Low Impact Development Short Course for Developers and Builders

Transcription

1 Low Impact Development Short Course for Developers and Builders Location: Impact Hub, Seattle, WA Date: October 19, 2017 Time: 10:00 a.m. to 2:00 p.m. Module: 7.0 Time Topic 10:00 10:15 Introduction to course and instructors Overview of program Agenda Learning objectives Logistics 10:15 10:30 Background (A. Castle) Why LID? (the development community perspective) 10:30 11:30 NPDES Municipal Stormwater Permit (R. Dugopolski) Phase I permit Phase II permit Minimum requirements o Overview of all minimum requirements o Focus on Minimum Requirement #5 List #1 and #2 LID performance standard Hands on exercise Infeasibility criteria Statewide LID Training Program 1

2 Low Impact Development Short Course for Developers and Builders Time Topic 11:30 12:15 Assessing LID site feasibility prior to purchase (M. Miller) Building the team for site assessment and feasibility Site assessment tools and interpretation o Office reconnaissance o Field assessment (geology, hydrology) Site layout principles 12:15 1:00 Lunch (on your own) 1:00 1:30 LID project case study (C. Hinman and M. Miller) Meadow on the Hylebos 1:30 2:00 Q&A and wrap up Statewide LID Training Program 2

3 Statewide LID Training Program Rebecca Dugopolski, PE Senior Engineer Curtis Hinman Senior Scientist Key project experience: Research specialist in the performance and design of LID practices. Matt Miller Principal Geotechnical Engineer INSTRUCTORS Key project experience: Stormwater monitoring, design, and NPDES Permit compliance Key project experience: Geotechnical designer for the sub surface elements of LID, including infiltration and bio filtration media. 2 1 introduction 2 why LID (developer community perspective) 3 4 assess site feasibility and layout permits and minimum requirements case study Q&A and wrap up AGENDA 3 1

4 INTRODUCTORY INTERMEDIATE ADVANCED OVERVIEW OF PROGRAM Introduction to LID for Inspection & Maintenance Staff Intermediate LID Topics: NPDES Phase I & II Requirements Advanced Topics for Long term LID Operations: Bioretention Advanced Topics in LID Design: Hydrologic Modeling Intermediate LID Design: Bioretention Advanced Topics for Long term LID Operations: Permeable Pavement Advanced Topics in LID Design: Bioretention Media and Compost Amended Soils Intermediate LID Design: Permeable Pavement Advanced Topics in LID Design: Bioretention Developer LID Course Intermediate LID Design: Site Assessment, Planning & Layout Advanced Topics in LID Design: Permeable Pavement Intermediate LID Design: Rainwater Collection Systems & Vegetated Roofs Advanced Topics in LID Design: Site Assessment, Planning & Layout Intermediate LID Design: Hydrologic Modeling Advanced Topics in LID Design: Rainwater Collection Systems & Vegetated Roofs 4 INTRODUCTORY INTERMEDIATE ADVANCED OVERVIEW OF PROGRAM Introduction to LID for Inspection & Maintenance Staff Intermediate LID Topics: NPDES Phase I & II Requirements Advanced Topics for Long term LID Operations: Bioretention Advanced Topics in LID Design: Hydrologic Modeling Intermediate LID Design: Bioretention Advanced Topics for Long term LID Operations: Permeable Pavement Advanced Topics in LID Design: Bioretention Media and Compost Amended Soils Intermediate LID Design: Permeable Pavement Advanced Topics in LID Design: Bioretention Developer LID Course Intermediate LID Design: Site Assessment, Planning & Layout Advanced Topics in LID Design: Permeable Pavement Intermediate LID Design: Rainwater Collection Systems & Vegetated Roofs Advanced Topics in LID Design: Site Assessment, Planning & Layout Intermediate LID Design: Hydrologic Modeling Advanced Topics in LID Design: Rainwater Collection Systems & Vegetated Roofs 5 LEARNING OBJECTIVES 1. Identify permit requirements and understand the regulatory process for designing and implementing LID projects. 2. Gain an understanding of overall site assessment and basic layout principles. 3. Compare LID and conventional site assessment and design processes. 6 2

