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assess quality control, one primary sample will be split into two portions and one portion assigned a fictitious sample code to serve as a field duplicate All samples will be analyzed for ' TPH-G and BTEX 3.2.2 Geotechnical Review ' A geotechnical review of the relationship of the existing building onsite to the extent and depth of the additionally proposed excavation will be conducted The primary focus will be to ' determine if catastrophic failure or settling sufficient to damage the building may occur If catastrophic failure is a possibility, demolition of the building will be recommended If possible settlement damage is possible, a cost benefit analysis of installing shoring will be conducted to ' determine if shoring or demolition is preferable 3.2.3 Additional Tank Area Excavation Procedures The maximum depth of the additional tank area excavation is targeted at 40 feet below grade To allow excavation to this depth, the following procedure will be used soil stockpile® Relocate the existing (after additional sampling is complete) to the northeast corner of the property 0 Construct a ramp down to the level of approximately 20 feet below grade to access the previous excavation Soil from the ramp which will come from the unaffected area onsite will be stored separately to fill the ramp area upon completion of the protect. O Excavate the prior excavation area to a maximum of 40 feet below grade utilizing a ' mobile laboratory to control the excavation Sampling and analysis will be conducted on every 50 cubic yardsof soil removed All soils will be stockpiled separately on plastic ' sheeting and saver ecision on xn isposa ion a cons usion of the excavation, i total of eight samples wiTrYe en Trom the excavation floor and lower sidewalls for analysis o TPH-G and BTEX to confirm that soil containine elevated ' by rocar on concentrations has been removed During the excavation, air monitoring will be conducted in the area of the excavation with an ' Organic Vapor Monitor instrument Should the instrument indicate sustained reading in the breathing zone above background concentrations determined prior to the start of excavation operations, Draeger tube monitoring will be utilized to specifically test for benzene If the tube ' monitoring shows concentrations above 1 ppm, excavation operations will cease and the protect will be re-evaluated Should no benzene be detected, operations will continue unless the OVM readings exceed 50 ppm (based on ethylbenzene exposure cntena) in which case operations will ' also be discontinued pending evaluation of the source of the air emissions 3.2.4 Handling and Disposition of Soils Assuming offsite disposal is the preferred alternative for disposition of the sods and the onsite SVE approach is not resurrected, disposal of the sods will either be accomplished by ' transportation to a Class II landfill (if TPH-G does not exceed 1,000 mg/Kg) or to a Class I 12 11/13/92 ' SThCSRP'I'SIAREG3QTR WP G