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I <br /> �. GROUNDWATER TECHNOLOGY i <br /> STANDARD OPERATING PROCEDURE <br /> CONCERNING GROUNDWATER MONITORING <br /> SOP, B <br /> Groundwater monitc:ring of wells at the site shall be <br /> conducted using nn ORS Interface Probe and Surface <br /> Sampler. The Interface Probe is a hand held, battery <br /> operated device for meavuring depth to petroleum product <br /> and depth to water as me4sured from an established datum <br /> (i.e., top of the well caning which has been surveyed) . <br /> Product thickness is then calculated by subtracting the <br /> depth to product from the depth to water. In adaition, <br /> water elevations are adjusted for the presence of fuel <br /> with the fallowing calculation: <br /> (Product Thickness) C+B) Elevation) <br /> o <br /> CorzectedWaterElevation <br /> Note; The factor of o.8 acccunts 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 <br /> the <br /> sensor's signals to the reel assembly, where <br /> alarr., sounds a continuous tone when the sensor is <br /> immersed in petroleum product and an oscillating tone <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 and 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 wafter. <br />