5 LOGISTICS SCHEDULE 4 hour training with 45 minute lunch OTHER LOGISTICS Restroom location Lunch on your own Turn off cell phones Sign in and sign out 7 1 introduction 2 why LID (developer community perspective) 3 4 assess site feasibility and layout permits and minimum requirements case study Q&A and wrap up AGENDA 8 WHY LID DEVELOPER COMMUNITY PERSPECTIVE 9 3

6 WHY LID DEVELOPER COMMUNITY PERSPECTIVE 10 WHY LID DEVELOPER COMMUNITY PERSPECTIVE Conventional End of the Pipe Control Maintaining Peak Discharge Only Very Limited Control on Small Storms Stuck in the 60 s Low-Impact Source Control Mimic Pre Development Hydrologic Conditions Full Control on Small Storms Pollution Prevention 11 WHY LID DEVELOPER COMMUNITY PERSPECTIVE Development/Construction Costs Comparison 12 4

7 WHY LID DEVELOPER COMMUNITY PERSPECTIVE Development/Construction Costs Comparison 13 WHY LID DEVELOPER COMMUNITY PERSPECTIVE WWHM3: Flow Credits Rain Garden Modeling Results 14 WHY LID DEVELOPER COMMUNITY PERSPECTIVE Good Drainage Paradigm 15 5

8 WHY LID DEVELOPER COMMUNITY PERSPECTIVE Roadways, Paved Surfaces and Turf Used to Collect and Convey Runoff Good Drainage 16 WHY LID DEVELOPER COMMUNITY PERSPECTIVE Stormwater Prison 17 WHY LID DEVELOPER COMMUNITY PERSPECTIVE 18 6

9 WHY LID DEVELOPER COMMUNITY PERSPECTIVE Small Controls 19 1 introduction 2 why LID (developer community perspective) 3 4 assess site feasibility and layout permits and minimum requirements case study Q&A and wrap up AGENDA 20 PERMITS AND MINIMUM REQUIERMENTS NPDES MUNICIPAL STORMWATER PERMIT National Pollutant Discharge Elimination System (NPDES) Municipal Stormwater Permits ( permit cycle) Municipal Stormwater Permittees in Washington State Phase I Permittees Western Washington Phase II Permittees Eastern Washington Phase II Permittees Seattle Tacoma Clark County King County Pierce County Snohomish County 82 Cities 5 Counties 18 Cities 5 Counties Secondary Permittees: Approximately 45; such as ports and universities To see a listing of permittees visit

10 NPDES MUNICIPAL STORMWATER PERMIT: Minimum Requirements (MRs) 1. Preparation of Stormwater Site Plans 2. Construction Stormwater Pollution Prevention Plan (SWPPP) 3. Source Control of Pollution 4. Preservation of Natural Drainage Systems and Outfalls 5. On Site Stormwater Management 6. Run off Treatment 7. Flow Control 8. Wetlands Protection 9. Operations and Maintenance 22 NPDES MUNICIPAL STORMWATER PERMIT: MR #1 MR #1 Preparation of Stormwater Site Plans Prepare a Stormwater Site Plan for local governmental review in accordance with Volume I, Chapter 3 of the Stormwater Management Manual for Western Washington (SWMMWW) 23 NPDES MUNICIPAL STORMWATER PERMIT: MR #2 and MR #5 MR #2 Construction SWPP New element #13 is now required by Construction Stormwater General Permit (CSWGP): Protect LID BMPs from sediment and compaction MR #5 On site Stormwater Management Infiltrate, disperse, and retain runoff on site to the extent feasible Lotus Springs. Photo: Curtis Hinman 24 8

