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uo La u ru:oa rg.♦ aca ata •ovu a U L -' Phase 1 - Environmental Sitt-Assessment Page 9 8.23 Acre Parcel, 3291 South Highway 99 Stockton, California April 24, 1998 CTE Job No. 20-0641 Planned locations of these borings are shown in Appendix C. (Analyses results from this investigation were not included in the file copies received,) As a result of this field investigation, the California Regional Water Quality Control Board (CRWQCB) agreed with the conclusion that activities on the site have not contributed to background levels of lead and the site does not pose a threat to water quality and no further assessment is required (letter from Twila Leclerc, CRWQCB,to Jack Jurges, Arrowhead Technologies, May 9, 1990). This CRWQCB letter stated that"The sample results indicate that extractable lead in all samples is below the detection limit of 0.5 ppm. Also, lead levels in contaminated soil were the same as the background levels of lead" • A memo om Charbel.Yamuni, Manufacturing Engineer, Scantronic Inc., to Mr. Miller, dated September 2, 1991 states that a washless flux has been used for the past previous months in the wave soldering process, and that the washing machine has been removed, all sewer connections were plugged, and that process water was no longer being discharged to the septic system. • Other chemical analyses data consist of six reports between June 1993 and March 1994. Elevated constituents seen in these reports include lead,bis2,phenol, toluene, chloromethane, and methyl phenol. Results for these constituents are presented in Table 2. Comparison of the values shown in Table 2 with regulatory standards shows that all of these values are below regulatory standards except for bis (2-ethylbexyl)phthalate (BI92EPH). BIS2EPH is a component of plastics manufacturing. However, phthalates are common analytical laboratory contaminants and artifacts(EPA, 1994), For this reason,it is suggested that the observed values for BIS2EPH are not cause for concern. • Mr. Steve Woodruff Facilities Manager, Arrowhead Technologies,was interviewed regarding past manufacturing processes at the Arrowhead Technologies facility at 3291 South Highway 99. It was his opinion that the phenol and toluene leached from circuit boards during washing. Apparently, even though the circuit board washing machine was removed and the drain plugged, circuit boards continued to be washed in a sink. This explains the phenol and toluene concentrations seen in the data from 1993-1994. According to Mr.Woodruff, in late 1994/early 1995 the company switched to a different circuit board vendor, this eliminated the need to wash the circuit boards. 4.4.2 Aerial Photo Review. Aerial photographs from 1928, 1952, 1963, 1975, and 1983 were reviewed. These photos showed that past uses (i.e. before construction of the present building in 1982/1983) for the site were agricultural. No evidence for use or release of ha2ardous chemicals was