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i <br /> Section No. 6 <br /> Revision No ' 0 • <br /> Date September 5, 1991 <br /> r , <br /> Page 3 of 55 <br /> I y <br /> I 11 <br /> to determine whether spills have taken place ;on' 'the `4si'te, to locate these <br /> spills, and, if' subsurface conditions are favorable', ,�o' indTand delineate <br /> groundwater VOC plumes by the presence of VOC's, in' overlying soils <br /> The analytical requirements for real-time mobile-laboratory analysis are <br /> different than the conventional VOC analyses prescribed by EPA protocols. <br /> The laboratory productivity, that is, the number of„analyses required per <br /> unit time, must be much greater for the mobile facility Otherwise, the <br /> value of using the data to modify the investigation is diminished <br /> Despite the need for greater productivity, the other , analytical <br /> requirements for detection limits, yvariety 'oIf, analytes, land freedom from <br /> I ' <br /> laboratory contamination are if anything, more ,stringent than those of fixed <br /> laboratory facilities + r <br /> i <br /> 12- _-1 -I _.. 4 .� --i _ _ _.}_ 1 .� �- Lt_.. <br /> The_samp] methods included included in the protocol have been designed to�.._,_;;u_ <br /> allow accurate; contamination-free sampling of soil gas These methods offer <br /> I <br /> a detection limit of 0 01 Ng/l for many compounds Additional, simultaneous <br /> + analys'is is provided for total petroleum hydrocarbons, methane, and total , <br /> chlorinated hydrocarbons. The following sections document the materials, <br /> apparatus, and procedures used <br /> 6 21 1 Sampling Equipment <br /> 6 2 1 1 Sampling Probes and Drive Point Rigs - Sampling probes consist ' <br /> of 5 foot sections of 1 3/8” hardened EW drill rod with Acme threads The <br /> " r <br /> points are machined of high carbon steel and are left behind when the pipe is <br /> hydraulically pulled back to expose the formation to pumping The probes are <br /> 4 <br /> 6-3 <br />