11 NPDES MUNICIPAL STORMWATER PERMIT: MR #6, #7, and #9 MR #6 Runoff Treatment Provide water quality treatment for pollutiongenerating areas MR #7 Flow Control Control flow peaks and flow durations MR #9 Operations and Maintenance Provide an operations and maintenance manual for all proposed stormwater treatment and flow control BMPs/facilities 25 NPDES MUNICIPAL STORMWATER PERMIT: On Site Stormwater Management BMPs Includes the following LID BMPs: Rain Gardens (BMP T5.14A) Bioretention (BMP T5.14B) Permeable Pavement (BMP T5.15) Vegetated Roofs (BMP T5.17) Downspout Full Infiltration (BMP T5.10A) Downspout Dispersion (BMP T5.10B) Concentrated Flow Dispersion (BMP T5.11) Sheet Flow Dispersion (BMP T5.12) Compost amended soils (BMP T5.13) 26 NPDES MUNICIPAL STORMWATER PERMIT: MR #5 New Development Thresholds Min. Requirements #1 #9: > 5,000 sq. ft. new and replaced hard surface area*, or >3/4 acre vegetation to lawn/landscape, or >2.5 acres native vegetation to pasture Min. Requirements #1 #5: > 2,000 sq. ft. new and replaced hard surface area, or > 7,000 sq. ft. land disturbance *Note: additional thresholds for replaced hard surfaces apply to application of Min. Requirements #6 and #7 27 9

12 NPDES MUNICIPAL STORMWATER PERMIT: MR #5 Redevelopment Thresholds Min. Requirements #1 #9: > 5,000 sq. ft. new hard surface area*, or >3/4 acre vegetation to lawn/landscape, or >2.5 acres native vegetation to pasture Min. Requirements #1 #5: > 2,000 sq. ft. new and replaced hard surface area, or > 7,000 sq. ft. land disturbance *Note: additional thresholds for replaced hard surfaces apply to application of Min. Requirements #6 and #7 28 NPDES MUNICIPAL STORMWATER PERMIT: MR #5 Implementation options: List #1 List #2 LID Performance Standard SEA Street 29 NPDES MUNICIPAL STORMWATER PERMIT: MR #5 MR #5 applies to: Projects triggering MR #1 #5 only List #1 or LID Performance Standard Applies Projects triggering MR #1 #9 List #2 or LID Performance Standard Applies Outside UGA ( 5 acres) LID Performance Standard Applies 30 10

13 MINIMUM REQUIREMENT #5: List Option Lawn and Landscaped Areas Roofs Other Hard Surfaces Consider all the BMPs in the order listed and use the first BMP that is considered feasible. 31 MINIMUM REQUIREMENT #5: List #1 Lawn and Landscaped Areas Roofs Other Hard Surfaces 1. Soil Quality and Depth (BMP T5.13) 1. Full Dispersion or Downspout Full Infiltration (T5.30 or T5.10A) 2. Rain Gardens or Bioretention (T5.14A or B) > 5% of drainage area 3. Downspout Dispersion Systems (T5.10B) 4. Perforated Stub out Connections (T5.10C) 1. Full Dispersion (T5.30) 2. Permeable Pavement, Rain Gardens, or Bioretention (T5.15, T5.14A, T5.14B) Rain Garden or Bioretention area > 5% of drainage area 3. Sheet Flow Dispersion, or Concentrated Flow Dispersion (T5.12 or T5.11) 32 MINIMUM REQUIREMENT #5: List #2 Lawn and Landscaped Areas Roofs Other Hard Surfaces 1. Soil Quality and Depth (BMP T5.13) 1. Full Dispersion or Downspout Full Infiltration (T5.30 or T5.10A) 2. Bioretention (T5.14B) > 5% of drainage area 3. Downspout Dispersion Systems (T5.10B) 4. Perforated Stub out Connections (T5.10C) 1. Full Dispersion (T5.30) 2. Permeable Pavement (T5.15) 3. Bioretention (T5.14B) > 5% of drainage area 4. Sheet Flow Dispersion, or Concentrated Flow Dispersion (T5.12 or T5.11) 33 11

