Crediting BMPs Used for New and Redevelopment

Transcription

1 Crediting BMPs Used for New and Redevelopment

2 Welcome to the Webcast To Ask a Question Submit your question in the chat box located to the left of the slides. We will answer as many as possible during Q&A. To Answer a Poll Question Simply select the preferred option. For those viewing this session alongside several colleagues, respond in a manner that represents your organization as a whole. We ARE Recording this Session All comments and questions will be recorded and included in the archives. We will notify you as soon as the recording and related resources are loaded on the web. We Appreciate Your Feedback Fill out our evaluations our funders need to hear it!

3 Chesapeake Bay Stormwater Training Partnership To learn how you can have access to: FREE Webcasts Free 1-day design, inspection & maintenance workshops Intensive master stormwater seminars Direct On-site technical assistance Self guided web-based learning modules Visit:

4 Speaker Info Scott Crafton, Louis Berger Tom Schueler, Executive Director Cecilia Lane, Stormwater Coordinator

5 Poll Question #1 How many people are watching with you today? Just me 2-5 people 6-10 people > 10 people

6 Poll Question #2 Tell us a little about yourselves who are you representing today? Local government Private sector Regulatory agency Non-profit Academia Other tell us in the chat box

7 Poll Question #3 Why do you care about calculating BMP removal rates? I am involved in design/plan review of stormwater BMPs I am a local implementer trying to meet our load reduction requirements I am a state or federal regulator wanting to understand how the reductions are calculated Some other reason tell us in the chat box!

8 Today s Agenda Evolution of the Stormwater BMP Removal Rates Performance Standards for each Bay state Redevelopment Frequently Asked Questions

9 Evolution of Stormwater BMP Removal Rates At least 10 different sets of rates published in the last 25 years Each new set of studies reflects: More research, Different treatment technologies, more stringent practice design criteria, more sophisticated analysis Analysis of individual performance studies showed considerable variability in nutrient removal efficiency from storm to storm

10 Variability was normalized by computing a median removal rate for each individual practice and then computing a group mean for all practices in the same group Practice Group TP% Soluble P% TN% Soluble N% Dry ponds Wet ponds Wetlands Infiltration Filtering systems Water quality swales n=175

11

12 Limits of Percent Removal 1. Provides general performance data but little to no insight into the practice design features INPUTS? OUTPUTS One size does not fit all

13 Limits of Percent Removal 2. Limits on the amount of reductions a BMP can achieve = irreducible concentration from: Pass-through Re-packaging Biological activity Nutrient leaching/release 3. Research based on newly installed, well-designed practices, does not apply to older, poorly installed or maintained practices which may not be getting the same reductions

14 Limits of Percent Removal 4. Only focuses on nutrient reductions not flow reductions! LID practices are able to reduce runoff as it passes through a practice Runoff reduction is defined as the total volume reduced through canopy interception, soil infiltration, evaporation, rainfall harvesting, engineered infiltration, extended filtration or evapotranspiration (Photo credit: CDM Smith)

15 Runoff Reduction Approach Each practice has two design levels with specific nutrient removal rates LEVEL 1 DESIGN LEVEL 2 DESIGN RR = 40%, TP = 55%, TN = 64% RR = 80%, TP = 90%, TN = 90% Treats the 90% storm HSG C and D soils and/or underdrain Filter media at least 24 deep One cell design Treats the 95% storm HSG A and B soils OR has 12 stone sump below underdrain invert Filter media at least 36 deep Two cell design

16 Protocol for determining BMP removal rates Extensive review of current BMP performance research Developed a table of different classes of BMPs Determined composite Anchor Rates Developed a series of new BMP removal rate adjustor curves

17 Classification of BMPs All practices sorted into 2 categories: Runoff Reduction Practices (RR) Bioretention Dry Swale Infiltration Permeable Pavement Green Roof Achieve at least 25% reduction of annual runoff volume Stormwater Treatment Practices (ST) Constructed Wetlands Filtering Practices Wet Swale Wet Ponds Traditional practices

18 Composite Approach to Derive Nutrient Mass Load Reductions for RR ad ST Runoff Reduction Practices 1, PRACTICE TP Mass Reduction (%) TN Mass Reduction (%) Bioretention Dry Swale Infiltration Permeable Pavers Green Roof/Rain Tank Average RR Wet Ponds Const. Wetlands Filtering Practice Wet Swale Average ST Source: Table A-5, nutrient rates computed using the average mass reduction for both Design Level 1 and Level 2. 2 This value was subsequently discounted by 18% to reflect the impact of nitrate migration from runoff reduction practices described later in this appendix.

