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Report of Investigation Former Underground Storage Tanks 3105 South El Dorado Street Stockton California Sierra-Pacific Project No 96-620 01 ' mounted, hollow-stem auger drill rig The bore hole diameter was 8 inches The hollow-stem auger provided minimal interruption of drilling while permitting soil sampling at desired intervals A ' California-registered geologist from Sierra-Pacific continuously logged each bore hole during drilling and constantly checked drill cuttings for indications of both the first recognizable occurrence of ground ' water and contaminants, using a portable photoionization detector The stainless-steel split spoon sampler used for collection of the soil samples was decontaminated prior to sampling and between samples using a solution of tap water and a non-phosphatic surfactant (Alconox®) The sampling equipment was then rinsed in tap water and again in de-ionized water prior to air drying for use All the ' brass sample sleeves were similarly pre-cleaned prior to their one-time use, to minimize the potential for cross-contamination The split-barrel sampler was driven at intervals into the bottom of each soil boring by a 140-pound drop hammer as the boring was advanced, through the hollow stem of the 8-inch diameter continuous-flight ' augers The sampler was extracted from the bore hole and the brass tubes, containing the soil samples, were removed Upon removal from the sampler,the selected brass tubes were immediately trimmed and ' capped with Teflon® sheets and plastic caps The samples were then sealed, labeled, and were placed in a cooler on ice for hand delivery, under cham-of-custody protocols, to the analytical laboratory on the ' same day they were collected The analytical laboratory selected for sample analysis was Exelchem Environmental Labs in Roseville, California A portion of each soil sample collected was analyzed in the field using a portable photoionization ' detector(PID) The purpose of this field analysis was to qualitatively determine the presence or absence of hydrocarbons The soil sample was sealed in a Ziploc' plastic bag, and was left in the sun for a few ' minutes to allow for some volatilization of VOC's, if present The PID was then used to measure the concentrations of hydrocarbons within the headspace inside the plastic bag The data was recorded on the boring logs at the depth corresponding to the sampling point (see discussion of PID data in Section Sierra-pacific Groundwater Consultants, Inc 5 1