1. High Rock Lake Nutrient Modeling Update Pam Behm - NC Division of Water Resources Environmental Management Commission Water Quality Committee Information Item July 9, 2014

2. PURPOSE To provide an update on the status of the High Rock Lake nutrient modeling and information on the next steps in the process of developing a Nutrient Management Strategy for the lake.

3. OUTLINE Description of Lake and Watershed Impairment History Addressing the Impairment Role of Technical Advisory Committee Model Development Next Steps

4. High Rock Lake Watershed Yadkin Neuse Cape Fear

5. History 1928 - Dam construction completed Dam owned and operated by Alcoa Power Generating, Inc www.gorowan.com

6. High Rock Lake Crane Creek Abbotts Creek Swearing Creek Second Creek Yadkin River Flat Swamp Creek Grants Creek South Yadkin River

7. High Rock Lake Watershed Population: 850,000

8. 2007 Land Cover 47% Forest 30% Pasture/Crop 18 %Developed

9. Point Sources Municipal and Industrial Wastewater

10. Impairment History Mid-1970s – Highly nutrient over-enriched conditions first documented 1992 – DWQ NC Lake Assessment Report –One of the most nutrient over-enriched lakes in NC –Algal blooms throughout, blue-green algae predominant –Recommended “management strategies”

11. Impairment History Early 2000s – Wastewater Treatment Plant Improvements –Abbotts Creek dischargers (3) receive summer phosphorus limits –Consolidation of Salisbury/Spencer discharges 2004 303(d) List –Portions of lake listed for chlorophyll-a and turbidity

12. Addressing the Impairment Questions Where are the nutrients coming from and how much? ▫ Tool: Watershed Model What reductions in nutrient loading are necessary to achieve water quality standards in the lake? Nitrogen? Phosphorus? Both? ▫ Tool: Nutrient Response Model

13. Addressing the Impairment 2005 – DWQ formed Technical Advisory Committee (TAC) 2007 – 319-grant awarded to Yadkin/Pee Dee River Basin Association (YPDRBA) for an intensive monitoring study of the lake/watershed 2009 – EPA contract awarded to Tetra Tech for model development

14. Watershed Model Estimates what is happening on land that results in nutrient export to receiving water (i.e. High Rock Lake) Provides relative loading by source (agriculture, developed, point sources, etc.)

15. Nutrient Response Model Result of Model Determines nutrient load reductions that will achieve water quality standards Existing loading from all sources Lake Response Chl-a Lake Response Chl-a Reduced loading

16. Technical Advisory Committee (TAC) WHO: Stakeholders – state and local agencies PURPOSE: Assist … with the development of mathematical tools for the management of nutrients and turbidity in High Rock Lake

17. High Rock Lake TAC Members APGI DHHS – Environmental Health Section Dept of Transportation Div of Soil and Water Conservation DWR Duke Energy Keep Iredell Clean Kernersville Piedmont-Triad Regional Council Salisbury Winston-Salem Yadkin Riverkeeper

18. TAC Modeling Training TAC Inputs: ▫ Modeling Goals ▫ Monitoring Plan ▫ Model Performance Targets ▫ Model Review – “Tell us how to make it better”

19. Status of Nutrient Response Model Draft model review completed by TAC Model revisions completed by EPA to address TAC review comments DWR reviewing model and finalizing report – Does the model sufficiently represent the lake’s response to nutrient loading?

20. Next Steps Finalize nutrient response model Final TAC meeting END of TOOL DEVELOPMENT (Step 1 in NMS Development Process)

21. Nutrient Management Strategy Development Process Step 1: Build the tools Who: DWR and TAC What: Monitoring Modeling Step 2: Develop the strategy Who: DWR and Stakeholders What: Model scenarios Reduction targets Point and nonpoint strategies

22. Questions? Pam Behm pamela.behm@ncdenr.gov 919-807-6419