NPDES - PCSM National Pollutant Discharge Elimination System Post Construction Stormwater Management Permit Preparation Jim Pillsbury PE, Kathy Hamilton RLA Engineer s Workshop March 17-18, 2016 WCD 2015
Who needs NPDES? ANY earth disturbance on 1 acre or more General Permit for WWF, TSF, CWF Individual Permit for HQ, EV, or Act 2 WCD 2015
NPDES Permit Components 03/2016 E&S Control Plan PCSM Thermal Impact Analysis Critical Stages Antidegradation Analysis (Individual NPDES) Completeness review Checklist Worksheets 1 5, 10 (General NPDES) Worksheets 1 13 (Individual NPDES) WCD 2016
PCSM Post Construction Stormwater Management: IS Stormwater Management with an emphasis on the 2 year storm WCD 2015
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 (WWF-HQ) WCD 2015
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 WCD 2015
PCSM Plan NPDES Form Worksheets Narrative and calculations Drawings WCD 2015
NPDES Section C Fills, cut-fill-balance Waters of the Commonwealth MS4 s: new standards soon TMDL s: are you causing an increase? Impaired: is it impaired by something similar to what you are doing? WCD 2016
NPDES Section D E&S and PCSM Plan 1-2. E&S Plan and PCSM Plan information 3. Summary Table for Supporting Calculation and Measurement Data 4. Summary Description of PCSM BMPs 5. Off Site Discharge Analysis 6. Potential Pollution Causing Materials 7. Riparian Buffers 8. Thermal Impacts Analysis 9. Critical Stages WCD 2015
X
X
3. Summary Table for Supporting Calculations The numbers for this table come from the Chapter 8 Worksheets Show increase (+) or decrease (-) Don t leave it blank!! Box 8 should be zero or negative (-)
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The site, pre-development
Construction almost complete on this site
4. Summary Description of PCSM BMPs The numbers for this chart come from the Chapter 8 Worksheets The BMP s listed on this chart must agree with Worksheet 5 Notice, it says Treated
X X X 250 cft 0.11 ac X X X 250 cft 0.11 ac X X X 2,160 cft 0.12 ac X X X X 700 cft 0.02 ac
Would you only choose one item?
5. 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 Level spreader for discharge
6. Potential Pollution Causing Materials Identify naturally occurring geologic formations or soil conditions which may cause pollution Provide BMPs to avoid or minimize any pollution or impacts during earth disturbance
7. Riparian Buffer Does the project take place in an HQ or EV watershed (Special Protection)? Protect, convert, or establish a Riparian Buffer? Functionally Equivalent BMP s to replace lost buffer Buffer Offset to replace lost buffer
New Buffer Requirements WCD 2016
More buffer info Demonstrate BMP equivalency for buffer areas lost, in the zone between 100 and 150 feet from the stream Use WS 14 to quantify the pollutant loading from the impacted area Use WS 15 to demonstrate that the BMP s chosen will address the pollutant load
more buffer info For buffer areas lost within 100 feet from the stream, must provide buffer offsetting Offset buffer area should be within the same watershed, or, within another HQ/EV watershed Offset buffer must be forested & have a depth of at least 100 feet Demonstrate functional equivalency
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8. Thermal Impacts How thermal impacts are avoided, minimized or mitigated: Minimal impervious surfaces Green roof Porous pavement Shade, maximize use of vegetated areas Discharge from bottom of impoundments Subsurface impoundments WCD 2015
EXISTING TREES TO REMAIN, COMPLETE SITE LANDSCAPING, PLANTS IN THE BIO-INFILTRATION AREAS, VEGETATED ROOF, STORMWATER RELEASED FROM BOTTOM OF POOL
9. Recommended Critical Stages Sequence / stable contributory area Excavation to subgrade / site preparation Stormwater management BMP construction: Earthwork / embankment construction Underdrain (stone layer / geotextile) Pipe materials / connections (underdrain, outlet riser, barrel, cleanout) Soil mix / soil placement / soil ripping Seeding / blankets / mulching / stabilization Plants and plantings
CONSTRUCTION OF BASIN EMBANKMENT, INSTALLATION OF BASIN OUTLET STRUCTURE, INSTALLATION OF BIO- INFILTRATION AREAS, TOPSOIL RIPPING AND PLACEMENT OF SOIL AMENDMENTS AND SEEDING
NPDES Section E Antidegradation Analysis Module for Individual NPDES Permits in HQ/EV watersheds Non-Discharge Alternatives Evaluation Choose some, don t leave blank! Antidegradation Best Available Combination of Technologies (ABACT) Choose some, don t leave blank!!
