Low Impact Development in Western Washington

Transcription

1 TRAINING LOGISTICS Restroom Location Low Impact Development in Western Washington Cell Phones please turn off or set to vibrate to minimize interruptions Alice Lancaster, PE Rebecca Dugopolski, PE May 23, AGENDA Time Topic Length 1:00 1:15 Introductions (Herrera & WSC) 15 min 1:15 2:00 Introduction to LID 45 min 2:00 2:30 LID BMP Details (Part I) 30 min 2:30 3:00 WSU LID Tour 30 min 3:00 3:45 LID BMP Details (Part II) 45 min 3:45 4:00 Break 15 min 4:00 4:15 Case Studies 15 min 4:15 5:00 Tools to Implement LID 45 min INTRODUCTIONS Washington Stormwater Center Kurt Marx, Center for Urban Waters 3 4 Alice Lancaster, PE Rebecca Dugopolski, PE INTRODUCTIONS Introduction to LID Stormwater Impacts PRESENTATION OVERVIEW Stormwater Regulations & Standards Low Impact Development Defined LID Best Management Practices (BMPs) BMP Components & Design Criteria Siting Criteria BMP Performance Construction & O&M Costs 5 6 1

2 Case Studies What can go right? What can go wrong? PRESENTATION OVERVIEW Tools to Implement LID Requirements Hydrologic modeling tools Simplified sizing tools Checklists (O&M and Plan Review) STORMWATER IMPACTS MARINE & FRESH WATER DECLINE Stormwater a primary driver for marine, stream and wetland decline...degradation can occur at very low levels of development. Water quantity and WQ implicated. Structural stormwater approach alone has limitations for protecting water resources. 7 8 STORMWATER IMPACTS STORMWATER IMPACTS URBANIZATION Land with 50% tree cover decreased by 37% in Puget Sound region HYDROLOGIC REGIME CHANGES Urban Rural Satellite images of Puget Sound Dark color in lowland areas indicates clearing of vegetation (Source: American Forests) 9 Hydrograph for Pre- & Post-developed Watersheds: Stormflow frequency and magnitude increase with development 10 STORMWATER IMPACTS STREAM CHANNEL DEGRADATION ADDITIONAL IMPACTS STORMWATER IMPACTS Combined Sewer Overflows Flooding/Capacity Channel impacts: Excessive streambed and stream bank instability / Enlarged cross sectional area / Loss of habitat structure & hydraulic diversity Loss of biotic integrity

3 STORMWATER IMPACTS COMPREHENSIVE SW MGMT PROGRAM Land use planning Standards equal to Ecology s Site plan review Construction site inspections Maintenance Source control Illicit discharges & problem response Public education & involvement Watershed or basin planning Monitoring Stable funding Low impact development From Puget Sound Water Quality Management Plan 13 OVERVIEW Department of Ecology NPDES Municipal SW Permit (Phase I & II) Flow control & treatment standards LID standards & requirements EPA Local Jurisdictions REGULATIONS 14 MUNICIPAL SW PERMIT OVERVIEW Clean Water Act (1972) NPDES Permit Four main categories of NPDES Permits Permit Authority Fishable, swimmable waters, prevent the release of toxics National Pollutant Discharge Elimination System Municipal, Construction, Industrial, Boatyards Delegated to the Washington State Department of Ecology by EPA MUNICIPAL SW PERMIT OVERVIEW Phase I (populations 100,000) Phase II (generally populations >10,000) Issuance date = January 17, 2007 Modification dates = June 17, 2009 and September 1, 2010 (Ph. I only) Original permit term = 5 years (expected effective date of revised permit is currently August 2012) PERFORMANCE STANDARDS (PH I &II) Flow control thresholds PERFORMANCE STANDARDS (PH I &II) Flow control standard Match predeveloped flow duration from ½ 2-year to 50-year flow Predeveloped = forested land cover unless: Historic information shows prairie prior to settlement 40% impervious since 1985 Creek Erosion Protection

4 PERFORMANCE STANDARDS (PH I &II) Runoff treatment thresholds 19 PERFORMANCE STANDARDS (PH I &II) Runoff treatment standard Treat volume from the 24-hour storm with a 6-month return frequency (or infiltrate 91%) Specific treatment required depending on site type and/or location: Basic (TSS) Enhanced (dissolved metals) Phosphorus Oil 20 CURRENT LID REQUIREMENTS PHASE I New Development, Redevelopment & Construction Sites: CURRENT LID REQUIREMENTS PHASE II New Development, Redevelopment & Construction Sites: Must allow non-structural preventative actions and source reduction approaches such as LID techniques. Provisions to allow non-structural preventive actions and source reduction approaches such as LID techniques. Must require non-structural preventive actions and source reduction approaches including LID techniques where feasible (to be defined). Provisions for LID should take into account site conditions, access, and long term maintenance CURRENT LID REQUIREMENTS PHASE I & II Education and Outreach: - LID site design, pervious paving, and retention of forests and mature trees PHASE II LID report (due March 2011): Summary of barriers to LID and measures to address them LID that can be implemented within the permit term Potential or planned LID Goals and metrics to identify, promote, and measure LID use PROPOSED LID RQMNTS (PH I & II) Proposed permit language Thresholds Proposed LID standard Mandatory list of LID BMPs Feasibility considerations Status/schedule

5 PROPOSED LID RQMNTS (PH I & II) New Development, Redevelopment & Construction Sites Review and revise local development related codes, rules, standards, or other enforceable documents to incorporate and require LID principles and BMPs to the maximum extent practicable. The intent of the revisions shall be to make LID the preferred and commonly used approach to site development. PROPOSED LID STANDARD (PH I & II) Single family residential projects with < 10,000 SF effective impervious area and < ¾ acres native conversion: Roof downspout control Dispersion Soil amendment Permeable pavement Bioretention PROPOSED LID STANDARD (PH I & II) 10,000 SF effective impervious area and/or ¾ acres native vegetation conversion Project Type and Location New development or redevelopment inside the UGA or outside UGA on a parcel < 5 acres New development or redevelopment outside UGA on a parcel 5 acres Requirement LID standard or mandatory list (applicant option) LID standard PROPOSED LID STANDARD (PH I & II) LID Performance Standard Match predeveloped flow duration from 8% of the 2-year to 50% of the 2-year* * Flows with a 10% probability of exceedance through flows with a 1% probability of exceedance PROPOSED LID STANDARD (PH I & II) Mandatory List of LID BMPs Roof downspout control Dispersion Soil amendment Infiltration below pavement (permeable pavement or impermeable pavement with stormwater collection and redistribution below) Bioretention (minimum 7.5% of total area for residential dev. and 4% for commercial dev.) Green roof or an impervious roof with runoff routed below pavement (commercial buildings) 29 PROPOSED LID RQMNTS (PH I & II) Feasibility Considerations (Bioretention / Rain Gardens) Landslide hazard areas Slopes > 15% Setback requirements Infiltration rate < 0.15 inches per hour (can use an underdrain) Safety or reliability of pre-existing underground utilities or storage tanks Usable space at re-development sites 30 5

