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r 09 January 2003 - AGE-NC Project No. 95-0114 Page 6 of 9 CPT6-120 and CPT7-120 at 4.1 µg/l and 2.6 µg/1, respectively, and TCE was reported in sample CPT6-120 at 2.0 µg11. In addition, 1,2-Dichloroethane(1,2-DCA)was detected for the first time in the off-site CPT samples CPT3-110, CPT4-110,CPT5-120 and CPT6-120 at concentrations of 2.9 gg/l, 1.6 µg/l, 2.4 gg/l and 3.2 gg/l, respectively. Vinyl Chloride was not detected at or above laboratory reporting limits in the ground water sample. The laboratory report (CTEL Lab I.D. 0211-125-01 to 08, 0211-205-01 to 06 and 0212-005-01 to 04) QAJQC report and chain-of-custody form are included in Appendix B. Analytical results of the CPT grab ground water sample is summarized in Table 1. 3.4. CONCEPTUAL SITE MODEL The site was occupied by large-volume dry cleaners from approximately the 1930's until 1980's. Based on current site configuration, the majority of the dry cleaners appear to have operated at the western edge of the site;however,based on an extensive network of sub-grade and covered piping, the dry cleaners may have also operated on the eastern side of the building on the site. AGE has developed a site model for the release, migration and distribution of the contaminants in the subsurface based on the available data to date. • The subsurface is composed predominantly of interbedded fine-grained soil, mainly clay, silty clay and silt; three laterally continuous clay layers were identified. Coarse-grained sediment is limited to laterally discontinuous layers of sandy silt, silty sand and sand. • Based on CPT-generated lithologic properties,AGE identified a vadose zone extending from surface grade to approximately 25 feet bsg and six hydrologic units. Three hydrologic units (HU 1,HU3 and HU5)are clay layers of low dynamic pore pressures.Three units(HU2,HU4 and HU6) are predominantly zones of interbedded clayey silt, silt and stiff fine-grained sediment, with occasional, laterally discontinuous sand lenses; pore pressures within these intervals vary from medium low to high. • The dominant ground water flow direction at the site ranged between north-northwest to northeast at low hydraulic gradients,based on ground water monitoring data collected since November 1993. • In January 1991,eight underground storage tanks(USTs)were removed from the site. Tanks Nos. 1 through 5, 7 and 8 were removed from a common excavation along the southern portion of the property(tank pit No.1); tank No. 6 was removed from beneath the sidewalk along Van Buren Street (tank pit No.2). AGE has been informed that the tanks contained stoddard solvents used in dry cleaning processes; subsequent analyses of soil samples collected from the common tank pit indicated an unauthorized release of dry-cleaning Advanced GeoEnvironmental,Inc.