SITE INFORMATION AND CORRESPONDENCE

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page 2 Drilling and sampling procedures and olfactory examination. Soil is described using the Unified Soil Classification System. A portion of this soil may be temporarily placed in a plastic bag and used for examination with a portable organic vapor analyzer. All field descriptions and measurements are documented on borehole logs. Ground-Water Monitoring Well Construction Ground-water monitoring wells are constructed according to the general specifications shown on the attached Well Construction Diagram. The wells shall extend a minimum of 10 feet into the upper aquifer, unless a clay layer greater than five feet in thickness is found. The wells shall not extend through a laterally extensive clay layer below the upper aquifer unless circumstances warrent the investigation of deeper aquifers. In the event an extensive clay layer must be penetrated care shall be taken to assure that mixing of water or contaminated soil does not occur. For single-cased wells, the monitoring well casing, with an end cap, shall extend to the base of the borehole or into a bentonite plug. The casings shall be factory perforated to the specifications delineated in the site work plan and compatible with the lithology of the aquifer found in the field. The perforated casing will extend five feet above the top of the aquifer or known high water level. Properly graded, clean filter sand will be used in the annulus of the well and prevent the migration of fine particles into the well. The filter sand will extend at three to five feet above the perforated interval in the well. A seal of at least three to five feet of bentonite shall be placed above the filter. Sack or neat cement will be used to seal the annulus from the bentonite pellets to the ground surface where a well box will be installed. All sand, bentonite, and cement will be placed with a tremie pipe.