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COLORADO DEP SRTMENT OF PUBLIC HEALTH AND ENVIRONMENT WATER QUALITY CONTROL DIVISION WATER QUALITY PROTECTION SECTION GROUND-WATER PEIL'v1IT GUIDANCE SUGGESTED MONITORING WELL SAMPLING PROTOCOL B. CrROUPiD-WATER SAMPLE COLLECTION Ground-water sampling shall consist of ground-water sampling equipment decontamination, sample collection, sampling equipment decontamination and documentation of sample collection. 1. Collection of Ground-Water Samples Priot to initiating ground-water sampling activities, the monitoring person or personnel stall have calibrated all field test equipment and decontaminated all equipment used to obtain aground-water sample. For a well with a dedicated pump no decontamination of the pump is necessary. In those circumstances where anon-dedicated pump (and generator) are utilized, the pump and the tubing need to be thorougiily cleaned with a laboratory detergent, like Alconox, or equivalent, followed by several rinses with deionized water. If the sampling equipment has been badly contaminated, the equipment needs to be cleaned with a soft brush and hot-ware: detergent wash prior to the deionized water rinses. Titis same procedure is applicable for a bailer and iL= cable,~rope. Purging of each well is to be accomplished by a dedicated pump or by a bailer cr by a non-denc~ated pump. During the purging process, temperature, pH, conductivity and dissolved oxygen are to be determined. Most permits do not require dissolved oxygen at this time. However, in time, all permits ;hall require dissolved oxygen be dete„„^.,ined during the purging, process and prior ro sample collection. The megst:red temperature, pH anal conductivity are to be entered onto a log or sampling form. After approximately three casing volumes, a ground- water sample will be collected once there is stabilization (within 1C%) between the most recent sample and the previous two readings. If the mete: readings for oH, temperature and conductivity do ne stabilize, field personae! need only remove five casing volumes before taking aground-water sample. Aarsuant to the monitorine requirements in the ground-water discharge permit, ground water collected from the monitoring wells shall, typically; 'oe analyzed for chloride. sulfate, rut-,ate and total coliform bacteria. In accordance with the "The Basic Standards for Ground Water", the field peaonnel shall finer the samples fer nihate, chloride and sulfate prior to preservation. [Refer to Regula[ion No. 41, "The Basic Standaras for Ground Water", to determine which parameter; are required to be filtered prior to preservation.] The filter is a ~5-micron filter. Some samples require preservative and same do not. The field personnel should obrzin the required bortles from the laboratory that is performing the analyses. All samples are to be iced in a cooler until they are handed to the laboratory personnel. Water in the well is to be withdrawn by sampling pumps, such as Watera inertia pumps or by using a bailer (it is prefered that the bailer be a double check valve bailer). The sampling pumps may be dedicated to the upgraaient and downgradient wells. Dedicated sampling pumps eliminate the potential for cross-contamination between wells and thus need for sampling equipment decontamination. In purging and samptins wells with inertia pumas, a flow rate of approximately one gallon per minute (gpm) is reccmmended rate to minimize loss of any voiadle compounds (This is only a cencem for a volatile !isred as a permit limit.) iiom the water to be sampled and analyzed. Provide a description and specifications of the pump(s) or bailer to be utilized.