ARCHIVED REPORTS XR0000207 - Laserfiche WebLink

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California Department of Transportation July 7, 1994 Project No 102818-01 1987 to 1992 In 1992, groundwater samples could only be collected from five of the twelve existing mon to n wells In 1993, an additional eleven soil borings were drilled at the facility and six t gs ere converted into monitoring wells, for a total of 18 existing a ' wells GROUNDWATER MONITORING WELL SAMPLING On May 24, 1994, a representahve of Ninyo & Moore measured the depth to the static water level in groundwater monitoring wells located at the site (Figure 2) Groundwater monitoring wells MWA through MW-6 were dry The monitoring wells were first checked for the presence of unnvscible layers using a product-sensing interface probe No product was detected The depth to the static water level was then measured relative to the ' reference marking on the top of the well casing The water level measuring instrument was x decontaminated after each use by washing the probe and lead line with a solution of potable water and tnsodium phosphate, followed by a potable water rinse, and a deionized water rinse � Groundwater at the site is present at an approximate65 feet below surface depth of g (bgs) and flows to the north at an approximate gradient of 0 0033 feet per foot It should be noted that the groundwater elevations measured may be influenced by irngation wells located to the east on the San Joaquin County Fairgrounds A groundwater gradient map is presented as Figure 3 The groundwater elevation measurements are summarized in Table 1 Groundwater samples were collected from nine of the groundwater monitoring wells Groundwater monitoring wells MW-10, MWA 1, MW-12, MW-13, MW-14, MW-16, MW-19, MW-20, and MW-24 were sampled between May 25 and May 27, 1994 Groundwater monitoring wells were ed using a 2-inch diameter submersible pump The submersible pump and associated Z=dwntaminated after each use with a solution of potable t water and tnsodium phospha4 " otable water rinse and a deioruzed water rinse The interior and exterior of the pum and hoses were washed by submersing the equupment in the solutions and drawing wash and rinse water through the pump system 2 Mi