19 Removal Rates BMP removal rates are a function of runoff depth captured and the amount of stormwater treatment (ST) or runoff reduction (RR) achieved by the practice

20 Total Phosphorus Removal (%) 100% 95% 90% 85% 80% 75% 70% 65% 60% 55% 50% 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% Total Phosphorus Removal for RR and ST Stormwater Practices ST RR Runoff Depth Treated per Impervious Acre (inches)

21 Removal Rate Adjustor Curves Use of Rainfall Frequency Analysis to determine the amount of bypass and pollutant removal above and below 1.0 Converted to series of New BMP Removal Adjustor Curves

22

23

24

25 Same approach for Retrofits!

26 Performance Standards by State In last 7 years, each Bay State has revised regulations to improve the performance of stormwater practices. All of the States have increased the volume of runoff treated on-site and encourage/require the use of runoff reduction and ESD practices. Each State has unique regulations, performance standards, compliance models and design criteria

27 STATE NEW DEVELOPMENT PERFORMANCE STANDARD RAIN DEPTH CONTROLLED DC Retain runoff volume on-site 1.2 DE Provide runoff reduction to have zero effective impervious for RPE 2.7 EPA Control 95% storm event on-site using RR to METF MD NY PA VA Use ESD to the MEP to achieve runoff for woods in good condition Provide runoff reduction for a fraction of WQv for 90% rain event No increase in total runoff volume for all events up to the two year storm TP load from new development may not exceed 0.41 lbs/ac/yr WV Provide on-site runoff reduction 1.0

28 STATE DC DE EPA MD NY PA VA REDEVELOPMENT REQUIREMENT On-site retention of runoff from the 1.2 rainfall event 50% reduction in existing effective impervious for the site On-site runoff reduction for the 95% rainfall event Reduce existing imperviousness by 50%, or treat runoff from 1.0 inch of rainfall, or combination Reduce by 25% through IC reduction, BMPs or alternative practices 20% WQ treatment for the site Reduce existing phosphorus load by 10 to 20% depending on disturbed area WV inch of on-site runoff reduction 2

29 Questions Is my new development project nutrient neutral because I am using the new state performance standards? Does my redevelopment project garner pollutant reduction credits? If I comply with my state standards, what do I report to the state for Bay TMDL purposes?

30 Site Land Cover Treatment Volume Treatment Volume Assumed Pre-Development Condition Examples: CN for woods in good condition Initial abstraction Assumed pre-development 2-year volume Volume = 0.41 lbs/acre/year of TP

31 Different Names for Volume Controlled DC = Stormwater Retention Volume (SWRv) cubic feet DE = Runoff Reduction Depth inches FED = 95% Rainfall Depth inches MD = ESD Runoff Volume cubic feet NY = Water Quality Volume acre-feet PA = Volume Control Guideline inches VA = Treatment Volume cubic feet WV = Treatment Volume cubic feet

32 How to Compare? Tempting to compare rainfall depth controlled.can be misleading Every State has a unique pre-development hydrologic baseline and modeling approach (CN or Rv) Results in different Engineering Parameter (EP) for each State Unitization! Actual Volume Controlled By BMP or Stormwater Plan

33 State Stormwater Compliance Spreadsheets Site Data Site Name: Site Information Indicate Post-Development Land Cover Rv Coefficients Cover Type Area (acres Land Cover Type Rv Natural Cover Natural Cover 0.00 Compacted Cover Compacted Cover 0.25 Impervious Cover Impervious Cover 0.95 Total 0.00 Land Cover Summary % Natural Cover #DIV/0! % Compacted Cover (acres) #DIV/0! % Impervious Cover #DIV/0! Site Rv #DIV/0! MD VA DC PA WV DE Is Site a Federal Facility? No Regulatory Rain Event for Retention (inches) 1.2 Stormwater Retention Volume, SWRv (cubic feet) #DIV/0!

