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GROUNDWATER TECHNOLOGY, INC. STANDARD OPERATING PROCEDURE NO. 8 GROUNDWATER MONITORING • Groundwater monitoring of wells at the site shall be conducted using an ORS Environmental Equipment (ORS) INTERFACE PROBE'' or SURFACE SAMPLER'. The INTERFACE PROBE'is a • hand-held, battery-operated device for measuring depth to petroleum product and depth to water as measured from an established datum (i.e., top of the well casing which has been surveyed). Floating separate-phase hydrocarbon (product) thickness is then calculated by subtracting the depth to product from the depth to water. In addition, water elevations are adjusted for the presence of floating product with the following calculation: (Product Thickness) x (0.8) + (Water Elevation) W Corrected Water Elevation Note: The factor of 0.8 accounts for the density difference between water and petroleum hydrocarbons. The thickness of dense non-aqueous phase liquids (DNAPLs) is calculated by subtracting the depth at which the DNAPL is encountered from the total depth of the well. Water-level elevations are not typically corrected for the presence of DNAPLs. • • The INTERFACE PROBE'" consists of a dual-sensing probe which utilizes an optical liquid sensor and electrical conductivity to distinguish between water and petroleum products. A coated steel measuring tape transmits the sensor's signals to the reel assembly where an audible alarm sounds a continuous tone when the sensor is immersed in petroleum product and an oscillating tone when immersed in water. The INTERFACE PROBE'" is accurate to 0.01 inch. • A SURFACE SAMPLER' shall be used for visual inspection of the groundwater to note sheens (difficult to detect with the INTERFACE PROBE'), odors, microbial action, etc. The SURFACE SAMPLER'used consists of a 12-inch-long case acrylic tube with a Defrin bail which closes onto a conical surface creating a seal as the sampler is pulled up. The sampler is calibrated in inches and centimeters for visual inspection of product thickness. To reduce the potential for cross contamination between wells, the monitoring shall take place in order from the least to the most contaminated wells. Wells containing separate-phase hydrocarbons (free product) should be monitored last. Between each monitoring the equipment shall be washed with laboratory-grade detergent and double rinsed with distilled water. r CONCORID.sOP fZM41 - _JR GROUNDWATER r =. I TECHNOLOGY, INc.