NJTA Design Manual Drainage Design SECTION 4 DRAINAGE DESIGN Table of Contents Page No 4.1 GENERAL INFORMATION .......................................................................................1 4.1.1 INTRODUCTION ................................................................................................1 4.1.2 DEFINITIONS AND ABBREVIATIONS.....................................................................2 4.1.3 DESIGN PROCEDURE OVERVIEW .......................................................................4 4.1.4 PLAN PREPARATION AND SUBMISSION CRITERIA ................................................5 4.2 DRAINAGE LAW ......................................................................................................8 4.3 PERMITS / REGULATORY COMPLIANCE ..............................................................8 4.3.1 FEDERAL .........................................................................................................9 4.3.2 STATE .............................................................................................................9 4.3.3 LOCAL ...........................................................................................................10 4.3.4 STORMWATER MANAGEMENT .........................................................................11 4.3.5 FLOOD HAZARD AREA ....................................................................................12 4.3.6 SOIL EROSION AND SEDIMENT CONTROL .........................................................14 4.4 DRAINAGE PROCEDURE AND CRITERIA ............................................................14 4.4.1 STORMWATER MANAGEMENT AND NON-POINT SOURCE POLLUTION CONTROL ..14 4.4.2 ALLOWABLE WATER SURFACE ELEVATION ......................................................16 4.4.3 RECURRENCE INTERVAL .................................................................................17 4.5 HYDROLOGY .........................................................................................................17 4.5.1 INTRODUCTION ..............................................................................................17 4.5.2 SELECTION OF HYDROLOGIC METHODS ...........................................................18 4.5.3 RATIONAL FORMULA ......................................................................................19 4.5.4 US NATURAL RESOURCES CONSERVATION SERVICE (NRCS) METHODOLOGY ..27 4.5.5 TIME OF CONCENTRATION (TC)........................................................................30 4.5.6 COMPUTATION OF TRAVEL TIME AND TIME OF CONCENTRATION: ......................31 4.5.7 FLOOD ROUTING ............................................................................................32 4.6 CHANNEL DESIGN ................................................................................................35 4.6.1 INTRODUCTION ..............................................................................................35 4.6.2 CHANNEL TYPE ..............................................................................................35 4.6.3 SITE APPLICATION .........................................................................................36 4.6.4 CHANNEL DESIGN PROCEDURE ......................................................................37 May 2007 Revised March 2014 NJTA Design Manual Drainage Design 4.7 DRAINAGE OF ROADWAY PAVEMENT ............................................................... 40 4.7.1 INTRODUCTION .............................................................................................. 40 4.7.2 RUNOFF COLLECTION AND CONVEYANCE SYSTEM TYPE .................................. 40 4.7.3 TYPES OF INLETS USED BY THE AUTHORITY .................................................... 41 4.7.4 FLOW IN GUTTERS (SPREAD) ......................................................................... 41 4.7.5 LIMITS OF SPREAD ......................................................................................... 42 4.7.6 INLETS .......................................................................................................... 43 4.7.7 CAPACITY OF GUTTER INLETS ON GRADE ........................................................ 45 4.7.8 CAPACITY OF GRATE INLETS AT LOW POINTS .................................................. 45 4.7.9 LOCATION OF INLETS ..................................................................................... 47 4.7.10 SPACING OF INLETS ....................................................................................... 49 4.7.11 DEPRESSED GUTTER INLET ............................................................................ 49 4.7.12 SNOW MELT CONTROL ................................................................................... 50 4.7.13 ALTERNATIVE RUNOFF COLLECTION SYSTEMS – TRENCH DRAINS .................... 51 4.8 STORM DRAINS ..................................................................................................... 52 4.8.1 INTRODUCTION .............................................................................................. 52 4.8.2 MATERIAL AND STRUCTURAL REQUIREMENTS ................................................. 52 4.8.3 CRITERIA FOR STORM DRAINS ........................................................................ 53 4.8.4 STORM SEWER DESIGN ................................................................................. 56 4.8.5 PRELIMINARY PIPE SIZE ................................................................................. 57 4.8.6 HYDRAULIC GRADE LINE COMPUTATIONS ........................................................ 60 4.9 MEDIAN DRAINAGE .............................................................................................. 70 4.9.1 INTRODUCTION .............................................................................................. 70 4.9.2 MEDIAN INLET TYPE ....................................................................................... 70 4.9.3 MEDIAN DESIGN CRITERIA - CONTINUOUS GRADE ........................................... 70 4.9.4 PROCEDURE FOR SPACING MEDIAN DRAINS .................................................... 70 4.10 CULVERT DESIGN ................................................................................................. 71 4.10.1 INTRODUCTION .............................................................................................. 71 4.10.2 CULVERT TYPES ............................................................................................ 71 4.10.3 CULVERT LOCATION....................................................................................... 71 4.10.4 CULVERT SELECTION ..................................................................................... 72 4.10.5 CULVERT HYDRAULICS ................................................................................... 72 4.10.6 CULVERT END STRUCTURES .......................................................................... 75 4.10.7 FLOOD ROUTING AT CULVERTS ...................................................................... 76 4.10.8 FISH PASSAGE .............................................................................................. 76 May 2007 Revised March 2014 NJTA Design Manual Drainage Design 4.11 RESET CASTINGS - MANHOLES AND INLETS ....................................................79 4.11.1 RESET CASTINGS AND CONSTRUCTION PRACTICES .........................................79 4.11.2 EXTENSION RINGS AND FRAMES .....................................................................79 4.11.3 EXTENSION RINGS - MANHOLES ......................................................................80 4.11.4 EXTENSION FRAMES - INLETS .........................................................................80 4.11.5 RAMPING .......................................................................................................81 4.12 STORMWATER MANAGEMENT ............................................................................82 4.12.1 INTRODUCTION ..............................................................................................82 4.12.2 METHODOLOGY .............................................................................................83 4.12.3 STORMWATER MANAGEMENT FACILITY LOCATIONS ..........................................85 4.12.4 STORMWATER MANAGEMENT FACILITY DESIGN FEATURES ...............................85 4.12.5 STORMWATER MANAGEMENT FACILITY MAINTENANCE .....................................89 4.13 WATER QUALITY ...................................................................................................89 4.13.1 INTRODUCTION ..............................................................................................89 4.13.2 METHODOLOGY .............................................................................................90 4.13.3 WATER QUALITY TREATMENT FACILITIES AND DESIGN .....................................90 4.14 FIELD INFORMATION ............................................................................................93 4.15 EROSION PREVENTION AND SEDIMENTATION CONTROL ...............................93 4.15.1 INTRODUCTION ..............................................................................................93 4.15.2 PLAN FORMAT ...............................................................................................93 4.15.3 TEMPORARY CONTROL MEASURES .................................................................94 4.15.4 PERMANENT CONTROL ...................................................................................95 4.16 UNDERDRAINS