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HORIZON ENVIRONMENTAL , INC. GROUNDWATER MONITORING '-' FIELD METHODS AND PROCEDURES The following section describes field procedures that will be completed by Horizon r: a Environmental Inc. (Horizon) personnel in performance of the tasks involved with this project. 1.0 GROUNDWATER DEPTH DETERMINATION Each monitoring well is opened and allowed to equalize to atmospheric pressure prior to sounding. Depth-to-water is measured to the nearest 0.01-foot using an electronic, hand-held, water-level indicator. The measuring point is the survey mark on the top of the well casing. The tip of the probe is examined in order to determine the presence or absence of product sheen. 2.0 MONITORING WELL PURGING & SAMPLING Prior to purging, a clean, transparent bailer is lowered into the well, and a sample of groundwater is hoisted to the surface. The sample fluid is inspected for the presence of free- floating product on its surface. Sampling activities conducted subsequent to the initial well f'= development activity will be preceded by purging a minimum of three well-volumes by hand- bailing or the use of an electrically-operated pump. Purge water will be monitored for the parameters of temperature, pH, and electrical conductivity until stabilized. If required, field readings for dissolved oxygen (d02), displayed in tenths of parts per million (ppm x 0.1), will be obtained utilizing Hanna Instruments' hand-held, HI-9142 Portable Dissolved Oxygen Meter. Generally, higher d02 concentrations are expected in samples which are unimpacted or marginally impacted by hydrocarbons than for samples collected from monitoring wells which yield hydrocarbon-impacted water. A well is allowed to recharge to at least 80% of its prepurge volume prior to sampling. If a well dewaters, it will be allowed to recharge for a minimum of one to two hours prior to sampling. 1