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4 Sampling Design and Rationale As discussed in previous sections of this FSP, the START reviewed available site information to determine past site activities and previously identified contaminants potentially present at the subject property.This information was used to determine the areas of concern at the site where sampling is required,as well as to determine the COPCs. 4.1 Analytes of Concern The COPCs are listed in Tables 1 &2 (Appendix B). The COPCs are based on data from previous investigations and historical land uses.The soil COPCs consist of TPH-g, TPH-d,TPH- mo,VOCs(including BTEX and methyl tertiary butyl ether-MTBE)and metals. Groundwater COPCs consist of TPH-g,TPH-d,TPH-mo,and VOCs(including BTEX and MTBE). The analytical methods for the COPCs will be modified EPA Method 8015 for TPH-g,TPH-d, and TPH-mo; EPA Method 8260 for VOCs(including BTEX and MTBE); and EPA Method 6010/7473 for metals. A summary of the analyses that will be conducted as part of this assessment is presented in Tables 3 and 4 (Appendix B). 4.2 Sampling Design and Rationale This sampling design is intended to supplement the data collected in the 2000 Lowney Associates investigation,where eight borings were advanced in a triangular grid established across the site. During that investigation, samples were collected from depths of 10 to 15 feet bgs in eight borings,and from approximately 5 feet bgs in three of the eight borings(B-2, B-4, and B-5).The identified data gaps include surface and near surface soils as well as groundwater beneath the site. Proposed boring locations are shown on Figure 4(Appendix A). 4.2.1 Soil Sampling A total of eight borings are proposed for the El Concilio No. 1 site. The borings will be placed in a triangular grid similar to that established during the 2000 Lowney Associates investigation that provides random coverage over the majority of the site. Visual Sample Plan (VSP) software (Batelle Memorial Institute,version 5.9,2009)was used to confirm that using an approximate 134-foot triangular grid across the 2.67 acre site results in eight sampling locations with an 85% probability of detecting a hotspot with a radius of 65 feet(Battelle Memorial Institute 2009). Geographic information system coordinates of the previous boring locations are not available; therefore,borings will be located based on professional judgment,VSP grid size,and using the information available on Figure 3. Surface(0 to 0.5 feet bgs) and near surface (2 to 2.5 feet bgs) soil samples will be collected from the eight proposed borings to assess whether contamination exists at the site related to previous site activities, including surface spills,and also determine whether or not the fill material on site is potentially contaminated.Additional soil sampling at depth is not required, as the 2000 Lowney Associates investigation did not detect TPH above action levels in any of the samples collected(5 to 15 feet bgs). Soil samples will be analyzed for TPH-g,TPH-d, and TPH-mo by 14:002693.1401.01BR 4-1 E1 Coocilio No.1