34 State Compliance Spreadsheet Resources Delaware s DURMM v. 2 Model DC General Retention Compliance Calculator MD Compliance Spreadsheet Pennsylvania DRAFT Compliance Spreadsheet Virginia New Development Compliance Spreadsheet Virginia Redevelopment Compliance Spreadsheet West Virginia Spreadsheet Not all are state sanctioned!

35 Engineering Parameters State-specific compliance spreadsheets will give you input for a BMP or site-specific EP Need to unitize in order to compare the performance standards across the Bay states X = (12 x EP) / IA Where: EP = State-Specific Engineering Parameter (ac-ft) IA = Impervious Area (acres)

36

37 NOTE: Removal rates apply to entire BMP drainage area or site area, NOT just impervious area. Reporting = entire treatment area

38 NOTE: Dry Ponds & Dry Extended Detention Ponds are Classified as ST Practices Use Table B-5 in Expert Panel report for (lower) removal rates Runoff Reduction Practices (RR) Classification of BMPs Stormwater Treatment Practices (ST) Bioretention Dry Swale Infiltration Permeable Pavement Green Roof Constructed Wetlands Filtering Practices Wet Swale Wet Ponds

39 Design Examples Low Density Residential Development of 25 acre site in 1/2-acre lot residential subdivision in Pennsylvania Predevelopment conditions: 50% forest, 50% meadow + 100% C soils Post-development land cover: 25% impervious, 50% turf, 25% forest Will use a mix of RR practices

40

41 Low Density Residential Design Example Using the New Development Equation: = (12 x EP) / IA EP = Engineering Parameter = 1.16 ac-ft IA = Impervious Area = 6.25 acres (12 x 1.16) / 6.25 = 2.23

42 Low Density Residential Design Example Pollutant Removal Efficiencies of the practice TP TN TSS 78% 67% 84%

43 Residential Planned Unit Development 100-acre site developed with a mix of single family homes, apartments and townhouses in MD Predevelopment = 100% forest, C soils Post-development = 90% impervious, 10% turf Use of ST practices

44 High Density Residential Example Using the New Development Equation: = (12 x EP) / IA EP = Engineering Parameter = 7.5 ac-ft IA = Impervious Area = 90 acres (12 x 7.5) / 90 = 1.00 Pollutant Removal Efficiencies of the practice TP TN TSS 55% 35% 70%

45 Basic Reporting Unit Number of treated acres that fully meet the state s stormwater performance standard Typical duration for the removal rate is twice the MS4 inspection cycle yrs Removal rate can be extended based on field verification of performance

46 REDEVELOPMENT Redevelopment standards apply to sites with existing untreated impervious cover States are moving toward more stringent redevelopment requirements Differs across the states

47 Redevelopment Protocol Applies to redevelopment projects that meet the new redevelopment standards from 2010 and beyond Requires that designers confirm project is properly classified as redevelopment and not served by preexisting stormwater treatment practices Report Impervious Cover acreage treated

48 REDEVELOPMENT Site-specific EP generated from each State s spreadsheet Used in the Redevelopment Equation X = (12 x EP) / SA Where: EP = State-Specific Engineering Parameter (ac-ft) SA = Redevelopment Site Area (acres)

49 Design Examples Redevelopment Redevelopment of a 2-acre facility in DC Predevelopment = 50% impervious, 50% turf Post-development = 50% impervious, 50% turf 100% D soils Site will use RR practices

50 Design Examples Redevelopment Using the Redevelopment Equation: = (12 x EP) / SA EP = Engineering Parameter = 0.12 ac-ft SA = Site Area = 2 acres (12 x 0.12) /2 = 0.72 Pollutant Removal Efficiencies of the practice TP TN TSS 62% 53% 67%

51 Individually, load reductions from redevelopment are not impressive But across a community and over 15 years, they can really add up!

