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Geological Technics Inc Page 4 g g Appendix A Project No 281 2 August 11, 1995 ' The detection limits for these analyses are as follows benzene, toluene,ethylbenzene, total xylenes 0 3 µg/l,and TPH-Diesel 50µg/l ' 28 Soil Boring Installation The soil borings will be drilled using a continuous flight hollow stem auger to a total depth to be determined but not to intercept the groundwater Soil cuttings will either be containerized in DOT approved 55 gallon drums,labeled or lain on and covered by plastic sheeting,and stored on site until their proper disposition can be arranged Soil samples will be collected for geological and analytical evaluation at five foot intervals Soil samples will be collected in 6 0 inch brass liners using a 2 0 inch modified California split spoon sampler All soil samples will be sealed with aluminum foil,capped, labeled and placed in a cooler at 4° Celsius for transport to the laboratory following Chain of Custody protocol Because every soil sample collected will not be submitted for laboratory analysis, a screening process will be used to gather additional information through field observation noting sediment type, ' especially grain size and clay content, moisture content, visible evidence of contamination, i e, color change due to reduction of iron or discoloration from hydrocarbons and other pollutants, and the readings above background on a organic vapor meter (OVM) The OVM is a field portable photo ionization detector that uses a 10 0 eV lamp to detect compounds with ionization potential below 10 0 eV(hydrocarbon range) The soil borings will be closed as follows after the last soil sample has been collected the augers will be lifted 3 feet and 50 pounds of bentonite will be poured through the hollow stem of the augers and hydrated with clean tap water A tremie pipe of sufficient length to reach the total depth of the boring will be installed through the center of the hollow stem augers and then the augers will be withdrawn from the hole The borehole annulus will be closed by pumping a neat cement grout (<4%bentonite/cement) through the tremie tube up to grade 2 9 Monitoring Well Construction The monitoring wells will be constructed with 4 0 inch diameter, schedule 40 PVC casing with flush threaded joints A screened interval will consist of 0 020 inch perforations extending from approximately 15 feet below and 5 feet above the water table A number three sand will be used to form a filter pack about the saturated zone(0 020") perforations and will extend two feet above this screened interval An annular sea] will be constructed by installing 100 pounds of granular bentonite that will be hydrated with tap water and be allowed to expand for a period of one hour In the remaining annulus, neat cement grout will be installed using a slurry pump and tremie pipe The well will be secured with a watertight locking cap encased within a traffic safe well box A well construction schematic is attached as Figure 3 Relative well collar elevations may be surveyed by a competent surveyor 210 Monitoring Well Development Within 48 hours of well installation after well sealing materials have had time to set, each monitoring well will be developed by mechanical surging and pumping until a clear stream is obtained All