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1 Tools & Guidance for Developing Your Post- Construction Stormwater Management Program September 3, 2008 David J. Hirschman, Center for Watershed Protection John Kosco, Tetra Tech, Inc. Steven Hubble, Stafford County, VA Nikos Singelis, US EPA Guide to Our Webcasts For Technical Support click the Help button To Ask a Question - Type your question in the text box located in the lower left-hand corner of your screen and click on the Submit Question button To Answer a Poll Question Click on the radio button to the left of your choice and click submit. Do not type your answer in the Ask a Question box To See Closed Captioning Turn your pop-up blocker off and click on the closed captioning button To Complete the Survey Turn off your pop-up blocker To Obtain a Certificate Watch 1 hour and 30 minutes of the webcast and then click Download Certificate. If you are in a room with multiple attendees please wait until the last slide to obtain the URL to customize your own certificates 1

2 Managing Stormwater in Your Community 2

3 Post-Construction Program Tools Tool 1: Program Self- Assessment Tool 2: Program & Budget Planning Tool 3: Model Ordinance Tool 4: Codes & Ordinance Worksheet Tool 5: Manual Builder Tool 6: Checklists Tool 7: Performance Bonds Under Development Tool 8: BMP Performance Verification Manhole Graphic: Session Overview Stormwater Guide & Tools Stormwater BMP Quiz Getting the BMPs We Want: Stormwater Criteria Promoting Innovative Practices/LID Stafford County, VA criteria/lid Site Design Example Program Planning Tool 1: Self-Assessment 3

4 Session Overview Stormwater Ordinance Stafford County ordinance Tool 3: Model Ordinance Stormwater Manuals Tool 5: Manual Builder Stafford County Manual updates Maintenance Stafford County LID maintenance Summary 1. Which BMP Does the Best Job of Reducing the Overall Volume of Runoff? 4

5 A Bioretention B Green Roof C Riparian Restoration D Wet Pond A Bioretention B Green Roof 40 80% 45 60% C Riparian Restoration D Wet Pond % % 5

6 2. Which Would You Rather Maintain? A Pervious Parking B Underground System C Preserve Sensitive Site Features D 1963 VW Bus 6

7 A Pervious Parking B Underground System L -- M H ++ C Preserve Sensitive Site Features D 1963 VW Bus L H 3. Which BMP(s) Must Be Considered Early in the Design Process? 7

8 A Dry Pond B Small Scale Practices C Wetland Swale D Preserve Riparian Corridor A Dry Pond B Small Scale Practices No Yes C Wetland Swale D Preserve Riparian Corridor Maybe Yes 8

9 Take Home Points 1. Overall, stormwater impacts can be reduced through site design and source controls, in additional to built BMPs 2. Many stormwater approaches need to be considered EARLY in the site planning process 3. Initial BMP selection will affect cost and long-term maintenance burden 4. Local program should provide incentives and/or credits for the BMPs they want to see built in the community 5. Stormwater criteria in the ordinance/design manual influence BMP choices Take a systematic approach to getting the BMPs you want in the community Why Are There So Many? Copyright 2000, Center for Watershed Protection 9

10 The Fact Is We Ask For It Stormwater Criteria Design Standards & Manuals Getting The BMPs We Want: A Systematic Approach 1. Ordinance Credits/Requirements 2. Design Manual Specs/Details 3. Plan Review Early Consideration 4. Inspection Verification 5. Maintenance Performance 6. Tracking Program Benefits 10

11 Getting The BMPs We Want From 1. Ordinance 2. Design Manual 3. Plan Review 4. Inspection 5. Maintenance 6. Tracking Ch. 5 Ch. 6 Ch. 7 Ch. 8 Ch. 9 Ch. 10 Stormwater Criteria 1. Natural Resources Inventory 2. Runoff Reduction/Recharge 3. Water Quality Volume 4. Channel Protection 5. Flood Control 6. Redevelopment 7. Sensitive Receiving Waters See Chapter 4: Tables 4.7 through

12 How Criteria Relate to the Receiving Stream 10-yr CP v WQ v Re v Base Flow Photo adapted from NRCS, Stream Corridor Restoration: Principles, Processes, and Practices, 10/98, by the Federal Interagency Stream Restoration Working Group (FISRWG)." Nested Approach to Stormwater Sizing (1) Flood Control Typical: 10-year or 25-year post to pre 12

