Rulemaking Workgroup Briefing Summary - Arsenic Anthropogenic Sources Provision

Because we are proposing numeric arsenic criteria that represent a higher risk level than DEQ uses for most of our toxics criteria, DEQ agreed to consider including a provision in our water quality regulations that would limit anthropogenic sources of arsenic to streams with ambient arsenic levels below the numeric criteria but above some defined level (e.g. the calculated value at 10^-5; the 0.5 µg/l quantitation limit, etc.).

A sub-group was formed to work on this provision at the June Rulemaking Workgroup meeting. The subgroup has met twice in the interim and has been considering a variety of ideas. The following are some of the points we have discussed.

Purpose of provision: While DEQ will propose numeric criteria for arsenic that protect human health at an acceptable level given the presence of natural sources of arsenic in the state, the purpose of this rule provision is to maintain the lowest added human health risk from anthropogenic sources of arsenic practicable, even when ambient arsenic concentrations are below the numeric criteria.

Additional objectives:

1.  The provision should focus on known sources that add arsenic to Oregon waters, not to natural sources or sources that concentrate natural sources. Perhaps likely sources could be identified by SIC code or other industrial category.

Considerations:

2.  Does the rule need to be a water quality standard and be approved by EPA?

3.  If so, how can it be written so that it is a wq standard and where in the regulations should it be placed (toxics standard rule, antidegradation policy, other)?

4.  If a trigger level is needed to prompt a requirement or action, what should that be?

5.  What would be required of NPDES sources?

6.  How can we identify significant nonpoint sources of arsenic? What would be required of nonpoint sources?

7.  Are there sources that discharge to WWTPs that could be reduced through pretreatment?

8. How can reductions be accomplished without undue expenditure of agency resources?