Retrofitting Revisited: A Post-Expert Panel Perspective

Transcription

1 Retrofitting Revisited: A Post-Expert Panel Perspective

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!

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4 CSN s 2016 Spring Webcast Series Thursday, June 16: Crediting Floating Treatment Wetlands in the Chesapeake Bay Thursday, June 30: Street Sweeping and Storm Drain Cleaning in the Chesapeake Bay Register here:

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 Tell us what YOUR role in retrofitting is: I design them I construct them I record/track/account for them to meet my permit/restoration/tmdl requirements I conduct retrofit/watershed assessments What is a retrofit?

8 Speaker Info Tom Schueler Chesapeake Stormwater Network Cecilia Lane Chesapeake Stormwater Network

9 My Early Retrofitting Years Wiggle-tail 1964

10 Today s Agenda 1. Retrofit Classification 2. Envisioning Restoration 3. The Retrofit Discovery Process 4. Tom s Short Cut Process 5. Retrofit Evaluation: Removal and Costs 6. Some FAQs for Retrofits 7. Some Other Options 8. Discussion

11 Why Retrofit? ~ 10 to 30% TP and TN load reductions needed from existing development Massive Increase in Retrofitting 15 Years to Get It Done

12 Stormwater Retrofit Classification

13 Category 1 RETROFIT EXISTING BMPS 1. BMP Conversions 2. BMP Enhancements 3. BMP Restoration Can be the most cost effective type of retrofit since it represents existing stormwater infrastructure that you already own or control

14 EXISTING RETROFITS BMP CONVERSION DRY POND CONSTRUCTED WETLAND

15 Retrofit Existing Stormwater Basins 1. Excavate Storage Wet pool Sand filter 2. Raise Embankment

16 Retrofit Existing Stormwater Basins 3. Modify Riser

17 Retrofit Existing Stormwater Basins 4. Trade Storage

18 OTHER BMP CONVERSIONS Adding Bioretention or Sand Filters to Dry Ponds

19 EXISTING RETROFITS BMP ENHANCEMENT Increase treatment volume, hydraulic residence time or other design elements to improve pollutant removal * * Expert panel did not provide a lot of specifics

20 EXISTING RETROFITS BMP RESTORATION DREDGING AN UNDERPERFORMING POND TO RESTORE FULL PERFORMANCE

21 Retrofit Category 2: NEW BMPs Near Existing Stormwater Outfalls Source: CWP

22 NEW BMPs Within the Existing Conveyance System * * Impervious Cover Disconnection EP provides new design methods for this kind of retrofit Source: CWP

23 NEW BMPs Adjacent to Large Parking Lots Source: CWP Wet Pond Bioretention

24 NEW BMPs Green Streets

25 NEW BMPs Residential Stewardship Practices A lot of resources, design tools, tracking systems and incentive programs have been developed for this class of retrofits in recent years

26 Questions?

27 Envisioning Restoration

28 Retrofitting requires: Sleuthing skills to determine what can work at highly constrained sites Simultaneously envisioning restoration possibilities and anticipating potential problems

29 What would you do here?

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35 Activity

36 The Retrofit Discovery Process

37 Source: USRM 3, CWP

38 Step 1. Retrofit Scoping Purpose Define a retrofit strategy to meet local restoration objectives Key tasks Review local stormwater management infrastructure and practices Define restoration objectives Define preferred retrofit practices and locations

39 Step 1. Retrofit Scoping Consult with stakeholders Understand watershed conditions and develop restoration objectives Select subwatersheds Identify target land uses to treat

40 Step 2. Desktop Retrofit Analysis Purpose Rapidly search for and identify potential retrofit sites across the subwatershed Save time in the field Key tasks Secure GIS layers and other mapping data Conduct a structured desktop search for retrofit sites Prepare base maps for field investigation

41 Step 2. Desktop Analysis Analyze mapping and metrics to find prospective sites Aerial photos Topography Hydrology Ownership Land cover Storm sewers Existing BMPs Outfalls Road

42 Good Desktop Search Targets Publicly owned property Institutional property Existing stormwater ponds Stormwater outfalls Large impervious cover with adjacent open land Conveyance system intersected with open space Where roads cross ditches Streets that meet width and slope criteria and include a nearby storm drain.