13 Nested Approach to Stormwater Sizing (2) Channel Protection Flood Control Flood Control Typical: 24-hour detention of the 1-year, 24- hour storm Nested Approach to Stormwater Sizing (3) WQV Channel Flood Channel Protection Control Flood Control Typical: Capture & treat runoff from 90 th percentile storm event 13

14 Nested Approach to Stormwater Sizing (4) WQV Runoff Reduction Channel Water Quality Flood Channel Protection Control Flood Control Replicate predevelopment recharge volume for soil groups No increase in volume for all storms up to 2- year, 24-hour storm Nested Approach to Stormwater Sizing (5) WQV Runoff Reduction Channel Water Quality Flood Channel Protection Control Redevelopment Flood Control Reduce impervious cover 10% in load from pre-development Use innovative practices Contribute to watershed project 14

15 See Chapter 4: Figure 4.2 Ponds are prevalent because they can be designed with capacity to meet stormwater criteria in local codes 15

16 Other (innovative) BMPs must be authorized or given credit/incentives by the local program if they are to be used Stafford County, Virginia Northern Virginia Suburb of Washington DC-Located approximately miles south Approximate Population=120,000 Area= +/- 270 square miles 16

17 Stafford County VA NPDES Phase II Community-Permitted in 2003 Subject to Virginia s Chesapeake Bay Act (requires local governments to implement land use controls, buffers etc. to protect water quality) Stormwater Design Criteria Water Quantity Stream Channel Erosion 24 hour extended detention of the one year, 24 hour storm Flooding 10 year storm, post development peak rate of runoff must not exceed pre-development rate 17

18 Stormwater Design Criteria Water Quality Post development stormwater runoff shall be treated by an appropriate technology based BMP based on the imperviousness of the drainage area as specified in the Stormwater Management Design Manual Redevelopment projects shall reduce post development pollutant loads to 90% of predevelopment levels Stormwater Design Criteria Low Impact Development The stormwater management concept plan shall utilize LID site planning to the maximum extent practicable. Stormwater runoff for parking lots shall utilize infiltration or filtering BMPs. LID Design Plans shall satisfy water quantity and quality requirements of the County SWM Ordinance. Calculations for LID Designs shall be in accordance with the EPA/Prince George s County Design Manuals As a consequence of these requirements, LID has become the first option for complying with stormwater management requirements in Stafford County. LID is not mandatory, however its use must be evaluated before opting for conventional SWM designs. 18

19 Stormwater Programs/Manuals That Authorize Innovative Practices ( Credits ) Maryland Stormwater Design Manual Georgia Stormwater Management Manual Vermont Stormwater Management Manual Western Washington Stormwater Management Manual Minnesota Stormwater Manual Various Local Manuals Runoff Reduction Method Tool 5: Manual Builder for more examples Objective: Better Mix of Conventional & Innovative BMPs How Do Credits Work? Give credit for conserving hydrologically significant natural areas, reducing site impervious cover, and LID: 1. Reduce Runoff Volume 2. Reduce Water Quality Volume (WQ v ) 3. Simple Point System 4. Reduce storage volume required for larger storms (CP v, Q 10, Q 100 )by: Adjusting Curve Number (CN) or Increasing Time of Concentration (Tc) Result: Fewer and smaller structural BMPs 19

20 Runoff Reduction (RR) Runoff reduction is defined as the total volume reduced through canopy interception, soil infiltration, evaporation, rainfall harvesting, engineered infiltration, extended filtration or evapotranspiration at small sites Recharge, water quality, and even channel protection requirements can be collapsed into a single runoff reduction volume that would maintain predevelopment runoff conditions Stormwater Practices Differ Sharply in Ability to Reduce Runoff Volume Wet Ponds, ED Ponds and Constructed Wetlands and Filters Reduce Runoff Volumes by zero to 10% Bioretention, Infiltration, Dry Swales and Related Practices Reduce Runoff Volumes by 50 to 90% 20

21 Credit: Runoff Reduction (RR) Table 6. Runoff Reduction for various BMPs (from Table 2) Practice RR (%) Green Roof 45 to 60 Rooftop Disconnection 25 to 50 Raintanks and Cisterns 40 Permeable Pavement 45 to 75 Grass Channel Bioretention Dry Swale Wet Swale Infiltration ED Pond Soil Amendments Sheetflow to Open Space 10 to to to to 90 0 to to to 75 > Resources > Controlling Runoff & Discharges > Stormwater Management > Runoff Reduction Technical Memo Filtering Practice Constructed Wetland Wet Pond Range of values is for Level 1 and Level 2 designs see Section 9 & Appendix D Runoff Reduction Practices * 1. Protected Open Space Receiving Runoff from Developed Areas 2. Rooftop Disconnection 3. Pervious Parking 4. Green Roof 5. Grass Channels 6. Bioretention & Dry Swales 7. Wet Swales 8. Infiltration * Forest conservation, soil conservation, soil restoration are self crediting 21

