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I ' (100%corg • • GROUNDWATER MONITORING AND SAMPLING PROCEDURES (Includes No-Purge Sampling) ' Groundwater Monitoring and Decontamination Method Prior to beginning, a decontairunation area is established Decontamination procedures consist of scrubbing down-well equipment in a Liquidnox9 solution wash (or equivalent degreasing compound), and rinsing in potable water and a final rinse of de-ionized (or distilled) water before and after each well Any non-dedicated down-well equipment is decontaminated prior to use on ' site Prior to purging and sampling a well, the static water level is measured to the nearest 0 01 feet with an electronic interface probe and/or water level meter Depth to bottom is typically measured every ' quarterly event The water level meter and tape will be decontaminated between each well If floating phase-separated hydrocarbons (PSH) are suspected or previously confirmed, an electronic interface probe is used to measure the well fluids to the nearest 0 01 feet PSH may alternatively be ' measured using a clear, open-ended product bailer, and the thickness is measured to the nearest 0 01 feet in the bailer Any monitoring well containing a measurable thickness of PSH before or during purging is not additionally purged and no sample is collected from that well Wells containing hydrocarbon sheer; are sampled unless otherwise specified by the project manager Field observations such as well integrity as well as water level measurements and PSH thickness are recorded in the field '• Well Pur2in� When well purging is required, each monitoring well to be sampled is purged using, a truck- mounted vacuum pump, a polyvinyl chloride (PVC) bailer or a submersible pump Physical ' parameters (pH, temperature, and conductivity) of the purge groundwater are monitored during purging activities to assess if the water sample collected is representative of the aquifer If required, parameters such as dissolved oxygen, turbidity, salinity etc are also measured Samples are considered representative if parameter stability is achieved Stability is defined as a change of Iess than 0 25 pH units, less than 10% change in conductivity in micro mhos, and less than 1 0 degree centigrade (1 8 degrees Fahrenheit) change in temperature Parameters are measured in a discreet sample decanted from the bailer separately from the rest of the purge groundwater Parameters are measured during purging, initially, and at volume intervals of one well or borehole volume (dependent on local regulations) Purging continues until the required well or borehole volumes have been removed, until the well completely dewaters, or until measured parameters stabilize as indicated above When wells dewater or demonstrate a slow recharge, wells may be sampled although fewer than required volumes have been removed Well purging information is recorded on I the Purge Data sheet All meters used to measure parameters are calibrated daily Purge water is sealed, labeled, and stored on site in D O T -approved 55-gallon drums After being chemically profiled, the water is transported to an appropriate disposal facility by a licensed waste hauler Groundwater Sample Collection After purging, groundwater samples are collected after at least 80% of its static water level is recovered in the well If recharge is extremely slow, the well is allowed to recharge until sufficient volume has accumulated for sample collection No-purge groundwater samples are collected when prior approval by the lead regulatory agency has been permitted When no-purge . samples are collected the same procedures are followed excluding well purging All groundwater samples are collected using polyethylene disposable bailers attached with new, clears string or rope Groundwater samples being analyzed for compounds most sensitive to volatilization