14 MINIMUM REQUIREMENT #5: LID Performance Standard Match pre developed durations from 8% of the 2 year peak flow to 50% of the 2 year peak flow Flow Control Standard addresses higher, less frequent stormwater flows Flow Control LID LID Performance Standard addresses lower, more frequent stormwater flows Source: Ecology SWMMWW Presentation 34 EXERCISE 35 MINIMUM REQUIREMENT #5: INFEASIBILITY CRITERIA The feasibility of each LID BMP is determined by: 1. Infeasibility Criteria (bioretention, rain gardens, permeable pavement, downspout infiltration) Some infeasibility criteria require a geotechnical evaluation and written recommendation 2. Design Criteria 3. BMP Limitations 4. Competing Needs Criteria (Volume V, Chapter 5) 36 12

15 MINIMUM REQUIREMENT #5: Infeasibility Criteria: Bioretention Requires site geotech evaluation & written recommendation Erosion, slope failure, or flooding Threaten pre existing underground utilities, structures, roads No safe overflow pathway Threaten existing below grade basements or shoreline structures Source: Ecology SWMMWW Presentation 37 MINIMUM REQUIREMENT #5: Infeasibility Criteria: Bioretention Criteria not requiring justification, but possibly professional services Where not compatible with surrounding drainage system government decision Where facility would be in an area designated as an erosion hazard or landslide hazard Within 50 feet from top of slopes that are greater than 20% and over 10 feet of vertical relief Within 10 feet of small onsite disposal drainfield, including reserve areas On a slope 8% Based on local government geographic designation of high groundwater or inadequate infiltration rates ( preponderance of evidence ) 38 MINIMUM REQUIREMENT #5: Infeasibility Criteria: Bioretention Criteria not requiring justification, but possibly professional services Within certain areas with soil or groundwater contamination Within 100 feet of a closed or active landfill Within 100 feet of a drinking water well, or spring used for drinking water Infiltration < 0.30 inches/hour Where less than the minimum vertical separation to groundwater or other impervious layer 39 13

16 MINIMUM REQUIREMENT #5: Infeasibility Criteria: Permeable Pavement Requires site geotech evaluation & written recommendation Erosion, slope failure, or flooding Where adjacent impervious pavements compromised Threaten below grade basements Fill soils that can be unstable when saturated Excessively steep slopes meeting certain conditions Threaten pre existing underground utilities tanks, road subgrades Inadequate strength for heavy loads at industrial facilities 40 MINIMUM REQUIREMENT #5: Infeasibility Criteria: Permeable Pavement Criteria not requiring justification, but possibly professional services Area designated as erosion or landslide hazard Within 50 feet from top of slopes greater than 20% Known soil or groundwater contamination Fill soils that can be unstable when saturated At multi level parking garages and over culverts & bridges Where saturated conditions within 1 foot of bottom of base course 41 MINIMUM REQUIREMENT #5: Infeasibility Criteria: Permeable Pavement Criteria not requiring justification, but possibly professional services Roads that receive more than very low traffic volumes and more than very low truck traffic (> 400 vehicles on average daily and through truck traffic) Native soils don t meet soil suitability criteria Infiltration < 0.30 inches/hour Soils unsuitable for loads when saturated Replacing impervious unless non pollutiongenerating impervious surface over soil > 4 inches/hour 42 14

17 MINIMUM REQUIREMENT #5: Infeasibility Criteria: Permeable Pavement Criteria not requiring justification, but possibly professional services In high use sites Areas with industrial activity Where concentrated spill risk is higher Routine heavy sand applications in frequent snow zones Based on local government geographic designation of high groundwater or inadequate infiltration rates ( preponderance of evidence ) 43 1 introduction 2 why LID (developer community perspective) 3 4 assess site feasibility and layout permits and minimum requirements case study Q&A and wrap up AGENDA 44 ASSESS SITE FEASIBILITY AND LAYOUT BUILD THE TEAM Owner/Developer Public Agency Reviewers Site Reviewers Engineer/Architect Community Stakeholders Funding Partners Maintenance Staff Insurance/Other? 45 15