6 PROPOSED LID RQMNTS (PH I & II) Feasibility Considerations (Permeable Pavement) Landslide hazard areas Setback requirements Slope > 5% (asphalt) or > 6% (concrete) Underlying native soils do not meet treatment criteria (can amend with 6 inches of media) High sediment deposition rates (erosion, snow/ice control) Risk of concentrated pollutant spills (gas station, truck stops, industrial chemical storage) Seasonal high groundwater 31 PROPOSED LID RQMNTS (PH I & II) Feasibility Considerations (Green Roofs) Slope > 20% Building cannot technically be designed to accommodate structural load 32 PROPOSED LID RQMNTS (PH I & II) Public Comment Period on LID and Monitoring Language (May 16 June 17, 2011) Draft Permit for Formal Public Comment (October 19, February 3, 2012) Workshops and Public Hearings (December 1, 2011 February 3, 2012) Permit Issued (July 2012), Effective (August 2012) 33 OTHER STANDARDS EPA Combined Sewer Overflow Limits LID Standard: retain the 95th percentile rain event on site (~1 inch SEA-TAC) Local Jurisdictions OTHER AGENCIES Peak flow standards for capacity constrained basins * Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act 34 LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STRATEGY INTEGRATING: site design & planning techniques emphasizing conservation and use of small-scale engineered controls to closely mimic pre-development hydrologic processes. 35 PREDEVELOPED FOREST LOW IMPACT DEVELOPMENT 2005 LID Manual 36 6

7 DEVELOPED CONDITION LOW IMPACT DEVELOPMENT Developed Condition 2005 LID Manual OBJECTIVES LOW IMPACT DEVELOPMENT Reduce the development envelope Reduce impervious surfaces Protect and restore native soils/vegetation Manage SW as close to its origin as possible Reduce concentrated surface flow, minimize stormwater contact with impervious surfaces, and increase stormwater contact with soils and vegetation LID SITE PLANNING & L MINIMIZE DISTURBANCE & LAYOUT MITIGATE DISTURBANCE LID BMPS Minimize Impervious Surface Preserve Native Soils Protect Native Vegetation Infiltration Filtration Storage Evaporation Transpiration Replace Predeveloped Hydrologic Functions LID BMPs = Green Stormwater Infrastructure (GSI) SOIL AMENDMENT Infiltration Filtration Storage Evaporation Transpiration LID BMPS TREES Infiltration Filtration Storage Evaporation Transpiration LID BMPS

8 LID BMPS DISPERSION BIORETENTION (RAIN Infiltration Infiltration Filtration Filtration Storage Storage Evaporation Evaporation Transpiration LID BMPS GARDENS) Transpiration Natural dispersion along Hwy 195, WSU Pullman LID BMPS LID BMPS PERMEABLE PAVEMENT GREEN ROOFS Infiltration Infiltration Filtration Filtration Storage Storage Evaporation Evaporation Transpiration Transpiration Seattle City Hall Park Place LID BMPS RAINWATER HARVESTING Infiltration Filtration Storage Evaporation Transpiration Volume Rdxn without Infiltration LID BMPS LOW IMPACT FOUNDATIONS Infiltration Filtration Storage Evaporation Transpiration Fremont, Seattle Chicago Center for Green Technology

9 LID BMP DETAILS DESIGN, SITING, PERFORMANCE & COST Soil Amendment Retaining & Planting Trees Bioretention Permeable Pavement Green Roofs Rainwater Harvesting REQUIREMENTS Post Construction Soil Quality and Depth BMP T5.13 Every construction site should leave at least 12 of un-compacted soil The upper 8 of soil should have sufficient organic content to support a healthy landscape and soak up most rainfall SOIL AMENDMENT Source: Soils for Salmon REQUIREMENTS SOIL AMENDMENT Post Construction Soil Quality and Depth: Retain native soil and duff wherever possible All areas cleared and graded require 8 soil depth: Organic matter content 10% dry weight ( 5% for turf) Use native topsoil, amend existing soil with compost, or import topsoil blend Subsoil scarified 4 below 8 topsoil layer Protect amended soil from compaction Mulch after planting Maintenance practices to replenish organic content 51 BENEFITS SOIL AMENDMENT Builds soil structure, moisture-holding capacity Increases surface porosity Biofiltration of urban pollutants Improved fertility & plant vigor: Reduced need for fertilizers and pesticides Reduced maintenance costs Increased regrowth of protective canopy Reusing wastes (yard waste, manure, biosolids, construction, land clearing waste) Reduced summer irrigation needs 52 SOIL AMENDMENT GUIDELINES & RESOURCES MANUAL Manual developed regionally with experts 10% organic matter for landscape beds 5% organic matter for turf Develop a Soil Management Plan for each site Choose pre-approved or custom calculated amendment rates Simple field inspection and verification procedures Includes model specs written in CSI and APWA formats 53 SOIL AMENDMENT GUIDELINES & RESOURCES MANUAL Four Options for Soil Management: 1) Leave native vegetation and soil undisturbed, and protect from compaction during construction. 2) Amend existing site topsoil or subsoil with compost to meet the soil organic matter requirements: Till 3 of compost in to an 8 depth for planting beds Till 1.75 of compost in to an 8 depth for turf Scarify subsoil to a 12 depth Source:

