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Indiana Final Adopts Revised Chloride and Sulfate Water Quality Criteria


The March/April 2012 issue of the Environmental Letter reported on Indiana’s proposed revision of the numeric water quality criteria for chloride and sulfate.  These criteria are used to calculate numeric water quality based effluent limitations (WQBEL) that are placed in National Pollutant Discharge Elimination System (NPDES) permits issued to wastewater dischargers and are used to develop impaired water listings and watershed management plan goals.  The Indiana Department of Environmental Management (IDEM) reports that there are 69 industrial dischargers and 18 municipal dischargers whose NPDES permits are impacted by these water quality criteria. 

On May 23, 2012, the Water Pollution Control Board (WPCB) final adopted the chloride sulfate water quality standard rule without making any changes from the proposed rule.  IDEM submitted the promulgation packet to the Attorney General’s Office the week of June 11th, 2012.  From this point, the remaining review, approval, filing steps, publication, and waiting period needed for the rule to become effective is expected to take between two to three months.  Once the rule becomes effective, the amended water quality criteria will be submitted to EPA for approval.  IDEM expects EPA to approve the rule.

The final rule replaces the current chloride criteria in 327 IAC 2-1-6(a)(3) (non-Great Lakes system waters) and 327 IAC 2-1.5-8(a)(3) (Great Lakes System waters) that are expressed as a specific value with equations.  These equations will allow the aquatic life chloride criteria to vary depending on the hardness and sulfate concentrations in a waterbody. This change to the chloride criteria will apply to all surface waters in Indiana. The sulfate criteria for non-Great Lakes system water bodies in 327 IAC 2-1-6(a)(5) is also amended because the sulfate criteria are expressed as a function of both chloride concentrations and hardness with a current maximum chloride concentration of 230 mg/l.

IDEM reports that in most instances chronic aquatic life chloride criteria calculated using the rule will be less stringent than the current 230 mg/l criterion. However, acute aquatic life criteria calculated using the equation in the rule will be more stringent than the current 860 mg/l criterion.

The final rule amends Lake Michigan’s chloride criteria by deleting the current 860 mg/l criterion maximum concentration and 230 mg/l criterion continuous concentration.  Once the final rule becomes effective, these criteria will be replaced by a single chloride criterion of 250 mg/l.  Lake Michigan’s sulfate criterion will remain at 250 mg/l.

While permit holders will continue to have costs associated with meeting chloride permit limits and monitoring requirements, IDEM expects the costs may be less than under the currently established chloride water quality criteria.  Moreover, dischargers with permit limits will need to sample and analyze for sulfate if they are not already doing so.

To view a complete PDF of the May/June 2012 issue of the Environmental Letter, click HERE.

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