APWA Green Pavement Alternatives

Transcription

1 Civil Engineering Landscape Architecture Environmental Restoration Planning APWA Green Pavement Alternatives Kathryn Gwilym, PE, LEED AP June 24,

2 Topics to Cover Introduction to Four Types of Porous Pavements Examples of Porous Pavement Applications Benefits of Porous Pavements Basic Design Considerations General Construction Issues Operations and Maintenance Questions and Answer

3 SvR s Participation Nationally and Locally APWA National Subcommittee on Sustainable Transportation Steering Committee, Complete Streets National Organization Washington State University Puget Sound Partnership Permeable Pavement Workshop Series Washington State Transportation Improvement Board Sustainability and Its Integration into Streetscapes University of Washington Multiple LID and Sustainability Courses Numerous Projects Implemented / Involvement

4 Terms Permeable Porous Pervious Used interchangeably but essentially mean same thing water can filter through the top wearing course. Pick one term and be consistent in your standard plans and specifications. Currently moving towards standardizing to: Pervious Concrete Porous Asphalt Permeable Interlocking Pavers

5 Types of Porous Pavements (where they ve been used) Pervious Concrete (streets, sidewalks, patios, basketball courts, bike lanes, parking lots) Porous Asphalt (streets, sidewalks, patios, basketball courts, bike lanes, parking lots) Permeable Interlocking Pavers (patios, parking lots, plaza, walkways, streets) Open-celled flexible paving grids (trails, walkways, parking lots)

6 Other Applications for Porous Pavement Public Walkways Parks Plazas and Patios Parking Greenhouse Floors Surface Course for Tennis Courts Basketball Courts Noise Barriers / Walls Private Parking lot, Seattle Bicycle lane, Bellingham, WA Park in Seattle, WA

7 Examples of Porous Pavements in the Public ROW N. Gay Ave, Portland. Porous Asphalt Concrete ( porous AC over 6 Subbase) Permeable Interlocking Paver (Photo from Portland OR at 32 nd Ave. SW, Seattle. Pervious Concrete ( PPCC over 18 subbase) Other Example Applications: -Retrofits for public alleys in Chicago -Park-n-Ride lots -Retrofit in streets for utility upgrades -Retrofit for CSO control by implementing in public streets and alleys

8 Benefits of using Porous Pavements? Provides stormwater management system Reduces/eliminates need for stormwater flow control facility In some cases, can reduce overall costs in stormwater treatment facility (capital and maintenance) Provides basic water quality treatment if underlying soils are suitable Can be placed during light wet weather Potential benefits with reduction to heat island affect (more study data needed) Provides some noise absorption in the pavement system LEED credit (pervious concrete and permeable concrete pavers) Note: It is not applicable to all sites. Consider porous pavement as another tool for the stormwater management kit.

9 Key to Success: Integrative & Interdisciplinary Team For a successful project, the team needs to follow the right BMPs for all phases: Planning Design Installation Construction Operations/Maintenance Requires collaboration between Owner, Geotechnical Engineer, Civil Engineer, Landscape Architect, Architect, Planner, Contractor, Maintenance, etc.

10 Design - Users Who will be the users of the facility? Pedestrian, Bicyclists, ADA Parking Lot Low-Volume Residential Streets Other Serene Way Sidewalk Photo by: Randy Sleight, Snohomish County

11 Design - Site Selection & Location Topography (ideal slopes 0 to 5%) Proximity to Hazardous Materials Potential for run-on from unstabilized areas/erosive soils (will increase maintenance effort) Low Volume traffic loading (residential street, parking lots) Infiltration Rate of Existing Subgrade Soil Design infiltration rates can be below.25 in/hr depending upon design storm for flow control Local Agency guidelines for ground water protection areas, wellhead protection zone, sole source aquifer, aquifer sensitive areas etc. Pervious Concrete Parking Lot, Seattle, WA Porous Asphalt Drive, Pierce County, WA Photo courtesy: Timothy Lowry, Seattle Public Utilities

12 Design - Stormwater Management Parameters Porous pavements can be designed to provide one or more of the following: Reduce Impervious Footprint Flow Control Facility via the storage within the gravel subbase Water Quality Treatment (if subgrade soils are suitable)

13 Design - Subgrade Slope and Storage Capacity Ideal 0% to maximize storage but can increase excavation Sloped conditions (1% to 5%) reduces the amount of useable storage space but decreases amount of excavation. Use periodic impermeable check dams, or gravel trenches or other measures to allow water to backup & infiltrate or to direct water away.

