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S E C ® R • Conceptual Site Model March 24, 2004 Page 14 F- Excerpts from the former ARCO service station reports are presented in Appendix JQor,� 6.4 The Transmission Shop 641 Site Description The site is currently occupied by a transmission repair shop, located on the northwest corner of West Charter Way and South Lincoln Street The site previously developed as a retail service station Retail gasoline operations were terminated in the 1950s Historical records indicate that sub-surface a facilities consisted of two USTs One of the USTs was removed in February 1996 Based on a x 4 review of available documents during a file review, the second UST removal date could not be determined These activities are summarized in EMCON's February 5, 1997 Preliminary Investigation and Evaluation Report 642 Remedial Activities eve A SVE system has been in operation at the site since February 2000 Four SVE wells (VW-1 "n through VW-4) were installed adjacent to the former USTs, dispenser island, and in the northwest corner of the site As of the first quarter of 2003 the SVE system had removed approximately 3,171 • pounds of TPHg, and 4 5 pounds of benzene The SVE system was shut down due to decreasing vapor concentrations 643 Historical Report Summary September 1996, five soil borings (B-1R thru B-5R)were advanced at The Transmission Shop Three soil borings were converted to dual-completion vapor extraction wells (VW-1 through VW-3), and one boring was converted to a groundwater monitoring well (MW-1) The fifth boring was abandoned by backfilling with neat cement In October 1996, a single sod boring was advanced and converted to a vapor extraction well (VEW-4) The purpose of the six borings was to evaluate residual hydrocarbons in the sod and dissolved hydrocarbons in the groundwater in the area of the former UST's and dispenser islands Soil analytical results reported TPHg at concentrations ranging from 53 mg/kg (S-30 5-B1 R) to 11,000 mg/kg (S-21 5-64R) Benzene was reported in sod at concentrations ranging from 0 11 mg/kg (S-40 5-131 R) to 5 4 mglkg (S-40 5-132R) MtBE was reported in sod at concentrations ranging from 0 68 mg/kg (S-25 5-13211) to 18 mg/kg ( S-40 5-132R) Groundwater samples collected from MW-1 R reported TPHg, benzene, and MtBE at concentrations of 33,000 pglL, 1,400 pg/L, and 550 pg/L, respectively These activities are summarized in EMCON's February 5, 1997 Preliminary Investigation and Evaluation Report In March of 2003, Shaw Environmental Inc (Shaw) installed two (MW-4RS, MW-4RD) wells onsite to evaluate the vertical and lateral extent of petroleum hydrocarbons in soil and groundwater The groundwater flow direction calculated from groundwater level measurements made in these wells was to the west 0 01 to 0 04 ft/ft This flow direction conflicts with other investigations showing the flow gradient fluctuating from the northeast to the east-southeast These activities are summarized in Shaw's June 2003, Additional Assessment and Remedial Feasibility Test Report b 1 ICht�vron1920331REPORTSICSMICSM 92033 1fiEV B! doc