52 Frequently Asked Questions

53 Q: Does this new method supersede my state s stormwater calculations? Several Bay states require slightly different site based spreadsheet pollutant load calculations as part of development review. Answer: No.

54 Q: What happens if my project has a mix of runoff reduction and stormwater treatment practices? Answer: Use the curve associated with the practices that provide a majority of the runoff capture or storage volume for the site as a whole For example, Site C has RR practices providing 60% of the runoff capture volume and ST practices provide the rest. Use the RR curve

55 TP Q: I have trouble reading the curves can you provide the actual equations for them so I can plug them into a spreadsheet and calculate the removal rates directly? A brilliant idea! While they are shown here, they are also in the FAQ document. RR y = x x x x x ST y = x x x x x TN RR y = x x x x x ST y = x x x x x TSS RR y = x x x x x ST y = x x x x x

56 Q: Why are dry ponds and dry ED ponds not included in the practice classification table? 56

57 These practices have limited pollutant removal capability and the curves cannot be reliably used to calculate their pollutant removal Most Bay states are discouraging their use in new development projects If your project uses either of these practices, use the rates in Table B-5, Appendix B to calculate their efficiency

58 Q: What type of practice are Regenerative Stormwater Conveyance practices? Dry RSC practices can be treated as an upland BMP Use the RR curve for determining removal rates Wet channel RSC practices are considered to be a stream restoration practice see webcast from April, 2014 Cabin Branch RSC project

59 Q: Do the curves apply to filter strips? No. The expert panel came up with an alternative method for determining their pollutant removal associated with new development projects. See webcast! vents/webcast-ms4-implementersand-the-bay-tmdl-retrofits/ Photo credit: Ryan Winston, NCSU

60 Q: What happens if my redevelopment site is currently served by an existing BMP? Answer: Unless it was previously reported to the state for credit in the model, you don t have to account for it (the removal rates for older practices are very low) If it was reported, you may still get credit for your new BMP as a retrofit

61 Q: How do I deal with historic BMPs that were reported in the past? Answer: When dealing with older BMPs that reported using the unit removal rates from Table 5 (dry ponds etc) there are 2 options: 1. Keep the rates and then inspect and verify your legacy BMP in the next permit cycle 2. Based on field conditions, you may re-compute the removal rates using the adjustor curves for each practice based on its current capacity and DA

62 Q: What do I do with discovered BMPs? Answer: When identifying a BMP that was not previously reported to the Chesapeake Bay Program and was built before 2006 (the final year of the CBP Watershed Model calibration period) it can only be retrofitted (converted, enhanced or restored) and receive credit that way.

63 Q: Is it possible to receive credit for retrofitting a water body that was not originally designed for stormwater quality treatment and not originally reported to the state? Answer: Yes, but under some fairly stringent conditions. When identifying a water body that was not originally designed for stormwater quality treatment, such as a farm pond, a PL-566 reservoir or a flood control facility the removal rate would be calculated using the incremental difference between the original removal rate and the higher removal rate caused by retrofitting the facility (conversion, enhancement or restoration) after In addition, both the treatment volume and drainage area of the original facility and its retrofit will need to be substantiated to quantify the change in removal rate due to the post 2005 retrofit.

64 Q: What if I want to use a practice that is not included in my state design manual? Good question! Two possibilities: Determined by future expert panels based on the priority assigned by the USWG Practice can be mapped into existing urban BMP credit Floating Treatment Wetland Photo credit: Sarah White, Clemson University

65 Urban BMP Interpretations Not all BMP requests require the launch of a full blown urban BMP expert review panel Not enough research Similar to existing BMP credit

66 Some examples of recent requests Residential BMPs (Rain garden, rain barrel, pervious pavers) Smart BMP Retrofits Combination of retrofits and stream restoration Urban agriculture Enhanced N or P removal (filter media inputs, specific plant species, sumps etc)

67 Prerequisites Cannot be a proprietary practice Represents a real change on the ground that occurs in the present day (e.g., no historic BMP finds) Have verification procedures that are as stringent or more stringent than their parent BMP Cannot create problems when it comes to reporting in Scenario Builder

