Permeable Interlocking Concrete Pavements. The Stormwater Problem

Transcription

1 Permeable Interlocking Concrete Pavements The Stormwater Problem 1

2 Stormwater Management Objectives Water Quantity Accommodate water volumes & peak flows Water Quality Control pollutant levels A Low Impact Development Solution 1. Source controls = Infiltrate 2. Conveyance controls = Filter & detain 3. End of Pipe Controls = Retain in ponds 2

3 Permeable Pavements Advantages Reduces impervious cover Reduces surface water runoff volumes Cost savings due to reduction or elimination of stormwater drainage system requirements (retention ponds, piping systems and hardware) Increased groundwater recharge Reduced and delayed peak flows Reduces pollutants Advantages (continued) Helps reduce downstream erosion from reduced volumes & peak flows Reduced runoff water temperature No need for false grading of large parking areas Reduces microclimate temperatures and contributes to urban heat island reduction Eliminates surface water ponding Reduces ice hazards & deicing salt use Eligible for Leadership in Energy and Environmental Design (LEED ) credits (CaGBC and USGBC) 3

4 Pervious, Porous and Permeable Pavements Permeable interlocking concrete Pervious concrete Porous asphalt PICP System Components Concrete Pavers Permeable Joint Material Open-graded Bedding Course Open-graded Base Reservoir Open-graded Subbase Reservoir Underdrain (as required) Optional Geotextile Under Subbase Uncompacted Subgrade Soil 4

5 No. 8 Bedding, base and subbase stone sizes No. 57 No. 2 ASTM No. 57 Base Sieve Size Percent Passing 37.5 mm (1½ in.) mm (1 in.) 95 to mm (½ in.) 25 to mm (No. 4) 0 to mm (No. 8) 0 to 5 ASTM No. 2 Subbase Sieve Size Percent Passing 75 mm (3 in.) mm (2½ in.) 90 to mm (2 in.) 35 to mm (1½ in.) 0 to mm (¾ in.) 0 to 5 5

6 Full Exfiltration Partial Exfiltration 6

7 No Exfiltration m) Typical Application 7

8 Typical Application Typical Application Seneca College King Campus, Ontario Three year monitoring Toronto & Region Conservation Authority 8

9 Paving Layer Design Considerations Infiltration Structural Capacity Infiltration - Porosity and Permeability 9

10 Source of Water - Rainfall Source of Water - Contributing Area 10

11 Supplementary Surface Drainage Design for Supplementary Surface Drainage 22 11

12 Supplemental Drainage Retention Drainage Outflow 12

13 Pipe Subdrain System Plan View Cross-Section View Structural Design - AASHTO 13

14 Structural Design - AASHTO W = design traffic load in equivalent single axle loads (ESALs) Z R = standard normal deviate S 0 = standard deviation SN = structural number of the pavement = a i * d i a i = structural layer coefficient d i = layer thickness p i = initial serviceability p t = terminal serviceability M R = subgrade resilient modulus Truck Volumes and Axle Weights Affect Performance Traffic characterized by! Equivalent Single Axle Loads! 18,000 lb (80 kn) ESALs 14

15 Truck Factor = ESAL per Truck 5 Axle Truck 50 kn (11 kips)! 2 x 80kN (18 kips)! 2 x 70 kn (15.8 kips)! Single ( ) LEF = ( ) = 0.6 (x2) ( ) LEF = = 1 (x2) LEF = = 0.15 TF = = 3.35 ESALs Typical Truck Factors 2- and 3-axle trucks axle trucks axle trucks and + axle trucks

16 Subgrade Support - Resilient Modulus Dynamic stiffness under repeated load AASHTO T I Permanent deformation Reliability, Serviceability and Standard Error Reliability Serviceability Standard Error = Typically 0.44 for low volume roads 16

17 Structural Design Example Structural design for: 175,000 ESALs Subgrade modulus = 40 MPa (5,800 psi) Initial serviceability = 4.1 Terminal serviceability = 2.2 Reliability = 70 percent Standard error = 0.44 Calculated required structural number from the AASHTO design equation = 63 mm (2.5 in) Layer Thickness Required Required Layer Thickness Structural Layer Coefficient Structural Equivalency Number Paving 130 mm x 0.30 = 39 mm Base 100 mm x 0.06 = 6 mm Subbase 300 mm x 0.06 = 18 mm Total SN 63 mm Paving 5 1/8 in. x 0.30 = 1.54 in. Base 4 in. x 0.06 = 0.25 in. 17

18 Permeable Design Pro Software for PICP Design PICP for Hydrologic and Structural Design 18

19 Define PICP Pavement & Surrounding Area Select/Design Pavement Material Properties 19

20 Traffic Analysis for Structural Design AASHTO Structural Design Analysis 20

21 Establish Hydrologic Conditions and Design Storms Calculate Total Water In-Flow 21

22 Run Analysis Select Drainage Parameters and Conditions 22

23 Repeat Analysis to Fine Tune PICP Design 23

24 Live Demonstration Sustainable Design Development that meets the needs of the present without compromising the ability of future generations to meet their own needs. Considers the triple-bottom-line: social, economic & environmental impacts LEED = Leadership in Energy & Environmental Design rating system v2.2 US Green Building Council 24

25 LEED Rating System LEED Ratings for Certification Certified Silver Gold Platinum points points points 52 or greater Types of projects: New construction LEED-NC Existing buildings Commercial interiors Building core & shell Homes LEED Rating System LEED credits offered when projects. Decrease pollution through sustainable sites Increase building water use efficiency Reduce energy and atmospheric pollutants Conserve minerals and resources Improve indoor air quality Offer innovative ideas and designs Offer innovative upgrades, operations & maintenance 25

26 LEED Points Credit 6.1 Stormwater design: Quantity control 1 <50 percent site imperviousness Reduce to pre-development peak discharge & quantity for a 2 year, 24-hour storm >50 percent site imperviousness 25 percent volume decrease from 2 year, 24-hour storm Achieve both objectives with permeable interlocking concrete pavements LEED Points Credit 6.2 Stormwater design: Quality control 1 Capture & treat 90% of average annual Rainfall (0.5 to 1 in. depending on region) Remove 80% of total suspended solids Achieve Total Suspended Solids (TSS) removal with permeable interlocking concrete pavements 26

27 LEED Points Credit 7.1 Heat Island Effect: Non-roof 1 50 percent of site hardscape using Tree shade in 5 years Paving with minimum 29 Solar Reflectance Index (SRI) Grid pavement OR Place parking under roof or ground Minimum 29 SRI on roof or deck Conservation of Materials and Resources Credit LEED Points 3.1 5% reused content (i.e. crushed concrete) % reused content % recycled waste content (e.g. flyash) % recycled waste content % manufactured regionally (<500 mi.) % materials extracted regionally (<500 mi.) 1 27

28 Green Infrastructure Reduced combined sewer overflows Less expensive than separating storm & sanitary sewers Supports tree growth Improves neighborhood character Other Environmental Benefits Reduce erosion & salt water intrusion, protect water quality 28

29 ICPI Resources Tech Spec 16 Achieving LEED Credits with Segmental Concrete Pavements Covers U.S. & Canadian LEED requirements Interlocking Concrete Pavement Institute Park Center Road Suite 270 Herndon, Virginia Tel: Canada: P.O. Box Brant Street Burlington, ON L7R 4K2 29