NPDES MS4 Permit Renewal Application Package February 28, 2017 Cover: Aerial View of Oswego, Oregon, 1956. Photo courtesy of the Lake Oswego Library. Lake Oswego MS4 Permit Renewal Package 2017 City of Lake Oswego, Oregon National Pollutant Discharge Elimination System Municipal Separate Storm Sewer System Permit 2017 Permit Renewal Application Package Prepared for the Oregon Department of Environmental Quality February 28, 2017 This page intentionally left blank. Lake Oswego MS4 Permit Renewal Package 2017 City of Lake Oswego NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES) MUNICIPAL SEPARATE STORM SEWER SYSTEM PERMIT RENEWAL APPLICATION PACKAGE February 28, 2017 I, the undersigned, hereby submit this National Pollutant Discharge Elimination System (NPDES) Municipal Storm Water System Permit Renewal Application Package in accordance with NPDES Permit Number 101348. I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted. Based on my inquiry of the person, or persons, who manage the system, or those persons directly responsible for gathering the information, the information is, to the best of my knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for known violations. ________________________________ Name: Scott D. Lazenby Title: City Manager City of Lake Oswego i This page intentionally left blank. Lake Oswego MS4 Permit Renewal Package 2017 Table of Contents List of Figures ..................................................................................................................................... v List of Tables ...................................................................................................................................... v List of Abbreviations ......................................................................................................................... vi Section 1 Introduction and Overview ............................................................................................... 1-1 1.1 Permit Overview .......................................................................................................................... 1-1 1.2 Description of Permit Area and Coordination with Co-Permittees ............................................. 1-2 1.2.1 Description of City of Lake Oswego Permit Area ............................................................. 1-2 1.2.2 Summary of Clackamas County Co-permittees ............................................................... 1-2 1.2.3 Summary of City Coordination with Co-Permittees ........................................................ 1-2 1.3 Organization of Document .......................................................................................................... 1-2 Section 2 Maximum Extent Practicable Evaluation ........................................................................... 2-1 2.1 How the Existing Stormwater Management Program Addressed 2012 Permit Requirements .. 2-1 2.1.1 Annual Adaptive Management ........................................................................................ 2-2 2.1.2 Results of the Existing MEP Program Evaluation ............................................................. 2-2 2.2 How the Proposed Stormwater Management Program Meets the MEP Requirement ............. 2-8 Section 3 Proposed Modifications to the Stormwater Management Plan .......................................... 3-1 Section 4 Service Area Expansions and Total Annual Pollutant Load Updates .................................... 4-1 4.1 Introduction ................................................................................................................................. 4-1 4.2 Description of Projected Service Area Expansions ...................................................................... 4-1 4.2.1 Definition of the City’s NPDES MS4 Permit Area ............................................................. 4-1 4.2.2 Identification of Projected Service Area Expansions ....................................................... 4-2 4.3 Updated Estimate of Total Annual Pollutant Loads .................................................................... 4-3 4.3.1 Modeling Methods and Assumptions .............................................................................. 4-3 4.3.2 Updated Estimate of Total Annual Pollutant Loads ......................................................... 4-6 4.4 Qualitative Evaluation ................................................................................................................. 4-7 4.4.1 Service Area Expansion .................................................................................................... 4-7 4.4.2 Pollutant Loads Discharge ................................................................................................ 4-7 4.4.3 Conclusion ........................................................................................................................ 4-8 Section 5 Wasteload Allocations and Benchmarks ............................................................................ 5-1 5.1 BMP Identification ....................................................................................................................... 5-2 5.2 TMDL Benchmark Results and Discussion ................................................................................... 5-3 iii Lake Oswego MS4 Permit Renewal Package 2017 Section 6 Fiscal Evaluation............................................................................................................... 6-1 6.1 Fiscal Evaluation .......................................................................................................................... 6-1 6.1.1 Expenditures for the Current Permit Cycle 2012-2017 ................................................... 6-1 6.1.2 Expenditures for the Upcoming Permit Cycle .................................................................. 6-2 Section 7 Monitoring Program Objectives and Modifications ........................................................... 7-1 7.1 Proposed Changes ....................................................................................................................... 7-1 7.1.1 Ambient Instream Monitoring ......................................................................................... 7-1 7.1.2 Wet Weather Stormwater Monitoring ............................................................................ 7-2 7.1.3 Other Environmental Monitoring .................................................................................... 7-2 Appendix A: Stormwater Management Plan Appendix B: Public Comments and Response to Comments Appendix C: TMDL Pollutant Load Reduction Evaluation and Benchmarks Appendix D: Monitoring Plan Appendix E: MS4 Maps iv Lake Oswego MS4 Permit Renewal Package 2017 List of Figures Figure 4-1. Lake Oswego annexations (2000 – present) ............................................................................ 4-3 Figure 6-1. Relative stormwater expenditures over the current permit cycle 2012-2017 ........................ 6-4 Figure 6-2. Regulatory compliance level of effort over the current permit cycle 2012-2017 by functional activity ......................................................................................................................... 6-4 List of Tables Table 1-1. Permit Renewal Submittal Components ................................................................................... 1-3 Table 2-1. Status of City Actions On 2012 NPDES MS4 Permit Requirements .......................................... 2-3 Table 4-1. Land Use EMC Values used in the Total Annual Pollutant Load Estimate ................................ 4-4 Table 4-2. Modeled Area by Land Use and Impervious Percentage .......................................................... 4-6 Table 4-3. Updated Annual Estimate of Pollutant Loads for the City of Lake Oswego .............................. 4-6 Table 5-1. Lake Oswego Applicable WLAs ................................................................................................. 5-1 Table 5-2. Projected Stormwater Facilities and Drainage Areas for 2022 Benchmarks ............................ 5-3 Table 5-3. TMDL Benchmarks for 2017–2022 ............................................................................................ 5-3 Table 6-1. Surface Water Utility Fiscal Status, Current MS4 Permit 2012-2017 ....................................... 6-3 Table 6-2. Projected Surface Water Utility Fiscal Status, Upcoming MS4 Permit Term 2017-2022 ......... 6-3 Table 7-1. Monitoring Objective Matrix .................................................................................................... 7-3 v Lake Oswego MS4 Permit Renewal Package 2017 List of Abbreviations µg microgram(s) ac acre(s) ACWA Association of Clean Water Agencies BOD5 5-day biochemical oxygen demand CFU colony-forming unit(s) City City of Lake Oswego COD chemical oxygen demand COM commercial DEQ Department of Environmental Quality DO dissolved oxygen EMC event mean concentration EPA U.S. Environmental Protection Agency IND industrial L liter(s) lb pound(s) LCL lower confidence level LUCS Land Use Compatibility Statement MFR multi-family residential mg/L milligram(s) per