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GROUNDWATER TECHNOLOGY <br /> STANDARD OPERATING PROCEDURE <br /> �,. CONCERNIiNG GROUNDWATER MONITORING <br /> SOP 8 <br /> Groundwater monitoring of wells at the site shall be <br /> " conducted using an ORS Interface Probe and Surface <br /> Sampler. The Interface P,,obe is a hand held, battery <br /> operated device for measuring depth to petroleum product <br /> and depth to water as measured from an established datum <br /> (i.e. , top of the well casing whish has been surveyed) . <br /> Product thickness is then calculated by subtracting the <br /> �., depth to product from the depth to water. In addition, <br /> water elevations are adjusted for the presence of fuel <br /> with the following c:.1culation: <br /> (Product Thic:kness) ( .8)+(Water Elevation) <br /> Corrected Water Elevation <br /> -• Notes The tactor of 8.8 accounts for the density <br /> difference between water and petroleum <br /> hydrocarbons. <br /> The Interface Probe consists of a dual sensing pro;, <br /> k utilizing an optical liquid sensor and electrical con- <br /> ductivity to distinguish between water and petroleum <br /> products. iA coated steel measuring tape transmits the <br /> ., sensor's 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 tone <br /> when immersed in water. The Interface Probe is accurate <br /> �:o 1/16-inch. <br /> A Surface Sampler shall be used for visual inspection of <br /> r the groundwater to note sheens (difficult to detect with <br /> the Interfa( a 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 /> r>> wells the monitorings shall take place in order from the <br /> least to most contaminated wells. Wells containing gree <br /> product should be monitored last. Between each monitoring <br /> the equipment shall be washed with laboratory grade <br /> detergent and double rkised with distilled water. <br />