ARCHIVED REPORTS_XR0004841 - Laserfiche WebLink

Home Browse Search

' Manteca Unified School District Soil&Groundwater Investigation eport Page G were analyzed for Total Petroleum Hydrocarbons (diesel) and BTX&E (Benzene, Toluene, Xylene, and Ethyl Benzene) 25 Groundwater Sampling ' A travel blank provided by the laboratory accompanied the sample vials from the time of pick up from the lab to the time of delivery back to the lab All sampling t equipment including the pump, bailers, and cables, used by sampling personnel, were disassembled, and steam-cleaned prior to commencement of sampling These procedures were also followed between each well, sampling point and at the end of the sampling day De-ionized or organic-free water (also provided by the laboratory) was then introduced into the bailer as a final stage of cleaning This water was then poured into sample vials to be used as a bailer blank ' Immediately prior to sampling, water levels and well depth measurements were taken in all wells at the site Each well was evacuated using a stainless steel ' bladder pump, which does not introduce air into the water column The pH, temperature, and electrical conductivity of the water were monitored as the well was evacuated These parameters are noted on a field log Instruments calibrated to known standards were used to monitor these parameters At least 5 well volumes were evacuated from each well, and more, if necessary, until the above parameters stabilized The wells or other sampling points will be sampled in order of the least to the most contaminated, as best known or estimated The samples were carefully poured from a Teflon bailer into clean glass vials with ' Teflon-lined screw caps Care was taken to ensure that no air space existed in the vials by inverting to check for bubbles and re-sampling if necessary ' The samples were analyzed or extracted within 14 days according to their EPA methods The water samples were analyzed for Total Petroleum Hydrocarbons (diesel) and BTX&E (Benzene, Toluene, Xylene, and Ethyl Benzene) ' GeoAnalythcal Laboratories, Inc in Modesto, California conducted analysis ' 3.0 SITE CONDITIONS ' 3.1 Site Geology & Groundwater Occurrence The site is characterized by interbedded sands, silts, and clays The shallow water-bearing ' unit is a medium to coarse-grained unconsolidated sand that occurs approximately 17 to 27 feet below grade The unit is thickest in the southernmost well, MW3, and dramatically thins to the north where it is underlain by a silty clay The northernmost well ' MW1 consists of silts and silty clays with the coarse sandy zone present at approximately 25 feet below grade