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<br /> guidelines, RTD identified where in the subject report the information requested is located Based on
<br /> RTDs review/comparison, the only item missing was a map showing underground utilities RTD
<br /> obtained underground utility location information from the California Water Company (water
<br /> mains/laterals), the City of Stockton, and the East Stockton Sanitary Sewer District (sewer
<br /> mains/laterals) RTD prepared a map showing the location of these underground utilities
<br /> In August 1995, groundwater sampling was conducted using five of the seven onsite wells Total
<br /> Petroleum Hydrocarbons as Diesel (TPHd) were detected in one shallow screened interval well and
<br /> two deeper screened interval wells The wells were sampled again later in August 1995 and indicated
<br /> TPHd in one deeper screened and one shallow screened well These detections were likely related to
<br /> the increase in groundwater levels following the wet winter of 1995 Based on those results, RTD
<br /> proposed to conduct additional groundwater sampling, onsite hydraulic testing, and to prepare a CAP
<br /> In December 1995, RTD, working in conjunction with Doulos Environmental Company (DEC),
<br /> conducted groundwater sampling and hydraulic conductivity testing at the subject site Generally, for
<br /> the deeper screened wells, a Grunfos Redi-Flo submersible pump was used for constant rate discharge
<br /> testing during the purging process For the shallow screened wells, the submersible pump was used to
<br /> evacuate a slug of groundwater for slug testing prior to purging Following purging, the wells were
<br /> sampled with new disposable bailers for TPHd, TPH as gasoline (TPHg) and benzene, toluene,
<br /> ethylbenzene, and total xylenes (BTEX) RTD collected extra samples from each well for possible use
<br /> as a decanted sample for analysis of TPHd without suspended solids In addition groundwater
<br /> samples were analyzed for geochemical indicators of intrinsic bioremediation, including alkalinity,
<br /> total iron, nitrate, mtrite, phosphate, sulfate, total sulfur, total dissolved solids, and pH Following
<br /> groundwater sampling, dissolved oxygen (DO) was measured in each well using a YSI Model 57 DO
<br /> meter equipped with a submersible probe
<br /> The primary conclusions from the data collected in December 1995 include 1) the levels of the
<br /> geochemical indicators of intrinsic bioremediation showed no evidence of reduction reactions
<br /> involving alternate electron acceptors and are fairly consistent in both shallow screened and deeper
<br /> screened wells, with the exception of slightly higher DO levels measured in the deeper screened wells,
<br /> 2) the hydraulic conductivity results were consistent within each group with the deeper screened wells
<br /> exhibiting high values and the shallow screened wells exhibiting moderate to low values, 3) minor and
<br /> limited TPHd concentrations were detected in groundwater samples from only two deeper screened
<br /> wells, 4) the TPHd detected in groundwater samples is representative of soil impacts, not groundwater
<br /> impacts, and 5) the remaining TPHd levels in soil are too low to dissolve detectable levels in
<br /> groundwater The lack indicators of bioremediation is evidence in support of the fact that
<br /> groundwater is not impacted with petroleum hydrocarbons
<br /> Physical and Chemical Characteristics of Petroleum Hydrocarbons
<br /> The petroleum hydrocarbons identified at the site are primarily diesel fuel with lesser amounts of
<br /> gasoline Each of these products are composed of many individual compounds Rather than testing
<br /> for each individual compound, the products are quantified in separate groups depending on boiling
<br /> point ranges for the different products Gasoline can be considered a low boiling point range
<br /> petroleum product and diesel fuel oil can be considered a middle boiling point range petroleum
<br /> product
<br /> Low Boiling Point Range Hydrocarbons
<br /> While there is some variation is the composition of gasoline this product should conform to the
<br /> ASTM requirements for distillation range, distillation residue, vapor/liquid ratio, vapor pressure, lead
<br /> • content, sulfur content, copper strip corrosion, existent gum, oxidation stability, antiknock, and water
<br /> tolerance The most common constituents of gasoline are alkanes (36- to 71-percent) which range
<br /> from C4 to Cie, aromatics (22- to 54-percent) which range from Co to Ca, and alkenes (5- to 13-
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