Pennsylvania Stormwater Best Management Practices Manual

Transcription

1 Pennsylvania Stormwater Best Management Practices Manual Presented by the Pennsylvania Department of Environmental Protection Bureau of Watershed Protection In cooperation with: Cahill Associates Environmental Consultants Stormwater Oversight Committee Villanova Urban Stormwater Partnership

2 Stormwater information (manual revisions, meetings, training, etc.) will be posted on the DEP Stormwater page DEP Keyword: stormwater General information Stormwater Oversight committee

3 Draft Stormwater Best Management Practices Manual Cover and Table of Contents Section 1 - Introduction and Purpose of BMP Manual Section 2 - Stormwater and PA's Natural Systems Section 3 - Stormwater Management Principles, Goals, and a Management Model Section 4 - Comprehensive Stormwater Management: Integrating Site Design, Non-Structural, and Structural BMP's Section 5 - Comprehensive Stormwater Management: Non-Structural BMP's Section 6 - Comprehensive Stormwater Management: Structural BMP's Section 7 - Stormwater Management for Special Areas Section 8 - Stormwater Calculations and Methodology Section 9 - Case Studies Innovative Stormwater Management Approaches and Practices Appendix A - Water Quality Appendix B - Pennsylvania Native Plant List Appendix C - Soil Infiltration Testing, System Design and Construction Guidelines Appendix D - Case Study with Stormwater Calculations

4 Chapter 1 Introduction & Purpose To improve stormwater management throughout Pennsylvania. Emphasis on water quality and water resources. Describes management methods and practices that can prevent, reduce, and mitigate the impacts of stormwater.

5 Stormwater Management Relationship Land Use and Water Integrated Approach Manage Stormwater: Volume Water Quality Peak Rate Groundwater Recharge Stream Impacts Construction NPDES Permits ACT 167 Planning Program COMPREHENSIVE SW POLICY BMP Technical Manual NPDES Phase II MS4 Permits

6 Chapter 2 Stormwater and Pennsylvania s s Natural Systems Hydrologic Cycle. Pennsylvania Rainfall: Avg. 36 to 44. Impacts of Development and Impervious Surfaces. Water and Environmental Quality. Pennsylvania Watersheds, Soils, Geology.

7 Stormwater Impacts Increased Runoff Volume Compacted Soils Erosion and Stream Channel Changes Decreased Base-flow Pollutants and Temperature Impacts Decreased Evapo-transpiration and Groundwater Recharge Increased Frequency of Runoff Events Faster Conveyance of Water Impacted Aquatic Life SOIL WATER TABLE (DEVELOPED CONDITIONS) STREAM BEDROCK WELL AQUIFER Cahill Associates Environmental Consultants Green Valleys Association

8 Chapter 3 Stormwater Management Principles and Goals Recommended Site Control Guidance: Comprehensive Watershed; Hydrology. Effective Prevents impacts. Equitable New and re-development. Flexible Variable conditions; Creative.

9 Ten Principles for Stormwater Management Prevent stormwater impacts first. Mitigate second. Manage stormwater as a resource. Maintain water cycle balance-quality and quantity. Integrate stormwater in the initial site design. Preserve and utilize natural systems-soil, vegetation. Manage stormwater close to the source. Disconnect/Decentralize/Distribute. Slow it down, don t speed it up. Do as much with as little as possible.

