High Rock Lake TMDL Development

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High Rock Lake TMDL Development

• Michelle Woolfolk, NC DWQ
• May 24, 2005 Stakeholder Meeting

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Topics to cover

• Regulatory basis
• Process for strategy development
• Timeline
• Monitoring and modeling
• Questions and discussion

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Acronyms, acronyms

• Environmental Management Commission (EMC)
• North Carolina List of Impaired Waters (303(d)
  List)
• National Pollutant Discharge Elimination System
  (NPDES)
• Division of Environmental Management (DEM)

• Total nitrogen (TN)
• Total phosphorus (TP)
• Total Maximum Daily Load (TMDL)
• US Environmental Protection Agency (EPA)
• US Geological Survey (USGS)
• Alcoa Power (APGI)

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Regulatory basis

• High Rock Lake appears on the 2004 North Carolina
  303(d) list
• 5568.8 acres impaired due to chlorophyll a
• 11,305 acres impaired due to turbidity
• Clean Water Act requires TMDLs for waters
  impaired by a pollutant

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40CFR130.7(c)

• States (and EPA) shall establish TMDLs for the
  water quality limited segments (identified in the
  303(d) list)
• TMDLs shall be established at levels necessary to
  attain and maintain the applicable narrative and
  numerical water quality standards, with seasonal
  variations and a margin of safety
• Determinations of TMDLs shall take into account
  critical conditions for stream flow, loading, and
  water quality parameters

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40CFR103.7(c) cont.

• All TMDLs for water quality limited segments
  (303(d) list) will be submitted to EPA for review
  and approval.

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What does TMDL stand for?
Total Maximum Daily Load
TMDLs are written plans for attaining and
maintaining water quality standards, in all
seasons, for a specific waterbody and pollutant.
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Elements of a TMDL
1. Problem identification
2. Target analysis
3. Source assessment
4. Linkage of source and target
5. Determine maximum allowable load
6. Allocation of load/wasteload
7. Public participation
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Federal regulatory authority

• EPA Region IV oversight
• Modeling
• Target setting
• Allocations (Reasonable assurance)
• NPDES permitting
• Compliance schedules
• Approval/Disapproval of final TMDL

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Strategy development process

• Step 1
• Build the tools (models)
• Systematic planning
• Monitoring
• Modeling

• Step 2
• Develop the strategy
• Target setting
• Allocations
• Point and nonpoint strategies
• Environmental Management Commission

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Systematic planning

• Based on EPA guidance for environmental projects
• Development of a monitoring and modeling study
  plan
• Outlines project responsibility
• Describes project goals
• Describes modeling approaches
• Outlines monitoring plan

Step 1. Build the tools
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Describe the impairment

• What is the water quality standard?
• Addressing duration and frequency
• At what location was the reason for listing
  determined?
• DWQ ambient monitoring location(s)
• Coalition/Basin Association monitoring

Step 1. Build the tools
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Supporting Information

• Data availability
• Ambient monitoring (DWQ or coalition)
• NPDES instream monitoring
• USGS flow stations
• Special studies (DWQ, discharger, coalition,
  USGS, university, other?)
• Rarely have all of the data listed above.

Step 1. Build the tools
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Monitoring

• Monitoring plan and data needs in monitoring and
  modeling study document
• Monitoring plan for scoping study available on
  internet as stand-alone memorandum.

Step 1. Build the tools
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Modeling Linking causes and sources

• Model selection
• Data availability
• Watershed and reservoir characteristics
• EPA guidance (e.g., Nutrient TMDL Protocol)
• Experience (personally and as a unit)
• Schedule
• Model calibration
• Critical conditions

Step 1. Build the tools
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OK, now we have a calibrated nutrient response
model, what next?
Figure out how to use it!!!!
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Addressing the standard

• What are the critical conditions? How are they
  determined?
• Frequency of violations, magnitude of violations
• Temporal averaging
• Spatial averaging

Step 2. Develop strategy
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Target setting

• Assimilative capacity determination
• Reduction needed? (TMDL needed) Loading cap?
  Remaining capacity?

How much can I pour without going over?
Step 2. Develop strategy
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Target setting, cont.

• Water quality standards
• Chlorophyll a
• Turbidity
• Dissolved oxygen
• pH
• Control of TN and/or TP may be needed

Step 2. Develop strategy
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Allocations

• Typically allocated the allowable load between
  point sources (wasteload) and nonpoint sources
  (load)
• Who gets the biggest piece of the pie?
• Equity versus efficiency

Step 2. Develop strategy
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How are targets achieved?

• Point source allocations
• Each discharger assigned a mass loading
  allocation
• Provisions for another compliance group
• May require rulemaking
• Nonpoint source management
• May include buffers, stormwater controls on
  existing and/or new development, agriculture
• May require rulemaking

Step 2. Develop strategy
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State regulatory authority

• The NC Environmental Management Commission
• NPDES permitting
• Nonpoint source management
• Rulemaking

Step 2. Develop strategy
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Strawman schedule
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Questions?
Michelle Woolfolk or George Hunt NCDWQ Modeling
TMDL Unit 1617 Mail Service Center Raleigh, NC
27699-1617 [phone] ext. 505 Michelle.Woolf
olk_at_ncmail.net George.Hunt_at_ncmail.net