68 Process Proposer provides supporting documentation for consideration by USWG USWG can accept, accept w/ modification, reject or require a full blown expert panel States can individually opt out if they are not comfortable with the technical basis for the decision, reporting requirements and/or verification protocols Modelers will be consulted prior to any decision

69 How? Anybody can make this request but highly recommend that you work with an official USWG member to sponsor the request Submissions should include a brief memo outlining the technical basis for the request and including any supporting scientific or engineering information Specifically reference the definition and crediting protocols from an existing approved urban BMP that this practice fits into

70 Q: What do I need to report to the state and to whom do I send it?

71 Blue = initial reporting to CBP Black = report to maintain credit

72 Hey MS4s Pay Attention to This so you get credit for your BMPs! Blue = initial reporting to CBP Black = report to maintain credit

73

74 State-Specific Reporting: Example VA MS4 TMDL Action Plan Guidance (August, 2014)

75 Who Reports What to Whom? MS4s to State: State-specific BMP & land use reporting in annual MS4 report Non-MS4s to State: State-specific reporting, TBD in some cases State to CBP (NEIEN, Scenario Builder): Applies performance curves to derive official load reductions, enters data, reports back to locals Locals to Themselves: Track unofficial load reductions using local tools (e.g., spreadsheets, watershed treatment model, other tools)

76 How Long is a BMP Removal Rate Good For? 10 years max (5 years for on-site retrofit) Localities need to submit verification inspections prior to June, 2023 Use State-specific or CBP verification procedures:

77 Visual Indicators for BMP Verification (Level 2) PURPOSE Ensure BMP still exists and is providing the pollutant removal it was designed to achieve or if it requires major restoration AUDIENCE MS-4 Permit/ TMDL FREQUENCY Once ever 5-10 years SKILL LEVEL Trained person

78 Visual Indicators Tool for BMP Verification 4/technical-bulletin-no-10-bioretentionillustrated-a-visual-guide-forconstructing-inspecting-maintaining-andverifying-the-bioretention-practice/

79 Q: Who do I contact at my Bay state with questions regarding stormwater BMPs? State Stormwater Contact Data Manager DC Brian VanWye Brian.vanwye@dc.gov Marty Hurd martin.hurd@dc.gov DE Randy Greer Randell.Greer@state.de.us Marcia Fox Marcia.Fox@state.de.us Mary Dela Dewa (MS4) mary.dewa@maryland.gov MD Ray Bahr rbahr@mde.state.md.us Greg Sandi (Non-MS4) gsandi@mde.state.md.us NY Carol Lamb-Lafay calambla@gw.dec.state.ny.us Dave Gasper calambla@gw.dec.state.ny.us Jen Orr (construction) jeorr@pa.gov PA VA Ron Furlan (MS4s) Fred Cunningham rfurlan@pa.gov Ted Tesler thtesler@state.pa.us Frederick.Cunningham@deq.virgini william.keeling@deq.virginia. a.gov Bill Keeling gov WV Sebastian Donner Sebastian.Donner@wv.gov Alana Hartman alana.c.hartman@wv.gov

80 Webcast Resources U-2 Stormwater Practices for New and Redevelopment Projects Fact Sheet Chesapeake Bay Program Expert Panel Resources: Final Expert Panel Report on Stormwater Performance Standards Frequently Asked Questions for Stormwater Performance Standards and Retrofit Expert Panel Reports Bay TMDL Accounting Guidance: Accounting for Stormwater Wasteload Allocations and Impervious Acres Treated Chesapeake Bay TMDL Action Plan Guidance Bay State Stormwater Compliance Spreadsheets for each of the Bay states Verification Resources Bioretention Illustrated: A Visual Guide for Constructing, Inspecting, Maintaining and Verifying the Bioretention Practice Final Recommended Guidance for Urban Stormwater BMP Verification

81 Evaluation Please take a few moments to answer our 6 question survey to help us better serve your needs in our webcast series. We use this information to report it to assess our work, your needs and to report it to our funders for future webcasts!