January 17, 2003

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 December 19, 2002, during a storm event. TriMatrix Laboratories, Inc. (TriMatrix), of Grand Rapids, Michigan, analyzed the samples for polychlorinated biphenyls (PCB) using U.S. Environmental Protection Agency (EPA) SW-846 Method 8082 and for total suspended solids using EPA Method 160.2.

Tetra Tech reviewed TriMatrix'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 enclosed table summarizes TriMatrix's analytical results qualified as needed by Tetra Tech. Irregular recoveries associated with some of the peaks used to quantify some of the PCB mixtures were the only items outside quality control (QC) limits. Specifically, the percent difference between the average initial calibration factor and the continuing calibration factor exceeded the QC limits of 15 percent for the primary (quantitation) column or 20 percent for the secondary (confirmation) column. However, at all times, results for at least one column were within the QC limits. Furthermore, all results for Aroclor 1248, the only Aroclor detected in these samples, were within their QC limits. No qualifications are warranted for the observed irregularities.

Both samples contained the same PCB mixture, which was a fair match to the Aroclor 1248 standard and a worse match to the other Aroclor standards. Therefore, TriMatrix quantified all sample results against the Aroclor 1248 standard. Both samples contained relatively high PCB concentrations, so the sample extracts were analyzed at a 10-fold dilution to bring the results within calibration range. The five peaks used for quantifying Aroclor 1248 results yielded different quantitative results, with the highest peak being about five times the lowest peak. Therefore, the reported average Aroclor 1248 results for the five peaks are flagged "I" as estimated because of this difference with the standard.

The TriMatrix analytical results are usable for all purposes as qualified. If you have any questions regarding the storm event surface water analytical results, please call me at (312) 946~491.