10 Site Control Guidance Volume CG-1 Volume CG-2 Do not increase runoff volume, pre-development to postdevelopment, for up to the 2-year frequency, 24-hour duration rainfall. ** Capture and remove runoff generated by 1.5 inches of rainfall with infiltration of the runoff from the initial 0.5 inches of rainfall. Groundwater/ Water Table/ Stream Base Flow & Stream Conservation/ Stream Channel Protection Extended Detention (CG-2 only) Provide 24-hour extended detention of the 1-year frequency, 24-hour duration rainfall. Stream Conservation/ Stream Channel Protection Peak Rate (CG-1 and CG-2) Do not increase peak rate of runoff for larger storms (1-, 2-, 10-, 25-, 100-year storms at minimum), pre-development to post-development; as necessary, provide additional peak rate control for largest storms through the Act 167 planning. Flood Protection: 1- through 100-Year Storms, Site by Site Cumulative Flood Protection as Needed through Act 167 Planning Water Quality (CG-1 and CG-2) A reduction of 85% of particulate-associated pollutants (as represented by TSS), including 85% of Total Phosphorus. In addition, removal or prevention of 50% of solutes (as represented by NO3-N) is required. BMPs shall not result in a temperature increase of 3 degrees Farenheit. Groundwater Quality Surface Water Quality - reduction of 85% particulate-associated NPS; reduction of 50% solute loads Temperature * These guidelines are recommended for use in watersheds throughout Pennsylvania. Guidelines may be further modified in Special Stormwater Management Areas and other zones where different stormwater guidelines for quantity and quality control are warrant ** Existing (pre-development) non-forested pervious areas must be considered meadow or its equivalent.

11 Control Guidance 1 Do not increase the post development total runoff discharge volume for up to the 2 year storm. Flood protection peak rates held to existing levels for the year storm. Notes: Existing condition is defined as those that occurred predevelopment, i.e. the current land cover (including impervious area). Existing non-forested pervious areas are classified as meadow or its equivalent.

12 Control Guidance 2 Base flow Infiltrate runoff from the first 1/2 of rainfall. Calculated as 0.5 x impervious area. Water Quality Infiltrate or capture runoff from the next 1 of rainfall. Capture is defined as permanent removal from runoff volume. Volume credits added to promote green practices. Channel Protection Control the 1 year peak discharge to the equivalent flow achieved by 24 hour extended detention of 1 year, 24 hour storm. Flood Protection Peak Rates held to existing levels for the year storm.

13 Chapter 4 Integrating Site Design Comprehensive design process. Emphasize non-structural BMP value. Stormwater not an afterthought.

14 Chapter 5 Non-Structural BMPs Each technique presented as a BMP. Incentives and values for non-structural BMPs. Emphasis on preventing/reducing stormwater. Soils Vegetation Reduced impervious surfaces. Natural area conservation. Small scale structural BMPs.

15 Protect Sensitive and Special Value Resources - Protect sensitive/special value features. - Protect/conserve/enhance utilize riparian areas. - Protect/utilize natural flow pathways in overall stormwater planning and design.

16 Cluster and Concentrate - Cluster uses at each site; build on the smallest area possible. - Concentrate uses areawide through smart growth practices.

17 Minimize Disturbance and Minimize Maintenance - Minimize total disturbed area grading. - Minimize soil compaction in disturbed areas. - Re-vegetate and re-forest disturbed areas, using native species.

18 Reduce Impervious Cover - Reduce street imperviousness. - Reduce parking imperviousness.

19 Disconnect/Distribute/Decentralize - Rooftop disconnection. - Disconnection from storm sewers.

20 - Street sweeping. Source Control

21 Chapter 6 Structural BMPs Volume/Peak Rate by Infiltration. Volume/Peak Rate Reduction BMPs. Quality/Peak Rate Reduction BMPs. Restoration. Other.

22 Structural BMPs Volume/Peak Rate by Infiltration Porous Pavement Infiltration Basin Infiltration Trench Dry Well / Seepage Pit Rain Garden/Bioretention Vegetated Swale Constructed Filter Infiltration Bed Vegetated Filter Strip Berm

23 Volume/Peak Rate Reduction BMPs Vegetated Roof Rooftop Runoff Capture & Reuse

24 Runoff Quality/Peak Rate BMPs Constructed Wetland Wet Pond / Retention Basin Dry Extended Detention Basin Water Quality Filter

25 Restoration BMPs Landscape Restoration Riparian Buffer Restoration Soils Amendment & Restoration

26 Other BMPs Level Spreader Special Detention Areas Parking Lot, Rooftop

27 BMP Elements One- page Overview Description and Pictures AutoCAD Details Variations Applications (examples) Design Considerations Detailed Stormwater Functions Construction Sequence Maintenance Issues Cost Information Specifications 10 to 15 pages per BMP

28 Structural BMPs One-page Overview: Snapshot of Key Design/Function Elements Description, Diagrams, and Pictures

29 Structural BMPs Cont d. Design Considerations Detailed Functions

30 Structural BMPs Cont d. Maintenance Considerations Cost Issues Specifications

31 Chapter 7 Stormwater Management for Special Areas Urban areas. Mined lands. Highways and Roads. Karst areas. Brownfields. Source water protection area.