18 ASSESS SITE FEASIBILITY AND LAYOUT BUILD THE TEAM OWNER/DEVELOPER Project Proponent Selects team Drives project Includes: Land Owners / Investors Contractors 46 ASSESS SITE FEASIBILITY AND LAYOUT BUILD THE TEAM PUBLIC AGENCY REVIEWERS Represents interest of the public Ensures regulations are followed Includes Land use planners Transportation planners and engineers Utility engineering and operations Stormwater management Fire Marshall Note: engage local jurisdiction early in the site scoping and design process! 47 ASSESS SITE FEASIBILITY AND LAYOUT BUILD THE TEAM SITE REVIEWERS Assess and interpret site conditions Provide maps and design data Review designs Interpret applicability of regulatory requirements for the team Includes Surveyor Geotechnical engineer Hydrogeologist Wetland/wildlife biologist Arborist On site septic designer 48 16

19 ASSESS SITE FEASIBILITY AND LAYOUT BUILD THE TEAM ENGINEERS AND ARCHITECTS Coordinate with site reviewers Advise owner on feasibility of certain designs Provide design for horizontal and vertical construction systems Prepare plans, specifications and technical reports for permitting Includes Civil engineer Architect Landscape architect On site septic designer 49 ASSESS SITE FEASIBILITY AND LAYOUT BUILD THE TEAM STAKEHOLDERS, PARTNERS, MAINTENANCE, AND OTHERS Stakeholders review and comment on project proposal Funding partners provide capital and review project economic feasibility Maintenance staff review designs as they are developed for ease of maintained Insurance carriers review the project s risk factors Legal team reviews legal documents and relationships between owner, tenant, and the public 50 ASSESS SITE FEASIBILITY AND LAYOUT SITE ASSESSMENT PRIOR TO PURCHASE Prior to purchase: Stormwater Minimum Requirements (MR) Site access Site reconnaissance Site soil information Vegetation and habitat Site drainage patterns Environmental critical areas Adjacent land use Zoning Utilities 51 17

20 ASSESS SITE FEASIBILITY AND LAYOUT SITE ASSESSMENT PRIOR TO PURCHASE ENVIRONMENTAL CRITICAL AREAS Geologic hazard areas Critical aquifer recharge areas Mapped flood plains & floodways Streams and wetlands Fish and Wildlife Habitat Conservation Areas Abandoned landfills Critical areas influence the ability to infiltrate water and the degree to which the developer has to control stormwater on site. 52 ASSESS SITE FEASIBILITY AND LAYOUT SITE ASSESSMENT PRIOR TO PURCHASE INFILTRATION ASSESSMENT Readily available resources USGS and DNR Geologic Maps Publicly available logs at DNR Washington State Geologic Information Portal Well logs at Ecology Streams, lakes, and wetlands generally indicate groundwater elevations 53 ASSESS SITE FEASIBILITY AND LAYOUT SITE ASSESSMENT PRIOR TO PURCHASE ADJACENT LAND USES Used to determine source, quantity, and quality of stormwater runoff, as well as type and scale of development in context of that land use. Agricultural Urban Suburban Recreation Commercial Industrial 54 18

21 ASSESS SITE FEASIBILITY AND LAYOUT SITE ASSESSMENT PRIOR TO PURCHASE SITE RECONNAISSANCE Prior to site visit: Gather existing analyses, maps, inventories, and historic information on site During site visit: Verify mapped conditions and characterize hydrologic, geologic, and biologic conditions 55 ASSESS SITE FEASIBILITY AND LAYOUT SITE ASSESSMENT PRIOR TO PURCHASE VEGETATION AND HABITAT Identify significant trees Identify diseased or hazard trees Review local tree preservation ordinances Review the site for regulated habitat (i.e. wetlands) Preserved trees may be used for stormwater dispersion and project amenity Preserving native soil and vegetation can significantly reduce construction and project cost 56 ASSESS SITE FEASIBILITY AND LAYOUT SITE ASSESSMENT PRIOR TO PURCHASE SITE DRAINAGE PATTERNS Site should be reviewed for natural drainage pattern (preserving natural drainage pattern is a regulatory requirement) Identify any run on or off site sources Identify any habitat supported by the on site/off site drainage patterns (i.e. wetlands and streams) Review the surrounding watershed for regional drainage patterns and if the project intersects more than one threshold discharge area (TDA) 57 19