10 SOIL AMENDMENT GUIDELINES & RESOURCES MANUAL 3) Stockpile existing topsoil during grading, and replace 8 of topsoil before planting: Amend if needed to meet the organic matter requirement Scarify subsoil to a 12 depth 4) Import a topsoil mix that meets the organic content and depth requirements: Scarify subsoil to a 12 depth or till in some of the topsoil 55 OVERVIEW Trees provide flow control benefits: Transpiration Evaporation Increase Infiltration Benefits vary by: Established or New Tree Type Canopy Size Overlap with Impervious Area TREES 56 RETAINED TREES TREES NEWLY PLANTED TREES TREES Evergreen Min. 6 DBH 20% canopy area (min. 100 sf) Deciduous Min. 6 DBH 10% canopy area (min. 50 sf) Must be within 20 impervious Max credit is 25% imp. area Evergreen Min. 4 height 50 sf / tree Deciduous Min sf / tree Must be within 20 impervious Max credit is 25% imp. area COMPONENTS Pre-Settling / Flow Entrance Ponding Area (earthen depression or impermeable reservoir) Bioretention Soil/Amended Soil BIORETENTION Mulch/compost Vegetation Underdrain (optional) Overflow 59 BIORETENTION PRESETTLING/FLOW ENTRANCE Presettling Reduce clogging potential Larger drainage area/sediment load e.g., filter strip, pre-settling basin, etc. Dispersed/low velocity flow entrance types preferred e.g., vegetated filter strip, wide curb cuts Concentrated flow entrance e.g., piped, rock channel, narrow curb cuts Requires erosion protection (e.g., rock) in entrance Flow entering should be non-erosive ~ less than 1.0 fps 60 10

11 PONDING AREA Size area and ponding depth for standard & drawdown Min freeboard Max planted side slope Max contributing area Infiltration facility? Impermeable Reservoir BIORETENTION Earthen Depression 61 BIORETENTION SOIL Purpose Supports plants & microbes Removes pollutants Options Amend native soils in place Over excavate and place imported soil Minimum soil depth 12 inches for flow control 18/24 inches for water quality treatment BIORETENTION 62 MULCH/COMPOST BIORETENTION Purpose Reduces weed establishment Regulates soil temp & moisture Adds organic matter to soil Attenuates heavy metals Composition Compost in the bottom of the facilities Wood chip mulch composed of shredded or chipped hardwood / softwood on cell slopes Depth Max 3 inches compost or 4 inches wood chips 63 UNDERLYING SOIL Measured Infiltration Rate is short-term rate Design Infiltration Rate is long-term rate Correction factors applied (site variability, # tests, influent quality, maintenance) For soil underlying imported bioretention soil Design rate = Measured rate (no correction!!) BIORETENTION Treatment credits when 91% influent infiltrated through soils meeting Ecology requirements (e.g., bioretention soil) 64 BIORETENTION UNDERDRAINS: WHY/WHEN? Infiltration not permitted Near sensitive infrastructure that may flood Soil infiltration rates not adequate to meet maximum pool and system drawdown rates UNDERDRAINS: WHAT? Seattle Specifications PVC Slotted Pipe BIORETENTION Filter Material (Ag 26) BR Soil BIORETENTION WITH UNDERDRAIN

12 BIORETENTION FILTER FABRIC? PERMEABLE PAVEMENT COMPONENTS Inhibits infiltration Potential for clogging Can use aggregate blanket between soil and underdrain Gradation difference between bioretention soil and native soil is typ. small so no migration of fines Wearing Course Native Underlying Soil Leveling/Choker Course Subsurface Berms Aggregate Storage Reservoir PERMEABLE PAVEMENT WEARING COURSE PERMEABLE PAVEMENT WEARING COURSE Porous Asphalt Pervious Concrete Permeable Interlocking Concrete Pavers Reinforced Grass & Gravel 69 PERMEABLE PAVEMENT AGGREGATE STORAGE RESERVOIR 70 PERMEABLE PAVEMENT SLOPED SUBGRADE Rainfall Minimum aggregate depth sized to: Store and infiltrate stormwater Support design loads Run-on from other areas may be directed to facility Lateral flow along relatively impermeable subbase Rainfall Exfiltration Key : Size Effective Aggregate Depth 71 Wearing Course Aggregate Subbase Subbase slopes 0 2% Can neglect lateral flow Effective storage depth = aggregate thickness 72 12

13 SLOPED SUBGRADE Max. WSE PERMEABLE PAVEMENT Check dam UNDERLYING SOIL PERMEABLE PAVEMENT Design Infiltration Rate Requires Correction d1 Exfiltration Average d2, d2 d2 Design Minimum Correction Factor Not Receiving Run-on 2 Receiving Run-on from Area < twice facility size Receiving Run-on from Area > twice facility size 2 4 Key : Wearing Course Aggregate Check Dam Subbase * Function of slope, check dam height, and check dam spacing Subbase slopes >2% Effective storage depth = average subsurface ponding depth before berm overtopping or overflow* 73 Treatment credits when 91% influent infiltrated through: soils meeting Ecology requirements or imported treatment layer 74 LID TOUR COMPONENTS GREEN ROOFS Plants Drainage Layer Mulch or Fabric Root Barrier Growth Medium (4 min) Waterproof Membrane 75 Filter Fabric Roof Structure 76 GREEN ROOFS GREEN ROOFS Vegetated roofs Living roofs Eco-roofs Roof gardens Portland, Oregon Bend, Oregon BENEFITS Wildlife habitat Improved air quality Social Happier workers Lower stress levels Increased productivity Reduced sick days Noise reduction Economic Energy cost savings Reduce size of HVAC equipment Extend roof membrane life Higher lease rates Multi-function (can be used for stormwater flow control, food growth) City Hall - Seattle Ballard Library - Seattle

