./600/R-10/083
United States
Environmental Protection
Agency
ace Infiltration Rates of Permeable Surfaces:
Six Month Update (November 2009 through April 201
Office of Research and Development
National Risk Management Research
ter Supply and Water Resources Division
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Surface Infiltration Rates of Permeable Surfaces:
Six Month Update (November 2009 through April 2010)
Michael Borst
Amy A. Rowe
Emilie K. Stander
Thomas P. O'Connor
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Water Supply and Water Resources Division
2890 Woodbridge Ave (MS 104)
Edison, NJ 08837
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Disclaimer
The U.S. Environmental Protection Agency, through its Office of Research and Development,
funded and managed, or partially funded and collaborated in, the research described herein. It
has been subjected to the Agency's peer and administrative review and has been approved for
publication. Any opinions expressed in this report are those of the author (s) and do not
necessarily reflect the views of the Agency, therefore, no official endorsement should be inferred.
Any mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
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Abstract
At the end of October 2009, EPA opened a parking lot on the Edison Environmental Center that
included three parking rows of permeable pavement. The construction was a cooperative effort
among EPA's Office of Administration and Resources Management, National Risk Management
Research Laboratory, and the facility owner, Region 2. The lot serves as an active parking area
for facility staff and visitors and also as a research platform.
Key unknowns in the application of green infrastructure include the long term performance and
the maintenance requirements. The perceived uncertainty in these is a barrier to widespread
adoption of the installation of permeable surfaces for stormwater management. EPA recognizes
the need for credible long-term performance maintenance data and has begun a long-term
monitoring effort on this installation.
This document outlines the methods and results of the surface infiltration monitoring of the
permeable parking surfaces during the first six months of operation.
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the
Nation's land, air, and water resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement actions leading to a compatible balance between
human activities and the ability of natural systems to support and nurture life. To meet this
mandate, EPA's research program is providing data and technical support for solving
environmental problems today and building a science knowledge base necessary to manage our
ecological resources wisely, understand how pollutants affect our health, and prevent or reduce
environmental risks in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's center for
investigation of technological and management approaches for preventing and reducing risks
from pollution that threaten human health and the environment. The focus of the Laboratory's
research program is on methods and their cost-effectiveness for prevention and control of
pollution to air, land, water, and subsurface resources; protection of water quality in public water
systems; remediation of contaminated sites, sediments and groundwater; prevention and control
of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public
and private sector partners to foster technologies that reduce the cost of compliance and to
anticipate emerging problems. NRMRL's research provides solutions to environmental
problems by: developing and promoting technologies that protect and improve the environment;
advancing scientific and engineering information to support regulatory and policy decisions; and
providing the technical support and information transfer to ensure implementation of
environmental regulations and strategies at the national, state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term research plan.
It is published and made available by EPA's Office of Research and Development to assist the
user community and to link researchers with their clients.
Sally Gutierrez, Director
National Risk Management Research Laboratory
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Table of Contents
List of Tables 6
List of Figures 7
Chapter 1 Introduction 8
Chapter 2 Measurement Methods 10
Chapters Statistical Methods 13
Hypotheses 13
Chapter 4 Results 14
HI: Infiltration rate by surface type 14
H2: Infiltration rate by side 15
H3: Infiltration rate of porous concrete sections 16
H4: Infiltration rate changes with time 17
H5: Stripe effect 18
Chapters Conclusions 20
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List of Tables
Table 1. Location and results of the December 2009 surface infiltration measurements 22
Table 2. Location and results of January 2010 surface infiltration measurements 24
Table 3 Locations and results for February 2010 surface infiltration measurements 25
Table 4. Locations and results for March 2010 surface infiltration measurements 26
Table 5. Locations and results for April 2010 surface infiltration measurements 27
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List of Figures
Figure 1. Photograph of measurement apparatus 11
Figure 2. Drawing showing location of measurement locations 12
Figure 3 Graph showing the infiltration rate of the three surface materials 15
Figure 4. Graph showing the infiltration rate of the east and west sides porous concrete 16
Figure 5. Graph showing monthly measured surface infiltration rate of each surface 18
Figure 6. Photograph of the wetted area after removing the test apparatus showing leakage 20
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Chapter 1 Introduction
The U.S. Environmental Protection Agency (EPA) constructed a parking lot on the Edison
Environmental Center that incorporates three permeable pavement surfaces. The parking lot has
110 spaces in three double (head-to-head parking) rows and two single car rows. The three
double rows have permeable surfaces (interlocking concrete pavers, porous concrete, and porous
asphalt). The northernmost (single) row is paved with porous concrete. The driving lanes and
the southernmost single parking row are traditional impervious asphalt. All surfaces were placed
during the fall of 2009 by installers certified by their respective trade organizations.
