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Indiana Preliminarily Adopts Revised Chloride and Sulfate Water Quality Criteria


In 1990, Indiana adopted numeric water quality criteria for chloride and sulfate based on criteria developed by the U.S. Environmental Protection Agency (EPA).  These criteria are important because they 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.  There are 69 industrial dischargers and 18 municipal dischargers who will be impacted by this change.

Since the chloride and sulfate standards were first developed, there has been progress in the scientific understanding of toxicity of chloride to aquatic life.  The amendment of the water quality criteria is being done as part of the Clean Water Act requirement that states conduct a triennial review of water quality standards and update the standards as needed.  The amendment will update the existing chloride criteria for the Non-Great Lakes system and Great Lakes system and make changes to the Non-Great Lakes system sulfate criteria and Great Lakes system implementation procedures to accommodate the updated chloride criteria.

The Indiana Department of Environmental Management (IDEM) is proposing to replace 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 proposed change to 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) will also be 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 proposed rule will be less stringent than the current 230 mg/l criterion.  However, acute aquatic life criteria calculated using the equation in the proposed rule will be more stringent than the current 860 mg/l criterion.

The amendment will affect Lake Michigan’s chloride criteria, deleting the current 850 mg/l criterion maximum concentration and 230 mg/l criterion continuous concentration.  These would be replaced by a single chloride criterion of 250 mg/l.  Lake Michigan’s sulfate criterion would remain at 250 mg/l.

While permit holders will continue to have costs associated with meeting chloride permit limits and monitoring requirements, according to IDEM 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.

On March 14, 2012, the Water Pollution Control Board (WPCB) preliminarily adopted the draft chloride sulfate water quality standard rule without making any changes.  The next step is for the proposed rule to be submitted to the Indiana Register (IR) for posting along with a notice of public hearing.  There will be no third comment period for the proposed rule because it was unchanged from the draft rule that was posted in the IR at second notice.  The date of the WPCB hearing to consider final adoption has not yet been determined.  Once the WPCB adopts the rule and the rule becomes effective, the amended water quality criteria will be submitted to the EPA for approval.

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

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