U.S. Environmental Protection Agency

1. Understanding Total Maximum Daily Loads with Stormwater Sources and theNPDES Stormwater Permitting Process U.S. Environmental Protection Agency

2. Learning Objectives • Provide an overview of TMDLs and NPDES stormwater permitting • Provide an understanding of how TMDL writers can address stormwater in TMDL development • Provide an understanding of how NPDES permit writers can develop permits to implement TMDLs

3. Presentation Roadmap • Overview of the TMDL program • Overview of the NPDES stormwater permitting process • Basics of TMDL and stormwater permit integration • What’s different about TMDLs for stormwater sources? • What’s different about stormwater permits to implement TMDLs? • Quiz

4. Overview of Total Maximum Daily Loads (TMDLs) • Wasteload allocations (WLAs) set loading cap for point sources • Load allocations (LAs) set loading cap for nonpoint sources • Reserve capacity sets aside allocation for future development • Margin of Safety (MOS) allocation accounts for uncertainty Reserve Capacity Point Source #1 MOS Point Source Nonpoint #2 Source #4 Point Source Nonpoint #3 Source #3 Nonpoint Nonpoint Source #1 Source #2

5. Reserve Capacity Point Source #1 MOS Point Source #2 – WLA Point Source #3 Wasteload Allocations (WLAs) • WLA used to determine WQBEL • WQBEL implemented through NPDES permits Nonpoint Source #4 Nonpoint Source #3 Nonpoint Nonpoint Source #1 Source #2

6. Brief Overview of Regulated Stormwater Sources • Three primary types of sources (40 CFR 122.26(a) and 122.26(b)) • Municipal separate storm sewer systems (MS4s) • Construction • Industrial • Other sources as designated by the permitting authority • Two types of NPDES stormwater permits • Individual • General

7. Types of NPDES Permits • Individual Permit • 1 application submitted  1 permit issued • Appropriate where discharger needs site-specific permit conditions Permit Application • Draft Permit and Fact Sheet Development • Effluent Limits • Monitoring Conditions • Standard Conditions • Special Conditions Public Notice and Public Comments Administrative Record Final Permit

8. Types of NPDES Permits • General Permit • 1 permit issued  many applications submitted • Appropriate where multiple dischargers require relatively uniform permit conditions Identify Need and Collect Data • Draft Permit and Fact Sheet Development • Effluent Limits • Monitoring Conditions • Standard Conditions • Special Conditions Public Notice and Public Comments Administrative Record Final Permit Notice of Intent (NOI) to be Covered

9. Overview of Regulated Stormwater Sources: MS4s • Not just municipalities • Phase I MS4s • Based on population served (100,000+) • Individual permit with detailed application process • Phase II MS4s • Small regulated MS4s within the boundaries of an ‘urbanized area’ or designated by permit authority • Two permit types • MS4 general permit with 6 minimum control measures • Individual permit under special circumstances

10. Overview of Regulated SW Sources: Construction • Phase I: disturb 5 acres or more • Phase II: disturb between one and 5 acres • Permit types • Construction General Permit (CGP) • Individual permits are an option under certain conditions • Discharge to impaired waters • Reasonable potential to cause or contribute to water quality standard exceedance

11. Overview of Regulated SW Sources: Industrial Activity • Eleven categories of industrial activity • Covered under multi-sector general permit (MSGP), although individual permits are an option under certain conditions • Able to certify to a condition of no exposure in lieu of permit coverage

12. Permitting Other SW Sources: Residual Designation • Authorizes NPDES permitting authorities to designate other stormwater sources for permit coverage • Cause or contribute to water quality standard excursion • Significant contributor of pollutants to surface waters • Implications for how TMDLs are developed that include both regulated and currently unregulated stormwater sources

13. Let’s Review. . . • Three types of regulated stormwater sources • MS4s (Phase II MS4 GP) • Industrial (MSGP) • Construction (CGP) • Other sources using RDA • Stormwater sources assigned WLAs • WLAs translated to WQBELs in permits

14. Basics of TMDL & Stormwater Permit Integration • WLAs for regulated stormwater sources • Needed to promote effective implementation • As specific for each regulated stormwater source as possible • NPDES stormwater permits must be consistent with assumptions and requirements of WLAs • TMDL and permit writers should work together throughout the process

