ARCHIVED REPORTS_XR0005851 CASE 2

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1 ' Ground Water Sampling S1 Remove the locking and protective caps ' 2. Sample the air in the well head for organic vapors using either a photoionization detector or an organic vapor analyzer, and record ' measurements 3. Gently lower a clear disposable bailer into the well tojust below the fluid level and retrieve a sample Use of a clear bailer is best for visually ' determining the presence of very thin or sheen-type layers 4 If a measurable thickness of floating product is detected, lower an ' interface gauging probe or a weighted tape coated with commercially available reactive indicator paste into the well to determine the depth to the air/LNAPL and the LNAPL/water interfaces ' The air above the well head should be monitored to determine the potential for fire,explosion,or health and safety hazards. Air monitoring also serves as a first ' indication of the presence of LNAPLs The presence of LNAPLs precludes the exclusiveuse of water level sounders to make a determination of static water level The interface probe serves two related purposes First, as it is lowered into the ' well,the probe registers when it is exposed to an organic liquid and thus identifies the presence of LNAPLs Secondly,after passing through the LNAPL layer, the probe indicates the depth to water Careful recording of the depths of the ' air/LNAPL and LNAPL/water interfaces establishes a measurement of the thickness of the LNAPL in the well casing Extra health and safety precautions should be taken when LNAPLs or DNAPLs are expected in a well, and the lead ' regulatory agency should be notified when they are detected The approach to collecting LNAPL samples depends on the depth to the floating layer surface and the thickness of the layer A sample of the LNAPL should be collected prior to well purging To collect an LNAPL sample, a bottom valve bailer is the equipment of choice The bailer should be lowered slowly until contact is made with the surface of the LNAPL The bailer should then be ' lowered to a depth less the that of the LNAPL/water interface depth, determined beforehand using the interface probe ' DNAPL Detection/Collection RPs should specify in the SAP the following procedures for detecting the presence ' of DNAPLs These procedures should be followed before the well is evacuated for conventional sampling ' 1 Remove the locking and protective caps I 2. Sample the air in the well head for organic vapors using either a photoionization detector or an organic vapor analyzer, and record ' measurements 5 1 '