DEP Bureau of Water Quality Pushing Regulation to Reclassify Manganese as a Toxin

The Pennsylvania Department of Environmental Protection’s Bureau of Water Quality is proposing a new rule which could require a much higher standard for the treatment of Manganese at mine discharge sties.

The change is being implemented as a result of Act 40 of 2017 which directed the EQB to propose a regulation requiring the water quality criteria for Manganese be consistent with the exception in 25 Pa. Code 96.3 (d) effectively moving the point of compliance for Manganese from the point of discharge to any downstream public water supply withdrawal.

Under the proposed rulemaking, the DEP proposes deleting the Potable Water Supply (PWS) criterion of 1.0 mg/L for manganese and adding manganese to the table of Human Health and Aquatic Life Criteria for Toxic Substances of 0.3 mg/L in 25 Pa Code Chapter 93, effectively labeling it as a toxic substance.
Currently, Pennsylvania regulations have two different treatment standards for Manganese (Mn). The first more stringent standard enforced by the DEP Bureau of Water Quality requires treatment for Manganese at 1.0 mg/L standard.

The second standard occurs in Pennsylvania’s mining program under 25 Pa Code Chapters 87,88, 89 and 90 and requires treatment to meet Federal guidelines a 2.0 mg/L effluent standard. However, if a mine is located in a TMDL, the DEP applies the more stringent 1.0 mg/L potable water supply effluent standard.

In an effort comply with new state law, the Department has put forth two point of compliance alternatives point of compliance alternatives. The first alternative is a proposed regulation that changes the point of compliance for manganese in Chapter 96 from “being achieved in all surface waters” to being met “at the point of all existing or planned surface potable water supply withdrawals.”

Under this alternative, if no potable water supply exists or is planned then no water quality-based effluent limits will apply. However, Federal ELGs would still apply to the mining discharges, as would the limits set in 25 Pa Code Chapters 87, 88, 89 and 90. For all other point source discharges of manganese there would be no water quality criteria or Federal ELGs to limit the amount of manganese discharged into the surface water.

However, if a potable water supply is located on the stream, a discharger’s point of compliance with the proposed manganese criterion will be modeled from the upstream point of discharge to the point of potable water supply withdrawal, allowing for attenuation of the effluent as it travels downstream. The discharger’s effluent limitation would be determined based on achieving the proposed manganese criterion of 0.3 mg/L at the point of potable water supply intake.

The second method of compliance the Department is considering would be applied to all surface waters to protect “all relevant uses in accordance with 96.3 (c). This would require that 0.3 discharge criteria be met at the point of discharge.”

Under this alternative, the DEP argues that “additional protections will be provided to the Potable Water Supply use and other protected water supply uses (e.g., Irrigation, Livestock Water Supply and Wildlife Water Supply).

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