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• March 31,2005 Mr.M. Scott Mansholt—CEMC ISite Investigation Workplan,Mountain House Sites 44 and#5 Page 4 of 5 SAIC proposes to collect soil samples from selected borings for use in a future human health risk assessment(HERA). These soil samples will be collected from an approximate depth shallower than 10 feet bgs from the proposed soil borings. SAIC will submit a minimum of one soil sample from the upper 10 feet of borehole at either the 1 or 5 foot-bgs interval if no impacted soil is ' observed to the depth of 10 feet bgs,or above groundwater if water is observed shallower than 10 feet bgs. However, if affected soil is observed above 10 feet bgs, SAIC will collect a soil sample for HHRA purposes from the most affected interval. Soil samples collected for the HHRA will ' be analyzed for the same constituents as all other samples. However,soil samples collected for HHRA purposes will be analyzed using a detection limit that is sensitive (low)enough to detect concentrations of constituents that are not of human health concern. ' PROPOSED ANALYSES SOIL SAMPLE ANALYSES Soil samples from selected borings will be collected from depths that coincide with affected intervals observed in previous borings or from the most affected soil interval encountered in new borings. Selected soil samples will be submitted to Lancaster Laboratories (Lancaster) in ' Lancaster, Pennsylvania(ELAP# 2116),under proper chain-of-custody protocol. Selected soil samples will be analyzed for benzene,toluene, ethylbenzene and xylenes(BTEX)by EPA Method 802113,TPHc by EPA Method 8015 modified, and polynuclear aromatic hydrocarbons ' (PAHs)by EPA Method 8270C Selective Ion Monitoring(SIM). Following completion of the soil borings,the open boreholes will be destroyed according to SJCPHS requirements. GROUNDWATER SAMPLE ANALYSES ' SAIC will obtain grab groundwater samples from selected borings and submit them to Lancaster under proper chain-of-custody protocol for the following chemical analyses: BTEX by EPA Method 826013;TPH as gasoline(TPHg)and TPH as diesel(TPHd)by EPA Method 8015 modified; TPHd by EPA Method 8015 modified with silica-gel cleanup for positive detections by EPA Method 8015; and PAHs by EPA Method 8270C SIM. 1 To facilitate the use of groundwater samples in a HHRH, SAIC recommends that detection limits for BTEX and PAHs be requested from the laboratory that are lower than the EPA Region IX Preliminary Remediation Goals(PRG). The benzene detection limit for use in a HHRA should I be less than the EPA tap water PRG of 0.34 micrograms per liter(µg/l,). A detection limit of <0.1 µg/L should be requested for benzene. A detection limit of<1.0 µg/l, is adequate for toluene,ethylbenzene, and total xylenes. Groundwater detection limits for all PAH compounds ' should be requested at<0.01 µg/l, except for benzo(a)pyrene and dibenzo(a,h)anthracene, which should be requested at<0.005 µg/L to ensure the grab groundwater data is adequate for use in a HHRA. 1 QUALITY ASSURANCE/QUALITY CONTROL This investigation will be conducted in accordance with SAIC's SOPS Quality Assurance and ' Quality Control Sample Collection, Handling, and Analysis Guidelines and the CTA(Geomatrix 2002). One trip blank water sample and one equipment blank water sample will be collected and analyzed. Quality control samples will be analyzed for: BTEX by EPA Method 826013; TPHg and TPHd by EPA Method 8015 modified; TPHd by EPA Method 8015 modified with silica-gel cleanup for positive detections by Method EPA 8015; and PAHs by EPA Method 8270C SIM.