The lot is actively used, providing parking for facility staff and visitors. In addition to providing
the facility with needed parking, EPA's National Risk Management Research Laboratory
(NRMRL) is using the parking lot as a platform to monitor the performance of the three
permeable surfaces as a stormwater management practice. The site is also being used as an
outreach tool to demonstrate a working example of the stormwater control.
Part of the planned NRMRL research is to collect information that will allow users to create an
a priori estimate of the maintenance requirements and predict the associated operating costs.
While many owners will routinely clean the parking area for litter and debris control, a more
aggressive cleaning may be required periodically to maintain or restore the surface infiltration
capacity. Cahill and others (2003), for example, recommend maintaining with an industrial
vacuum system twice each year while simultaneously noting that installations that have not been
maintained continue to function well for many years. Balades and others (1995) noted no
reduction in infiltration rates during the first year and rapid reductions in unmaintained systems
in the following year. Conceptually, the infiltration rate decreases as solids accumulate in the
surface pores (Legret and Colandini 1999). The accumulated solids decrease the open area
available for water passage and, therefore, decrease the surface infiltration capacity. Periodic
cleaning removes the solids, reopening the passages and restoring the infiltration capacity.
Currently there is insufficient information to forecast the cleaning frequency necessary to
maintain the needed infiltration capacity or assess the effectiveness of the cleaning. This
knowledge gap precludes generating estimates of operating and whole-life costs that, in turn, are
perceived barriers to increased use.
The NRMRL research uses an imaginary north-south line to divide each permeable parking area
into an eastern half and a western half. The planned research approach will clean half of each
parking area after a certain decrease in infiltration. The remainder of the parking area will not be
maintained until a later time to allow comparison. Monitored infiltration rates will provide clear
results demonstrating the presumed infiltration capacity recovery produced by the periodic
cleaning and demonstrate any longer-term degradation of the infiltration rate of the unmaintained
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surfaces.
Surface infiltration rates are measured monthly and the current plan is to use regenerative air
vacuum systems to vacuum the lot based on measured changes in infiltration rates. This
document presents the first set of infiltration measurements collected during the first six months
of parking lot use. The period was predominantly the winter months. The first infiltration
measurements were completed during December 2009, the second month that the parking lot was
in use.
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Chapter 2 Measurement Methods
Infiltration measurements were made following a modified version of the ASTM method C1701
(ASTM 2009). Although the method was developed specifically for porous concrete, this testing
applies the same method to all three permeable surfaces. The sole modification was the sealing
method between the 12-inch diameter PVC cylinder and the surface. The pipe used in this
testing is 15 cm high with parallel black lines drawn 10 and 15 mm from the pipe bottom. This
work substitutes ^-inch thick Neoprene sheeting compressed with applied weight (See Figure 1)
for the plumbers' putty seal described in the ASTM method. The Neoprene sheeting is trimmed
to align with the inside circumference of the pipe. The wooden frame holds 5-gallon buckets
filled with stone. Tie-down straps spanning the PVC cylinder support the frame slightly above
the parking lot surface. The weight of the buckets on the pipe compresses the Neoprene sheet to
form a gasket with minimal leakage. When used on the pavers, additional Neoprene strips
placed in the gaps between the individual paver blocks dam the openings. Similar sealing
mechanisms have been used successfully by others (e.g., Backstrom and Bergstrom 2000; Bean
2007; Houle 2008).
After positioning the pipe and applying the weight, 3.60 kg of water is poured into the area
isolated by the cylinder while keeping the water level between the two lines drawn on the interior
during the pouring. The pipe is oriented so that the lines are at the lower (southern) side. The
time required for the water to drain, called the prewet time, is measured and recorded. The time
begins when the water first impacts the permeable surface and stops when water is no longer
visible on the surface.
If the prewet time is less than 30 seconds, then the infiltration measurement is completed with
18.00 kg of water. If the time is 30 seconds or more, then the infiltration measurement is made
using 3.60 kg of water. The testing is done within 2 minutes of the prewet measurement and
measurement sites must be separated by at least 1 m. No testing is undertaken within 24 hours of
measurable rainfall.
