Permeable Interlocking Concrete Pavement A Low Impact Development Tool. Training for Design Professionals

Transcription

1 Permeable Interlocking Concrete Pavement A Low Impact Development Tool Training for Design Professionals Presented by: Interlocking Concrete Pavement Institute (ICPI) The Low Impact Development Center, Inc. North Carolina State University Permeable Interlocking Concrete Pavement A Low Impact Development Tool This program is registered with the AIA/CES and ASLA CPE for continuing education professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA or ASLA of Any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. Revised Dec. 19, 2008 Program Learning objectives: Identify PICP Components Understand hydrological & structural design principles for pavement base/subbase Work through a PICP sizing example Basics of Construction Maintenance Costs

2 Contents PICP System & Materials PICP Benefits Runoff & Pollutant Reduction Green infrastructure Environmental benefits LEED & Sustainable Design Infrastructure cost savings ADA Compliant improved tax base Sizing example Construction/Inspection Maintenance PICP Costs PICP Resources Pavement is a Culprit in Flooding State and federal officials say flooding in many places has been exacerbated by the roads, parking lots, patios, and yes, driveways that define our urban and suburban landscapes. The collective way we live as a society creates acres and acres of impervious surfaces we didn t have before Boston Globe 4/5/2010 The Stormwater Problem

3 Cover (percent of land area) /4 acre Residential 1/2 acre Residential Industrial Commercial & business Shopping Centers? Stormwater Management Objectives Retain/infiltrate stormwater Capture first flush, e.g., first ½ inch Limit amount of impervious cover Imitate pre-development runoff volume Design to drainage system capacity Control specific nutrients and metals Permeable pavements address all approaches How PICP Manages Stormwater Water Quantity Reduces volumes & peak flows via infiltration Imitates predevelopment conditions: no runoff from common storms Reduces or eliminates retention/detention facilities & conserves land Reduces stormwater utility fees Recharges groundwater Helps maintain dry-weather stream flows Water Quality Reduced downstream erosion, preserves drainage system Filters & reduces nutrients and metals Filters oil drippings Reduces runoff temperatures

4 Monolithic Porous Pavements Porous Asphalt Pervious Concrete What is PICP? Permeable Interlocking Concrete Pavement PICP System Components Concrete Pavers Permeable Joint Material Open-graded Bedding Course Open-graded Base Reservoir Open-graded Subbase Reservoir System Components Underdrain (As required) Optional Geotextile Under the Subbase Uncompacted Subgrade Soil

5 Concrete Paver Characteristics Meet or exceed ASTM C-936 High Strength psi Low Absorption - Maximum 5% Skid & Slip Resistance Choice of Colors Design Flexibility High Quality & Exceptional Durability Low Maintenance Easy to Repair Many shapes comply with ADA opening limit PICP Benefits Local Stormwater Regulations Green Infrastructure & LID Retrofits Environmental Benefits LEED & Sustainable Design Infrastructure Cost Savings Durable ADA Compliant Surface Improved Tax Base PICP Hydrology Example

6 Primary Goal of LID Design each site to protect, or restore, the natural hydrology of the site so that the overall integrity of the watershed is protected. This is done by creating a hydrologically functional landscape. Basic LID Principles Conserve natural areas Minimize development impacts Maintain site runoff rate Use integrated stormwater management practices Implement pollution prevention, proper maintenance and public education programs Integration with Other BMPs Reduce inbound sediment to PICPs through upstream cover Grass swales, bioswales & filter strips Sand & organic filters Bioretention/ rain garden areas

7 Low Impact Development Stormwater Controls Green Infrastructure & LID Retrofits PICP Downstream Treatment Train. PICP overflows to grassy swale & rain garden Goldsboro, NC Retrofit LID Project. Water quality & green infrastructure integration River Front Trails, Payallup, WA Green Infrastructure Portland, OR Reduced combined sewer overflows Less expensive than separating storm & sanitary sewers Supports tree growth Improves neighborhood character Chicago Green Alley, Chicago, IL Two images above courtesy of Chicago DOT

8 PICP Integrated with LID: a step toward Sustainable Communities Stormwater management using natural systems Reduced urban heat Island with cooler pavements Improved neighborhood character Conventional vs. LID Approach to Stormwater Conventional Collect Convey Discharge LID Approach Reduce volume Minimize impacts Distributed controls Treatment trains Infiltration Hybrid systems Mimic predevelopment hydrology Runoff & Pollutant Reduction Jordan Cove Pre Construction

