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Mr Nuel Henderson,Jr, SJCPHS July 1,2003
<br /> Remedial Action Plan
<br /> ARCO Station No 6100
<br /> Page 11
<br /> Bioventing stimulates the natural in situ biodegradation of any aerobically degradable
<br /> compounds in soil by providing oxygen to existing soil microorganisms In contrast to
<br /> sail vapor vacuum extraction, bioventing uses low air flow rates to provide only enough
<br /> oxygen to sustain microbial activity Oxygen is most commonly supplied through direct
<br /> air infection (using a blower) into residual contamination in soil via vadose zone wells
<br /> In addition to degradation of adsorbed petroleum hydrocarbons, volatile compounds are
<br /> biodegraded as vapors move slowly through biologically active soil Infection points
<br /> may also be used to introduce nutrients to the vadose zone if necessary Insitu
<br /> bioremediation through bioventing is a viable and cost effective remedial alternative
<br /> PROPOSED REMEDIAL ACTION PLAN
<br /> Given the distribution of petroleum hydrocarbon impact, potential for vertical migration
<br /> and impact to groundwater in Sand 2, and presence of a supply well onsite, Stratus
<br /> proposes soil vapor extraction and air bubbling to mitigate the petroleum hydrocarbon
<br /> impact to the subsurface
<br /> Stratus proposes to extract soil vapors from exiting vapor extraction wells VW-1, VW-3,
<br /> VW-4, VW-6, VW-7, VW-8, VW-9, VW-11, VW-12, VW-13, VW-14, VW-16, and
<br /> MW-2 through MW-9 Well VW-7 is not currently connected with the laterals During
<br /> system startup, Stratus will connect well VW-7 to extract soil vapors Figures 6 through
<br /> 13 present the radius of influence (ROI) for each of these wells The ROI information is
<br /> presented in conjunction with the extent of impact data, to evaluate if adequate coverage
<br /> is available to extract soil vapors from various depths where petroleum hydrocarbon
<br /> impact exists
<br /> Vapor extraction wells VVY-1, VW-3, VW-4, VW-6, VW-9, VW-11, VW-12, VW-14, - j i•"` � 7 g
<br /> and VW-1�6 are screened at depths ranging from 9 5 to 45 feet bgs targeting the upper silt
<br /> zone Vapor extraction wells VW-3;'VW-4vVW-7,/ VW-8;VW-9f and VW-13*and
<br /> monitoring wells MW-2JMW-4, MW-6/and MW-8 are screened at depths ranging from,-
<br /> 45
<br /> rom45 to 74 feet bgs targeting Sand 1 Vapor extraction well VW-8;�and groundwater s i,
<br /> monitoring wells MW-3; MW-5;MW-7;and MW-9 are screened at depths ranging from 0 ,,Ie a sc wr
<br /> 72 to 95 feet >bgs, targetingSand 2 The well construction details, p historical depth to
<br />�I�f w4)(1fe54�6"i
<br /> "t water, exposed screen available for vapor extraction, and height of water column details
<br /> for all wells are presented in Table I Review of the petroleum hydrocarbon impact to
<br /> soil, location of vapor extraction wells, screen intervals, and ROI indicates that existing
<br /> facilities provide adequate coverage for SVE
<br /> In addition to using SVE to mitigate impact to soil and groundwater, Straus proposes to
<br /> use air bubbling to increase the DO content in groundwater and expedite the remediation
<br /> . of the perched groundwater Stratus proposes to use wells VW-1, VW-3, VW-4, VW-6,
<br /> P 1Bp-Arco for URS161001ReportslArco 6100 RAP doc
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