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48 Step 3. Field Investigation Characterize drainage patterns and retrofit potential at each parcel

49 Take photos, measurements, notes Sketch retrofit and drainage area.

50 Look at Existing Stormwater Infrastructure & Feasibility Factors

51 Understand the Plumbing at the Site

52 Rooftop Connections

53 Follow the Runoff

54 Weep Hole Drainage Chute Eroded Conveyance Grass Channel

55 Available Hydraulic Head Storm Drain Pipe Invert

56 Detention Areas

57 10-year 100-year 2-year

58 Storm drain Storm drain Manholes Curb Drop Inlet

59 Cable Utilities! GAS Water line Sanitary Sewer

60 Stream Impacts Forest Buffers Our friend the beaver. Trees in general

61 High quality wetlands Low quality wetlands

62 Soil Depth Saturated Soils Soil Indicators Compacted Soils

63 Develop Conceptual Design Develop conceptual designs

64 Step 4. Compile Retrofit Inventory

65 Retrofit Inventory Compilation Update parcel-based database with field data Input into master database spreadsheet or similar format

66 Step 5. Evaluation and Ranking Consult with stakeholders Use ranking factors based on predetermined subwatershed objectives Assign weights to ranking factors Develop system to assign scores to individual sites Create a prioritized list

67 Step 6. Subwatershed Analysis

68 Step 7. Final Design and Construction Convert concept to a construction drawing Requires site analysis and construction plan More realistic construction costs come to light

69 Step 8. Inspection, Maintenance and Verification

70 Questions?

71 Initial Verification of Retrofit Installation Localities to verify that retrofits: Installed properly Meets/exceeds design standards Functions hydrologically as designed Initial verification should be provided by the designer or inspector as condition of project completion

72 Retrofit Verification CBP emphasizing verification of BMPs installed for the TMDL The Retrofit Removal Rate is not perpetual Good for 10 years, and can be renewed based on field inspections (5 years for on-site LID retrofits) Use of simple visual indicators

73 Performance Verification Ensure BMP still exists and is providing the pollutant removal it was designed to achieve or if it requires major restoration State BMP Reporting for Bay TMDL MS-4 Permit/ Bay TMDL Once every 9-10 years Trained evaluator Facility BMP Inventory 73

74 Retrofit Tracking

75 Tom s Short Cut Method Evaluate the condition of your legacy stormwater ponds to optimize the nutrient reduction, safety and habitat value of your existing stormwater infrastructure

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78 Retrofit Evaluation Defining Retrofit Pollutant Removal Evaluating Retrofit Cost Individual Retrofits Administering a Local Retrofit Program

79 Retrofit 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

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

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84 Design Examples New Retrofit Facility Constructed Wetland A constructed wetland is built on a federal facility as a retrofit, classified as a ST practice The retrofit storage is estimated to be 1.67 acre-feet Treats runoff from 50 acre residential neighborhood with 40% impervious cover

85 Design Examples New Retrofit Facility Constructed Wetland Using the Standard Retrofit Equation: X = (RS x 12) / IA RS = Retrofit Storage 1.67 ac-ft IA = Impervious Area = 20 acres (1.67 x 12) / 20 = 1.0 inch

86 Design Examples New Retrofit Facility Constructed Wetland Pollutant Removal Efficiencies of the practice TP TN TSS 55% 35% 70%

87 Retrofit Example 1 Constructed Wetland Total Nitrogen Total Phosphorus Suspended Sediment Pounds/acre/year Tons/acre/year IMPERV PERV IMPERV PERV IMPERV PERV MDE Loading Rates Area (acres) Baseline Load Removal Rate Load Removed ac 30 ac 20 ac 30 ac 20 ac 30 ac 500 lbs/yr 57.9 lbs/yr 11.3 tons/yr 35% 55% 66% 175 lbs/yr lbs/yr 7.91 tons/yr * Example using MDE guidance loading rates

