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COLORADO DEPARTMENT OF PUBLIC I:EALTH AND ENVIRONMENT WATER QUALITY CONTROLDlVISION WATER QUALITY PROTECTION SECTION GROUND-WATER P=P.MiT GUIDPNCE SUGGESTED MONITORING WELL SANIPLiNG PROTOCOL S. CROUhT~-`eiTAT`ER ~AIl/tPLE ~,C'LLECT'ZO~ht 2. METHOD A FOR SAMPLE COLLECTION This method is to be utilized for [hose weds that produce a sufficient volume of water and have a rapid recovery rate. a. Prior to purging~sampling, calibrate all test equipment used in the field according to manufacture's specifications. Enter all equipment calibration data into a field logbook. Clean all field test equipment and eround-water sampling equipment. b. Purge the well water into a collection container to be able to measure and record temperature, pH, conductivity [and dissolved oxygen]. Continue purging until the stzgnant water in the casing has been replaced by forrnazion ware:. This is be=_: determined by log,ing the readings for temperar~re, pH, conductivity [and dissolved oxygen, where applicablel readings. After approximately three casing volumes have been removed firor.. the well and once foe most recent ..,adinr is within 10% of `se previous two readings for each individual field parameter, a ground-water sample will be taken. If the field parameters do not stabilize, a minimum of five casing volumes shall be removed from the well prior to fakirs a ~rpund-wale: samoie. c. If a bane: is used to purge the we!I and to take the ground-water sample, the bailer is to be lowered in*.o the well to what hereinafter is referred to'as the "sample depth". "Sample depth" is determined by lowering the bailer to the bottom of the well. Once the bailer is gently resting on the bottom, the field person is to mark this location on the cable. The mark is to be placed directly across from the measuring point while the cable is held taut Raise the bailer one-foot above the bottom of the well. Mark the cable or place adhesive tape on the cable to indicate the sample depth for future reference. Tak:ng a sample at :his eleva[ior. should avoid undue amounts or sedimeau in the sample and prevent sediment inteH'e:ing with closure of the bailer valve. T'ne we!1 should be purged by bailing from the bOCOm of the well, unnl the water level is drawn down to the lowest possible level. Take a `throw-away" sample to dete.-mine temperature, pH and conductivity. Record the values and the volume bailed..411ow the water level to recharoe to at least tour feet in the bottom of the will, or to whatever depth Lase water recovers in well (less than four tee[;. Take another "throw away" sample. Continue ~Sis procedure until approximately three volumes have been removed and the parametea aze within 10% of the previous two readings for each parameter. At this tame, the field person will take a sample. If the 5eld parameters do not stabilize, a minimum of five casing volumes shall be removed from the well prior to taking aground-water sample. d Prevent samplin, eGUiomert from com;n_ into contact with the ground or a potentially contaminated surface.