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lower detection limits are as follows EPA method 5030,modified 8015, and 8020 for Total
<br /> Petroleum Hydrocarbons as gasoline (TPHg) 1 mg/Kg, Benzene 0 005 mg/Kg, Toluene 0 005
<br />• mg/Kg, Ethylbenzene 0 005 mg/Kg, Xylenes 0 005 mg/Kg. EPA method 8260 modified for
<br /> Methyl-tert Butyl Ether (MTBE) 0 005 mg/Kg, Di•siopropyl Ether (DIPE) 0 005 mg/Kg, Ethyl tert-
<br /> Butyl Ether (ETBE) 0.005 mg/Kg, tert-Amyl Methyl Ether (TAME) 0 005 mg/Kg and tert-Butanol
<br /> 0 025 mg/Kg EPA method 8260 for Ethylene Dibromide (1,2-Dibromoethane) 0 005 mg/Kg and
<br /> 1,2 Dncholorethane (1,2-DCA) 0 005 mg/Kg
<br /> On-site soil borings obtained samples ranging in depth between 25 and 65 feet below the surface.
<br /> The highest concentration of gasoline range hydrocarbons (TPHg) in soil was found at the 50 foot
<br /> depth in the original site assessment borings (boring #1, boring 42, boring #3, MW1, MW2, MW3,
<br /> and MW10) Bormg #3 contained 11000 mg/Kg TPHg, 73 mg/Kg Benzene, 140 mg/Kg Toluene,
<br /> 78 mg/Kg Ethyl Benzene and 360 mg/Kg Xylenes Confirmation borings were drilled and sampled
<br /> in June 1997 SB6 was drilled within ten feet down gradient of boring #3. Boring #1 contained
<br /> 600 mg/Kg TPHg, 4 7 mg/Kg Benzene, 2 5 mg/Kg Toluene, 6.9mg/Kg Ethyl Benzene, and 35
<br /> mg/Kg Xylenes Confirmation soil boring SB4 was drilled within 5 feet downgradient of boring
<br /> #1 The following table shows the better than 99% reduction in soil sample results
<br /> SB3 SB6 % remove SBI SB4 % remove
<br /> Dec 1988 June 1997 Dec 1988 June 1997
<br /> mg/Kg m m K mg/Kg
<br /> TPI! 11000 87 9921% 600 16 99.73%
<br /> f Benzene 73 <0 5 100% 47 <0 005 1000/0
<br /> Toluene 140 <0 5 100% 2.5 <0 005 1000/0
<br /> Ethly Ben 78 <0 5 100% 69 <0 005 100%
<br /> X lenes 360 <0 5 100% 35 0 051 99.85%
<br /> Mass balance calculations comparing the earlier site assessment soil sample results to the
<br /> confirmation soil sample results show that in March 1989 an estimated 62,434 5 pounds of TPHg
<br /> and 729 8 pounds of Benzene was associated with the soil The June 1997 confirmation borings
<br /> indicated that 212 9 pounds of TPHg remained and complete removal of Benzene and Toluene had
<br /> occurred indicting a 99.66% reduction in TPHg and 100% reduction of Benzene and Toluene,
<br /> see Table 4 Of the analytes tested in the confirmation borings, only trace amounts of Ethyl
<br /> Benzene remained in soils at the 55 foot depth of SB4 (0.36 mg/Kg) and at the 61 foot depth of
<br /> SB5 (0 18mg/Kg) Trace amounts of Xylene isomers remained in the soil at SB4 at the 50 and 55
<br /> foot depths(0 051 and 0.62 mg/Kg respectively), SB5 at the 40, 45, 50, and 61 foot depths (0 039,
<br /> 1.6, 3, and 1.7 mg/Kg respectively), SB7 at the 45, 50 and 60 foot depths (0.99, 7 7, and 0 37
<br /> mg/Kg respectively). SB7 was converted into a groundwater monitoring/vapor extraction well.
<br /> Vapor extraction/air sparging occurred until December 19, 1998, see Table 3
<br /> Groundwater Contamination
<br /> Groundwater contamination levels beneath the site have been reduced from free phase product to
<br /> below laboratory lower detection limits for TPHg, Benzene, Toluene, Ethyl Benzene, and Xylenes
<br /> for MWI, MW3 and MW4 MW2, located in low conductivity portion of the aquifer, contains 840
<br /> 6 R-603 Jan 2001
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