The location for each measurement was selected using the random number1 function in an Excel
spreadsheet (Microsoft Corp. 2003). The spreadsheet was created to identify a set of three
locations on the eastern and western half of each surface. The surface area of each half of the
double parking rows is about 250 m2. The ASTM method requires measurements at three
1 Microsoft has tested the algorithm used in the RAND function of Excel 2003 using the Diehard
tests. The testing shows that the pseudo random number generator repeats only after 1013
function calls. See http://support.microsoft.com/kb/828795
10
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locations for areas up to 2,500 m2 with one additional measurement for each additional 1,000 m2
of area. The locations are specified as a distance from the adjacent curb and from the north edge
of the permeable surface with all measurements rounded to the nearest inch. A pair of spare
locations was also designated for situations where parked vehicles prevented the measurement
for multiple days. Figure 2 shows the locations where measurements were completed.
Locations where the positioning of the ring spanned a painted line were noted and, after the
December measurements, the water temperature was measured and recorded.
The 24 monthly measurements can be completed in a single day by two people if the water
containers are prepared the previous day and there are no complications during the process. The
measurements must be scheduled around the weather as the method requires a 24-hr antecedent
dry period, and rain events trigger other sampling procedures in the parking lot. Weather and
other factors combined to delay the February measurements until March 1, 2010. The March
measurements were mostly completed on March 10, 2010. The time between the measurements
is not uniform from month to month.
•
.
,
-
Figure 1. The weight of the 5-gallon buckets of stone applied to the PVC compresses the Neoprene sheeting to form a
leak-free seal with the parking surface. Collectively the buckets weigh 150 to 200 kg.
11
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Thermistors embedded in the surface material during construction monitor the pavement
temperature at 10-minute intervals. The temperature of the surfaces are noted to potentially
adjust for known temperature-related effects (Backstrom and Bergstrom 2000; Braga, Horst et al.
2007; Emerson and Traver 2008) that may introduce seasonal infiltration patterns.
North
PC
Pavers
PC
PA
D
Figure 2. The location of the measured infiltration rate was selected using a random number generator within each half of
each permeable section. PC designates porous concrete, PA designates porous asphalt. The X's show the location of
entry doors to the building at the bottom. Colors indicate the month the measurements were made. The far right-hand
parking row is traditional impervious asphalt. The circles are to approximate scale. The color codes are December,
January, February, March, and April.
12
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Chapter 3 Statistical Methods
Using the known area and water mass (either 3.60 kg or 18.00 kg, depending on the measured
prewet time), the measured time required for the water to drain from the pipe through the surface
was converted to an infiltration rate. Each measurement is associated with a permeable surface
material, measurement date, and location in the parking lot (east or west) in anticipation of the
future vacuuming. The two porous concrete areas are identified separately as either the middle
(row 2) or northern row (row 0). All analyses used Statistica 9.0 (Statsoft 2010) with the
significance levels set to 95% (a=0.05). Other than the testing for H5 that uses a one-way
analysis of variance (ANOVA), the results are analyzed as a repeated-measures ANOVA.
Hypotheses
The data are analyzed to test five hypotheses on the infiltration rates (/) of the pavers, porous
concrete (PC) and porous asphalt (PA) surfaces during this six-month pre-maintenance period.
HI: The infiltration rates differ from surface to surface.
-* Pavers ^ * PC ^ * PA
H2: The infiltration rates of the east and west side of a given surface are equivalent..
Ii,E =It,w for *=Pavers, PC, PA
H3: The infiltration rates of the two porous concrete sections are equivalent.
*PC,0 ~ *PC,2
H4: The infiltration rates of each section decrease with passing time.
^Dec > ^Jan > *\F* > *t Mar ^ i =PaVerS, PC, PA
H5: Measuring on a paint stripe will reduce the measured infiltration rate.
< »*. for ^P^ers, PC, PA
13
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Chapter 4 Results
Table 1 through Table 5 list the locations, measured infiltration times and calculated infiltration
rates for each measurement made from December 2009 through April 2010.
The prewet times required that the tests use 18.00 kg of water for all measurements on the pavers
and the porous concrete. The pre-wet time required 3.60 kg of water for all measurements on the
porous asphalt but one during the January measurements that used 18.00 kg.