14 INTENSIVE 6 of growth medium Trees, shrubs, etc. Often accessible 50+ psf Expanded planting palette Highest cost Highest maintenance GREEN ROOFS Millennium Park Chicago, IL Source: SEMI-INTENSIVE 25% above or below 6 growth medium May be turf/lawn May be accessible or partially accessible psf Moderate planting palette Moderate cost and maintenance GREEN ROOFS Vancouver Public Library Source: EXTENSIVE < 6 growth medium Lightweight Larger areas psf Somewhat limited planting palette Typically inaccessible Lowest maintenance and cost Amenable for retrofits GREEN ROOFS Academy of Sciences San Francisco, CA Source: 81 CISTERN COMPONENTS RAINWATER HARVESTING Downspout Connection Filter Flow Dissipator Overflow Pipe Flow Control Orifice Outlet 82 CISTERNS Above or below ground Tight fitting covers to exclude contaminants and animals Above ground tanks should not allow penetration of sunlight to limit algae growth RAINWATER HARVESTING CISTERNS Fiberglass Polyethylene Concrete Metal Wood RAINWATER HARVESTING Source: PSAT LID Manual 83 Source:

15 RAINWATER HARVESTING RAIN BARREL COMPONENTS Downspout Connection Screened Inlet Overflow (back to the downspout drainage system, to a safe area, or a rain garden) Level Base (packed earth, concrete or rock pad, concrete or wood blocks) Faucet 85 BENEFITS Reduced runoff can help reduce flooding and erosion in small streams by reducing runoff volume Healthier plants rainwater does not contain chlorine and fluoride, both of which can be found in tap water and are not necessary for plant growth. RAINWATER HARVESTING Water savings can conserve water and reduce water bills (savings depend on the storage capacity of the system & proper use and maintenance). 86 USES AND RESTRICTIONS Irrigate lawn and garden areas. Avoid watering vegetables and herbs with water collected from asphaltshingle roofs. Do not use collected water for drinking, cooking, or bathing. RAINWATER HARVESTING To use harvested water for other purposes (toilet flushing, laundry, etc.) refer to: - Georgia Rainwater Harvesting Guidelines (Chapter 5) - Texas Manual on Rainwater Harvesting (Chapter 3) 87 OVERVIEW LID Principles When they apply Large vs. Small Restrictions Setbacks INFILTRATION SITING HIGH POINT, SEATTLE, WA 88 LID PRINCIPLES Manage rain where it falls! Hydrology & SW Managemnt = organizing principle guides site layout Minimize disturbance to vegetation and soil Distribute BR (and other LID practices) across site Smaller facilities, managing water from smaller drainage areas Minimize concentrating flows Locate infiltrating BR in areas with best soils WHEN DO THEY APPLY? Facilities that infiltrate water into underlying native soils City of Seattle Run-on from other areas INFILTRATION SITING Rainfall PERMEABLE PAVEMENT WITH RUNON City of Seattle 89 BIORETENTION WITHOUT UNDERDRAIN 90 15

16 INFILTRATION SITING LARGE SCALE VS SMALL-SCALE Large-scale Infiltration BMPs: infiltration basins, dry wells and injection wells concentrate stormwater flows and infiltrate large volumes at discrete points with high infilt. rates Bioretention & Permeable Pavement: should be small and distributed across a site with a hydrologic regime closer to a natural vegetated condition 91 INFILTRATION SITING RESTRICTIONS (SOURCE: SEATTLE CRITERIA) Infiltration not permitted in: Landslide-prone critical area Steep slopes (and setback above slope) Arterial ROW/dense underground infrastructure Insufficient vertical separation from bottom of facility to the underlying water table, bedrock, etc 3 feet clearance if the contributing area meets or exceeds: 5,000 square feet of pollution-generating impervious surface 10,000 square feet of impervious area ¾ acres of lawn and landscaped area 1 foot clearance for smaller contributing areas 92 INFILTRATION SITING SETBACKS (SOURCE: SEATTLE CRITERIA) Infiltration not permitted within: Setbacks from on site and off site structures: 5 ft from structure w/o basement and 10 ft from structure w/ basement for small sites Structure shall not intersect with a 1:1 slope from the bottom edge of facility for larger sites (no less than small site setback) Setbacks from contaminated soil 100 ft of drinking water supply wells or springs Groundwater protection area 100 ft of septic systems or drain fields 10 ft of underground storage tanks 5 ft from property lines (without agreement) 93 NATIVE SOIL CHARACTERIZATION Why soils affect siting Soil variability Short-term infiltration rates Design infiltration rates 94 WHY NATIVE SOIL AFFECTS SITING Important for infiltrating facilities ONLY Infiltrating facilities sized based on infiltration rates No minimum infiltration rate (most jurisdictions) Bioretention may be used on some till sites Maximum rate for water quality treatment ( 12 in/hr)- achieved with BRS Locate BR in areas with best soils 95 NATIVE SOILS CAN VARY WIDELY!!!!! Site 3 SOIL VARIABILITY Site 1 Site 2 BROADVIEW GREEN GRID, SEATTLE, WA 96 16

17 SITE 1: LOAM SOIL VARIABILITY SITE 2: BEACH SAND SOIL VARIABILITY BROADVIEW GREEN GRID, SEATTLE, WA 97 BROADVIEW GREEN GRID, SEATTLE, WA 98 SITE 3: GLACIAL TILL (HIGH CLAY CONTENT) SOIL VARIABILITY ESTIMATE BY SOIL PROPERTIES SHORT-TERM INFILTRATION RATES USDA Soil Textural Classification ASTM Gradation Testing Not Recommended BROADVIEW GREEN GRID, SEATTLE, WA IN-SITU FIELD MEASUREMENT SHORT-TERM INFILTRATION RATES PILOT INFILTRATION TEST (PIT) SHORT-TERM INFILTRATION RATES Small Scale (typically not accepted by Ecology) EPA Falling Head Double ring infiltrometer test Pilot Infiltration Test (PIT) Ecology Manual Appendix III-D Considering reducing fill depth Seattle Modified Pilot Infiltration Test (PIT) Shorter test period than PIT Appendix E of manual Recommended

