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Additional Soil and Groundwater Cnvestigation Report Canepa s Car Wash(Paris Street) ' July 12,2004 Page 10 . monitor shallow, intermediate, and deep groundwater contamination concentration trends, and to obtain ! hydraulic gradient information for the site Condor prepared this work plan addendum at the request of Mr Remo Canepa ' All work conducted by Condor will be performed under the supervision of a California Registered Geologist The fieldwork and reporting will be conducted in accordance with SJCEHD and California Regional Water Quality Control Board (CRWQCB) guidelines and requirements This work plan ' addendum includes a description of the field, laboratory, and reporting procedures proposed to conduct the work, and a project schedule ' 7 1 FIELD AND ANALYTICAL METHODS This section includes a description of the site preparation, monitoring well installation, development, surveying, and sampling procedures, and laboratory analyses 7 2 SITE PREPARATION Condor will prepare drilling and monitoring well installation permit applications and will obtain the required permits from the SJCEHD, City of Stockton, and Caltrans prior to conducting the fieldwork At least 48 hours in advance of the fieldwork, Underground Service Alert (USA) will be notified to locate I and identify underground utilities in the vicinity of the work area However, because some of the proposed well locations are on private property and utilities contacted by USA may not mark their lines past property boundaries and into the site, it is the responsibility of the property owner to locate and identify underground utilities in and near the work area • 7 3 MONITORING WELL INSTALLATION Five multi-screened, discrete depth monitoring wells will be installed to depths of approximately 150 feet bgs to monitor contaminant concentrations and to collect hydraulic gradient information from up to five discrete water-bearing zones identified by the CPT investigation The proposed locations of the monitoring wells are shown in Figure 7, attached One of the five proposed well locations (furthest down- gradient location, in the paved parking lot) is on private property and will require execution of a site access agreement The monitoring well borings will be advanced using "sonic", or vibratory drilling techniques employing high-frequency vibration, low speed rotation, and down-pressure to advance a 4 1/2-inch diameter bit on a ten-foot long sampling core barrel Following advancement and collection of the undisturbed core sample, a 6 5/8-inch casing is advanced down over the inner drill rods and core barrel, the sample is removed and retained in a clear plastic liner, and the core barrel is reinserted and advanced to the next sampling depth The process is repeated to the desired well construction depth The well is constructed inside the 6 5/8-inch casing at the desired depth and the casing is gently vibrated out of the borehole The multi-screened, discrete depth monitoring wells will be constructed using Continuous Multi- Chamber TubingTM (CMT) The CMT is comprised of seven channels and allows for placement of screen intervals at up to seven discrete depths The tubing is installed in the boring and conventional well construction techniques are used to complete the well using a suitable filter pack around the screen intervals and time release bentonite pellets used to seal the annulus between the screen intervals The ` vadose zone/initial groundwater interface screen interval will be from approximately 20 to 35 feet bgs The deeper water bearing zones will be screened at intervals of five feet or less, and will correspond with the relatively laterally extensive, permeable horizons identified by the CPT investigation which occur at �� CONDOR