HI: Infiltration rate by surface type
The first hypothesis tests whether the surface infiltration rates vary from surface to surface. The
ANOVA groups the two porous concrete rows into a single category and shows that the surface
infiltration rates are significantly different (F(2, 21)=119.5, p«0.001). The trend (observed
unweighted means) is from porous concrete (4000 cm/hr) to pavers (2,400 cm/hr) to porous
asphalt (200 cm/hr). Figure 3 shows the results for the three surfaces.
14
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Current effect: F(2, 21)=119.47, p<0.00001
Vertical bars denote 0.95 confidence intervals
5000
4500
4000
3500
3000
2500
2000
1500
11000
!
2. 500
Figure 3 The ANOVA shows differences in the infiltration rate of the three surface materials. This analysis pools the
porous concrete measurements across both rows.
H2: Infiltration rate by side
The east and west side of each surface have received nearly the same treatment during the first
six months of operation. The time required for the installation of any surface was no more than a
few days. The lot is used to near capacity so most parking stalls are routinely filled during the
work day; however the west side of the parking lanes is nearer the building entrance and may
receive preferential parking when there are excess spaces. Snow management has been similar
on each side of the lot with plowing using a rubber-edged blade and salt applications but no sand
application. Overall, the expectation is that before maintenance occurs to differentiate the two
sides, the east and west sides of each parking row will have the same infiltration rate.
In comparing the infiltration rates of the halves, the parking rows are each tested separately. The
infiltration rate of the western side of the middle porous concrete row (4,000 cm/hr) is
significantly (F(l, 4)=9.3, p=0.038) smaller than the infiltration rate of the eastern half of that
15
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row (5,000 cm/hr). Figure 4 shows the differences in infiltration rates for the middle porous
concrete row. The infiltration rates on the eastern and western halves of the northern concrete
row, the interlocking pavers, and the porous asphalt are not significantly different.
Middle Porous Concrete row
Current effect: F(1, 4)=9.3448, p=0.038
Vertical bars denote 0.95 confidence intervals
6000
5500
5000
4500
4000
§,3500
^3000
| East West
Figure 4. The infiltration rate of the east and west sides of the middle porous concrete are significantly different
H3: Infiltration rate of porous concrete sections
The third hypothesis, that the infiltration rate of the two porous concrete rows is the same,
recognizes that the two rows were poured during the same two-day period and have received
similar use and maintenance as already outlined. The northern row includes some parking
spaces designated as handicapped parking that appear to be used less frequently than the
remaining parking spaces. The larger gap between the handicapped parking spaces to allow for
wider door openings is not generally used for parking. The northern row is a single row which
means that the infiltration measurements are denser than the measurements in middle row, which
is a double row. This approach maintains the minimum of three measurements locations for an
area outlined in the ASTM test method. During the installation, it was noted that the northern
parking row is thicker than the middle concrete row (20 cm vs. 15 cm).
16
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The ANOVA shows that the infiltration rate of the northern row (3,600 cm/hr) is significantly
(F(l,10)=9.050, p=0.013) smaller than the infiltration rate of the middle parking row
(4,500 cm/hr).
H4: Infiltration rate changes with time
The fourth hypothesis addresses the research on the maintenance needs of the permeable surfaces
by tracking the infiltration rate. The expectation is that, with time, the vehicles using the parking
lot will transport particulates to the parking surface that, along with wind-blown particulates,
accumulate in the surface openings. The accumulation of particulates will progressively block
the openings and reduce the infiltration capacity. Solids accumulate from, among other sources,
particulates carried by the vehicles, tire deterioration, wind-blown solids and run on from
adjacent areas. Anecdotally, the particulates accumulate more rapidly when roadways receive
traction sand that is carried onto the surface by vehicles even if it is not directly applied to the
permeable surfaces.
The measurements show no significant changes in the infiltration rate of the porous asphalt or
the pavers during the monitored period. The porous concrete, however, shows a more surprising
trend. The infiltration rates measured from February through April are larger than the December
and January measurements. Figure 5 shows the monthly mean infiltration rate for each
permeable surface.
17
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6000
5000
4000
3000
2000
w
CD
1000
I
JO
December
January
February
March
April
Porous
Concrete
Interlocking
Pavers
Porous
Asohalt
Figure 5. The monthly measured surface infiltration rate of each surface is shown above. This analysis pools the
measurements from both rows of porous concrete. There is no change in the measured infiltration rates of the
interlocking pavers or porous asphalt, but the infiltration rates of the porous concrete increase.
