ARCHIVED REPORTS_2018 REV SITE INV WK PLAN+

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• Page 3 Brusca File No. 137-002 February 12,2018 Murphy Parkway Property Soil Gas Monitoring Wells outside the limits of planned pavements for the upcoming development at the site (so that the wells would not be disturbed during construction). The two soil gas monitoring wells SGMW1 and SGMW2 were installed at the site on January 16, 2018 by a C57-licensed contractor. Drilling and well installation operations were performed under the direct supervision of a Professional Geologist from our office and with oversight by a representative from the SJCEHD. The monitoring wells were constructed within approximate eight-inch diameter borings drilled with a track-mounted drill rig using hollow-stem augers. The boring for SGMW1 encountered relatively uniform native alluvial deposits comprised of silty fine sands at the surface and extending to the total boring depth of 13 feet (see Plate 4). No visual or olfactory evidence of chemical contamination conditions was observed in the soils encountered in the boring. Additionally, no fill or waste materials were encountered in this boring. Groundwater was encountered in this boring at the termination depth of 13 feet. Per the request of the SJCEHD and the provisions of the referenced Workplan Addendum, the soil gas well was installed to a depth of 12 feet within this borehole (about one foot above the groundwater level). Based on the groundwater depth observed in the SGMW1 boring, and recognizing that the ground surface elevation at the SGMW2 location is about two feet lower than at the SGMW1 location, it was decided to advance the boring for SGMW2 to a total depth of 10 feet, and install the soil gas well at this location to that depth (so that the bottom of the well would be about one foot above the groundwater level). The boring for SGMW2 encountered relatively uniform fill soils comprised of silty fine sands at the surface and extending to the total boring depth (see Plate 5). The fill materials encountered in SGMW2 are considered to be backfill materials placed in this area following excavation and removal of wastes from this area (South Waste Cell) in 2015. No visual or olfactory evidence of chemical contamination conditions was observed in the soils encountered in the boring for SGMW2. Additionally, neither waste materials nor groundwater were encountered in this boring. Following drilling, two-inch diameter Schedule 40 PVC casing was used to construct the soil gas monitoring wells within the boreholes. For SGMW1 the casing was screened (0.020-inch slots) from a depth of five feet to 12 feet, and for SGMW2 the casing was screened from three feet to 10 feet. The upper portions of the casings are solid and extend above the ground surface. The annular space surrounding the screened portion of the wells and extending one foot above was backfilled with washed graded silica sand. An approximate one-foot-thick bentonite plug was placed and hydrated within the annular space directly above the sand filter in each well. The remaining annular space above was grouted with neat-cement to the ground surface. A soil gas sampling port was installed at the upper end of each well casing and the portions of the well casings above the ground surface were protected with locking steel risers/monuments. The configurations of the soil gas monitoring wells are shown on Plates 4 and 5. ABANDONMENT OF SOIL GAS MONITORING WELL VP-1 As a part of site investigative work performed in 2015, Advanced GeoEnvironmental installed a soil gas monitoring well identified as VP-1 on the property (see Plate 2). Past sampling of this well reportedly has not revealed methane or VOCs in soil gas at levels that would be a concern;