Delaware County Regional Water Quality Control Authority (DELCORA) CSO Long Term Control Plan Update Existing Service Area Characterization Report (Final) August 2017 Delaware County Regional Water Quality Control Authority CSO Long Term Control Plan Update Existing Service Area Characterization Report REVISION CONTROL REV. DATE PREPARED DESCRIPTION OF CHANGES NO. ISSUED BY Delaware County Regional Water Quality Control Authority CSO Long Term Control Plan Update Existing Service Area Characterization Report Table of Contents Section 1 Introduction ............................................................................................... 1-1 1.1 Introduction ...................................................................................................................... 1-1 1.2 Regulatory Requirements ................................................................................................ 1-1 1.2.1 Requirements from the USEPA’s CSO Control Policy ..................................................... 1-2 1.3 Contents of this Report .................................................................................................... 1-3 Section 2 Overview of DELCORA’s Facilities and Service Areas .......................... 2-1 2.1 Overview of DELCORA’s Facilities .................................................................................. 2-1 2.2 DELCORA’s Service Areas .............................................................................................. 2-4 2.2.1 Eastern Service Area ....................................................................................................... 2-4 2.2.2 Western Service Area ...................................................................................................... 2-5 2.3 Model Area ....................................................................................................................... 2-5 2.4 Watersheds ...................................................................................................................... 2-8 2.5 DELCORA’s Treatment Facilities ..................................................................................... 2-8 Section 3 Characteristics of the Model Area Sewer System .................................. 3-1 3.1 Introduction ...................................................................................................................... 3-1 3.2 Sources of Collection System Data .................................................................................. 3-1 3.3 Overview of Sewer System Characteristics ..................................................................... 3-1 3.4 Characteristics of Separated Sewer Areas ...................................................................... 3-2 3.5 Characteristics of Combined Sewer System .................................................................... 3-2 3.5.1 Overall Configuration ....................................................................................................... 3-2 3.5.2 Sewer Mains .................................................................................................................... 3-6 3.5.3 Flow Diversion Structures and CSO Regulators .............................................................. 3-6 3.5.3.1 Flow Diversion Structure Components ........................................................................... 3-13 3.5.4 Interceptors .................................................................................................................... 3-14 3.5.5 CSO Outfalls .................................................................................................................. 3-16 3.5.6 Drainage Areas and Subcatchments .............................................................................. 3-16 3.5.7 Percent Imperviousness ................................................................................................. 3-16 3.5.8 Depression Storage ....................................................................................................... 3-17 3.5.9 Soil Infiltration Parameters ............................................................................................. 3-17 3.6 Collection System Pump Stations and Force Mains....................................................... 3-18 3.6.1 Force Mains ................................................................................................................... 3-19 Section 4 Collection of Precipitation and Sewer Flow Data ................................... 4-1 4.1 Introduction ...................................................................................................................... 4-1 4.2 Rainfall Monitoring and Analysis ...................................................................................... 4-1 4.3 Rain Event Summary ....................................................................................................... 4-3 4.4 Gauge-Adjusted, Radar Estimated Precipitation .............................................................. 4-4 4.5 Flow Monitoring ................................................................................................................ 4-4 4.6 Dry Weather Flow (DWF) Analysis ................................................................................. 4-14 i Delaware County Regional Water Quality Control Authority CSO Long Term Control Plan Update Existing Service Area Characterization Report Table of Contents 4.7 Wet Weather Flow Analysis ........................................................................................... 4-17 4.8 Wet Weather Event Selection for Model Calibration and Validation Flow Analysis ........ 4-18 4.9 Flow Monitoring Data Summary ..................................................................................... 4-18 4.10 Collection of WRTP Operational Data ............................................................................ 4-19 4.11 Summary ........................................................................................................................ 4-20 Section 5 Characteristics of the Receiving Waters ................................................. 5-1 5.1 Physical Characteristics ................................................................................................... 5-1 5.2 Watershed Drainage Basins............................................................................................. 5-5 5.3 Pollutants of Concern ....................................................................................................... 5-6 5.4 Receiving Water Use Designations and Applicable Water Quality Standards ................. 5-6 5.4.1 2014 PA Integrated Water Quality Monitoring and Assessment Report (303(d) list) ........ 5-7 5.4.2 PA Code Title 25 §93.9g .................................................................................................. 5-8 5.4.3 DRBC’s Water Quality Regulations and PA Code Title 25 §93.7 ..................................... 5-8 5.4.4 DRBC’s 2014 Delaware River and Bay Water Quality Assessment ................................. 5-8 5.5 Delaware River ................................................................................................................. 5-8 5.5.1 2014 PA Integrated Water Quality Monitoring and Assessment Report (303(d) list) ........ 5-8 5.5.2 Designated Critical Uses and Specific Water Quality Criteria from PA Code ................... 5-9 5.5.3 Designated Zone and Water Quality Regulations from the DRBC ................................. 5-11 5.5.4 DRBC Evaluation of Use Attainment Status ................................................................... 5-12 5.5.4.1 Water Contact Recreation .............................................................................................. 5-13 5.5.4.2 Aquatic Life .................................................................................................................... 5-13 5.5.4.3 Fish Consumption .......................................................................................................... 5-13 5.6 Chester Creek ................................................................................................................ 5-14 5.6.1 2014 PA Integrated Water Quality Monitoring and Assessment Report (303(d) list) ...... 5-14 5.6.2 Designated Critical Uses and Specific Water Quality Criteria from PA Code ................. 5-15 5.7 Ridley Creek ................................................................................................................... 5-15 5.7.1 2014 PA Integrated Water Quality Monitoring and Assessment Report (303(d) list) ...... 5-15 5.7.2 Designated Critical Uses and Specific Water Quality Criteria from PA Code: ................ 5-16 5.8 Pollutants of Concern in the Receiving Waters .............................................................. 5-16 5.8.1 Consent Decree Requirements for the Determination of POCs ..................................... 5-16 5.8.2 Methodology for Determination of the POCs .................................................................. 5-17 5.8.3 Summary of the Identified POCs for each Receiving Water ........................................... 5-18 5.9 Identification of Sensitive Areas ..................................................................................... 5-19 5.9.1 Regulatory Requirements .............................................................................................. 5-19 5.9.1.1 Consent Decree Requirements .....................................................................................