Indicator parameter groundwater standards

Indicator parameter groundwater standards. (1) Establishing background water quality. Background water quality at a facility, practice or activity at which monitoring is required shall be established by sampling one or more monitoring points at locations and depths sufficient to yield groundwater samples that are representative of background water quality at or near the facility, practice or activity. Background water quality shall be determined for indicator parameters specified by the department. Background water quality for indicator parameters shall be established by averaging a minimum of 8 sample results from each well. The department may exclude any sample result which is nonrepresentative of background water quality. In making the calculations required in this section, the department may use as many representative sample points as are available. (2) Establishing preventive action limits for indicator parameters. For each indicator parameter, except total coliform bacteria, for which groundwater monitoring is required by the department, the preventive action limit shall be established based upon a change of water quality with respect to background water quality according to the methodology specified in any of the following: (a) For field pH, the preventive action limit shall be one pH unit above or below the pH of the background water quality. (b) For field temperature, the preventive action limit shall be 3 standard deviations or 10ºF (5.6ºC), whichever is greater, above or below the temperature of the background water quality. (c) For all other indicator parameters, the preventive action limit shall be the background water quality for that parameter plus 3 standard deviations or the background water quality plus the increase of that parameter listed in Table 3, whichever is greater. (3) Total coliform bacteria indicator parameter. The preventive action limit for total coliform bacteria is 0. If the source of total coliform bacteria is determined to be from a regulated facility, practice, or activity, response actions under s. NR 140.24 may be required.