22 ASSESS SITE FEASIBILITY AND LAYOUT SITE ASSESSMENT PRIOR TO PURCHASE ZONING Comprehensive Plan goals and policies Zoning code Landscaping, Native Vegetation, Tree Protection, and Open Space Impervious Surface Standards Bulk and Dimensional Standards Site Plan Review Parking Development Code and Standards Clearing and Grading Standards Engineering and Street Standards 58 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION ASSESSMENTS Site characterization criteria (Volume 3, Section 3.3.5) Geology/soil characteristics Groundwater conditions Infiltration potential Mounding analysis 59 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION TESTS Exploration Continuous sampling At least 10 ft below base of facility Grain size analyses Exploration Approaches Exploration pits Deep exploration borings/wells Vactor explorations (cost effective in developed areas) 60 20

23 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS SITE SOIL INFORMATION Soils Review should consider Seasonal groundwater levels and presence of any springs Shallow and deep soil properties related to infiltration Regional geology Soil conditions and infiltration capacity significantly influence LID design and can vary widely across a site. 61 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION TESTS Design infiltration rate (3.3.3) Special Case Only Grain Size Distribution Outdated Small scale falling head test (EPA) Double Ring Infiltrometer Preferred Large diameter single ring Pilot scale PIT (large and small scale) 62 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION TESTS Percent Finer US STANDARD SIEVE NOS Grain Size, mm 0.1 #200 sieve silt/clay Ecology 2012, Sieve Analysis (USDA/ASTM) Recessional Outwash or Holocene only Need to assess if deeper layers will limit infiltration (equation 2 in not recommended)

24 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION TESTS Old school infiltration testing (not recommended) Falling head test (EPA) Scale too small for many applications Double Ring Infiltrometer Scale too small for many applications, time consuming and expensive for scale 64 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION TESTS Small scale Pilot Infiltration Test (PIT) Difference from Large Scale: Pit bottom area sf 65 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION TESTS Modified Pilot Infiltration Test (PIT) for finished sub grade 66 22

25 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION TESTS Large scale Pilot Infiltration Test (PIT) 67 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION ASSESSMENTS Groundwater Separation At least one foot between base of permeable pavement section and seasonal high groundwater table If site assessment shows at least 5 feet of separation, groundwater monitoring not required Separation from both groundwater and hydraulic restriction (perching) layer Ideally, groundwater monitoring occurs between Dec. 21 Mar 21 during a winter of normal to high precipitation Professional judgment may be sufficient 68 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION ASSESSMENTS Mounding analysis required if groundwater is less than 15 feet from base of permeable pavement section Depth to water table Infiltration rate of native soils Thickness and hydraulic conductivity of the saturated zone MODFLOW analysis by a qualified hydrogeologist 69 23

26 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION ASSESSMENTS Scale of infiltration tests 70 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION ASSESSMENTS Groundwater mound development 71 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION ASSESSMENTS Summary Geologic constraints and opportunities must be fully and correctly incorporated prior to site planning and engineering. Geology can help predict the nature of the physical environment