22 Example: Residential Site Site Characteristics Area = 37 acres 100 homes HSG A/B soils IC = 30%, Turf = 55%, Forest = 15% Residential Site Design Case I All runoff drains to constructed wetland Case II 75% rooftops (3.6 ac) simple disconnection 25% rooftops (1.2 ac) disconnect to rain gardens Rooftop overflow to grass channel Grass channel conveys water from road, driveways, and rooftop overflow to constructed wetland. 22

23 Curve Number Adjustment* Criterion WQv CPv FCv Case I No RR practices CN Case II With RR practices Adjusted CN * Conservative credit can also increase Tc or further adjustments to hydrographs to provide more credit at discretion of local program Water Quality Volume WQv Reduction: 48% Vol 49% Peak 23

24 Channel Protection CPv Reduction: 18% Vol 25% Peak Flood Control 10-yr Reduction: 6% Vol 5% Peak 24

25 Residential Site Design Required constructed wetland basin size, for 24 hour detention of WQv Case I 1.14 acre pond 3.1% of Contributing Drainage Area (CDA) Case II 0.59 acre pond 1.6% of CDA Any Credit System Should Have: Description of Applicable Practices Site Conditions & Restrictions Computation Procedures Inspection & Maintenance Procedures Signage & Visibility of Practices Public Outreach & Education 25

26 Capacity for Credits?: The Essentials Authorization to try new compliance approaches Strong interest and some experience in innovative design Development review that considers stormwater EARLY in the site design process Effective working relationships between designers and reviewers Commitment to field verification Local Policies, Procedures and Guidance Manuals to backup your decisions! Q & A Break 26

27 Program Planning Many programs in getting by mode Don t have defined budget or program plan for post-construction Widening divide between programs with and without stormwater utilities Need for phased program implementation Tool 1: Program Self- Assessment Who? How? Stormwater program managers Others interested in local program goals & milestones Checklist format Why? ID gaps ID short and long-term actions ID measurable goals 27

28 Program Self-Assessment: Questions for Program Evolution Group A: Initiating the Program Group B: Enhancing the Program Group C: Advancing the Program 28

29 The Stormwater Ordinance As of 2006, about half of Phase II MS4s have adopted a post-construction ordinance Other local codes (zoning, subdivision) may conflict with post-construction stormwater goals and practices Adopting an ordinance is key early step for the program 29

30 Key Stormwater Ordinance Elements Chapter 5 Regulatory Structure legal authority, applicability, waivers Design Elements criteria, regional or watershed approaches Plan Review Elements plan submission & review Maintenance Elements maintenance agreements, easements, inspections & reporting Enforcement penalties & remedies Major Ordinance Decisions Combine post-construction with ESC/IDDE Reference a separate design guidance and/or policy manual Redevelopment Special receiving waters (impaired, sensitive) Watershed-based approaches (fee-in-lieu) Concept plan stage Aligning other local codes 30

31 Stafford County Stormwater Ordinance As a result of a Better Site Design roundtable, a committee was convened and grant obtained for the County to develop a new stormwater ordinance that included options for the use of LID designs and practices. Stafford County revised its stormwater ordinance in 2003 to include LID practices as an option for complying with the water quality and quantity requirements of the County SWM ordinance. In 2004, the ordinance was revised again to require that new developments evaluate the use of LID to the maximum extent practicable Stafford County: LID Incentives, Aligning Local Codes Stafford County updated its Zoning and Subdivision ordinances in 2003 to remove hurdles and provide incentives for using LID LID Integrated Management Practices (IMPs) were allowed on private lots Curb and gutter requirements were relaxed in certain residential projects to allow for the use of open conveyance systems and engineered swales. Landscaping in LID facilities counts towards overall landscaping requirements Alternative pedestrian pathways were allowed in lieu of sidewalks in certain projects It should be noted that the use of these incentives to date, has been limited 31