NPDES Section F Consultant for this Project 1. Qualified professional engineer Structural BMPs 2. Qualified professional surveyor, landscape architect, or other Non-structural BMPs Certain structural BMPs WCD 2015
NPDES - Worksheets Don t leave blank! Everyone needs WS 1-5 Everyone needs WS 10 Some will use WS 12, 13 Don t CLAIM it unless you can PROVE it!
07/07/07 GreenForge Hempfield Twp Westmoreland County 3.0 ACRES Youghiogheny Sewickley Creek Jacks Run UNT to Slate Creek HQ-TSF X X
X X X X X X
NA NA NA NA
NA NA NA NA YES NA NA NA 0.58 0.58 0.48 0.48
GreenForge Stormwater Credits 1,125 sf Minimize Compaction 600 sf Protected Trees 0.48 ac Woodland Protected
0.48 0 0 0.48 3.0 0.48 2.52
1,125 23 600 25 48
x x x x x x
Criteria and Credits for BMP 5.6.3 Re-Vegetate and Re-Forest Disturbed Areas using Native Species
Worksheet 4 The numbers you generate go onto the NPDES Summary Table Don t CLAIM it unless you can PROVE it!
SCS METHOD 2 YEAR 2.7 X X 1.2 1.32 0.12 0.25 0.265 0.015 0.21-0.04 2.4 2.1-0.3
GreenForge 3.0 ac 2.7 3.0 0.48 2.52 B B 4,356 53,143 0.1 1.22 55 55 8.2 8.2 1.64 1.64 0.1 0.1 36 443 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 52,274 109,899 902 cft 0.93 1.2 2.52 95 55 0.5 8.2 0.1 1.64 2.2 0.1 (10,988 10,086 = 902) 7,466 436 10,988
A suburban watershed! Note the number of houses Note the length of streets What are some of the ground cover conditions you see here? What might be the curve number here?
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Curve Number Method (bottom of Worksheet 4) 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)
Worksheet 5 The numbers on this worksheet must agree with the BMP s listed on the NPDES Summary Description! Volume permanently removed should actually refer to volume treated by BMP s Area in square feet area of the BMP or area treated, make a note
GreenForge 902 cft 48 854 cft 5,400 2,160 700 700 9,000 750 150 250
700 700 9,000 750 150 250 3,860 854 3,006 cft
Would you only take one item?
2 OF THESE OR 4 OF THESE
Notice of Termination Inspection reports and monitoring records from critical stages (create your own) Final certification (see 102.8 paragraph) Record drawings Maintenance plan Responsible party - maintenance
Final Certification I (name) do hereby certify pursuant to the penalties of 18 Pa.C.S.A $4904 to the best of my knowledge, information and belief, that the accompanying record drawings accurately reflect the as-built conditions, are true and correct, and are in conformance with Chapter 102 of the rules and regulations of the Department of Environmental Protection and that the project site was constructed in accordance with the approved PCSM Plan, all approved plan changes and accepted construction practices.
Record drawings (what and how it has changed from original design) Location of BMPs, especially underground devices and individual lots Dimensions, elevations Pipe connections/materials/sizes Easements/right of ways/deed restrictions/covenants
Filing an Instrument (Recorder of Deeds) Parcel Information Project Information Index Information (permittee-copermittee) Acknowledgements (signatures, notary)
Project coordination Contract with client/compensation Construction sequencing, identification of critical stages Time involved pre-construction meetings, construction oversight, critical stage inspections, monitoring and reports, record drawings, final certification, maintenance plan
Stormwater Management is your friend
Draw the flow path (blue) Measure the length of the flow path Note the elevation change to calculate slope Will there be a natural stream or a series of pipes?
TIME OF CONCENTRATION
The Rational Method This equation tells you how much flow the culvert must carry