15. TMDL Process EPA Recommended Elements in a TMDL Submittal 1. Description of waterbody, pollutant of concern, pollutant sources, and priority ranking Problem Understanding TMDL Target Identification Source Assessment 2. Water Quality Standards and numeric WQ target* • Loading Capacity- Linking WQ and Pollutant Sources* • (including critical conditions*) Linkage between Loading and Waterbody Response 4. Load Allocations (LAs)* 5. Wasteload Allocations (WLAs)* 6. Margin of Safety (MOS)* 7. Seasonal Variation* Stakeholder Involvement & Public Participation Allocation Analysis 8. Reasonable Assurances+ 9. Monitoring Plan+ 10. Implementation Plan+ Implementation and Monitoring Plan 11. Public Participation* TMDL Report and Submittal * Required by regulation (40 CFR 130.7) + Recommended through guidance From Guidelines for Reviewing TMDLs under Existing Regulations issued in 1992 (May 20, 2002): http://www.epa.gov/owow/tmdl/guidance/final52002.html

16. Understanding SW Effects Precipitation Interception Transpiration Surface Runoff Evaporation Infiltration Groundwater Return Flow Percolation

17. Understanding SW Effects

18. Understanding SW Effects • Altered stream hydrology (“water quantity”) • Higher peak flows • Increased runoff volume • Lower base flows • Increased pollutant loading (“water quality”) • Higher runoff volumes • Exposure to stormwater sources • Less opportunity for filtering

19. Impairment Characterization • Waters impaired by stormwater sources often listed for: • Biological impairment • Habitat alteration • Focus on multiple pollutants and combined effects • Look at indicators of stormwater impacts • Flow patterns • Degraded biology/habitat • Imperviousness

20. Establishing Water Quality Targets • Water quality targets include… • Indicator • Associated target value • Water quality targets for TMDLs with SW sources • Consider multiple stressors due to changes in flow and increased pollutant loads • Could lead to use of a surrogate target, such as impervious cover, that represents combined SW effects

21. Stormwater Source Assessment • Challenging boundary issues • Snapshot in time • Construction sites ephemeral in nature • Industrial source no-exposure status could change • Less familiar point source databases • eNOI • state-specific stormwater database • Data generated by sources varies by type and permit requirement

22. Understanding Spatial Boundaries of SW Sources • MS4 system boundary ≠ municipal jurisdictional boundary • Phase II regulated small MS4s only within urbanized area boundary • Industrial and construction sources can be found in and out of MS4 boundaries

23. MS4 Generated Information

24. TMDL Approach Selection • Similar approaches to consider • Impairment/source specific information to consider • Use of a surrogate target such as IC or flow volume • Boundary/location of stormwater sources • Behavior of stormwater sources • Critical conditions

25. Categorizing Stormwater WLAs • WLAs for other point sources are presented for each individual point source facility • For regulated stormwater sources, TMDL writers might face challenges that limit their ability to provide individual WLAs for each regulated stormwater source

26. Challenges for Categorizing Stormwater Source WLAs • Data availability • Boundary issues • Varied implementation approaches

27. Residual Designation Authority and WLAs • Include language in the TMDL about potential changes in regulatory status • Currently unregulated stormwater sources have load allocations • Use of RDA to change designation means load allocation becomes a wasteload allocation • No need for TMDL resubmission • Might require WLA refinement • Change in overall loading cap would be subject to approval

28. Options for Categorizing and Expressing WLAs • Individual by each regulated stormwater source • Categorical by each type of stormwater source • Aggregated for all stormwater sources

29. Individual WLAs by Source: Overview

30. Tips: Individual WLAs by Source • Ensure consistency between source characterization and source WLAs • Provide information and assumptions about each source • Provide estimated baseline load for each source • Present WLA to support implementation

31. Categorical WLAs by Source Type: Overview

32. Tips: Categorical WLAs by Source Type • Create regulated stormwater source inventory • Indicate which regulated stormwater sources are included under each category • Provide recommendations for sub-allocating the categorical WLAs • Provide rationale for using this approach