32 Tool 3: Model Ordinance Who? How? Stormwater program managers State/regional ordinance developers Legal staff Adaptable Word document Why? Cull language for stormwater code updates Explore new program features Model Ordinance: Language for Program Evolution Basic Program Enhanced the Program Advanced or Alternative Program Elements Give us feedback! Consult with your legal staff Adapt to your local conditions & priorities 32

33 Stormwater Guidance Manuals See Chapter 6: Policy Manual Design Manual Stormwater Manuals Many states have manuals; many out-of-date Many do not have LID credits or specs/standards Great flurry of activity with manual updates Local programs should adapt, cut & paste 33

34 Stormwater Manuals Across the U.S. & Territories Percent of US States that: Have a manual: 73%* Have a modern manual: 22% * Using a liberal definition of design manual Tool 5: Manual Builder Who? How? Stormwater program managers Consultants working for local programs Design engineers Program staff: plan review, inspections Spreadsheet, links, users guide Why? Find the best examples for design & policy issues from across the country Don t need to start from scratch if assembling or revising a manual 34

35 Manual Stackage A true test of how manuals really measure up... Tool 5: Manual Builder Detailed BMP Design/Performance Specifications Prince George's Co, MD Bioretention Manual ncyindex/der/esd/bioretention/bioretention.asp?nivel=f -- Bioretention Filtration Lake Co, OH Bioretention Guidance -- Low Impact Development Technical Guidance Manual for App. 2, 3, Washington Puget Sound id_index.htm 4 Wisconsin Stormwater Management Technical Standards echstds.htm#post Std District of Columbia Stormwater Management Guidebook Currently Not Available Online -- Minnesota Minnesota Stormwater Manual Maryland Maryland Stormwater Design Manual edimentandstormwater/stormwater_design/index.asp 3.4 Center for Watershed Protection Design of Stormwater Filtering Systems -- Infiltration Pennsylvania Delaware New York Maryland Stormwater Best Management Practices Manual asp?a=1437&q=529063&watershedmgmtnav= 6.4 Green Technology: The Delaware Urban Runoff Management Stormwater/New/GT_Stds%20&%20Specs_06-05.pdf 2.6 New York State Stormwater Management Design Manual Maryland Stormwater Design Manual edimentandstormwater/stormwater_design/index.asp

36 Stafford County: Stormwater Management Design Manual Quickly after adopting LID requirements, there was an apparent need to update the County s design manual to provide additional design and policy guidance. The design manual update process has taken 3 years to complete and involved the work of County staff, our stormwater consultant and a committee of interested stakeholders. Stafford County: Stormwater Management Design Manual-Key Issues Defining Maximum Extent Practicable Underdrains Soil media composition Easements and maintenance access Setbacks from buildings, wells and septic fields 36

37 Stormwater Maintenance Challenges Locating stormwater facilities Identifying responsible parties Lack of maintenance and inspection staff BMP designs do not allow for easy maintenance Lack of enforcement authority and access Owners are unaware of maintenance responsibility Proliferation of BMPs that require intensive maintenance Maintenance Program Service Matrix 37

38 Three General Approaches to a Municipal Stormwater Maintenance Program Approach 1: Private Maintenance Typical budget: $5K - $100K Approach 2: Local Program Maintenance Typical budget: $100K - $1.5M Approach 3: Hybrid Approach Blend of Public and Private Maintenance Typical budget: $50K - $300K Stafford County: Maintenance of LID Facilities Drainage easements and maintenance agreements are required for all LID facilities in Stafford County Property owners or Homeowner s Associations are responsible for maintenance Detailed maintenance plans are required as part of the maintenance agreement and are recorded in the County s land records. Subdivision restrictions and covenants should address LID so that property owners are aware of LID facilities and required maintenance activities Active maintenance inspection program for post construction BMPs begins in the Summer of 2008 to comply with NPDES Phase II requirements 38

39 Post-Construction Program Tools Tool 1: Program Self- Assessment Tool 2: Program & Budget Planning Tool 3: Model Ordinance Tool 4: Codes & Ordinance Worksheet Tool 5: Manual Builder Tool 6: Checklists Tool 7: Performance Bonds Under Development Tool 8: BMP Performance Verification Manhole Graphic: Summary Getting the BMPs We Want: Criteria & credits Systematic approach Do a Program Plan Adopt or Update the Ordinance Cobble Together a Modern Manual Maintain It! 39

40 Q & A Break 40

41 Participation Certificate If you would like to obtain participation certificates for multiple attendees, click the link below You can type each of the attendees names in and print the certificates post_construction.pdf 41