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C A M B R I A During February 1996 Enviros, Inc. (Enviros) drilled two Geoprobe borings (GP-1 and GP-2) in the vicinity of the UST complex to investigate the extent of petroleum hydrocarbons detected during the December 1994 tank removal activities. Enviros drilled one angle boring beneath the UST complex and one vertical boring adjacent to the UST complex. Soil samples collected from both borings did not contain detectable concentrations of petroleum hydrocarbons, but did contain MTBE at concentrations ranging from 2.2 to 29 ppm. © Technical Rationale for Proposed Scope of Work • The vertical and lateral extent of MTBE detected during the February 1996 investigation has not been delineated. • SJCPHS indicates depth to ground water in the vicinity of the site is approximately 50 fbg. • To evaluate the vertical and lateral extent of MTBE, five soil borings are proposed at the locations shown on Plate 2. Soil (and ground water samples, if ground water is encountered) will be collected and analyzed to delineate the extent of MTBE in the vicinity of the UST complex. Work Tasks Permits: An appropriate permit for drilling will be obtained from SJCPHS. Health and Safety Plan: A site-specific Health and Safety Plan will be prepared for field work. Utility Clearance: Proposed drilling locations will be marked and their locations cleared through Underground Services Alert (USA) prior to drilling. I Site Investigation.{ Five exploratory soil borings (SB-I through SB-5) are proposed at the locations shown ora Plate 2. Boring SB-1 will be drilled at the location where MTBE was previously detected (in Boring GP-I at 22 fbg) to define the vertical extent of MTBE at this location. Boring SB-2, SB-3, and S134 will be drilled adjacent to and around the UST complex to assess the extent of MTBE previously detected beneath the UST complex. 240-0955 2