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Beacon Station No.474 December 28, 1998 <br /> _ .3440 East Main Street-Stockton..California _-_ _. <br /> -- .._.—� Amendment To Work Plan <br /> J <br /> .-_ The-:soil_samples selected-for-�analysis .from-boring-B77 will :be_analyzed`for <br /> }°� total: petroleum '•hydrocarbonsas _gasoline (TPHg) and khe volatile= gasoline <br /> constituents benzene;,-toluene, etliyibenzehe 'and total -xylenes {BTEX)_by - m <br /> -_ - Environmental Protection Agency {EPA)-Method:.. ' /8020 or.8260B, and the.= <br /> ` t - <br /> -seven oxygenated fuel additive-compounds,:rimethanol; ethanol. tertiary-.butyl: - <br /> _alcohol (TBA), rnethyl tertiary butyI.ether (MTBE), djJ4, ropyi ether DIPS , _ <br /> eth 1 testi bu 1 ether ETBE =and testi <br /> y - ' �'- __{.. -}�-- - ary:amyl.-methyl'ether:-(TAME) by <br /> - <br /> EPA Method 8260.-- . <br /> -=Task 2:2:. - Drill..-and sample a.'_°8;rnch :diameter -borings and_irisfaIf 2-inch-diarrieter <br /> - _ _ <br /> - = groundwater MW Wdmgmoilztoring wells <br /> - = locations shown ori-Figure.2- while_waiting for <br /> _ _ <br /> laboratory analytical data=foetr <br /> -the bong-B 7_.sain les.. Both monitorm vxllbe..coin leted.with 20 fe, <br /> -= <br /> of.0.020_inch factory-slotted.well•-screen-'Well-screen v f 1.be Placed beginning_ <br /> approximately 5 :feet:above the first encountered gro. water estimated•to be <br /> - - SS-to 60 =feet bsg.-°Wells ._MW-1:0:­and MW-11 z-are to help= <br /> = northwesternand=southern lateral limits of the dissolved hydrocarbon plume, _- <br /> respectively: - <br /> = Task 23_ -If nohydrocarbon-impacted 'soil or groundwater as encountered m soil boring <br /> B=7 at or nnear the-historical low--groundwatei.level,-the' soil boring .will-I <br /> grouted-up.to approximately-83 feet__bsg_ Ther grout:will be allowed to: cure <br /> -overnight. �Bentonrte_will be placed,above the grout;-as needed,.and a 2-inch = <br /> diameterPVC atr-sparge.weI1 'AS"1) will be installed"in the boring. Thee o ` <br /> - - <br /> five �feet .of-0.010-inch..factory=slotted _well "screen Will be-`instal'led from - <br /> __ -- <br /> ... approximately 80,to 85_feet-bsg or at a maximum total depth-of 20 feet below - - <br /> --_ wgroundwater Well AS Pwill-be ufilized for a future air-sparge test. <br /> -- If soil boring B 7 `encounters_hydrocarbon-impacted soil or-groundwater at - <br /> _-= near the histonca� w groundwatet level, the bortng will,be r_earned wrt 10 <br /> inch diameter:augers,to d <br /> the eepest 4 impacted interval,and_a 2-inch d_eter, _ - <br /> _ _ PVC:well..(MW }2} with 5 feet of V.O20-inch screen wll.be installed across the = <br /> deepest rmpacted interval .4ir sparge veli AS 1 .wrll then be installed_as a.dual - <br /> -.__ completion as shown on:the attached Figure 4 �If soil boring B 7`'encouzaters -jt k-f <br /> ltydrocarbon impacted <br /> soil groundwaten�at�or •near"the hrstoricai low.--- _ <br /> groundwater. level, then soil-borings:.B-8 and-B-9 will be drilled to attempt to� <br /> define the-lateral-=-exieht•--of=hydrocarboris ,af-or nearLL the``histoncal glow = - <br /> ___. groundwater-_.level.:. -Based on ;field_-conditions-encountered=at- lie time- of - <br /> - r - -drilling "ahe well construction.destgns maybe altered=after discus"cion wrth=and <br /> . ' <br /> approval of-SJPHS�.r -. <br /> -' <br /> Task 2:4_ .Drill'and sample coil_boring Bt4.south of the dispenser=islands at the location <br /> - - - shown on the enclosed Figure 2 to evaluate;.the-lateral:-and_vertical extertt of <br /> = hydrocarbons to the.vadosezone,.-and=to delineate;if necessary;the Iateral_limrt <br /> of any soil and groundwater hydrocarbon impacf at-,or�4- -i-the histoncal'aow <br /> groundwater level;at approximatelyw105 feet'bsg:-Discreet soil and-groundwater _, <br /> _ - = <br /> r <br /> -- — 1474-22°awp - :: " - =2r '= HORIZON_ENVIRONMENTAE, iNC. <br /> -- - <br /> - - <br /> - <br />