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. 5.3 Plume Delineation An eight-point soil and groundwater survey was conducted surrounding the area of known contamination to define the lateral extent of the contaminant plume and select locations for installing additional monitor wells Soil and groundwater grab samples were collected and analyzed during this process to document the delineation work Two geologic cross-sections constructed from this data, exhibit the approximate subsurface boundaries of the contaminant plume(Figure 5) 5 3 1 Soil Boring SEACOR supervised the drilling of eight additional soil borings surrounding the area of known contamination at the site (Figure 6) Only one of these bonngs was actually located on the subject property, whereas the remaining seven borings were located on three adjacent properties Site access permission letters were obtained from all three property owners prior to commencing drilling operations on any of these properties Drilling was performed by Geo-Environmental Drilling (Lic C57 9676923) of Yuba City, California using a Simco 2400 SK drilling rig equipped with 7-inch, outer-diameter, hollow-stem augers on March 29 and 30, 1994 The augers were steam cleaned prior to drilling each boring to prevent downhole or cross-boring contamination Each boring was drilled to a depth which coincided with 1 to 2 feet below the surface of the groundwater The depth of groundwater was apparent in every boring except for B7, groundwater did not enter the boring possibly because of denser soil, or . groundwater was bypassed during drilling and held out of the boring by the hollow stem augers Consequently, no groundwater sample was recovered from this boring These eight borings were drilled to total depths of approximately 21 5 to 26 5 feet below grade (approximately 1 to 5 feet below the groundwater surface) for the purpose of inserting a 2-inch diameter stainless steel well point casing Groundwater beneath the area was encountered in a relatively thin sandy layer at approximately 21 feet below ground surface and was underlain in most places by a medium gray, slightly stiff, clayey silt The locations of these soil borings were selected to represent groundwater in the downgradient and cross-gradient directions (Figure 6) 5 3 2 Soil and Groundwater Sampling Soil samples were collected at approximate 5-foot intervals in the borings using a California-modified split spoon sampler containing three clean stainless steel sleeves The sampler and sample sleeves were washed with laboratory soap and rinsed with clean water prior to each sampling event Following sample collection, the open ends of the lower sleeve were covered with plastic end caps and made airtight with duct tape This sleeve was labeled with SEACOR project and sample identification numbers and the date, and placed In iced storage Approximately one-half of the contents of the middle sleeve was placed in a sealable plastic bag, and after approximately 3 to 4 minutes, the probe of an organic vapor meter (OVM) was be inserted into the bag and the meter reading in ppm was recorded, however, because of a malfunction in the field, the OVM readings SEACOR 01441-1 par 12