88 Questions?

89 The Costs of Retrofitting

90 Retrofit Construction Costs for Existing BMPs (per impervious acre treated) BMP Conversions: BMP Enhancements: BMP Restoration: 5 to 15 K 5 to 10 K 2 to 5 K Less excavation, modify plumbing, own or control land, strong neighborhood support

91 Comparative New Retrofit Construction Costs * (per impervious acre treated) New Retrofits: 12 to 30 K Non-residential LID: 40 to 80 K * Residential LID: 80 to 120 K * Green Streets: 100 to 150 K * * Demonstration project phase, should drop

92 Caveats on Retrofit Cost Numbers Enormous variation within each retrofit category depending on site conditions These estimates represent the 25% easiest Major influence of the prototype effect

93 Breakdown of Retrofit Costs 1. Discovery Costs 2. Project Evaluation Costs 3. Design, Engineering and Permitting 4. Contracting 5. Construction 6. Retrofit Maintenance

94 Discovery Costs Cost to identify candidate sites for potential retrofits Involves desktop GIS analysis and subsequent field investigation Two options: 1. Comprehensive subwatershed evaluation 2. Limited assessment of existing BMP inventory

95 Discovery Costs Usually done by consultant, but can be done in house For a ten square mile subwatershed, plan on: 200 hours for comp subwatershed eval. 40 hours for BMP inventory assessment

96 Project Evaluation Costs Cost to: evaluate project feasibility develop concept design compute reductions and cost Rule of Thumb: 10 to 20 hours per site May requires some engineering review and neighborhood consultation

97 Retrofit Cost Inflators What is Fixed Wetland permitting Off-site haul of excavated materials Sewer or utility relocation Need easements or contested ROW Complicated plumbing (flow splitters) Parking, maintenance of traffic Amenity landscaping Take care in the stream corridor!

98 Design, Engineering and Permitting Costs Typically run be 30 to 50% of retrofit construction cost High end: demonstration projects, refiguring plumbing, unfamiliar practices Low end: Conversion, enhancement or restoration of existing BMPs

99 Contract Administration Costs Assume that 1 FTE is needed for every 1 to 2 million contracted in retrofit capital budget Project bundling, design/build, call contracts, bid incentives and other project management tools can reduce costs and improve quality

100 Tip 1. Develop multiple revenue streams and delivery mechanisms Capital Improvement Budget Stormwater Offset Fees Stormwater Utility Discounts Stormwater Maintenance Budgets Maintenance Enforcement Street Reconstruction Piggyback on Municipal Construction Projects Public/Private Partnerships

101 A slice of restoration Another slice of restoration

102 Frequently Asked Questions

103 Q: Are Regenerative Stormwater Conveyance practices considered retrofits? Yes! Dry RSC practices can be treated as an upland BMP or as a retrofit for treating stormwater runoff Use the RR curve for determining removal rates Wet channel RSC practices are considered to be a stream restoration practice Cabin Branch RSC project

104 Q: What about a Floating Treatment Wetland in an existing Wet Pond? Good question! Currently the focus of a CBP Urban BMP Review Panel Floating Treatment Wetland Photo credit: Sarah White, Clemson University

105 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

106 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

107 Q: What if I want to use a retrofit practice that is does not fall into the current retrofit classification? 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 CMAC Outfall Retrofit Photo credit: Marcus Quigley, OptiRTC

108 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

109 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

110 Other CBP-Approved Urban BMPs to Meet the Bay Pollution Diet 1. New State Performance Standards 2. Redevelopment Credits 3. Residential Stewardship Practices 4. Urban Nutrient Management 5. Stream Restoration 6. Enhanced Erosion and Sediment Control 7. Illicit Discharge Removal 8. Street and Storm Drain Cleaning 9. Shoreline Management 10. Septic System Upgrades 11. FTWs and UTC (this summer)

111 Resources U-1 Urban Stormwater Retrofits Fact Sheet USRM 3: Urban Stormwater Retrofit Practices CWP Stormwater Retrofitting Reconnaissance Videos: Part 1: Part 2: Part 3: Retrofit Expert Panel Report Retrofit FAQ Document

112 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!