18 DESIGN INFILTRATION RATES Design rate is long-term rate Correction factors applied to short-term rate based on: Site variability and number of locations tested Degree of long-term maintenance & influent control to prevent siltation and bio-buildup* * Not required for native soil under imported bioretention soil 103 FACILITY PERFORMANCE PERFORMANCE STANDARDS Flow Control: Non Exempt Receiving Water (Most Creek Basins)- Ecology requirement to match the peaks and duration to predeveloped condition (usually forest) Combined Sewer or Capacity Constrained Basins- Local requirements are typically peak-control based Water Quality: Ecology requirement to treat the 91st percentile of the 24- hour runoff volume Infiltrate 91 percent of the total runoff volume through soil meeting Ecology treatment criteria 104 FACILITY PERFORMANCE BMP CAPABILITIES BMP Flow Control Treatment * Soil Amendment Dispersion X X Retaining & Planting Trees Bioretention X X Bioretention (underdrain) Permeable Pavement X X Green Roofs Rainwater Harvesting * Meets basic, enhanced and phosphorus treatment when infiltrating through soil meeting Ecology treatment requirements 105 X X X X X FACILITY PERFORMANCE BMP CAPABILITIES Soil Amendment Partial Flow Control (combined with partial dispersion) Partial Dispersion Partial Flow Control Full Dispersion* Full Flow Control Full Treatment *65% site preserved in native vegetation & maximum 10% effective impervious area 106 FACILITY PERFORMANCE BMP CAPABILITIES Retained and Newly Planted Trees Partial Flow Control (Impervious surface reduction Credits) TreeType Design Variable Flow Control Credit (Forest Standard) Retained Trees Evergreen 20% canopy area (min 100 sf/tree) Deciduous 10% canopy area (min 80 sf/tree) New Trees Evergreen 50 sf / tree FACILITY PERFORMANCE BMP CAPABILITIES Bioretention with Infiltration Full Flow Control (with permeable soils) Full Treatment (with 18 BRS)* Bioretention without Infiltration (e.g., underdrain & liner/impermeable reservoir) Partial Flow Control Full Treatment (with 18 BRS)* Deciduous 20 sf / tree * Meets basic & enhanced treatment when infiltrates through soil meeting Ecology treatment soil requirements

19 FACILITY PERFORMANCE BMP CAPABILITIES Permeable Pavement Full Flow Control Full Treatment (when native soil meeting Ecology requirements or treatment layer)* Green Roofs Partial Flow Control Rainwater Harvesting Full Flow Control * Meets basic & enhanced treatment when infiltrates through soil meeting Ecology treatment soil requirements 109 CONSTRUCTION COSTS OVERVIEW Vary Depending upon Site Conditions Applicable standards Infiltration opportunities Available space, slopes Site location, material availability Costing Resources for: Rain Gardens Permeable Pavement Green Roofs Rainwater Harvesting (Cisterns and Rain Barrels) 110 RAIN GARDENS Location Self Installation (cost per SF) CONSTRUCTION COSTS Professional Installation (cost per SF) Average Size (SF) Source Great Lakes NA NA 70 Belan & Otto (2004) Wisconsin $ $ NA Edgewood College (2003) Wisconsin $ $ Kassulke (2003) General $ $ NA EPA (2008) Virginia $ $ James City County (2008) Lincoln, NE $ $ NA Lincoln (2008) Salt Lake City, UT $8.83 $16.63 NA Source: WERF LID Cost Calculator RS Means 100 Estimate of Elaborate Garden 111 RAIN GARDENS CONSTRUCTION COSTS Average cost for self installation = $5.15 per SF Average cost for professional installation = $16.05 per SF 112 RAIN GARDEN COMPONENTS CONSTRUCTION COSTS PERMEABLE PAVEMENT CONSTRUCTION COSTS Item Unit Estimated Unit Cost Permeable Pavement Type Cost per SF Excavation CY $8 10 Bioretention media CY $40 60 Filter fabric SY $1 5 Gravel CY $ inch perforated underdrain pipe LF $8 15 Plants each $5 20 Asphalt $ Porous concrete $ Grass/gravel pavers $ Interlocking concrete blocks $ Source: Source:

20 PERMEABLE PAVEMENT CONSTRUCTION COSTS Full stormwater management paving system (drains, reinforced concrete pipes, catch basins, outfalls, and stormwater connects): Conventional asphalt or concrete = $ per SF Permeable pavement = $ per SF PERMEABLE PAVEMENT COMPONENTS CONSTRUCTION COSTS Item Unit Estimated Unit Cost Excavation CY $8 10 Porous asphalt SF $ Porous concrete SF $ Concrete paving blocks SF $5 10 Aggregate CY $30 35 Geotextile fabric SF $ Source: GREEN ROOF COMPONENTS CONSTRUCTION COSTS Item Unit Unit Cost Source Root barrier SF $2.25 RS Means Sedum mat SF $13.25 RS Means Engineered growth media CY $4.00 RS Means Cement walking surface SF $8.50 RS Means Ornamental grasses Each $15 RS Means Annuals Each $2 RS Means Shrubs Each $10 RS Means Labor cost SF $3 8 Peck and Kuhn (2008) Irrigation costs SF $2 4 Peck and Kuhn (2008) Basic vegetation mat SF $2.50 Portland (2008) 5" growing medium SF $2.00 Portland (2008) Cost increase for lifting materials to taller roofs Percentage 10% if >5 stories RS Means Design costs Percentage 5-10% of total cost Peck and Kuhn (2008) Source: GREEN ROOF COMPONENTS CONSTRUCTION COSTS Item Unit Unit Cost Moisture Mat SF $0.50 Protection Board SF $ inch Growing Medium (with gravel drainage) SF $2.00 Plantings (sedums and grasses) SF $2.00 Irrigation System SF $0.50 Plant Establishment (labor cost) SF $0.50 Total Cost of Ecoroof Components SF $5.75 Source: Cost Benefit Evaluation of Ecoroofs (Portland BES 2008) 118 CISTERNS CONSTRUCTION COSTS CISTERNS CONSTRUCTION COSTS Material Size range (gallons) Average cost per gallon Source Steel ,000 $2.51 RS Means Fiberglass 10,000-35,000 $1.33 Manufacturer Concrete 2,000-35,000 $1.66 RS Means HDPE 50-1,500 $1.43 RS Means Location Tank Size (gallons) Cost of Tank Cost of Installation Source Maryland 10,000 $17,300 $9,300 Hicks (2008) Salt Lake City, UT Salt Lake City, UT Source: WERF LID Cost Calculator 8,000 $10,200 $7,000 Miller (2008) 2,000 $3,050 $1,850 Miller (2008) Source: WERF LID Cost Calculator