9 Jordan Cove 6 years Post Construction Pollutant Concentrations Variable Asphalt PICP Stone Runoff depth, mm TSS, mg/l * 33.7 Nitrate nitrogen, mg/l Ammonia nitrogen, mg/l Kjeldahl nitrogen, mg/l Total Phosphorous, mg/l Copper, ug/l (13/9) Lead, ug/l (65/2.5) Zinc, ug/l (120/120) *68% reduction Mean weekly pollutant concentration in stormwater runoff Metals: (acute/chronic) toxicity to freshwater aquatic life Pollutant Mass Export Reduction Clausen (2007) Residential Driveways Pollutant Export kg/ha/year Variable Asphalt PICP Stone Total Suspended Solids * 9.6 Nitrate nitrogen Ammonia nitrogen Kjeldahl nitrogen Total Phosphorous ** 0.04 *90% TSS reduction **69% TP reduction Van Seters (TRCA 2007): 81% TSS reduction Hunt (2004): 72% TSS & 63% TP reductions Booth & Leavitt (1999): significant metals reductions compared to asphalt runoff

10 Toronto & Region Conservation Authority Seneca College Parking Lot Water Quality Results Oils: below lab detection limits Lead & zinc significantly lower than asphalt runoff Deicing salts Requires less than asphalt Highly mobile regardless of pavement Maintain sufficient separation between PICP bottom & water table PICP Structural Soil Supports PICP and Tree Growth Pier A Park Hoboken, N.J., 1998 Image courtesy of Bruce K. Ferguson

11 PICP Contributes to LEED Credits Decrease pollution through sustainable sites (SS) Increase building water use efficiency (WE) Reduce energy and atmospheric pollutants (MR) Conserve materials and resources (MR) Improve indoor air quality (EQ) Offer innovative ideas and designs (ID) Conservation of Materials and Resources (MR) Credits - 1 LEED point each: 3.1 5% reused content (i.e. crushed concrete) % reused content 4.1 5% recycled waste content (i.e. flyash) % recycled waste content % manufactured regionally (<500 mi.) % materials extracted regionally (<500 mi.) ICPI Tech Spec 16

12 PICP Contributes to LEED Credits LEED Gold Project Peak flow & pollution reduction, University of Victoria, BC Design Steps 1. Determine type of traffic 2. Assess site & soil Type & strength 3. Establish hydrological objectives 4. Compute run-on volume from adjacent area 5. Calculate depth of base Collection Storage Exfiltration (24-48 hours) 6. Select proper materials to accomplish design objectives seated?

13 Pavement thickness must be adequate Support traffic loads Reduce stress on sub-grade to avoid deformation Protect against heaving caused by freezethaw Provide hydraulic capacity Must Analyze thickness needed for each requirement separately Specify greatest of the requirements Full Exfiltration Partial Exfiltration

14 No Exfiltration PICP Sizing Steps Determine: 1. Water runoff depth from design storm (typically 24-hr 2, 5, 10 or 25 yr event) 2. PICP base & sub-base volume to store water 3. PICP base & sub-base depth for storage & infiltration 4. Soil infiltration rate vs. water drainage time 5. PICP base & sub-base depth to support traffic 6. Thicker of two PICP bases from 3 & 5 for design 7. Total PICP depth & check depth to water table Given: PICP Sizing Example 3? in. (8 cm thick pavers) Project location: no-frost region Design storm = 3 in. (typ. 24-hr 2, 5, 10 or 25 yr event) PICP area = 30,000 sf Contributing area = 10,000 sf asphalt Contributing area runoff depth = 2 in. Depth to seasonal high water table = 5 ft.

15 PICP Sizing Example Given: Soil type: sandy clay Soil infiltration rate = 0.25 in./hr Soil strength CBR = 7% (R-value = 13) Base & sub-base porosity = 33% Drainage time = 48 hrs Traffic load & design life = 300,000 ESALs over 20 years PICP Sizing Example - Hydrological Determine: 1. Water storage volume Rainfall on PICP = 3 in. = 0.25 ft x 30,000 sf = 7500 cf Runoff from contributing area = 2 in. = 0.17 ft x 10,000 sf = 1700 cf Total water volume = = 9200 cf Total water depth = 9200 cf 30,000 sf PICP area = 0.3 ft or about 3.7 in. 2. PICP base & sub-base volume to store water 9,200 cf 0.33 base porosity = 27,879 cf PICP Sizing Example - Hydrological 3. PICP base & sub-base depth for storage & infiltration Total base volume PICP area 27,879 cf 30,000 sf = 0.93 ft = 11 in. say 12 in. 4. Soil infiltration rate vs. water drainage time Drainage time = 48 hours Soil infiltration rate = 0.25 in./hr Use 2X safety factor for long-term clogging 0.25 in./hr 2 = 0.12 in./hr design soil infiltration rate Total water depth = 3.7 in. 48 hrs. = 0.08 in./hr min. soil infiltrate rate required

