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the well and the thickness of the product visually measured and documented on the <br /> Well Gauging Form <br /> • When the interface probe contacts liquid, the visual/audible alarm on the reel will be <br /> activated An oscillating alarm indicates water, a continuous alarm indicates <br /> hydrocarbon To determine the exact thickness of a hydrocarbon layer, the probe <br /> should be slowly lowered to the air/hydrocarbon interface until the alarm is activated <br /> with the probe at the exact point where the alarm comes on, read the numbers on the <br /> tape to determine the distance from the predetermined top of casing elevation mark <br /> Next, lower the probe through the hydrocarbon layer and well into the water An <br /> oscillating alarm will be obtained The probe should then be raised slowly to the <br /> hydrocarbon/water interface until the point where the alarm changes from oscillating <br /> to continuous The thickness of the hydrocarbon layer is determined by subtracting the <br /> first reading from the second reading Record the calculated value on the Well Gauging <br /> Form and Groundwater Sampling Form <br /> Groundwater Sampling <br /> Groundwater samples will be collected from selected groundwater monitoring wells to provide data <br /> which will be statistically representative of local groundwater conditions at the site Groundwater <br /> samples will be collected as follows <br /> • All measuring and sampling equipment will be decontaminated prior to sample <br /> collection from each well and documented on the Groundwater Sampling Form <br /> • Prior to sampling activity, the water level of the well will be measured and the minimum <br /> purge volume of each well will be calculated using the purge volume calculation portion <br /> of the Groundwater Sampling Form A minimum of three casing volumes will be <br /> purged prior to sample collection The actual total volume purged will be recorded on <br /> Groundwater Sampling Form <br /> 0 Prior to sampling, a submersible pump, centrifugal pump, peristaltic pump, or a Teflon <br /> or stainless steel bailer will be used to purge a minimum of three casing volumes from <br /> each well Purge volumes will be estimated using a flow meter or a stopwatch and a <br /> bucket to estimate flow rate, from which a time to purge the required volume will be <br /> calculated The pump will be lowered to a depth of two to three feet from bottom of <br /> the well When bailers are used for purging, the bailer should be gently lowered into the <br /> water and allowed to fill then removed Care should be taken to not agitate the water <br /> which could release volatile organics <br /> A Whenever possible, groundwater parameters (pH, temperature (in degrees Celsius JCD, <br /> specific conductance (in micromhos per centimeters squared [umhos)), and turbidity Inn <br /> National Turbidity Units [NTUI) will be monitored and recorded on the Groundwater <br /> Sampling Form <br /> • If a well is purged dry before three casing volumes have been removed, the sample will <br /> be taken after the well has recovered to within $0 percent of the static water level prior <br /> to purging or after 4 hours when sufficient water volume is available to meet analytical <br /> requirements, whichever comes first Reasonable efforts will be made to avoid <br /> dewatering wells by using low-yield pumps as necessary <br /> Page 2 of 4 <br />