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1.0 INTRODUCTION As the result of the meeting between the Regional Water Quality Board and DDJC-Tracy,which occurred on 5 May 1997(Radian International, 1997)it was agreed that nine groundwater monitoring wells would be installed as part of the Depot's ongoing groundwater monitoring program. DDJC-Tracy recommended locations where one Upper Horizon well and four well pairs would be installed. Each well pair would have a well screened in the Upper Horizon and Middle Horizons. The position and depth of each well was selected to best monitor the efficiency of the existing OU 1 extraction wells located to the west along Banta Road, as well as provide additional monitoring points for tracking the movement of the TCE plume(Figure 1). These monitoring wells have been scheduled for installation during March 1999. The procedure that will be used for this work is summarized in the following sections. A more complete discussion of the well construction procedures is presented in the Comprehensive Field Work Plan (Radian International, 1998). 2.0 WELL INSTALLATION ACTIVITIES 2.1 Pre-Well Installation Activities Before any drilling is initiated. A county drilling permit shall be secured,as well as all of the locations shall be clear of above and below ground utility hazards. Each location will also be identified as being within the agreed legal property easement. The legal description for the Banta Carbona Irrigation District and the DDJC-Tracy easements is presented as an attachment at the end of this document. Figures 2 and 3 present the typical position that these wells will occupy within the legal easements within the Robertson property. 2.2 Field Documentation The Radian International field geologist will maintain an accurate log for all the borings. At a minimum, the log shall include: name of the project and site;boring number;dates drilled;location of the boring;type of drill rig;size and type of drilling method used;depth at which groundwater was first encountered;depth to the static water level and changes in static water level with hole depth;total depth of the hole;depth or location of any problems encountered(i.e.,heaving sands);lithologies of soil layers encountered;reference elevation for all depth measurements;boring abandonment procedures(if applicable);name of driller;and name and signature of the field geologist preparing the log. During the construction of each monitoring well an as-built diagram of the well will be recorded by the field geologist. Furthermore, a detailed log will be kept during the development of each well. The type of information that shall be included in each of these logs is discussed in the Comprehensive Field Work Plan (Radian International, 1998). 2.3 Drilling Requirements For all nine proposed monitoring wells, 8-to 9-inch diameter borings will initially be drilled with 4-1/4- inch internal diameter hollow stem augers to obtain a continuous core for llthologic logging.Upon completion of drilling and logging,the borings will be reamed to 12 inches for the 6-inch monitoring well installation.