WORK PLANS - Laserfiche WebLink

Home Browse Search

. 19 December 2003 p ' r ,I ri #- 4. AGE-NC-Project No 95-012$ ,Page 2 of 12 s r area of the-former USTs The hydrocarbon impacted soil was-limited to the eastern portion of the,- 'IS he „ UST-removal area and the dispenser- UST-rem'o'val ':-^ ; '-rte , Z. - ;+t - e.- In June of 2003,'tw;10;000-gallon;_double-walled USTs were.removed.from the site;alarigwith r the associated piping, in,orde'r to comply with State Water,Resources Control Boardrequirements Y for spill; release containment and-monitoring. ]MTBE impacted was detected in the soil samples.: - x � - collectedat the site f :f 7 r - - _ - 4, -2.3. SITE ASSESSMENT _ "T Between=1991 'and 1997, four soil=borings;+one vapor}extraction well and seven gidund' Water--:- s, r - monitoring wells were installed at the site::The the -lateral extent of Ylydrocarbon-impacted `soil has been delineated 'however tlte.latera.1 extent of h d ocarbon-impacted ground water_has not �_. y been delineated to the satisfaction ofthe EHD:-Data collectedfrom.the site-during the investigation •. of the former'UST site indicated thaYhydrocarbon4mpacted°soil is-pre-gent-in the vadose;zone from depths of:approxirriately'S-to55 feet-bsg. Rising`ground:water.elevatiori-has greatly:exceeded�the - . screened,intervals ofinoriitoring:wells MW=1,MW-2.and MW=3,rendenng:data collected-form these : L =_wells sus ect. H drocarbori-im acted oundTwater has been,encountered'.north and east of'the P -- y p t F -property in the down-gradient direction frarri`the„suspected,farmer source of the unauthorized 3 t—i hydrocarbon release;�bizt,is.not well con5trairied iri,then 'directions These-factors necessitated installation of the additional groundwater,monitoring wells "- A vapor'extraction fest, asconducted in December .1993 Slrice that time, ground water has risen '-from approximately 55'feefbsg to as high{as 25°.feet bsg,with.-the current ground,water,leuel-at 35 ' F feet bsg, reducing the vertical extent of the vadose.zone-open to the scrceried,interval of the vapor extraction well.ThZf e rise of ground water elevation has:also eliminated roost of the coarse=grained soil f f :from the vadose-zone;;leaving predominantly fine-grainedsoil in contact with:the-reduced open- ,screened-interval ofthe_vapo`r extraction well These ch`tinges:carrpotentialjy.dra"sticallyreduce the zone of in#lhencebf the vapor extraction well(s)and reduce fhe concentrations of hydrocarbon vapor: y recovered-by the extraction process.Therefore additional vapor wells will be required.to ensure the F - capture of the impacted-soil vapors. - e- -On-,29 and.30'April and O1_May 1998,seven probe borings(B.13-through B19)were advariced`off , ' ` site of the subject property`to'collect soil.an_d-grab;ground;water--sample's as'part'_of on-going M 4" assessment of the release of fuel hydrocarbons from the foriner:LTST facrltty:TPH-g�total petroleum: hydrocarbons-as diesCI(TPH-d}and benzene,toluene,ethyl benan zene d total xylene_(BTEX)_were 'Y, { . :not detected in any of_aheaoil samples analyzed,.however,methyl'`tertlary butyl'ether(MTBE)was , detected at-:180 micrograms pet kilo am - m the,sort sam le firam:boriri B 16=at'a.de th of t, g p S fag) . p_ g. p _ [ - } - z - k __ - �r'.�� _3 - _-_ 4 � _ tih•' f`,0. _ J _ �' ,'�- - ' � S . Z. L` Advanced Geo>nvirnnmental,Inc t- a x .