14 Design - Subbase Subbase depth varies with design parameters. Structural vs stormwater storage requirements. Size for both and larger depth governs. Voids can vary with subbase material so check with geotechnical engineer on what can be expected for storage. 20%? 30%? 40%? Subbase material should be free draining. Clean, crushed/fractured aggregate with low fine content (% passing #200 sieve). (e.g. AASHTO #57) Select materials that are readily available by multiple suppliers. Avoid custom specifications. Design so storage is within subbase and not top wearing course. Follow manufacturer guidelines for subbase materials. Non-woven Geotextile? Depends on conditions

15 Design - Overflow/Back-up System Provide for emergency overflow What is the flow path if water does not infiltrate? If 100% infiltration facility follow guidelines for closed depression infiltration facility Overflow subsurface drain? (slotted pipe above design water surface level)

16 Sources for Specifications Specification for Pervious Concrete Pavement from American Concrete Institute (ACI) publication and Report on Pervious Concrete ACI 522R-10 by ACI Committee 522. Porous Asphalt Pavements for Stormwater Management Information Series 131 from National Asphalt Pavement Association, Permeable Interlocking Concrete Pavements from Interlocking Concrete Paving Institute, Follow manufacturer recommendations for proprietary products, (open celled paving grids and interlocking pavers) Check for latest version of specifications and recommendations since specifications are dynamic with these technologies.

17 Construction & Inspection Key Issues Installer & Supplier have Qualifications Require Test Panel for pervious concrete Require mock-up for permeable interlocking pavers Plan Ahead Timing & Sequencing of when to install Protection from sediment through all phases Minimal disturbance of native subgrade Materials are per specifications Other QA testing

18 Construction - Installer Pre-qualifications TEST PANEL required. May require multiple test panels for new installers. If unable to install test panel, submit qualifications and results of multiple previous installations. Installers and Supplier Certification required. Pervious Concrete: National Ready Mixed Concrete Association has certification program for installer. Porous Asphalt: No national certification program known at this time Permeable interlocking concrete pavement manufacturers are implementing certification program for installers Training by Manufacturer Rep. and/or require Manufacturer Rep. to be present for installation for proprietary products. Recommend at least 2-3 persons per crew have certification.

19 Construction -Timing & Sequencing School in Medina, WA Plan Ahead Equipment Access Isolate Area from other construction activities Different methods may end up being used Avoid disturbing native subgrade until time of placement of subbase. Do not use as construction access/staging if feasible Above Photo: La Center Parking Lot, Washington

20 Construction - Subgrade Preparation Goal is to maximize infiltration rate of native subgrade Review requirements at preconstruction meeting Minimal to no compaction of native subgrade. Consult with geotechnical engineer to review subgrade preparation Do not seal subgrade Develop alternative haul route outside road section to keep traffic off subgrade Remove last 12 + of excavated subgrade just prior to placement of subbase and pavement section.

21 Construction - Temporary Erosion & Sediment Control (TESC) Install protection (TESC and Flow Diversion) measures prior to final excavation of porous pavement section. Prime contractor to inform other subs of requirements when working around pervious pavement Maintain Erosion Control BEFORE and AFTER construction. Permanently stabilize adjacent areas.

22 Construction - Inspectors PRE-precon with Inspectors to inform them of special issues related to porous pavement If possible, have Inspectors attend an installation training by manufacturer or industry. Designers: Discuss intent with Inspectors prior to construction Provide inspection checklists. General items to check: Installer certification Install Test Panel or review previous installations by crew TESC and Flow Diversion in place prior to excavation Materials meets specifications and matches submittals Subgrade free of sediment/fine deposits during construction Subbase protected from sediment/fines from construction stormwater TESC and flow diversion measures are being maintained throughout construction until adjacent areas are stabilized

23 Construction - General Post Installation QA Testing Field infiltration tests upon completion of paving section. ASTM C1701-Standard Test Method for Infiltration Rate of In Place Pervious Concrete Depth of Section (at least minimum design depth) Dry Unit Weight (cores) consistent with test panel See industry specification references for guidance on QA testing.

