PROJECT AT THE DENVER

Transcription

1 POROUS ASPHALT DEMONSTRATION PROJECT AT THE DENVER WASTEWATER BUILDING Ken A. MacKenzie, P.E. Manager, Master Planning Program Urban Drainage and Flood Control District 36 th Annual Rocky Mountain Asphalt Conference and Equipment Show Denver, Colorado February 19, 2009

2 Denver Wastewater Building

3 Denver Wastewater Building

4 Porous Asphalt Watershed 12,180 SF (0.28 Acres)

5 Porous Asphalt Area 90 x20

6 Porous Asphalt Section 3 porous asphalt 2 of #67 aggregate 7 of #3 aggregate 1 of C-33 sand Geotextile filter 6 of C-33 sand Geotextile filter 4 perforated pipe Impermeable liner Woven geotextile fabric meeting: ASTM D AOS U.S. STD. sieve #50 to #70 ASTM D Min. trapezoidal tear strength 100 X 60 lbs, Minimum COE specified open area of 4% ASTM C-33 Sand Base Course: #3 Aggregate (CDOT Section 703-2) AASHTO #67, all fractured faces; (CDOT SECT , #67 course aggregate) Open-Graded HMA 2% Min. Fill under-drain trench around pipe with AASHTO #67 stone 6.0" 6.0" 18.0" Min. 1" Thick sand cushion layer 2.5" 2.0" 16 mil impermeable liner under all paved areas wrapped to top of pavement Schedule 40 HDPE 4" Under-drain 7.0" 1.0" 6.0"

7 Demo the Site

8 Survey the subase for drainage

9 Prepare the underdrain

10 Place the underdrain and liner

11 Place the sand filter layer

12 Place the filter Place the filter fabric or geotextile

13 Place 1 sand atop the filter fabric

14 Place 1 sand atop the filter fabric

15 Place CDOT #3 Place CDOT #3 aggregate

16 Place CDOT #3 Place CDOT #3 aggregate

17 Place CDOT #3 aggregate

18 Place CDOT Place CDOT #67 aggregate

19 Bringinthe Bring in the asphalt

20 Check the temperature

21 Roll the asphalt Roll the asphalt not too much!

22 Placing the asphalt

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24 Miller Time!

25 Replace the inlet concrete

26 Earth Day ribbon cutting

27 Recognition of the partners time, money, and equipment contributions

28 Soaks the water right in!

29 PERFORMANCE TESTING

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34 INFILTRATION TESTING

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36 Infiltration Test Denver Wastewater Building 08/19/2008 Location Amt Liquid (ml) Height Liquid (in) Delta T (sec) (in/sec) Infiltration Rate (in/hr) PPPA

37 SAMPLING EQUIPMENT

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41 Tipping bucket rain gage measures every 0.01 of rainfall

42 1 1/8 hole for Pressure Transducer ¾ Orifice Hole Sampler Collection Line Cipoletti Weir

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44 Porous Asphalt Considerations (adapted from Dauphin County Conservation District, PA) Test soil to 2 feet below base of stone reservoir for permeability of at least 0.5 inch per hour. If less, use underdrain system. Porous surface permeability should be at least 8 inches per hour. Avoid compaction of soil base; if new fill is required, the addition of extra stone is recommended over adding compacted soil. Use light equipment with tracks or oversized tires during grading to prevent compaction of the soil base. Install at least 4 feet above the seasonal high groundwater table to avoid contamination Design should include overflow drainage to remove excess stormwater

45 Porous Asphalt Considerations (adapted from Dauphin County Conservation District, PA) Stone reservoir layer is placed in lifts and lightly rolled. Stone bedding layer should drain within 72 hours of a rain event. Slope of pavement surface should be less than 5%. Aggregate g for reservoir bed should be approximately 1 to 3 inches in diameter. Aggregate for reservoir must be clean-washed and contain at least 40% void space. Reservoir layer is typically 12 to 36 inches deep. Place porous asphalt directly on stone bed in a single 3.5 inch lift then roll to a finished depth of 2.5 inches.

46 Porous Asphalt Considerations (adapted from Dauphin County Conservation District, PA) Use 85 to 100% penetration grade to prevent surface from being scuffed by vehicle wheels. Temperature of asphalt should be between 240 and 260 F. Air temperature during paving must be at least 50 F. Not suitable for areas of recent fill (less than 5 years). Roll asphalt when it has cooled enough to withstand a ten-ton roller. Compact surface layer with one or two passes of roller; more frequent rolling can reduce infiltration capacity of pavement.

47 Porous Asphalt Considerations (adapted from Dauphin County Conservation District, PA) Control of sediment is critical - remove surface sediment with a vacuum or by sweeping; avoid power washing, as it will clog the system. Prohibit use of sand, salt or other de-icers that may clog system. Design must provide for a backup method for water to enter stone reservoir (ex. stone-edged drain near wheel stop if curbing is not in place). Not suitable for stormwater hot spots (truck stops, gas stations, etc.) due to high level of contaminants present. Use snow plows with caution during snow removal.

48 Porous Asphalt Considerations (adapted from Dauphin County Conservation District, PA) Not recommended for installation in areas of high traffic or heavy vehicle loads. Not recommended in areas where wind erosion supplies significant amounts of windblown sediment. Protect pavement from vehicular traffic for at least two days after installation. Post signs to prevent vehicles with muddy tires from entering area. Potholes and cracks may be patched with traditional patching mix, unless more than 10% of porous surface area needs to be repaired.