Contract Laboratory Program National Functional Guidelines for Organic Data Review" dated October 1999. The procedures were adjusted as necessary to meet the explicit requirements of EPA Method 1668.

The table in Enclosure 1 summarizes Paradigm's analytical results for the two surface water samples. Enclosure 2 provides the complete analytical results reported by Paradigm in its data package deliverable for the samples. No quality control problems arose during the analyses, so no qualifications were applied to the results by Tetra Tech. Of the 209 PCB congeners analyzed for using EPA Method 1668, about 168 distinct peaks are resolved in each sample chromatogram; Paradigm reports a combined concentration for various congeners that co-elute at about the same retention time and that are very difficult to quantitate separately.

Because the two samples were collected from the ICS treatment facility effluent only 10 minutes apart, they are essentially field duplicates and yielded practically identical results. (Paradigm deems a relative percent difference [RPD] of 30 percent to be routine, but the RPDs between the analytical results for the two samples varied from 0.0 to 16.2 percent.) The relative amounts of the homolog groups in the effluent samples are consistent with past analytical results because the ICS treatment facility effluent is usually identified as containing Aroclor 1248, and a typical homolog analysis of that PCB mixture shows about 20 percent trichlorobiphenyls (TriCB), 60 percent tetrachlorobiphenyls (TetraCB), and 20 percent pentachlorobiphenyls (PeCB). For comparison, a typical homolog analysis of Aroclor 1242 shows about 20 percent dichlorobiphenyls, 40 percent TriCB, 35 percent TetraCB, and 5 percent PeCB, and a typical homolog analysis of Aroclor 1254 shows about 16 percent TetraCB, 60 percent PeCB, and 24 percent hexachlorobiphenyls.

The Paradigm analytical results are usable for all purposes as reported. If you have any questions regarding the storm event surface water sample analytical results, please call me at (312) 946-6491.

Jeffrey Liflka
Site Manager