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CfARWATERE G R O y 'U' "P, I N C. borings. ;The advantages' .of using push-type tools '(e.g. Geoprobe or Hydropunch) at. this site were evaluated by Clearwater. They were not 1 selected for this ,sta a of the ass g essment because of geographical -restrictions such as the elevated Crosstown.Freeway'and utilities (both•.above-ground and, '" buried) 'along Lafayette Street. Furthermore, .only three monitoring ,wells have been installed at the site to date; additional monitoring wells are needed - to refine the estimates of the groundwater flow direction.: ' Five additional monitorin g -wells will be installed to evaluate' the lateral extent of groundwater contamination at the site. One monitoring well will be ' installed 'in 'an upgradient location. (relative to our current understanding of. groundwater flow at the site) and two wells °will be installed 'in cross-gradient locations. One.well will be installed .downgradient across .Lafayette Street, assuming Clearwater can obtain encroachment permits to drill on Caltrans property. The fifth groundwater 'monitoring well will be installed. through . the backfilled excavation. . The- proposed locations are' shown on Plate 2. ' Clearwater field -procedures for well installation and soil sampling ' are included in Appendix A. In. additio 'converted four soil borings will .be drilled and to soil vapor etraction (SVE) wells suitable for conducting an SVE pilot study at the site. The-SVE wells will be located in the vicinity of.the large excavation where the former tank field' was located (Figure 2). Well ' construction details are discussed below'. i ' . Groundwater Monitorin WV . ells - One deep'soil ,boring (total depth 60. feet bgs) will be advanced through, the center, of the large backfilled excavation..- Soil samples will be collected at five- = foot intervals from the bottom,,of the.excavation t X1 0 50 feet bgs; the samples " will be analyzed for TPHg, T'PHd, and , BTEX. ' The-'soil •b p boring will be converted to a four-inch-diameter .,groundwater. monitoring , well in ' 'accordance with Clearwater's 'well instarotocolAllation p ( ppendix A). The well.will be constructed using Schedule 40.PVC casirig and screen (Figure 3). The, screen-(0.020-inch slot size) will extend from 30 to 60feet bgs: A•sand ' filter,pack wg No. 3 ill be' constructed using 101. .1, sand. � Four additional' soil borings; to• be converted to monitoring wells, will be drilled and sampled in the locations 'shown'•on Figure 2. The boringsi 'ill.be . » drilled to a depth 'of approximately 60 feet bgs. SoiI 'samples' will,be,collected at five-foot intervals between.30 and 50 feet bgs; the samples will be analyzed for TPHg, . TPHd, and BTEX, The ' soil borings will be converted to groundwater monitoring wells by'installing two'inch-diaiiieter Schedule"4 a D-105WP 7/95