21 CISTERN COMPONENTS CONSTRUCTION COSTS CISTERN COMPONENTS CONSTRUCTION COSTS Item Unit Estimated Unit Cost Cistern material Small system Large system Rain barrel, excluding accessories and attachments Prefabricated cistern, excluding plumbing Source: Each $ Each $150-10,000 Galvanized steel $225 for 200 gal. $950 for 2,000 gal. Polyethylene $160 for 165 gal. $1100 for 1,800 gal. Fiberglass $660 for 350 gal. $10,000 for 10,000 gal. Ferro-cement Varies by location Varies by location Fiberglass/steel composite $300 for 300 gal. $10,000 for 5,000 gal. Source: O&M COSTS OVERVIEW Different O&M Activities than Conventional Skills sets (e.g., landscaping) Equipment (e.g., watering truck vs. vactor truck) Costing Resources for: Rain Gardens Permeable Pavement Green Roofs Rainwater Harvesting (Cisterns and Rain Barrels) RAIN GARDENS O&M COSTS Annual O&M Cost Maintenance Frequency for 400 SF Item Low Medium High (Medium) Vegetation Every 3 years 1/year 12/year $134 management Replace mulch Every 5 years Every 3 years 1/year $224 Till soil Every 10 years Every 5 years Every 4 years $90 Source: WERF LID Cost Calculator Total $ PERMEABLE PAVEMENT Maintenance Frequency Low Medium High O&M COSTS Annual O&M Cost for 5,000 SF (Medium) Item Inspection, reporting, and Every 3 years Every 3 years 1/year $47 data management Litter & minor debris removal Every 3 years 1/year 12/year $120 Sweeping Every 3 years 1/year 12/year $80 Source: WERF LID Cost Calculator Total $247 GREEN ROOFS Item Inspection, reporting, and data management Vegetation management Maintenance Frequency Low Medium High O&M COSTS Annual O&M Cost for 5,000 SF (Medium) 1/year 2/year 12/year $260 1/year 2/year 6/year $600 Irrigation repair 1/year 2/year 6/year $600 Corrective maintenance Every 5 years Every 2 years 1/year $1,243 Soil replacement Every 5 years Every 2 years 1/year $494 Total $3, Source: WERF LID Cost Calculator

22 GREEN ROOFS Source Annual O&M Cost (per SF) O&M COSTS Annual O&M Cost for 5,000 SF Literature range $ $300 6,250 Portland-specific range $0.025 $125 Source: Cost Benefit Evaluation of Ecoroofs (Portland BES 2008) CISTERNS Item Inspection, reporting, and data management Cleaning inflow filters Maintenance Frequency Low Medium High O&M COSTS Annual O&M Cost for 5,000 gallons (Medium) 1/year 2/year 12/year $260 1/year 2/year 12/year $480 Tank disinfection Every 2 years 1/year 2/year $240 Intermittent system maintenance Every 3 years Every 3 years Every 3 years $130 Pump replacement Every 5 years Every 5 years Every 5 years $198 Total $1,308 Source: Source: WERF LID Cost Calculator 128 BREAK 129 CASE STUDIES KING COUNTY MILITARY ROAD IMPVMNT PROJECT 1,100 SY of porous concrete sidewalks 285-ft long (0.12-acre) rain garden Construction = $1.1 million Ecology grant = $424,000 Transportation Imprvmnt Board grant = $640,000 Saved $44,000 over conventional treatment LowImpactDevelopment_MilitaryRd.aspx 130 CASE STUDIES COST BENEFIT EVALUATION OF ECOROOFS (PORTLAND) CASE STUDIES COST BENEFIT EVALUATION OF ECOROOFS (PORTLAND) Private Net benefit (over 40 years) is $404,000 (in 2008 $) In the near term, installation costs outweigh the benefits (shifts at 20 year mark) Cooling and heating reductions = $7,500 over 5 years and $43,500 over 40 years &c=50818 Public Net benefit (over 40 years) is $191,121 (in 2008 $) Immediate benefit due to reduced stormwater system improvements ($60,700) Long-term benefits include reduced O&M costs, carbon reduction, improved air quality, and habitat creation

23 WILSON MOTORS Brownfield Development Auto Recycling Yard Car Dealership Bellingham Whatcom Creek 303(d) List 2020 Engineering Conventional Design LID Design CASE STUDIES CASE STUDIES WILSON MOTORS Site Area 7.2 acres Conventional Design Impervious Asphalt Cement Catch Basins & Conveyance Pipes Cartridge Filters & Vaults LID Design Pervious Concrete (1.7 acres) High Traffic Areas Permeable Asphalt (2.1 acres) Low Traffic Areas Clay Soils so Detention in Quarry Spalls Perimeter Bioretention (0.7 acres) WILSON MOTORS Site Area 7.2 acres Conventional Design Impervious Asphalt Cement Catch Basins & Conveyance Pipes Cartridge Filters & Vaults LID Design CASE STUDIES $465,000 More expensive Pervious Concrete (1.7 acres) High Traffic Areas Permeable Asphalt (2.1 acres) Low Traffic Areas Clay Soils so Detention in Quarry Spalls Perimeter Bioretention (0.7 acres) WILSON MOTORS CASE STUDIES WILSON MOTORS CASE STUDIES WILSON MOTORS CASE STUDIES

24 CASE STUDIES CASE STUDIES SEATTLE SEASTREETS SEATTLE SEASTREETS 660 LF 2.3 acre drainage Goal: flow control via live storage Constructed years of continuous monitoring 99% reduction in total runoff volume CASE STUDIES CASE STUDIES SEATTLE SEASTREETS SEATTLE SEASTREETS Before After WHAT CAN GO WRONG? Poor Site Characterization Poorly draining soils High/perched groundwater Poor Construction Methods Over compaction Sedimentation -> clogging Lack of construction oversight Lack of Proper O&M CASE STUDIES FACILITY SIZING HYDROLOGIC MODELING Use of mathematical equations to estimate runoff as a result of - weather patterns, - land use, and - topography

