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GENERAL FIELD PROCEDURES <br /> Groundwater Monitoring and Sampling Assignments <br /> For each site, TRC technicians are provided with a Technical Service Request (TSR) <br /> that specifies activities required to complete the groundwater monitoring and sampling <br /> assignment for the site. TSRs are based on client directives, instructions from the <br /> primary environmental consultant for the site, regulatory requirements, and TRC's <br /> previous experience with the site. <br /> Fluid Level Measurements <br /> Initial site activities include determination of well locations based on a site map provided <br /> with the TSR. Well boxes are opened and caps are removed. Indications of well or well <br /> box damage, or of pressure buildup in the well are noted. <br /> Fluid levels in each well are measured using a coated cloth tape equipped with an <br /> electronic interface probe, which distinguishes between liquid phase hydrocarbon (LPH) <br /> and water_ The depth to LPH (if it is present), to water, and to the bottom of the well are <br /> measured from the top of the well casing (surveyors mark or notch if present) to the <br /> nearest 0.01 foot. Unless otherwise instructed, a well with less than 0.67 foot between <br /> the measured top of water and the measured bottom of the well casing is considered <br /> dry, and is not sampled. If the well contains 0.67 foot or more of water, an attempt is <br /> made to bail and/or sample as specified on the TSR. <br /> Wells that are found to contain LPH are not purged or sampled. Instead, one casing <br /> volume of fluid is bailed from the well and the well is re-sealed. Bailed fluids are placed <br /> in a container separate from normal purge water, and properly disposed. <br /> Purging and Groundwater Parameter Measurement <br /> TSR instructions may specify that a well not be purged (no-purge sampling), be purged <br /> using low-flow methods, or be purged using conventional pump and/or bail methods. <br /> Conventional purging generally consists of pumping or bailing until a minimum of three <br /> casing volumes of water have been removed or until the well has been pumped dry. <br /> Pumping is generally accomplished using submersible electric or pneumatic diaphragm <br /> pumps. <br /> During conventional purging, three groundwater parameters (temperature, pH, and <br /> conductivity) are measured after removal of each casing volume. Stabilization of these <br /> parameters, to within 10 percent, confirm that sufficient purging has been completed_ In <br /> some cases, the TSR indicates that other parameters are also to be measured during <br /> purging_ TRC commonly measures dissolved oxygen (DO), oxidation-reduction potential <br /> (ORP), and/or turbidity. Instruments used for groundwater parameter measurement are <br /> calibrated daily according to manufacturer's instructions. ! <br /> Low-flow purging utilizes a bladder or peristaltic pump to remove water from the well at a <br /> low rate. Groundwater parameters specified by the TSR are measured continuously until F <br /> they become stable in general accordance with EPA guidelines. <br /> Purge water is generally collected in labeled drums for disposal. Drums may be left on <br /> site for disposal by others, or transported to a collection location for eventual transfer to <br /> a licensed treatment or recycling facility_ In some cases, purge water may be collected <br /> directly from the site by a licensed vacuum truck company, or may be treated on site by <br /> r <br /> an active remediation system, if so directed, <br /> H <br />