8 CAR § 21-511. Mineral quality

(a) Site specific mineral quality criteria. (1) Mineral quality shall not be altered by municipal, industrial, other waste discharges, or instream activities so as to interfere with designated uses. (2) Site specific mineral quality criteria are found by ecoregion in Appendix A. (b) Ecoregion reference stream minerals values. The following values were determined from Arkansas's least-disturbed ecoregion reference streams and are considered to be the maximum naturally occurring levels. For waterbodies not listed above, any discharge that results in instream concentrations more than one-third (1/3) higher than these values for chlorides (Cl-) and sulfates (SO42-) or more than fifteen milligrams per liter (15 mg/L), whichever is greater, is considered to be a significant modification of the maximum naturally occurring values. These waterbodies should be considered as candidates for site-specific criteria development in accordance with 8 CAR §§ 21-306 and 21-308 (previously Rules 2.306 and 2.308). Similarly, site-specific criteria development should be considered if the following TDS values are exceeded after being increased by the sum of the increases to Cl- and SO42-. Such criteria may be developed only in accordance with 8 CAR §§ 21-306 and 21-308 (previously Rules 2.306 and 2.308). The values listed in the table below are not intended to be used by the Division of Environmental Quality to evaluate attainment of water quality standards for assessment purposes. (c) Domestic water supply criteria. In no case shall discharges cause concentrations in any waterbody to exceed two hundred fifty milligrams per liter (250 mg/L), two hundred fifty milligrams per liter (250 mg/L), and five hundred milligrams per liter (500 mg/L) of chlorides, sulfates, and total dissolved solids, respectively, or cause concentrations to exceed the applicable criteria, except in accordance with 8 CAR §§ 21-306 and 21-308 (previously Rules 2.306 and 2.308).