25 FACILITY SIZING HYDROLOGIC MODELING Single-Event: Appropriate for conveyance sizing Continuous Simulation Models: Required for sizing flow control or water quality BMPs Simplified Sizing Tools: Size BMP as function of drainage area, mean annual precipitation & soil conditions Prescribed design criteria Currently available in many jurisdictions (e.g., Seattle, Bellevue, Edmonds, Kitsap County, Pierce County) FACILITY SIZING SINGLE-EVENT METHODS Input Single Storm Event Output Peak Flow Rates Typical Methods SCS SBUH StormShed SWMM HEC-HMS Runoff (cfs) Time (hrs) Rainfall (in) Unmit. Runoff (cfs) Mit. Runoff (cfs) Rainfall (inches) FACILITY SIZING CONTINUOUS MODELS Input Long-Term Rainfall & Evaporation Data Output Continuous Runoff, Peak Flows, Duration Typical Programs SCS HSPF WWHM MGS Flood KCRTS SWMM SUSTAIN Runoff (cfs) Time (hrs) Rainfall (in) Unmit. Runoff (cfs) Mit. Runoff (cfs) Rainfall (inches) FACILITY SIZING CONTINUOUS MODELS MGSFlood Western Washington Hydrology Model (WWHM) LID BMP Modules PROJECT BACKGROUND Grant of Regional or Statewide Significance (GROSS grant) from Ecology Project Partners Kitsap County Thurston County Pierce County Kitsap HBA SIMPLIFIED LID SIZING TOOL City of Seattle City of Bellevue City of Everett City of Issaquah City of Sammamish Sizing Tool Available in July SIZING TOOL OVERVIEW SIMPLIFIED LID SIZING TOOL Sizing tool for LID BMPs as a function of: Site precipitation region & mean annual precip Contributing impervious area Predominant site soil type (till or outwash) Native soil design infiltration rate Assist developers & reviewers to size/ design LID without continuous modeling Reduce barriers to LID implementation

26 TOOL APPLICABILITY SIMPLIFIED LID SIZING TOOL Lowland areas of Western WA Up to 1,500 feet above sea level Higher elevations impacted by snow accumulation/melt Projects subject to selected standards: Ecology predeveloped forest duration standard (match 50% of 2-year to 50-year to forest condition) Ecology treatment standard for infiltration BMPs (infiltration 91% through soil meeting requirements) Kitsap County predeveloped recharge standard (Kitsap County only) 151 SIMPLIFIED LID SIZING TOOL LID BMPS Bioretention* with 3:1 side slopes (3-, 6- & 12-in ponding) Bioretention with vertical walls (6- & 12-in ponding) Permeable pavement* Low slope (up to 2% subgrade slope) Higher slope (>2 to 5% subgrade slope) w/ measures to create subsurface ponding Green roof w/ runoff routed to downgradient bioretention cell * No underdrain/liner 152 SIMPLIFIED LID SIZING TOOL LID BMPS Bioretention* with 3:1 side slopes (3-, 6- & 12-in ponding) Bioretention with vertical walls (6- & 12-in ponding) Permeable pavement* Low slope (up to 2% subgrade slope) Higher slope (>2 to 5% subgrade slope) w/ measures to create subsurface ponding Green roof w/ runoff routed to downgradient bioretention cell * No underdrain/liner Flow Control & Treatment Treatment Only Flow Control Only 153 Configuration Square & Linear Bottom Area Vertical Walls with Underdrain SIMPLIFIED LID SIZING TOOL BIORETENTION DESIGN REQUIREMENTS Design Requirements Bottom area = flat Bottom Shape (square or 2 wide) Side slopes = 3:1 Bioretention soil depth =12 inches (flow control) and18 inches (WQ treatment) Bioretention soil shall meet the Ecology treatment soil requirements Bioretention soil shall have a minimum porosity of 40% and a minimum design infiltration rate of 3 in/hr Drainage area to an individual facility 5,000 sf No underdrain Ponding depth as specified = 3, 6 or 12 inches Same as above, except with vertical walls and underdrain 154 Western Puget Sound SIMPLIFIED LID SIZING TOOL PRECIPITATION REGIONS SIMPLIFIED LID SIZING TOOL SIMPLIFIED LID SIZING TOOL SIZING RELATIONSHIPS Puget West Sites with 52 Annual Rainfall Western Coastal Region Vancouver Castle Rock Corridor Eastern Puget Sound 155 Bioretention Bottom Area (sf) Bioretention Cell (6" ponding) Sized for Predeveloped Forest Std 5,000 Infilt Rate = 0.25 inhr y = 0.420x 4,000 Infilt Rate = 0.50 in/hr y = 0.293x 3,000 Infilt Rate = 1.0 in/hr 2,000 y = 0.210x 1, ,000 4,000 6,000 8,000 10,000 Contributing Impervious Area (sf)

