ARCHIVED REPORTS XR0006438 - Laserfiche WebLink

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M- AffM� September 15, 1993 Working 3o Restore future Ruiz Grocery, Tracy, California and accompanies the samples to a laboratory certified by the State of California. Samples are transported to the laboratory promptly to help ensure that recommended sample holding times well not be exceeded Samples in our custody will be properly disposed of after their useful life has expired Reporting Results of Analyses Hydrocarbon constituents in soil samples are reported in urvts of parts per million. Hydrocarbon constituents in groundwater samples are reported by the laboratory in units of parts per billion (pcb) The maximum contaminant levels listed in Title 22 of the California Code of Regulations for benzene, ethylbenzene, and total xylene isomers in drinking water are 10, 680, and 1,750 pcb, respectively The action level established by the California Department of Health Services for toluene is 100 pcb To conform with the laboratory reports, we report groundwater chemical data in units of ppb. Evaluating the roundwater Flow Direction and Gradient The elevations and positions (Y and "y" lateral coordinates) of the monitoring well are surveyed by a licensed land surveyor with respect to a local datum that references the elevation according to mean sea level The elevation of the monitoring wells are measured within 0 01 foot of the local datum. The horizontal distances are measured to the nearest 0 1 foot The elevations are to be taken to either a notch or an arrow to be marked on the top edge of the well casing. The groundwater elevation for each monitoring well is calculated by subtracting the depth to water from the wellhead elevation. The groundwater elevation information is used to construct a potentiometric surface map, which is used to evaluate the direction of groundwater flow and the magnitude of the groundwater gradient. i I 12302o-1w