27 ASSESS SITE FEASIBILITY AND LAYOUT SITING AND SELECTION OF MATERIALS INFILTRATION ASSESSMENTS Summary Site characterization Infiltration rate testing Groundwater separation Correction factor Mounding analysis 73 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT OBJECTIVES Minimize disturbance Reduce impervious surface Protect and restore native soils and vegetation Manage stormwater close to the source in a system of distributed practices Disconnect impervious surfaces Traditional LID 74 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES Use site analysis to guide site planning, reducing environmental impacts and achieve LID design objectives Optimizing the development envelope for site protection Road layout Buildings Open space 75 25

28 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Optimize Development Envelope Four general objectives: Minimize disturbance Locate lots for dispersing stormwater to open space areas Orient lots to maximize on lot infiltration or open conveyance Locate lots adjacent to, or with views or, open space 76 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Optimize Development Envelope Prevalent Strategies: Cluster homes Narrow lot frontages to reduce road length per home Reduce front yard setbacks to reduce driveway length For grid or modified grid layouts, lengthen street blocks to reduce the number of cross streets and overall road network per home 77 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Optimize Development Envelope 2012 LID Technical Guidance Manual for Puget Sound 78 26

29 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Optimize Development Envelope Rural cluster 30% reduction in impervious surface when lot size reduced from 1.4 to 0.25 acres (MD Office of Planning). Increase in road network and driveways primary driver for impervious increase LID Technical Guidance Manual for Puget Sound 79 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Road Layout Typical grid road layout Impervious coverage: 27 36% Less adaptive to site features. Promotes transit and connectivity with more direct access to services. 80 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Road Layout Typical curvilinear road layout Impervious coverage: 15 29% More adaptive to site features. Generally discourages transit with longer, less connected system

30 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Road Layout Hybrid or LID road layout Impervious coverage: similar percentage to other layouts. Adaptive to site features and uses site features (particularly water as an organizing theme). Can provide good connectivity and fire and safety access. 82 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Road Layout Road width and turnarounds Incorporate stormwater controls into traffic calming designs 83 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Road Layout Design to enhance street scape and buffer pedestrians and homes from roadway Water Street, Port Townsend, WA 84 28

31 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Site Access Site access must include: Fire and safety access Site circulation and public access for vehicles and pedestrians Construction access for LID construction process Connectivity to adjacent properties 85 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Utilities Place utilities in disturbed areas where feasible Cluster utilities to minimize construction disturbance Separate proposed utilities and proposed infiltration areas Consider trench dams where utilities cross infiltration areas 86 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Buildings Reduce building footprint (build up) Locate buildings on least favorable soils for infiltration Orient the long axis of the building along topographic contours to reduce cutting and filling Control roof runoff onsite Use low impact foundations Limit clearing and grading to road, utility, building pad, landscape areas 87 29

32 ASSESS SITE FEASIBILITY AND LAYOUT DESIGN FEASIBILITY ANALYSIS SITE LAYOUT STRATEGIES: Open Space Create open space areas as community amenity and to store and slow stormwater flows during winter when the areas are less active recreationally Integrate stormwater controls into traffic calming designs Use open space to break up visual landscape for homes facing the road/each other Create open space pathways between homes (green streets) Danielson Grove 88 1 introduction 2 why LID (developer community perspective) 3 4 assess site feasibility and layout permits and minimum requirements case study Q&A and wrap up AGENDA 89 CASE STUDY Matthei Place Project Objectives: Utilize the community land trust strategy in a smart site location to create as many high quality, energy efficient, permanently affordable homes as appropriate for the site. Utilize the City of Bellingham s Demonstration Program for Innovative Permanently Affordable Homeownership Projects to show that dense urban infill can be achieved in a positive, sustainable, and affordable way; Become a successful pilot project for the LEED for Homes rating system. Utilize green technologies including LID to the greatest extent possible

