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Work Plan—Site Sampling Page 6 West Weber Site-Stockton GPE Project 536.2 2.0 DATA COLLECTION The following sub-sections describe the rationale and methods that will be used to obtain the samples and laboratory analytical information to be used in the completion of the investigation. Prior to commencing soil boring work, Underground Service Alert (USA) will be contacted to mark the locations of buried utilities so that the risk of damaging such installations along with associated health hazards, can be minimized. 2.1 Field Work Soil and groundwater samples will be collected at specific points on the subject site. These samples fall into the following categories: • Soil Gas Survey Points • Shallow Soil Targeted Samples • Shallow Soil Screening Samples • Soil Boring/Groundwater Samples • Background Metals Samples The following subsections provide details of these sample groups. 2.1.1 Sampling Strategy Sample sites are generally authoritatively or randomly selected, depending of what is known of the distribution of the possible contaminants. In cases where specific sites are known or suspected to have been affected by a release(s) samples are collected at points, or a series of points that are most likely to have been impacted. In cases where a large area may have been impacted by a release, or little is known of the source of a release, a suite of sample points may be selected randomly with the number random sample points being dependent on specific data quality objectives. In this case, all sample points were selected on an authoritative, or biased basis except for those targeted at the fill material area on the west side of the Stockton Cold storage part of the site, where a group of random samples will be collected. 2.1.1.1 Soil Gas Survey Points The three sites of past remedial investigations of leaking underground gasoline tanks (Tank Sites 1, 2 & 4) will be investigated by extracting samples of air from the pore spaces of the soil at each site tank. The purpose of the sampling is to determine if residual gasoline contamination at these sites might be sufficient to cause a health hazard from vapor intrusion into future residential buildings. Four points will be authoritatively selected at each or the three LUST sites for soil gas sampling. The sample points will be located at approximately equal-spaced points within the foot print of the original excavations (as near as can be determined). The gas sampler on a 2937 Veneman Avenue, Suite B240 Geo-Phase Environmental Inc. Phone: (209)569-0293 Modesto, Ca 95356 Fax: (209)569-0295