24 Post Installation: Observation review of Pervious Concrete Uniform Finish vs. Excessive Sealing Some factors that affect/cause sealing: Method of installation Mix non-uniform Porous Uniform Finish Porous Non-Uniform Finish

25 Post Installation: Observation review of Pervious Concrete/Porous Asphalt Uniform Finish vs. Excessive Raveling Factors that can affect/cause raveling: Non-continuous protective cover during curing (pervious concrete) Mix Design Weather (Temp and Wind) Loading pavement early or not as intended Pavement was placed early and used as a construction entrance for concrete deliveries. Pavement being covered immediately as it s being placed to hold moisture in for curing.

26 Post Installation: Open Celled Paving Grids/Interlocking pavers Follow manufacturer testing and installation guidelines Open celled flexible paving grids: Staples and staking spacing per manufacturer? Prefab interlocking pavers Right side up?

27 Maintenance Porous Pavement Maintenance: Is it different? The maintenance of LID facilities is essential to ensure that design stormwater management and other benefits continue over the full lifecycle of the installation. What to look for? Drainage Safety Aesthetics Allow for Training of Maintenance Crew Homeowner Private Crews Public Crews

28 Maintenance - Stabilization of Adjacent Areas Proactive vs. reactive Address the source Inform Staff of its location and protection measures

29 Maintenance - Adjacent Vegetation Remove leaves in the fall promptly. Ground Cover Migration Coordinate with the Landscape Architect on plant selection adjacent to porous pavement Options for Maintenance Modify planting plan and remove invasive plants Maintain adjacent landscaping Weed burners Ground cover migration happens even with conventional pavement.

30 Maintenance - Moss Growth in Pacific NW Be careful with expectations Moss is an issue with non-pervious pavements Options for Maintenance: Pressure washing Weed burner Sweeping During planning, consider impacts of shade to maintenance frequency Above: Pervious Concrete City Sidewalk with moss Right: Non-Pervious Concrete City sidewalk with moss

31 Maintenance - Snow Removal Pervious Concrete Street in Seattle, WA. Safety Governs Avoid sanding UNH Stormwater Center reported a reduction in salt use up to 75% but can vary with site conditions. Avoid sanding adjacent streets if possible since tires will track it onto the porous pavement and clog the pores. Adjust plow height to avoid scraping pavement/dislodging pavers Installed in cold climates such as Iowa, New Hampshire, Pennsylvania, Colorado, Ohio, Lake Tahoe. Above photo of non-pervious asphalt lot courtesy of National Ready Mixed Concrete Association and Center for Portland Cement Concrete Pavement Technology, 2005 via John Kevern at National Concrete Pavement Technology, Iowa State University

32 Maintenance - Permeable Interlocking Pavers Maintenance: Remove and replace pavers when repairs or utility cuts are needed Replace gravel when needed

33 Maintenance - Porous Asphalt No overlay/black topping Pavement sections can last longer than non-porous asphalt sections requiring an overlay because of the free draining subbase (if designed and maintained accordingly)

34 Maintenance - Utility Cut Protocols Implement measures to protect adjacent existing porous facility to remain Patch with same porous material Full panel replacement Use temporary patch until full panel can be replaced

35 Maintenance - Sediment removal for porous asphalt / concrete Vacuum sweeping annually or more frequently depending upon sediment loading from unstabilized adjacent areas. Follow manufacturer guidelines for mechanical equipment Care should be taken with pressure washers. Test small area first. Implement Preventive measures: Maintain stabilization of adjacent areas Avoid stockpiling landscape materials on pavement Remove leaves and large debris after they fall Inform maintenance crew of pervious material Above 2 photos from City of Bellevue, WA

