MPCA Nutrient Policy – Implementing river eutrophication standards

1. MPCA Nutrient Policy – Implementing river eutrophication standards Dennis Wasley with contributions from Steve Weiss, Steve Heiskary

2. Need for Lake & River Nutrient Standards • Nutrient enrichment negatively impacts aquatic biota and recreation • USEPA – States should develop nutrient criteria for lakes, streams, wetlands (must develop may be more accurate based on Florida where EPA promulgated) • MN promulgated ecoregion-based lake eutrophication standards in 2008 in MN Rules Chapter 7050; • River, navigational pool & Pepin site specific under promulgation (2010-2012)

3. Current Policy • Statewide phosphorus rule (2008) • 1 mg/L for expansions • Lake and Reservoir standards (2008) • Phosphorus decision tree (2010) • Balanced approach with reductions from non-point and point sources • Consider multiple dischargers in watershed • Use draft or completed TMDLs • WQBELs

4. Draft: Future policy • River nutrient standards • Summer average • Long-term average • Response variables • Non-point sources are very important • Streamflow • Examples • Nitrate toxicity standard

5. Draft river eutrophication criteria (summer-means) • Assessments based on minimum of 2 summers & 6 or more obs./summer; • Must exceed cause & one or more response (stressors)to be deemed impaired; • existing pH standard may be used also

6. River Nutrient Regions (RNR) • Regionalized criteria because of distinct differences among landform, land use, soil type, & stream water quality in MN • Consistent with lake criteria approach; • EPA Ecoregion map was base map: • Rivers classified based on relative ecoregion composition & • Changes in reach-specific WQ;

7. RNR-based TP distribution • CFD Summer-mean TP based on 128 (North), 239 (Central) and 209 (South) river sites. • Distinct regional patterns & % river-reaches potentially exceeding standards.

8. Draft criteria for main-stem rivers, Mississippi River pools & Lake Pepin.Expressed as summer averages. 1River eutrophication criteria-based. 2 Minimize frequency of severe blooms. 3 MN lake criteria-based. 4 Minimize frequency of blooms & meet Pepin requirements 5. Lake Pepin criteria based on mean from 4 sites. 6 Minimize frequency of severe blooms; WI standard of 100 µg/L applies to Pools 5-8 Designed to complement & be protective of downstream uses

9. Implementing river criteria at HUC-8 scale. First TMDL assessments 2013

10. Effluent limits 101 (RNS standards) • Establish background concentration of stream • Background concentration is dynamic for TP over summer period • Calculate load from facility • Standard applies during wet and dry times • Determine if load from facility drives concentration in stream above standard during a critical condition • Requires extensive concentration and flow data for stream • Dilution is the Solution • High flows do not always offer dilution

11. Single flow vs all flow (ug/L) 122Q10

12. Flow considerations • Very difficult to pick one flow to set limits on that would protect long-term summer average • High flows can be very high in TP • Important for downstream resources • Zero flows can occur in headwaters and western streams • How far downstream does effluent travel during low flows • Impact of zero flows on long-term average?

13. Examples

14. Bigfork River (meets RNS) High flow Low flow

15. Bigfork River (daily loads)

16. Bigfork River • Very minimal point sources • Non-point only exceeds standard at highest flows • This is expected and complies with RNS • Downstream impairment in Lake of the Woods (LOW) • Existing limits in Bigfork watershed will be adopted by LOW TMDL • Boise Cascade, North Kooch larger point sources • Complicated lake

17. Cottonwood River • TP exceeds RNS at watershed outlet • Response data is very limited • Downstream rivers do exceed both TP and response variable • Extensive non-point sources in cottonwood and downstream watersheds

22. Point source locations in Cottonwood Minnesota R. at Jordan Cottonwood at New Ulm Minnesota R. Mankato

24. Cottonwood: proposal • Very minimal point sources • No point source signature during low flow • Non-point drives impairment • Clearly exceed standards above median flow • Focus on non-point and set point source limits to protect MN River • Minnesota needs considerable non-point reductions and some point source reductions • Balanced approach to point sources in Minnesota R watershed

25. South Fork Crow River • Large point and non-point contributions • Recent point source reductions • Clearly exceeds TP and response variables of RNS • Restrictive WWTP limits and considerable non-point reductions will be needed to meet RNS

26. SF Crow River (high TP at all flows)

28. SF Crow loads

29. SF Crow • Considerable non-point reductions needed • Very difficult to drive concentration at moderate to high flows below 0.150 mg/L • Non-point trading options • Existing point sources overwhelm background at moderate to low flows • Could assume 0.075 – 0.10 mg/L based on other watersheds • Tremendous algal production at low flows • Low flow is really low flow in SF Crow?

30. Use available data to determine status of receiving reach and impact of point source on that reach (reasonable potential) Immediate stream exceeds TP standard No data at receiving reach Focus on downstream CWLSS or representative reach Limited response data or acceptable response data in immediate reach Response variables exceeded in immediate stream: Set limits to meet TP standard in immediate stream reach River meets TP standard Collect more data at receiving reach, Set TP limits based on downstream response Existing Facilities: Evaluate if existing design limits are sufficient to protect downstream waters (e.g. St. Cloud WWTP) Expanded/New Facilities:Design plant to meet RNS and applicable nondegradation requirements. Protect downstream waters. One permit cycle TP and response variables exceed standards in immediate reach Response variables do not exceed standards in immediate reach Maintain TP limits to protect downstream resources

31. Headwaters / small rivers • If good data for TP, response and flow • Proceed with same process as outlined in examples • Limited data at immediate reach • Set limits for downstream impairments • Require additional monitoring for immediate reach • Flow • TP • Response varibles

32. Other considerations • Seasonal relief (no downstream lakes) • State rule for October-March/April • RNS limit for April/May-September • Pond discharges • Adjust discharge window in watersheds where restrictive limits are needed • Maintain limits in watersheds where meet RNS or non-point is the major source reduction needed

33. Need for Nitrate Water Quality Standard • EPA: States to develop nutrient criteria for lakes, streams, wetlands; ecoregion-based; Miss. R/Gulf. • MN promulgated ecoregion-based lake eutrophication standards in 2008 and river in process. • Nitrate: conservative ion, ubiquitous, documented aquatic toxicity, concerns raised by stakeholders and legislature. • Current WQS only-Class 1 Drinking Water:10 mg/L.

34. Nitrate Water Quality Standard (WQS)s Development: Based on Aquatic Life Toxicity What’s Complete? • Water Quality Criteria calculations (EPA guidelines) • MPCA is also approaching nitrogen issues through a study of sources, trends, and loading. • EPA funded toxicity tests: 6 taxa (acute and chronic endpoints) • MN Draft WQSs (November 2010 Technical Support Document) • Class 2B (cool-warm waters) - 5.1 mg/L (nitrate-N) • Class 2A (cold waters) - 3.1 mg/L (nitrate-N) • Additional toxicity test endpoints are anticipated

35. Summary • Set limits on downstream reach with adequate data to make calculations • MPCA wants to be right the first time • Watershed approach, TMDLs and additional monitoring will refine original limit calculations • Non-point reduction considerations are critical to our approach • This is especially true during moderate to high flows

36. Questions? • dennis.wasley@state.mn.us (Implementation strategy) • 651-757-2908 • steve.weiss@state.mn.us (Phosphorus effluent limits) • 651-757-2814