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GROUNDWATER TECHNOLOGY, INC. <br />STANDARD OPERATING PROCEDURE <br />CONCERNING GROUNDWATER MONITORING <br />SOP 8 <br />Groundwater monitoring of wells at the site shall be conducted using an ORS Environmental Equipment <br />INTERFACE PROBE- Well Monitoring System and SURFACE SAMPLER' The INTERFACE PROBE" is a <br />hand-held, battery-operated device for measuring depth to petroleum product and depth to water as <br />measured from an established datum (i.e., top of the well casing which has been surveyed). Separate - <br />phase hydrocarbon (product) thickness is then calculated by subtracting the depth to product from the <br />depth to water. In addition, water elevations are adjusted for the presence of fuel with the following <br />calculation: <br />(Product Thickness) (0.8) + (Water Elevation) = Corrected Water Elevation <br />Note: The factor of 0.8 accounts for the density difference between water and petroleum <br />hydrocarbons. <br />The INTERFACE PROBE'" consists of a dual -sensing probe which utilizes an optical liquid sensor and <br />electrical conductivity to distinguish between water and petroleum products. A coated steel measuring <br />tape transmits the sensor's signals to the reel assembly where an audible alarm sounds a continuous <br />tone when the sensor is immersed in petroleum product and an oscillating tone when immersed in <br />water. The INTERFACE PROBE'" is accurate to 0.01 feet. <br />A SURFACE SAMPLER'" shall be used for visual inspection of the groundwater to note sheens (difficult <br />to detect with the INTERFACE PROBE'"), odors, microbial action, etc. <br />The SURFACE SAMPLER" consists of a 40 -inch -long cast acrylic tube with a Delrin ball which closes <br />onto a conical surface creating a seal as the sampler is pulled up. The sampler is calibrated in inches <br />and centimeters for visual inspection of product thickness. <br />To reduce the potential for cross contamination between wells, the monitorings shall take place in order <br />from the least to the most contaminated wells. Wells containing separate -phase hydrocarbons (free <br />product) should be monitored last. Between each monitoring the equipment shall be washed with <br />laboratory -grade detergent and double rinsed with distilled water. <br />o GROUNDWATER <br />TECHNOLOGY <br />