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1.2 InYeat4alLQn Summer In September 1990, at the direction of the property owner, WESTON submiEed a Work Plan to the EHD for a groundwater investigation in the vicinity of the former UST location at the Grantline Plaza site. The investigation consisted of the installation and develop- ment of three groundwater monitoring wells on the site and sampling and analysis of groundwater from each of the wells. The Work Flan was approved and the well permits were issued by the EHD. Field work took place in February, March and April 1991. 2.0 GROUNDWATER INVESTIGATION 2.1 Monitoril3a Well Instaltation In February 1991, three monitoring wells (MW-1, MW-2, and MW-3)were installed on the site (Figure 2). The purpose of the three wells was to provide data on groundwater quality and groundwater gradient. Drilling access to the north of the former tank location was severely restricted by the presence of a large building and by two underground lines (sewer and storm drain) as shown in Figure 2. The closest possible well site north of the former tank location would have been in front of the building, approximately 170 feet north of the former tank site, which was judged to be too far from the tank site for an initial monitoring well location. Consequently the wells were sited based on proximity to the former tank site and drilling access. The wells were installed using hollow-stern auger drilling techniques. Lithologic descriptions based on soil cuttings are presented in the Field Report, Appendix A. Each well consists of a four inch diameter PVC casing and screen and is approximately 19-19.5 feet deep with 15 feet of screen. Each well was devQloped by pumping until the produced water was essentially free of sand and silt. The well head elevation of each well was surveyed to the nearest 0.01 foot. As no actual benchmark was readily available, the well elevations were established with respect to an arbitrary datum elevation of 25 feet which is the approximate elevation of the site according to the Union Island Quadrangle, 7.5 minute series topographic map, published by the U.S. Geologic Survey. The horizontal location of each well was measured to the nearest foot with respect to permanent on-site structures. A detailed description of the well specifications as well as installation and development procedures is presented in the Field Report, Appendix A. 2.2 ling Groundwater samples were collected from all three monitoring wells on March 8, 1991. The wells were first purged by pumping then sampled with a Teflon bailer. The samples were collected in laboratory prepared containers and stored on ice in a cooler pending delivery to the laboratory for analysis. A complete description of the groundwater sampling procedure is presented in the Field Report, Appendix A. - 3 -