|
SECTION TWO Previous Investigations
<br /> concentrations in soil ranged from nondetect to 270 mg/kg, and TPH-d concentrations
<br /> ranged from nondetect to 12 mg/kg Benzene was detected above laboratory
<br /> detection limits in four soil samples with soil concentrations ranging from nondetect to
<br /> 4 4 mg/kg Toluene was detected above laboratory detection limits in two soil
<br /> samples with soil concentrations ranging from nondetect to 17 mg/kg Ethylbenzene
<br /> was detected above laboratory detection /units in two soil samples with soil
<br /> concentrations ranging from nondetect to 5 5 mg/kg Xylenes were detected above
<br /> laboratory detection limits in two soil samples with soil concentrations ranging from
<br /> nondetect to 30 mg/kg Alton Geoscience sampled groundwater monitoring wells
<br /> MW-7, IOW-8, and MW-10 through MW-12 Groundwater monitoring wells lid-1
<br /> through MW-6, and MW-9 were dry TPH-g and BTEX concentrations decreased in
<br /> groundwater monitoring wells MW-7 and MW-8 TPH-g concentrations in the new
<br /> monitoring wells ranged from nondetect (Nff-12) to 5,600 ug/L. (MW-10) TPH-d
<br /> concentrations ranged from nondetect (MW-11 and MW-12) to 1 8 ug/L (MW-10)
<br /> n A limited vapor extraction pilot test was conducted by Alton Geoscience in September
<br /> 1992 (Alton Geoscience, 1992)to evaluate the feasibility of using soil vapor extraction
<br /> em i ternative
<br /> o An additional environmental site investigation was conducted by Environmental Assessors
<br /> Inc in 1993 to evaluate the horizontal and vertical extent of petroleum hydrocarbons in soil
<br /> and groundwater Six additional groundwater monitonng wells were installed (MW-13,
<br /> MW--14, MW-16, MW-19, MW-20, and MW-24) were installed and four soil borings
<br /> (SB-15, SB-17, SB-18, and SB-22) One hundred and forty three soil samples were
<br /> collected and analyzed to a depth of 75 feet bgs for TPH-g and BTEX Selected soil
<br /> samples were analyzed for TPH-d TPH-g concentrations in soil ranged from nondetect
<br /> (116 soil samples)to 350 mg/kg, benzene concentrations ranged from nondetect (109 soil
<br /> samples)to 4 7 mg/kg,toluene concentrations ranged from nondetect(109 soil samples)to
<br /> 37 mg/kg, ethylbenzene concentrations ranged from nondetect (116 soil samples) to 7 2
<br /> mg/kg, and xylenes concentrations ranged from nondetect (104 soil samples) to 47 mg/kg
<br /> TPH-d were not analyzed for during flus investigation Groundwater concentrations for
<br /> TPH-g ranged from nondetect (MW-14, MW-16, MW-19, MW-20 and MW-24) to 1
<br /> ug/L (MW 13) Existing groundwater monitoring wells (MW-7, MW-10, MW 11, and
<br /> MW-12) were sampled during this investigation Groundwater concentrations for TPH g
<br /> and BTEX generally decreased in groundwater monitoring wells MW-7 and MW-11,
<br /> slightly increased in MW-12, and increased in MW-10
<br /> o Groundwater monitoring was performed in 1994 by Ninyo Moore Groundwater samples
<br /> collected from monitoring wells MW-10, MW-11, MW-12, MW-13, MW-14, MW-16,
<br /> MW-19, MW-20, and MW-24 were analyzed for TPH g, TPH-d, and BTEX TPH g
<br /> concentrations decreased in MW-10, MW-11, MW-13, slightly increased in MW-14, and
<br /> remained unchanged at below the laboratory detection limits in MVI--12, MW-19, and
<br /> MVV-20 BTEX concentrations increased in monitoring wells MlV6T 10,MW-14, and MW-
<br /> 24, generally decreased in NM-11,MW-13, and MW-16, fluctuated (some concentrations
<br /> slightly increased and some concentrations slightly decreased) in MW-12 and MW-19, and
<br /> ® T"DBmrim EAzTOCKTOM o-ou D=7.A11C3a91 rj=NA1sNA 2-2
<br />
|