36 Example of Maintenance Equipment from Portland OR N. Gay Avenue & Westmoreland projects, Portland OR Pavers, porous asphalt and pervious concrete public streets 1 to 2x / year - Vacuum sweepers used to collect fines: Tymco s 500x Schwarze s A7000 Elgin s Crosswind J-Plus Infiltration test of porous asphalt, pervious concrete and pavers Flusher truck spray water over pavement (calculate rate & area) vegetation growth in pavers did not appear to hinder infiltration on Rex St. (~63 in/hr) Source: Brett Kesterson, Portland, OR at APWA porous pavement webinar ( ) Photos from Portland OR at

37 Maintenance Monitoring Proactive vs Reactive: Annually check infiltration and clean areas on a quarterly/annual basis vs. wait until no longer infiltrating then do intensive cleaning Some have put off maintenance until surface ponding is observed then use vacuum with or without pressure washers to restore infiltration capability Annually check overflow subsurface drains to make sure functioning and not blocked Check water level in observation ports if installed Have an annual inspection checklist in the maintenance manual. Sample maintenance checklist on City of Bellevue, WA website. Develop maintenance schedule for crews

38 Example: Maintenance Schedule for Tasks

39 Interdepartmental & Interagency Agreements Determine maintenance agreement during design phase. Who maintains? Transportation? Utilities? Private Developer? Who maintains public or private? Varies with jurisdiction. Document location in books/records for future utility cuts and maintenance requirements GIS mapping of infiltration facilities? Continuously inform with staff turnover Document as-built conditions. Document what materials are required for repair (clean subbase etc.) Develop protection guidelines for future work in area. Develop agency inspection checklist to confirm being maintained.

40 Resources (1 of 2) American Concrete Institute s Specification for Pervious Concrete Pavement ACI , American Concrete Institute Committee 522 s Report on Pervious Concrete ACI 522R- 10, Interlocking Concrete Paving Institute s Permeable Interlocking Concrete Pavement, National Asphalt Paving Association National Ready Mixed Concrete Association Pervious Concrete Publications Freeze Thaw Resistance of Pervious Concrete, National Ready Mixed Concrete Association, May Pervious Concrete Contractor Certification, National Ready Mixed Concrete Association, August LID Technical Guidance Manual for Puget Sound, Lower Columbia River Field Guide to Water Quality Friendly Development City of Olympia, WA City of Portland, OR 2008 Stormwater Management Manual, Dierkes, Carsten, Lothar Kuhlmann, Jaya Kandasamy, George Angelis. Abstract: Pollution Retention Capability and Maintenance of Permeable Pavements. Presented at Global Solutions for Urban Drainage: 9th International Conference on Urban Drainage. Portland, OR. September 2002.

41 Resources (2 of 2) Porous Pavements, by Bruce K. Ferguson, Taylor & Francis Group, NC State University Permeable Pavement Research: Water Quality, Water Quantity, and Clogging, Eban Z. Bean, EL, PhD Candidate and William F. Hunt, PhD, PE, NWQEP Notes, North Carolina State University, Number 119, November Long-Term Stormwater Quantity and Quality Performance of Permeable Pavement Systems, by Benjamin O. Brattebo and Derek B. Booth, July 1, 2003, Center for Water and Watershed Studies, Department of Civil and Environmental Engineering, University of Washington at Pervious pavement in cold climates: Dietz, Michael E. Low-Impact Development Practices: A Review of Current Research and Recommendations for Future Directions. Springer Science + Business Media B.V Maintenance Guidelines for Porous Pavements University of New Hampshire, Stormwater Center City of Bellevue Natural Drainage Practices Maintenance Guidelines & Checklists City of Seattle Inspection Checklist for permeable pavements ructure/stormwatercodecompliance/inspectionverificationprocedures/ Resources from SvR Your local concrete, asphalt and paver suppliers and installers Multiple resources on web. Google: porous/pervious/permeable Kathryn Gwilym, PE; SvR Design Co.; ; [email protected],

42 QUESTIONS? Further questions contact: Kathryn Gwilym, PE, LEED R AP SvR Design Company Ph: [email protected]

43 Civil Engineering Landscape Architecture Environmental Restoration Planning