27 SIMPLIFIED LID SIZING TOOL SIZING FACTORS Puget West Sites with 52 Annual Rainfall Bioretention Cell (6" ponding) Sized for Predeveloped Forest Std SIMPLIFIED LID SIZING TOOL SIZING FACTORS Puget West Sites with 52 Annual Rainfall Bioretention Cell (6" ponding) Sized for Predeveloped Forest Std Bioretention Bottom Area (sf) 5,000 Infilt Rate = 0.25 inhr 4,000 Infilt Rate = 0.50 in/hr 3,000 Infilt Rate = 1.0 in/hr 2,000 1, ,000 4,000 6,000 8,000 10,000 Contributing Impervious Area (sf) y = 0.420x y = 0.293x y = 0.210x BR Area = 0.21 x Imp. Area Bioretention Bottom Area (sf) 5,000 4,000 3,000 2,000 1,000 0 Infilt Rate = 0.25 inhr Infilt Rate = 0.50 in/hr Infilt Rate = 1.0 in/hr Sizing Factors 0 2,000 4,000 6,000 8,000 10,000 Contributing Impervious Area (sf) y = 0.420x 42% y = 0.293x 29.3% y = 0.210x 21% BR Area = SF x Imp. Area SIMPLIFIED LID SIZING TOOL SIZING EQUATIONS All Puget West Sites SIMPLIFIED LID SIZING TOOL SIZING RELATIONSHIPS Puget East Sites with 48 Annual Rainfall Sizing Factor 60% 50% 40% 30% 20% 10% 0% Bioretention Cell (6" ponding) Sized for Predeveloped Forest Std Infilt Rate = 0.25 in/hr Infilt Rate = 0.5 in/hr Infilt Rate = 1.0 in/hr Slope (M) Sizing Y-Intercept (B) Factors y = x y = x y = x BR Area = Imp. Bioret Area Area x [(M = SF x Precip) x Imp. + Area B] Mean Annual Precipitation (inches) Sizing Factor Bioretention Bottom Area (sf) 140 Bioretention Cell (6 ponding) Sized for Water Quality Std 120 I = 0.25 (6 in ponding) 100 I = 0.5 (6 in ponding) y = 5E-06x x I = 1.0 (6 in ponding) y = 3E-06x x 40 y = 1E-06x x ,000 2,000 3,000 4,000 5,000 Contributing Impervious Area (sf) Predeveloped condition for flow control: forest on till & forest on outwash Design infiltration rates vary by soil type BMP and BMP: Sites Predominantly Underlain by: Bioretention (3-inch ponding) Bioretention (6-inch ponding) Bioretention (12-inch ponding) Permeable Pavement Surfaces SIMPLIFIED LID SIZING TOOL SOIL & INFILTRATION RATES Till Soils (in/hr) Outwash Soils (in/hr) X X X X X X X X -- X X X X X X X X X X X 161 BMP(s) Bioretention (square w/ 3:1 side slopes) Bioretention (square w/ 3:1 side slopes) Bioretention (square w/ 3:1 side slopes) Bioretention (linear w/ 3:1 side slopes) Bioretention (linear w/ 3:1 side slopes) Design Configuration SIMPLIFIED LID SIZING TOOL BIORETENTION CONFIGURATIONS Flow Control Trtmnt Till Infiltration Rates (in/hr) Outwash Infiltration Rates (in/hr) inch ponding X X x x inch ponding X X x x x x x x 12-inch ponding X X -- x x x x x 6-inch ponding X X x x x x x x 12-inch ponding X X -- x x x x x Bioretention (vertical wall 6-inch ponding with underdrain) NA X NA NA Bioretention (vertical wall 12-inch ponding with underdrain) NA X NA NA

28 SIMPLIFIED LID SIZING TOOL SIMPLIFIED LID SIZING TOOL OTHER BMPS PREVIEW BMP(s) Design Configuration Flow Control Trtmnt Till Infiltration Rates (in/hr) Outwash Infiltration Rates (in/hr) Retained Tree Evergreen & Deciduous X NA NA NA Newly Planted Tree Evergreen & Deciduous X NA NA NA Low-Slope Permeable Pavement Surface Permeable Pavement with subsurface berms Green Roof to Bioretention 2% subgrade slope X -- x x x x x x > 2-5% subgrade slope to bioretention 4-inch media to bioretention (6- or 12-inch) X x x x x x X -- x x x x x x AVAILABLE FOR MULTIPLE JURISDICTIONS Seattle WSU Ecology Pierce County Tacoma Redmond Bellevue O&M CHECKLISTS O&M CHECKLISTS SEATTLE (BIORETENTION CELLS & PLANTERS) Components Vegetation Mulch Noxious weeds Required Inspection Frequency Annually Monthly (March Sept.) Condition when Maintenance Required Bare spots (without much cover) are present or mulch depth less than 2 inches. Listed noxious vegetation is present. See King County noxious weed list: aws.htm Action Required Replenish mulch to cover bare spots and augment to minimum depth of 3 inches. By law, noxious weeds (class A&B) must be removed, bagged and disposed as garbage immediately. Reasonable attempts must be made to remove and dispose of class C noxious weeds. It is strongly encouraged that herbicides and pesticides not be used in order to protect water quality. Satisfactory Unsatisfactory Comments Weeds Monthly Weeds are present. Do not use herbicides or pesticides in order to protect soil microbes SEATTLE (PERMEABLE PAVEMENT) Components Required Inspection Frequency Condition when Maintenance Required Action Required O&M CHECKLISTS Satisfactory Unsatisfactory Comments SEATTLE (GREEN ROOFS) Components Required Inspection Frequency Condition when Maintenance Required Action Required O&M CHECKLISTS Satisfactory Unsatisfactory Comments Surface Soil/Growth Medium Permeable pavements, all Annually Ongoing Infiltration capacity of surface restricted due to clogging. None. Maintenance to prevent clogging with fine sediment. Remove sediment and debris. Maintenance methods include use of sidewalk sweepers equipped with vacuums, and brushes to remove surface debris during dry season. Use industrial pressure washer to restore permeability. Anticipate maintenance one to two times annually. Prohibit use of sand and sealant application and protect from construction runoff. Growth medium Growth medium Fallen leaves/debris Annually Annually B, W Water does not permeate growth media (runs off soil surface). Growth medium thickness is less than design thickness (due to erosion and plant uptake) Fallen leaves or debris are present. Aerate or replace medium Supplement growth medium to design thickness Remove/dispose Annually None. Remove sediment, debris, vegetation and any compacted materials such as trash

29 WSU-PUYALLUP (BIORETENTION) O&M CHECKLISTS WSU-PUYALLUP (PERMEABLE PAVEMENT) O&M CHECKLISTS WSU-PUYALLUP (RAINWATER HARVESTING) O&M CHECKLISTS WSU-PUYALLUP (GREEN ROOFS) O&M CHECKLISTS AVAILABLE FOR MULTIPLE JURISDICTIONS Ecology Seattle Pierce County Tacoma Redmond Bellevue PLAN REVIEW CHECKLISTS PLAN REVIEW CHECKLISTS DEPARTMENT OF (MINIMUM RQMNTS)

30 PIERCE COUNTY PLAN REVIEW CHECKLISTS TACOMA PLAN REVIEW CHECKLISTS REDMOND PLAN REVIEW CHECKLISTS SEATTLE (BIORETENTION) PLAN REVIEW CHECKLISTS RESOURCES CONTACT INFORMATION Low Impact Development Technical Guidance Manual for Puget Sound Rain Garden Handbook for WWA Homeowners Seattle Public Utilities GSI Seattle Stormwater Manual Seattle Right-of-Way Improvements Manual Portland Sustainable Stormwater Georgia Rainwater Harvesting Guidelines Texas Manual on Rainwater Harvesting ALICE LANCASTER, PE phone: REBECCA DUGOPOLSKI, PE phone: