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' 9000562C, Page 3 <br /> C <br /> B.3 DESCRIPTION OF WORK <br /> B.3.1 The purpose of this work is to drill out the concrete plug and granular backfill in <br /> two previously abandoned water wells, determine if groundwater within the wells is <br /> contaminated, evaluate the design and structural integrity of the wells, and permenently <br /> abandon the water wells and a damaged off-depot monitoirng well. <br /> B.4 ANTICIPATED HAZARDS AND RISK ASSESSMENT <br /> B.4.1 Chemical Hazard <br /> B.4.1.1 Previous studies have yielded detailed information about the chemical <br /> contaminants. The highest level of groundwater contamination for TCE and PCE was <br /> found to be 0.560 mg/L and 0.340 mg/L, respectively. Soil gas analyses found the highest <br /> concentration of TCE and PCE to be 0.240 mg/kg and 0.960 mg/kg. <br /> B.4.1.2 The risk of chemical exposure during drilling and sampling operations is <br /> low due to the fact that pure chemicals are not expected to be found. The use of personal <br /> protective clothing will prevent dermal exposures. Inhalation exposures are minimized by <br /> the use of respiratory protection, as stated in Section B.5.2, Air Monitoring. Proper <br /> decontamination (of equipment, samples and personnel) will prevent accidental exposures <br /> to chemical contaminants once personal protective equipment has been removed. <br /> B.4.1.3 Table 1 lists OSHA Permissible Exposure Limits (PEL's), American <br /> Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values <br /> (TLV's) and other physical data for TCE and PCE. <br /> B.4.2 Physical Hazards <br /> B.4.2.1 Drill Rig Operation <br /> B.4.2.1.1 Many mechanical hazards are associated with operating an engine-powered <br /> Cdrill rig and coring machinery. Two of the most common causes of injuries among drill rig <br />