Download
1 / 15
150 likes | 262 Views
Metropolitan Council. Environmental Services. Metro Permit Reissuance Proposed Changes and Potential Impacts. Presented to the Environment Committee August 24, 2010. Keith Buttleman, Assistant General Manager EQA Department, MCES. A Clean Water Agency. Background Information.
E N D
Metropolitan Council Environmental Services Metro Permit Reissuance Proposed Changes and Potential Impacts Presented to the Environment Committee August 24, 2010 Keith Buttleman, Assistant General Manager EQA Department, MCES A Clean Water Agency
Background Information • Metro Permit expired in April, 2010 – still in effect until new permit issued • PCA proposes to add new PFOS limit and tighten P limit in permit • No PFOS limit in existing permit (but monitoring at BL and Seneca
Renewal Issues • Phosphorus: • Current limit – 1 mg/L • Proposed interim limit – 0.6 mg/L(current flow) • PFOS • too soon to regulate
Proposed Phosphorus Limits • PCA proposing Metro interim limit of 200 MT/yr • Limit of ~0.6 mg/L at current flow rate; ~0.46 mg/L at permitted flow rate • Current discharge 0.3-0.4 mg/L • Current P discharged – under 100 MT/year • 2005 P discharged about 160 MT/yr
Concern with Numeric P Limit • Once number in permit, virtually cannot be raised; federal antibacksliding rules • Lose opportunity for “bubble permit” through post-TMDL permitting • Possible federal action on P (and N)
PCA Approach to PFOS Limits • PFOS limits: • 10 ng/L monthly average • 17 ng/L daily max • PCA asked MCES to propose final compliance date • Re: PCA • source control will meet PFOS limits • PFOS in fish tissue is 3M and Metro issue
PFOS in Wastewater • PFOS concentration appears to increase through wastewater treatment process (global) • Precursors/catalyst/mechanism of PFOS formation not reliably identified
Too Soon to Regulate PFOS • No Total Maximum Daily Load (TMDL) developed • Impairment is localized section of Mississippi River Pool 2, not entirety • Unknown precursors makes source control and timing estimate impossible
MRP2 MPCA Fish Sampling Areas Fish sample collection locations (yellow) 9
Too Soon to Regulate PFOS (cont’d) • Source for fish is sediment, not water • Contaminated sediment removal in 2011 • Question whether fish advisory continues post-remediation
Concern with Numeric PFOS Limit • Once number included in permit, federal antibacksliding rules prohibit increasing • Impairment applied to entirety of Mississippi River Pool 2 – should be focused on downstream area • PCA controlling as water column issue; data show is localized sediment source issue
MRP2 MPCA Fish Sampling Areas Fish sample collection locations (yellow) 12
PFOS – MCES Proposal • Allow time to: • evaluate impairment post-remediation • understand PFOS behavior and control in wastewater • PCA develop TMDL for PFOS & precursors • If still impaired, allocate loadings through TMDL
PFOS – Too Soon to Regulate • Limit (10 ng/L) way below drinking water standards (300 ng/L); may be unattainable • Unknown how plant effluent increase occurs • No consistent list of PFOS precursors • Impairment isolated to small area in Pool 2, not near Metro discharge point • Sediment, not water, is source of PFOS in fish • 3M cleaning up contaminated sediment in Pool 2, may remove impairment
Next Steps • MCES continues to make the case to MPCA that Metro does not “cause or contribute” to PFOS Impairment, so should not be regulated through permit limits • PCA planning to send draft permit shortly • May be need to contest permit
