The Iowa Department of Natural Resources (IDNR) is currently proposing to amend Iowa ambient water quality standards for chloride, sulphate and total dissolved solids (TDS). In addition, they are proposing a change to the default hardness value used to calculate ambient water quality standards for many chemicals, especially metals.
The changes being proposed include the following:
- Establish numerical water quality criteria for chloride for the protection of aquatic life uses.
- Establish numerical water quality criteria for sulfate for the protection of aquatic life uses.
- Remove TDS criteria and implementation approach
- Revises default hardness level used for hardness dependent chemical criteria from 100 mg/l (as CaCO3) to 200 mg/L.
IDNR will be accepting comments on these proposed changes until August 14, 2009.
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