The DEQ has followed up on its earlier temporary emergency rules of 10/27/2016 & 04/27/2017 that tightened 1,4-dioxane cleanup criteria from 85 ppb to 7.2 ppb. The plan is to make the 7.2 ppb permanent before the temporary emergency rules expire on 10/27/2017. Negotiations continue with Pall/Gelman to accept the new 7.2 ppb standard in changes to the Consent Judgement and in the Permit.

FWD: 1,4-Dioxane Rules

Michigan Department of Environmental Quality sent this bulletin at 08/02/2017 03:52 PM EDT

The DEQ is proposing an amendment to the Cleanup Criteria Requirements for Response Activity Rules, commonly known as the Part 201 Rules, for a single hazardous substance: 1,4-dioxane. This rule amendment will modify the cleanup criterion for 1,4-dioxane for the residential drinking water pathway only in the generic criteria table and the associated footnotes (R 299.44 and R 299.49). The Department issued an Emergency Rule on October 27, 2016 that established the 1,4-dioxane cleanup criterion for the residential drinking water ingestion pathway at 7.2 parts per billion, with the expectation that a comprehensive update to the Part 201 Rules for over 300 hazardous substances would be completed before the Emergency Rule expired.

Due to the impending expiration of the Emergency Rule and the anticipated timeline for the comprehensive Part 201 Rule amendment package, the DEQ has decided to move forward with this 1,4-dioxane amendment to preserve our ability to use the best available scientific information regarding 1,4-dioxane for the residential drinking water pathway at sites throughout the state.

The proposed rule amendment for the comprehensive Part 201 Rule package is forthcoming and will go through the Administrative Rule promulgation process as well. The comprehensive package will update the physical-chemical properties, toxicity data, and exposure assumptions for over 300 hazardous substances.

A copy of the 1,4-dioxane rule [2017-041 EQ] (see Pages 6, 18, and 23) is available on the Office of Regulatory Invention’s website. A public hearing for the proposed 1,4-dioxane rule will be held on August 22, 2017.

Action on the 29 ppb or 1900 ppb criteria vapor intrusion or other possible exposure pathways are on hold awaiting more study.