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40 <br /> 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 <br /> Equipment INTERFACE PROBE" Well Monitoring System and SURFACE SAMPLER" The <br /> INTERFACE PROBE" is a hand-held, battery-operated device for measuring depth to petroleum <br /> product and depth to water as measured from an established datum (r e , top of the well casing <br /> which has been surveyed) Separate-phase hydrocarbon (product) thickness is then calculated by <br /> subtracting the depth to product from the depth to water In addition, water elevations are <br /> adjusted for the presence of fuel with the following 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 <br /> measuring tape transmits the sensor's signals to the reel assembly where an audible alarm sounds a <br /> continuous tone when the sensor is immersed in petroleum product and an oscillating tone when <br /> immersed in 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 <br /> (difficult 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 <br /> closes onto a conical surface creating a seal as the sampler is pulled up The sampler is calibrated <br /> in inches and centimeters for visual inspection of product thickness <br /> To reduce the potential for cross contamination between wells, the monitorings shall take place in <br /> order from the least to the most contaminated wells Wells containing separate-phase <br /> hydrocarbons (free product) should be monitored last Between each monitoring the equipment <br /> shall be washed with laboratory-grade detergent and double rinsed with distilled water <br /> __.r'GROUNDWATER <br /> J' <br /> ! TECHNOLOGY <br />