City of Cambridge Illicit Discharge Detection and Elimination (IDDE) Program June 30, 2021 Prepared for: City of Cambridge, MA Prepared by: Stantec Consulting Services, Inc. CITY OF CAMBRIDGE ILLICIT DISCHARGE DETECTION AND ELIMINATION (IDDE) PROGRAM Table of Contents Abbreviations ....................................................................................................................................................... iv Glossary ................................................................................................................................................................ vi 1.0 Introduction ............................................................................................................................................... 1 1.1 MS4 Program ................................................................................................................................................. 1 1.2 Illicit Discharges ............................................................................................................................................. 1 1.3 Allowable Non-Stormwater Discharges ......................................................................................................... 2 1.4 Receiving Waters and Impairments ............................................................................................................... 2 1.5 IDDE Program Goals, Framework, and Timeline ............................................................................................ 3 1.6 Work Completed to Date ............................................................................................................................... 4 2.0 Authority and Statement of IDDE Responsibilities ...................................................................................... 7 2.1 Legal Authority............................................................................................................................................... 7 2.2 Statement of Responsibilities ......................................................................................................................... 7 3.0 Stormwater System Mapping ..................................................................................................................... 8 3.1 Phase I Mapping ............................................................................................................................................ 8 3.2 Phase II Mapping ........................................................................................................................................... 8 3.3 Additional Recommended Mapping Elements ............................................................................................... 9 4.0 Sanitary Sewer Overflows (SSOs) ............................................................................................................. 10 5.0 Assessment and Priority Ranking of Outfalls ............................................................................................ 12 5.1 Outfall Catchment Delineations ................................................................................................................... 12 5.2 Outfall and Interconnection Inventory and Ranking .................................................................................... 12 6.0 Dry Weather Outfall Screening and Sampling ........................................................................................... 16 6.1 Weather Conditions ..................................................................................................................................... 16 6.2 Dry Weather Screening/Sampling Procedure .............................................................................................. 16 6.2.1 General Procedure ............................................................................................................................... 16 6.2.2 Field Equipment ................................................................................................................................... 17 6.2.3 Sample Collection and Analysis ........................................................................................................... 18 6.2.4 Safety ................................................................................................................................................... 23 6.3 Interpreting Outfall Sampling Results .......................................................................................................... 23 6.4 Follow-up Ranking of Outfalls and Interconnections ................................................................................... 24 7.0 Catchment Investigations ......................................................................................................................... 26 7.1 System Vulnerability Factors ........................................................................................................................ 26 CITY OF CAMBRIDGE ILLICIT DISCHARGE DETECTION AND ELIMINATION (IDDE) PROGRAM 7.2 Dry Weather Manhole Inspections .............................................................................................................. 27 7.2.1 Public Notification................................................................................................................................ 29 7.2.2 Storm Drain Cleaning ........................................................................................................................... 29 7.2.3 Manhole Inspection Methodology ...................................................................................................... 29 7.3 Wet Weather Outfall Sampling .................................................................................................................... 31 7.4 Source Isolation and Confirmation............................................................................................................... 31 7.4.1 Dye Testing .......................................................................................................................................... 32 7.4.2 CCTV/Video Inspection ........................................................................................................................ 33 7.5 Illicit Discharge Removal .............................................................................................................................. 33 7.5.1 Confirmatory Outfall Screening ........................................................................................................... 33 7.6 Ongoing Screening ....................................................................................................................................... 33 8.0 Training .................................................................................................................................................... 35 9.0 Progress Reporting ................................................................................................................................... 36 10.0 References ............................................................................................................................................... 37 Appendix A ....................................................................................................................................................... 10.1 Appendix B ....................................................................................................................................................... 10.1 Appendix C ....................................................................................................................................................... 10.1 Appendix D ....................................................................................................................................................... 10.1 Appendix E........................................................................................................................................................ 10.1 Appendix F ........................................................................................................................................................ 10.1 Appendix G ....................................................................................................................................................... 10.1 Appendix H ....................................................................................................................................................... 10.1 Appendix I ........................................................................................................................................................ 10.1 Appendix J ........................................................................................................................................................ 10.1 Appendix K ............................................................................................................................................................ 1 LIST OF TABLES Table 1-1 Impaired Waters, Cambridge, Massachusetts ............................................................................................... 2 Table 1-2 IDDE Program Implementation Timeline ....................................................................................................... 4 Table 4-1 Report by Phone within 24 hours (Oral Notice) .........................................................................................