33. Single Aggregated WLA for All Stormwater Sources: Overview

34. Tips: Single Aggregated WLA for All Stormwater Sources • Create regulated stormwater source inventory • Indicate which regulated stormwater sources are included under the aggregated WLA • Provide recommendations for sub-allocating the aggregated WLA • Provide rationale for using this approach

35. Mixing WLA Options • Select options best suited to sources • Data availability • Permit requirements and implementation strategies • Consider other options for further categorizing WLAs • Subwatershed • Dry weather/wet weather

36. WLA Challenges and Considerations by Source Type

37. MS4 WLA Challenges • Regulated area based on system boundary • Regulated area might have pockets that don’t drain to the regulated system • Regulated area might contain nested sources

38. Charles River Pathogen TMDL MS4 WLA • Includes 35 MS4s • Assigns two WLAs to all MS4s for each type of surface waters • Expresses WLA as colonies/day • Calculated WLA using flow data from areas with impervious cover • Captures combined sewer areas • Presented on a segment-by-segment basis

39. Wissahickon Creek Siltation TMDL MS4 WLAs • Covers 16 MS4s in five subwatersheds • Estimates loads for five subwatersheds and distributes among MS4s • Contains existing load, WLA, percent reduction for each MS4 • Presents WLAs by subwatershed in appendix

40. Shingle Creek Chloride TMDL MS4 WLAs • Covers deicing activities by multiple MS4s • Nine municipalities • One county • MN Dept. of Transportation • Includes categorical MS4 WLA • Allows implementation flexibility

41. Construction Source WLA Challenges • Varied timeframes for construction activities • Change in source type after activity ends • Activities located in MS4 boundary • Activities located outside MS4 boundary

42. Potomac Drains (WV) Sediment TMDL Construction WLAs • Identified 176 regulated construction sources at outset of TMDL • Updated information during process with new active and pending permits • Assigns individual WLAs to 297 regulated construction sources • Includes future growth allowance

43. Industrial WLA Challenges • Regulated industrial stormwater sources might be located in the MS4 boundary • Regulated industrial stormwater sources might have a no exposure certification

44. Columbia Slough TMDLs Industrial WLAs • Lead TMDL (1998) • Aggregated WLA for permitted industrial area • Provides an approach for industrial facilities to calculate their individual WLA • Unit-area basis • Dependent on flow conditions Photo: Mark Gamba http://www.portlandmonthlymag.com/travel-and-outdoors/articles/1008-features-oasis/

45. Gauley River Watershed TMDL Industrial WLAs • Iron/TSS WLAs (2008) • Loads (lbs/yr) • Concentrations (mg/L) • Individual WLA assigned to each industrial facility • Facilities have iron and TSS benchmark values under MSGP • Facilities that meet benchmarks not considered a significant source • Assigning WLA necessary to allow SW discharge under MSGP

46. NPDES Permit Components Components of All Permits Cover Page Effluent Limitations Technology-based Water Quality-based Monitoring and Reporting Special Conditions Additional Monitoring / Special Studies Best Management Practices Compliance Schedules Standard Conditions

47. NPDES Permit Components Affected by TMDLs Components of All Permits Cover Page Effluent Limitations Technology-based Water Quality-based Monitoring and Reporting Special Conditions Additional Monitoring / Special Studies Best Management Practices Compliance Schedules Standard Conditions

48. 40 CFR 122.44(d)(1)(vii) (vii) When developing water quality-based effluent limits under this paragraph the permitting authority shall ensure that: • The level of water quality to be achieved by limits on point sources established under this paragraph is derived from and complies with all applicable water quality standards; and • Effluent limits developed to protect a narrative water quality criterion, a numeric water quality criterion, or both, are consistent with the assumptions and requirements of any available wasteload allocation for the discharge prepared by the State and approved by EPA pursuant to 40 CFR 130.7.

49. Effluent Limits in Stormwater Permits • Numeric limits • Pollutant loads and concentrations • Numeric parameters acting as surrogates for pollutants (i.e., impervious cover or flow) • Narrative BMP limits • Selected to meet the WLA • Possibly includes requirement to monitor BMP performance against benchmarks

50. Options for Numeric Effluent Limits in Stormwater Permits • Develop water quality-based effluent limitations (WQBELs) • Incorporate WLA as numeric effluent limit (e.g., bacteria concentration or sediment percent reduction)