16 PICP Sizing Example - Hydrological Verify PICP drains within 48 hrs Okay 0.08 in./hr required < 0.12 in./hr soil infiltration rate Not Okay? Design drain pipes to release excess water i.e., partial exfiltration design PICP Sizing Example - Structural 5. Determine PICP base & subbase depth to support traffic R-value > Traffic Index CBR 7% in. 8.5 PICP Sizing Example Hydrological & Structural 6. Select thicker of two PICP bases from steps 3 & 5 Compare: Step 3 base thickness (hydrological) = 12 in. Step 5 base thickness (structural) = 13 in. from table Round up to 14 in. for construction expediency (4 in. #57 stone + 10 in. # 2 stone)

17 PICP Sizing Example - Hydrological 7. Total PICP depth & check depth to water table Full or Partial Exfiltration No exfiltration 2 ft. 1 ft. Impermeable liner PICP Sizing Example Final Design 8. Total PICP depth & check depth to water table Cross section: in. thick concrete pavers 2 in. bedding material - chokes into base surface 4 in. thick No. 57 base (or similar) chokes into sub-base 10 in. thick No. 2 sub-base (or similar) Optional geotextile per manufacturer s recommendations Total cross section thickness ~ 19 in in. clear to seasonal high water table 43 in. total clearance required Permeable Design PRO Software integrates Hydrologic Design Structural Design To obtain software

18 Construction of PICPs Excavate area Compact sub-grade as needed Cover with geo-textile fabric / Mirafi Filter Weave Place & compact base in lifts Install edge restraints Place & screed stone setting bed Place & cut pavers Fill joints, sweep & compact Repeat sweeping & compaction until firmly seated Maximizing Long Term Performance Keep pavement clean Sweep periodically Avoid high pressure washing Vacuum when infiltration significantly reduced Replenish aggregate as needed Repair ruts & deformation exceeding ½ Replace broken pavers Minimize use of sand & de-icing salts Winter Performance Snow melts faster lower risk of ice hazards Surface does not heave when frozen Can be snow plowed Deicing salts okay Sand may clog system

19 Restoring Infiltration Clogging occurs in top 1 of opening Sweeping breaks up crust Vacuum when clogged Re-fill openings? Porous pavements cost competitive!!! Dense pavement: Porous pavement: Catch basins, underground pipe Built-in solution Cost analysis Dense asphalt Single function Permeable Pavement Includes cost to control stormwater To calculate comparative cost: Price cost of permeable pavers against asphalt and dense graded base Price permeable base against traditional appurtenances catch basin/pipe & retention/detention pond

20 Cost Comparison Autumn Trails, Moline, IL 2006 ~ 39,000 sf Cost per sf PICP Concrete Asphalt $10.95 No storm sewers $15.00 With storm sewers $11.50 With storm sewers Fort Stewart Life Cost Analysis PICP System Budget Costs Assumptions: Paver Thickness: 3 in. (8 cm) Bedding Layer: 2 in. Base Layer: 8 in. Total Area: 15,000-20,000 ft² Prevailing Wages Does NOT include design concrete curbs Excavation and pipe costs $ $ /sf

21 A Detention Facility that Supports Vehicles! Limitations For pedestrian or lowspeed roadways parking lots, local & collector roads Requires greater site evaluation/design effort Demands high level of construction skill Requires regular maintenance Avoid Drinking water wells (100 ft. min. distance) High water tables (< 3 ft from surface) High bedrock Industrial sites, fueling stations Expansive and fill soils Increase in impervious area after PICP The PICP Advantage! High strength 9000 psi support heavy traffic. Unaffected by tire shear Factory made ready to install year-round No cure time traffic ready! Available in SRI colors Does not use petroleum based material that leach into the soil. Winter friendly Snow Plow Safe Minimizes ice & deicer use Summer friendly Unaffected by heat No binder drain down Units can be removed and reinstated No evidence of patch Easy to clean & maintain Cost competitive Fact Sheets Design Manual Design Software Presentations PICP Resources

22 ? UNH Stormwater Facility UNH Stormwater Facility

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24 Good for the Community! Good for the Environment! Thank You? Questions? PICP Benefits ADA Compliant Handicapped parking over PICP stormwater detention system Burnaby, BC

25 PICP Benefits Local Stormwater Regulations Green Infrastructure & LID Retrofits Environmental Benefits LEED & Sustainable Design Infrastructure Cost Savings Durable ADA Compliant Surface Improved Tax Base Design Basics: Exfiltration Options Full base exfiltration Sandy soils No perforated drain pipes Partial detention & infiltration Silt/clay soils Perforated pipes at bottom of base None detention only High rock, water table, poor soils Overflow Drainage Overflow drain Drains to bioswale