32 Urban Areas

33 Stormwater BMP Challenges in Urban Areas 1. High imperviousness (50% to 100%). 2. High property values, limited physical space, etc. 3. Compacted soils, contamination. 4. Underground utilities. 5. Severely impacted streams; enclosed/buried in culverts. 6. Elimination of the original floodplain. 7. Direct connection of impervious surfaces. 8. Combined sewers. 9. High levels of trash, debris and pet waste. 10. Stormwater hot spots : industrial areas, vehicle service areas, public works storage areas, dumpsters, etc. 11. Regulations and ordinances that may conflict with current BMP design strategies. 12. Limited economic resources; need to encourage rather than discourage redevelopment.

34 Highways and Roads Table 8-1 Constituents and Sources in Highway Runoff * Constituent Particulates Nitrogen, Phosphorus Lead Zinc Iron Copper Cadmium Chromium Nickel Manganese Cyanide Sodium, Calcium Chloride Sulphates Source Pavement wear, vehicles, atmospheric deposition, maintenance activities Atmospheric deposition and fertilizer application Leaded gasoline from auto exhausts and tire wear Tire wear, motor oil and grease Auto body rust, steel highway structures such as bridges and guardrails, and moving engine parts Metal plating, bearing and bushing wear, moving engine parts, brake lining wear, fungicides and insecticides Tire wear and insecticide application Metal plating, moving engine parts, and brake lining wear Diesel fuel and gasoline, lubricating oil, metal plating, bushing wear, brake lining wear, and asphalt paving Moving engine parts Anti-caking compounds used to keep deicing salts granular Deicing salts Roadway beds, fuel, and deicing salts * From FHWA Stormwater Best Management Practices in an Ultra-Urban Setting

35 Highway and Road Stormwater Issues High levels total suspended solids. High levels pollutants. Use of vegetative, linear BMPs. Spills. Deicing. Temperature. Physical space constraints.

36 Chapter 9 Stormwater Calculations and Methodology Guidelines for volume, peak rate, and extended detention calculations. Flowcharts. Worksheets. Integration of volume and peak rate. BMPs provide volume and peak rate control.

37 Flowchart Examples

38 Worksheet Examples

39 Peak Rate Calculations ID existing methodologies/limitations Detailed routing Composite stage-storage-discharge Adjusted Tc for BMPs DURMM

40 Chapter 9 Case Studies Built projects around the state. Locations, information, contacts. Considering reference to web-site; updates.

41 Appendices Appendix A Water Quality Appendix B Pennsylvania Native Plant List Appendix C Soil Infiltration Testing; Infiltration System Design and Construction Guidelines Appendix D Case Study with Stormwater Calculations

42 Focus Groups Initial Focus Group Meetings January 19 Wilkes-Barre January 21 Williamsport January 25 Meadville January 26 Greensburg January 27 Harrisburg January 28 Norristown Follow-up Focus Group Meetings March 2 Meadville March 3 Greensburg March 7 Norristown March 10 Williamsport March 11 Harrisburg March 15 Wilkes-Barre

43 Beyond The Focus Groups Comments recorded from the second Focus Group meeting and subsequent written comments. Comments reviewed with the Stormwater Management Oversight Committee for discussion Manual revised. Public review and comment period. A final manual will prepared and distributed. Training.

44 Stormwater Information Stormwater information (manual revisions, meetings, training, etc.) will be posted on the DEP Stormwater page Keyword stormwater General information Stormwater Oversight Committee

45 Contacts Ken Murin Dennis Stum Questions?