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Murray & Associates <br /> STANDARD OPERATING PROCEDURE <br /> \ <br /> /CONCERNING GROUNDWATER MONITORING <br /> SOP 1 <br /> Groundwater monitoring of wells at the site shall be conducted using an ORS Interface Probe <br /> and Surface Sampler. The Interface Probe is a hand held, battery operated device for measuring <br /> 1 depth to petroleum product and depth to water as measured from an established datum (I e , top <br /> of the well casing which has been surveyed) Product thickness is then calculated by subtracting <br /> the depth to product from the depth to water In addition, water elevations are adjusted for the <br /> presence of fuel with the following calculation <br /> (Product Thickness)( 8) + (Water Elevation) = Corrected Water Elevation <br /> ' Note The factor of 0 8 accounts for the densitydifference erence between water and petroleum <br /> hydrocarbons <br /> The Interface Probe consists of a dual sensing probe utilizing 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 <br /> sounds a continuous toe when the sensor is immersed in petroleum product and an oscillating <br /> tone when immersed in water The Interface Probe is accurate to 1/16-inch <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 used d consists of a 12-inch long cast acrylic tube with a Delrsn ball which <br /> closes onto a conical surface creating a seal as the sampler is pulled up The sampler is <br /> calibrated in inches and centimeters for visual inspection of product thickness <br /> To reduce the potential for cross contamination between wells the monitoring shall take place <br /> in order from the least to most contaminated wells Wells containing free product should be <br /> monitored last Between each monitoring the equipment shall be washed with laboratory grade <br /> detergent and double nnsed with distilled water <br />