33 CASE STUDY PRIOR TO PURCHASE Matthei Place Project: Build the Team Developer: Kulshan Community Land Trust Public Agency Reviewers: Bellingham Public Works Department Architect: Zervas Group Architects Engineering: Chris Webb & Associates, Inc. Green Consultant: O Brien & Co. Contractor: Wellman & Zuck Landscape Design: Common Ground Environmental Community Stakeholders: City of Bellingham, Enterprise Community Partners, local banks, state agencies Maintenance: Homeowners 91 CASE STUDY PRIOR TO PURCHASE Matthei Place Project: Site Reconnaissance Previously an underutilized section of the 15 th Street right of way. Site reconnaissance to: Determine access points Survey soil Identify drainage patterns There is limited existing vegetation and no environmentally sensitive habitats or critical areas. 92 CASE STUDY PRIOR TO PURCHASE Matthei Place Project: Site Access 93 31

34 CASE STUDY PRIOR TO PURCHASE Matthei Place Project: Soil Survey Soil surveys recorded sandy loam soils. Dominated by sand particles, but contain enough clay to provide structure. Good for water infiltration and drainage. Project pre dated current LID soil assessment techniques 94 CASE STUDY PRIOR TO PURCHASE Matthei Place Project: Drainage Patterns Slight slope on property Soils on site drain approximately one inch per hour Site conditions support permeable pavement design. Design included a subsurface overflow pipe to protect adjacent properties from stormwater exfiltrating from the pavement. 95 CASE STUDY PRIOR TO PURCHASE Matthei Place Project: Adjacent Land Use 96 32

35 CASE STUDY PRIOR TO PURCHASE Matthei Place Project: Determine MR *Project permitted under the 2001 Stormwater Manual. This flowchart shows current MR requirements. MR #1 9 However, project was required to provide treatment and flow control per the 2001 Stormwater Manual. 97 CASE STUDY PRIOR TO PURCHASE Matthei Place Project: BMPs Selected Flow control (MR 7) Pervious pavement for onsite paving Detention vault for off site flows and some on site roofs Bioretention cell for some onsite roofs Water Quality Treatment (MR 6) On site PGIS: NA (pervious pavement) Off site PGIS: cartridge filter vault 98 CASE STUDY PRIOR TO PURCHASE Matthei Place Project: Zoning 99 33

36 CASE STUDY PRIOR TO PURCHASE Matthei Place Project: Utilities 100 CASE STUDY DESIGN Matthei Place Project: Site Layout 101 CASE STUDY DESIGN Matthei Place Project: LID BMPs Green Highlights Integrated design process that prioritized green attributes based on LEED for Homes Pilot Project Used advanced framing techniques and local engineered trusses Native landscaping reduces need for irrigation Rain garden, permeable pavement, and underground rainwater storage promote infiltration and minimize runoff Homeowners trained and provided written materials to maximize function, environmental benefits, and sustainability of their homes

37 CASE STUDY DESIGN Matthei Place Project: Cost Analysis Total Project Cost: $3.5 million Construction Cost: $2,468,000 Land Cost: $155,000 Fees and professional services: $911,000 Total Cost of Greening: $240,400 Rebates and Grants: $6,400 Net Cost of Greening: $234, introduction 2 why LID (developer community perspective) 3 4 assess site feasibility and layout permits and minimum requirements case study Q&A and wrap up AGENDA 104 Q&A AND WRAP UP RESOURCES Stormwater Management Manual for Western Washington: Low Impact Development Technical Guidance Manual for Puget Sound: Rain Garden Handbook for Western Washington Homeowners: Building Soil for Builders, Developers, and Landscapers: Protecting Water Resources with Higher Density Development: 03/documents/protect_water_higher_density1.pdf Using Smart Growth Techniques as Stormwater Best Management Practices: smart growth techniques stormwater bestmanagement practices Western Washington Low Impact Development (LID) Operations and Maintenance (O&M) Guidance Document, LID O&M training videos, and example inspection forms for bioretention and permeable pavement: (Maintain LID tab)

38 Q&A AND WRAP UP RESOURCES Municipal code, LID regulations for cities and counties King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities: andland/stormwater/documents/drainage maintenancestandards.aspx City of Seattle Green Stormwater Operations Manual: /webcontent/spu02_ pdf Pierce County Stormwater Maintenance Manual for Private Facilities: