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R , <br /> GROUND'WAT41t TECHNOLOCY <br /> STANDARD OPERATING PROCEDURE <br /> CONCERNING GROUNDWATER MONITORING <br /> SOP s <br /> Groundwater monitor:ing of wells at the site shall, be <br /> conducted using an ORS Interface Probe and Surface <br /> Sampler. The Interface Probe is a hand held, battery <br /> Operated device for measuring depth to petroleum product <br /> and depth to water as Ine.asilred from an established datum <br /> (i.e. , top of the well casing which has beer. surveyed). <br /> Product thicLness is ,.hen calculated by subtracting the <br /> depth to product f.Vori the depth to water. In addition, <br /> water• elevations arc_• adjusted for the presence of fuel <br /> with the folluw,ing calculation: <br /> (Product Thickness) (-$M Water Elevation) <br /> = Corrected Water Elevation <br /> Note: The factor of 0.8 &ccounts for the density <br /> difference between water and petroleum <br /> hydrocarbons. <br /> The Interface Probe consists of a dual sensing probe <br /> utilizing an optical liquid sensor and electrical con- <br /> ductivity to distinguish between water and petroleum <br /> products. A coated steel measuring tape transmits the <br /> sensoron signals to the reel assembly, where an audible <br /> alarm sounds a continuous tone when the sensor is <br /> immersed in petroleum product and an oscillating tore <br /> when immersed in water. The Interface Probe is accurate <br /> to 1,16--:inch. <br /> A Surface Sampler shall be used for visual inspection of <br /> the groundwater to note sheens (difficult to detect with <br /> the Interface Probe), odors, microbial action, etc_. <br /> The Surface Sampler used consists of a 12-inch long cast <br /> acrylic tube with a Delrin ball which closes onto a <br /> conical surface creating a seal as the sampler is pulled <br /> up. The sampler is calibrated in inches aad centimeters <br /> for visual inspection of product thickness. <br /> To reduce the potential for cross contamination between <br /> wells the monitorings shall take place in order from the <br /> least to most contaminated wells. Wells containing free <br /> product should be monitored last. Between each monitoring <br /> the equipment shall be washed with laboratory grade <br /> detergent and double rinsed with distilled water. <br /> err <br />