SITE INFORMATION AND CORRESPONDENCE

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Mr. Eric Jenks - 2 - 17 May 2012 Plan dated 15 June 2011. A total of twelve (12) CPT borings were advanced, approximately spaced at 110 -foot intervals along South Stockton Street between West 2" and West 5th Streets. CPTs were advanced to a depth below the deeper coarse- grained layer, which was anticipated at 60 to 80 feet bgs based on the CPT logs along South Argonaut Street. In order to investigate the stratigraphy deeper than 80 feet bgs, select CPTs (CPT -13, CPT -16, CPT -19, and CPT -22) were designated for a total depth of at least 100 feet bgs. Based on the geology encountered, two additional CPTs CPT - 21, and CPT -23 were also advanced to a depth up to 100 feet or more. A total of twenty two (22) grab groundwater samples were collected from borings within approximately three feet of each CPT location. The coarse-grained layers, which were identified in borings from approximately 50 to 115 feet bgs, were targeted. Grab groundwater samples were also collected from the 40 to 50 feet bgs range. Groundwater samples were analyzed for VOCs by EPA Method 8260B, and 1,2,3 -TCP by low-level method SRL 52M -TCP. Concentrations of 1,2-DCP were detected in groundwater ranged from 6 pg/L to 17 pg/L at depths ranging from 72 to 74 feet bgs. 1,2,3 -TCP was detected at 0.012 pg/L in groundwater at this depth. The report indicates that 1,2-DCP and 1,2,3 -TCP were the only VPCs detected in groundwater along South Stockton Street. The report recommends conducting a Phase III deeper groundwater investigation to characterize the vertical extent of 1,2-DCP and 1,2,3 -TCP and to identify the downgradient limit east of South Stockton Street. Proposed Work Plan The Work Plan proposes to advance additional five (5) offsite CPT borings CPT -13A, and CPT -24 through CPT -27 to identify the downgradient extent of 1,2-DCP and 1,23 - TCP in deeper groundwater east of CPT -13 through CPT -15 on South Stockton Street which were advanced as part of Phase II investigation. The Work Plan proposes to conduct the investigation in accordance with the CPT and grab groundwater sampling procedures detailed in the June 2011 Phase 11 Deeper Groundwater Investigation Work Plan. CPT -13A will be advanced immediately adjacent to the previous CPT -13, to as deep as the CPT rig can push until refusal, or until a maximum depth of 150 feet bgs. CPT -24 through CPT -26 are proposed in the public right-of-way of West 3 d Street and West 2nd Street. CPT -27 will be east of Interstate 5 in the City of Stockton Fleet Maintenance Yard, providing access can be obtained from the City. The CPT logs at these locations will be conducted to as deep as the rig can push until refusal, or until a maximum depth of 150 feet bgs. Groundwater samples will be collected from the coarse-grained water -bearing zone from approximately 70 to 90 feet bgs. Grab groundwater samples will be analyzed for VOCs including 1,2-DCP by EPA method 82608, and 1,2,3 -TCP by low level SRL 52M -TCP. The results of the Kam_ E. LoNaL r ScD, P.E., GKNR I PAMELA C. CAmD= P.E., SCEE, FOMMiE OFFICER f 1024 R%m Cr41Mr dHa #2M PAndb Ca'dera, CA 06M I www.walarhondLO&Qodaanbdrdiq ra ■.CVICLOO ~NH