NPDES - PCSM National Pollutant Discharge Elimination System Post Construction Stormwater Management Permit Preparation Jim Pillsbury, PE Engineer s Workshop - March 4 and 5, 2010
Who needs NPDES? Earth disturbance on 1 to 5 acres with a point source discharge Earth disturbance over 5 acres General or Individual
NPDES Permit Components E&S Control Plan PCSM Thermal Impact Analysis Antidegradation Analysis Worksheets
PCSM Post Construction Stormwater Management: IS Stormwater Management with an emphasis on the 2 year storm
Rainfall Events in SW PA
Pre-Development: illustrates the NATURAL hydrologic cycle
Post Development: illustrates the IMPAIRED hydrologic cycle
PCSM Plan Goals Maximize infiltration of ground water Protect structural integrity of streams Protect/maintain designated uses / classifications of streams
Important PCSM Plan Location Map on USGS Quadrangle Inclusions: Receiving Water / Watershed Name and Chapter 93 Receiving Water Classification Municipal Storm Sewer or Private Storm Sewer Operator
PCSM Technical Review NPDES Form Worksheets Narrative and calculations Drawings
NPDES Section C E&S and PCSM Plan 1. E&S BMPs and PCSM Plan information 2. Summary Table for Supporting Calculation and Measurement Data 3. Summary Description of PCSM BMPs 4. Off Site Discharge Analysis 5. Thermal Impacts analysis
What to Look For: ROCK CONSTRUCTION ENTRANCE, SILT FENCE, OUTLET PROTECTION
What to Look For: Hempfield Township
SCS METHOD 2 YEAR 2.7 1.2 1.32 0.12 0.25 0.265 0.015 0.21-0.04 2.4 2.1-0.3
GreenForge STORMWATER MANAGEMENT CONTROLS INFILTRATION PAVING GREEN ROOF DONOHOE ROAD BIO-INFILTRATION INFILTRATION PAVING PROTECTED TREES GREEN ROOF GREENFORGE INFILTRATION PAVING PROTECTED TREES INFILTRATION PAVING FOREBAY / WET POND PROTECTED WOODLAND
250 cft 0.11 ac 250 cft 0.11 ac 2,160 cft 0.12 ac 700 cft 0.02 ac
3. Summary Description of PCSM BMPs The numbers for this chart come from the Chapter 8 Worksheets
700 cft 0.02 ac 0.03 ac 750 cft 0.21 ac
Off-site Discharge Analysis Discharge of stormwater to areas other than surface water Demonstrate discharge will not cause erosion, damage or nuisance off-site Flow should be documented by legal authorization, easements
Thermal Impacts How thermal impacts are avoided, minimized or mitigated: Minimum impervious surfaces Green roof Porous pavement Shade, maximize use of vegetated areas Discharge from bottom of impoundments Subsurface impoundments
EISTING TREES TO REMAIN, COMPLETE SITE LANDSCAPING, PLANTS IN THE BIO-INFILTRATION AREAS, VEGETATED ROOF SHADE HAS BEEN PROVIDED FOR DETENTION BASIN AND BIO-INFILTRATION AREAS, STORMWATER IS HELD IN UNDERGROUND TANKS PRIOR TO RELEASE
NPDES Section D Antidegradation Analysis Module for HQ/EV 1. Non-Discharge Alternatives Evaluation 2. Antidegradation Best Available Combination of Technologies ( ABACT ) 3. Social or Economic Justification ( SEJ )
NPDES Section E Consultant for this Project 1. Qualified professional engineer Structural BMPs 2. Qualified professional surveyor, landscape architect, or other Non-structural BMPs Certain structural BMPs
NPDES - Worksheets Curve No.s consistent with SW methodology Infiltration/geotechnical report Drainage areas BMP strategy Control guidelines
Worksheets Flow Chart A Worksheets 1-3 Flow Chart B Worksheets 4-6 Control Guideline 1 Flow Chart C Worksheets 7-8 Control Guideline 2 Flow Chart D Worksheets 10-13
What to Look For: 07/07/07 GreenForge Hempfield Twp Westmoreland County 3.0 ACRES Youghiogheny Sewickley Creek Jacks Run UNT to Slate Creek HQ-TSF
Sewickley Creek Jacks Run UNT to Slate Run What to Look HQ-TSF For:
What to Look For: NA NA NA NA
What to Look For: NA NA NA NA YES NA NA NA 0.58 0.48 0.58 0.48
GreenForge Stormwater Credits 1,125 sf Minimize Compaction 600 sf Protected Trees 0.48 ac Woodland Protected
What to Look For: 0.48 0 0 0.48 3.0 0.48 2.52
1,125 What to Look For: 23 600 For Deciduous Trees Quantity of Native 2 Cal. or larger x 6 ft3 = 25 For Evergreen Trees: Quantity of Native 6 Ht. or larger x 10 ft3 = 48
x x x x x x
GreenForge 3.0 ac What 2.7 to Look For: 3.0 0.48 2.52 B 4,356 0.1 55 8.2 1.64 0.1 36 B 53,143 1.22 55 8.2 1.64 0.1 443 B 52,400 1.20 95 0.5 0.1 0.1 9,607 109,899 2.52 10,086 Metal roof 16,900 0.39 95 0.5 0.1 2.2 3,096 Asphalt paving Meadow B 40,725 52,274 109,899 0.93 1.2 2.52 95 55 0.5 8.2 0.1 1.64 2.2 0.1 7,466 436 10,988 902 cft (10,988 10,086 = 902)
Curve Number Method 1. Runoff (in) = Q = (P-0.2S)²/(P+0.8S) Where P = 2-year Rainfall (in) S = (1000/CN) 10 2. Runoff Volume (CF) = Q x Area x 1/12 Q = Runoff (in) Area = Land use area (sqft)
What to Look For: GreenForge 902 cft 48 854 cft 5,400 2,160 700 700 9,000 750 150 250
700 700 What to Look For: 9,000 750 150 250 3,860 854 3,006 cft
2 OF THESE OR 4 OF THESE
Stormwater Management is your friend