A Performance Evaluation of Porous Asphalt as a Stormwater Treatment Strategy January 2006

Transcription

1 A Performance Evaluation of Porous Asphalt as a Stormwater Treatment Strategy January 2006 By Dr. Robert M. Roseen, Dr. Thomas P. Ballestero, Joshua F. Briggs, James P. Houle

2 Stormwater Center Crew Dr. Thomas P. Ballestero--- PI Dr. Robert Roseen--Director Jamie Houle Facility manager Pedro Avellaneda Site wide Josh Briggs---Porous Asphalt Robert Wildey---Micro Darlene Brown, Tim Puls, Greg Sine, and Joel Ballestero

3 Research Objective To evaluate porous asphalt a stormwater management strategy The design sizing criteria was based on the need to provide storage for a 10 year rainfall event. That entails 4.3 of rainfall storage within approximately 15 of materials

4 Study Area REFERENCE LOT POROUS ASPHALT

5 Study Details March -Present: 4 storms included, 5 add tl to be analyzed, challenged by no-flow events A paired design: half dense mix asphalt, half porous, asphalt Located at the UNH Stormwater Center in Durham. Part of a 600+ space parking lot is standard dense mix asphalt used near capacity throughout the academic year. Activity is a combination of passenger vehicles and routine bus traffic. Time of concentration= 6 minutes, slopes = 1% Frequent plowing, salting, and sanding during the winter months. Contaminant concentrations are above or equal to national norms for parking lot runoff.

6 DESIGN SOURCES Modified After Vermont Agency Of Transportation Specifications for Open Graded Friction Course (Section 409). Michelle Adams, Cahill Associates, Environmental Consultants, 104 South High Street, West Chester, PA Porous Asphalt Pavements (2004) Information Series 131. The National Asphalt Pavement Association, Lanham, MD. Design, Construction, and Maintenance of Open-Graded Asphalt Friction Courses (2002). Information Series 115. The National Asphalt Pavement Association, Lanham, MD.

7 Porous Asphalt Cross-Section 4 of porous asphalt 4 choker coarse of ¾ crushed stone 8-12 thickness of porous reservoir subbase

8 Methods Data collection and storage by ISCO 6712FR Refrigerated Sampler Precipitation - Tipping bucket rain gauge (ISCO 674) Flow Compound weir (6 Thelmar) w/ ISCO 730 Bubbler

9 Data Synthesis Hyetograph Hydrograph: delay coeff and lag time by centroid analyses Cold Climate Assessment Infiltration Rates Event Mean Concentration (EMC)

10 What is Porous Asphalt?

11 Origins of Porous Asphalt - OGFC Porous asphalt is a modification of Open Graded Friction Course (OGFC) Porous asphalt for our purposes is a single pavement layer used for low traffic areas that allows subsurface infiltration to an open bottom reservoir base OGFC: Is a coarse-graded asphalt mixture overlying an impervious base, typically used on highways Water drains through OGFC to impervious layer, then to shoulder Improves traction, reduces spray, deadens tire noise Is cost competitive with Hot Mix Asphalt (HMA) Some evidence that stormwater movement through OGFC improves water quality

12 Porous Asphalt Pavement = binder + aggregate Modification of Open Grade Friction Course (OGFC) Aggregate gradation is coarse w/ few fines Asphalt binder often modified (polymers, fibers) but not necessary Air voids 18-22% Standard Porous Asphalt Mixes US Standard Sieve Size 1/2 in. 3/8 in. #4 #8 #16 #30 Percent Passing Percent bituminous % by weight 2

13 30 gpm infiltration test on porous asphalt

14 I-95 North, June, NO OGFC overlay

15 I-95 North, June, OGFC overlay

16 I-95 South, June, NO OGFC overlay

17 Misconceptions About Porous Asphalt Freezes Faster - rather increased speed in thawing compared to DMA, due to flow through by meltwater (Backstrom, 2000) Higher Maintenance and Cost - overall $$ is comparable Clogs - sure but still maintains high IR (10+ in/hr) Cannot Plow, Salt, or De-Ice - not true Heaving and Shifting - reduced due to vadose zone disconnect Lower Lifespan - increased due to reduced freeze thaw (Spelic, 2003)

18 Monitoring and Performance Data

19 Surface Inundation Test Surface Inundation Test provides estimate of infiltration rate (Bean, 2004) 1-foot dia. SS column sealed to pavement with putty or weighted base with foam 5 gallons water poured into cylinder; measure time to infiltrate into pavement surface

20 Surface Infiltration Rates 7,000 Surface Infiltration Rate, cm/hr 6,000 5,000 4,000 3,000 2,000 1,000 ; Point A Point B Point C 0 1/1 2/20 4/11 5/31 7/20 9/8 10/28

21 Surface Infiltration Rates at 3 Locations for Surface Infiltration Rate, cm/hr 7,000 6,000 5,000 4,000 3,000 2,000 1,000 0 A B C Location on Porous Asphalt Pavement

22 Frost Penetration Field assembled frost gauge (CRREL, 1976) Solinst LT Levelogger placed at variable levels in a shallow GW well

23 Frost Penetration Winter Frost Depths Air Temperature, deg. C Air Temp. Avg. Air Temp. Frost Depth 3/2 3/7 3/12 3/17 3/22 3/27 4/ Frost Depth, ft

24 Filter Media Frost Penetration 1/13/ 1/25/ 2/4/ 2/16/ 2/25/ 3/8/ 3/15/ 3/28/ Inches B-Sand D-Bio G-Gravel Rain Ave. Temp Temp *F

25 Rainfall and Runoff March 28, Storm and Snowmelt Event Flow (gpm) Influent Flow Porous Asphalt Flow Rainfall Antecedent Dry Period (days): 3.4 Rainfall Depth (in): 2.35 Peak Flow Reduction: 60% Lag Time (min): 750 Delay Coefficient: Minute Rainfall (in.) ,000 1,500 2,000 2,500 3, Time (min)

26 Rainfall and Runoff (cont d) May 21, Storm Event Flow (gpm) Time (min) Antecedent Dry Period (days): 3.0 Rainfall Depth (in): 0.91 Peak Flow Reduction: 80% Lag Time (min): 1,320 Delay Coefficient: M inute Rainfall (in)

27 TSS Performance TSS Event Mean Concentration (mg/l Influent J-PAS

28 DIN Performance 1.6 DIN Event Mean Concentration (mg/l Influent J-PAS

29 TPH-D Performance TPH-D Event Mean Concentration (ug/l 1, Influent J-PAS

30 Zinc Performance Zn Event Mean Concentration (mg/l Influent J-PAS

31 Conclusions Peak flow and volume reduction are substantialdependent on subdrain design Water quality performance is similar to sand filters--- excellent removal- except for NO3 IR rates declined initially and appear to have stabilized Long term infiltration rates will need to be monitored Coring is needed to determine mechanism of decreased IR Appears to be a sound alternative to conventional BMPs Maintenance impacts will need to be evaluated

32 Acknowledgements Funding Source:

33 Questions?