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t� 3� A.,�.: ...x�.j�. :'� ��.". .X�. _ _ ^ice.,,: . Mk�. , � � Gs.7- �'r is <br /> n . , 7?a r ;it _w ''' ° ,w_' H" S AGM 8881 ..a N� .� _. � <br /> ' �a,'� ��� <br />��'?�������_,-=� -e a -tea �`..�' r' <.� +'�f3�� mr.� '� •, —.�� � � — _ _ - �.�r� _ _:� <br /> hydrocarbon (TP10 contamination does not ,generally require ir..medieto <br /> •--� additional action. Board engineers emphasize that this does not maAn that <br /> 'Ramo action might not be required In the future. Stili, the site It axatgned <br /> o low priority unions it Is situated in an Arse of high hydrogeologlc <br /> concern. <br /> Us detection of more than 100 ppm TPN In the native soil beneath a tank in <br /> generally considered grounds for requiring an additional Investigation in the <br /> force of Roll borings and Installation of at leant one groundwater monitoring <br /> well followed by poriodlc monitoring. The detection of 1008 ppm TP1i is <br /> usually viewed by the Board as an unacceptable level of ruei saturation which <br /> will mandate excavation of the effected around down to the furthest <br /> practicable reach of sonventlonal excavating machinery foltowed by soil <br /> boring& and installation of groundwater monitoring wells. <br /> Other rergtons use different standards for determining when a groundwater <br /> Investigation will be required. For example benzene In often used in lieu of <br /> TPH. Even very tow levels of benzene are often seen at grounds for requiring <br /> a subsurface Invas:igatlon. This criterie may be relrxed or stiffened <br /> depondtn;g on the lotion of the site in relation to different groundwater <br /> systems, the depth to water, type of soil, and the concentrations of benzene <br /> Involved. <br /> The above standards apply only to fuels. Nhe.► sampler taken In connection <br /> with a waste oil tank or a solvent tank are found to contain even smell <br /> amounts of any of the EPA priority pollutants (such as TCE, PCE, DCE ate. <br /> which are detected by EPA methods 8010, 8020, and 6240) mora stringent <br /> standards are often applied. In thter cases, Hall borings End monitoring <br /> - well Installation may be required if there is any detectable amount of any of <br /> the EPA priority poNutant compounds. <br /> When contaminants are found to have reached the water underlying a site, the <br /> Berard customarily requires that additional work ba undertaken In order to <br /> define the extent of the contamination. <br /> s <br /> agy{y{ <br /> e <br /> f Y <br /> Sampling Report NOSS-C-2 CHEVRON 1918 12 <br /> y <br />