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of induration, calcareous content,presence of fossils and other distinctive materials. <br /> The original field logs will be retained by the Geomatrix office for review by the responsible <br /> professional and for storage in the project files. <br /> 4.0 GEOPHYSICAL LOGS <br /> Following completion of drilling, downhole geophysical logs may be performed after the drilling <br /> fluid has been circulated to decrease the amount of suspended sediment in the return fluid. <br /> Geophysical methods and equipment will be selected to provide stratigraphic or hydrogeologic <br /> data appropriate for the project. Geophysical logging will be done as quickly and promptly after <br /> drilling as feasible, while the boring sidewall is still in stable condition, to reduce the possibility <br /> of bridging. Instruments on the logging unit will be adjusted to.try to give the maximum defini- <br /> tion of strata boundaries. All downhole geophysical equipment will be cleaned before and after <br /> use in each borehole. <br /> 5.0 FIELD SCREENING <br /> Soil samples collected from the borings may be screened using a portable meter such as a <br /> photoionization detector(PID), a flame ionization detector(FID), a lower explosion limit(LEL) <br /> meter or other organic vapor meter. The meter may be used to assess the presence of volatile <br /> organic compounds (VOCs) or other gases in soil samples. Additional field screening techniques <br /> for chemical characterization of soils may include x-ray fluorescence (XRF) and thin-layer <br /> chromatography(TLC). Procedures for field screening are described in the protocol SOIL <br /> SAMPLING FOR CHEMICAL ANALYSIS. <br /> 6.0 DESTROYING SOIL BORINGS <br /> Soil borings that are not completed as monitoring wells will be destroyed by filling the holes <br /> with a neat cement grout, cement/sand grout, or cement/bentonite grout. Ahigh-solids bentonite <br /> DRILLING AND DESTRUCTION OF SOIL BORINGS Page 5 of 6 <br /> PROTO-DDAm REVISION DATE:MARCH 1996 DD-5 <br />