H5: Stripe effect
The construction specifications call for waterborne acrylic traffic paint to be used for the stripes
and other traffic markings on the parking lot. The lines designating the parking stalls and the
diagonal striping between handicap stalls are four inches wide. The lines designating the
handicapped parking are blue and the remaining lines are white. If the selected sampling
location happens to center on a line crossing; the painted surface can theoretically be more than
70% of the available infiltration area. If the paint hinders flow through the surface, then the
infiltration rate of the surfaces will be smaller when the measurement location spans a painted
surface.
Of the 120 sites where infiltration was measured during this period, 21 are noted to have
included a partly painted area. Most (16) measurements that span or partially span a line are on
the porous concrete surface. For the remainder, 3 are on the porous asphalt and only 1 is on
pavers. The one-way factorial ANOVA suggests that making a measurement where paint is
18
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partly on the infiltrating areas does not affect the measured infiltration rate (F(l, 118)=0.1,
p=0.90) for any of the surfaces. Examining the porous concrete as a subset because of the large
fraction of the measurements including a stripe made on the concrete supports the conclusion the
paint does not affect the measurements (F(l, 58)=0.04, p=0.91).
19
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Chapter 5 Conclusions
The compressed Neoprene sheet forms an effective seal that prevents leaks between the pipe and
the parking surface. Minimal leakage was observed on the porous asphalt and nearly no leakage
was observed on either the pavers or the porous concrete (see Figure 6).
Figure 6. The wetted area after removing the test apparatus shows the limited leakage through the seal formed by the
compressed Neoprene sheeting.
The infiltration capacity of all three surfaces is very large. Although the surface infiltration rates
vary by more than an order of magnitude, each is much larger than the reasonably expected rain
event. This translates into a difference in the amount of available excess capacity or the amount
20
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of impervious surface that can be serviced. The values are in reasonable agreement with values
reported by others (e.g., Ferguson 2005; Bean 2007) in the literature.
The data are highly variable with relative standard deviations usually exceeding 10% of the mean
value. The confidence interval for the mean infiltration rate made on a given surface in a given
month average 700 cm/hr and range from 480 to 900 cm/hr. This is partially attributable to the
high infiltration rates making the measurement difficult to execute. Pouring 18 kg of water into
the 12-inch diameter pipe while trying to maintain the water depth between the markings 5 mm
apart in the pipe is awkward. The high variability will make it difficult to detect meaningful
change. For example, the confidence interval for the porous asphalt does not exclude zero so, if
current uncertainty levels continue, even complete blockage will not be statistically different
from the current readings (see Figure 3 and Figure 5).
The surface infiltration rates of the east and west halves of the middle porous concrete row are
significantly different. The infiltration rate of the western half is smaller than the infiltration rate
of eastern half. If this difference is the result of preferential parking, then the western rate would
have decreased from the common starting point. The data do not support this, however. Post
hoc testing does not show significant time based changes for either half of the lot (F(4, 16)=0.74,
p=0.58) suggesting the cause is other than users selectively parking near the building.
The painted stripes do not affect the measured infiltration rates on the porous concrete. On the
concrete, the paint appears to mostly coat the surfaces surrounding the opening and not seal the
openings. All the measurements completed to date on a painted surface have been situated such
that the painted surface blocks a relatively small portion of the infiltrating area which may be
masking the potential effect. The large infiltration capacity of the unpainted area, particularly
with the variability of the measurements, will mask any effects.
The anticipated reduction in infiltration capacity from clogging has not occurred during this
period. The anecdotal information on infiltration reductions closely associated with winter
operations failed to materialize. The differences in the porous concrete measurements suggest an
increase in infiltration capacity with passing time during this period. The available temperature
data are rough estimates of the temperature of the infiltrating water and are not adequate to test
temperature-related effects. The water temperature, average air temperature, and temperature
recorded by the thermistors embedded in the wearing surface do not show an obvious correlation
to measured infiltration rates.
21
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Table 1. Location and results of the December 2009 surface infiltration measurements.
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0 does not have embedded thermistors. The temperature of the driving surface is recorded at
10-minute intervals using Campbell Scientific (Logan, UT) thermistors (model 107 and 108) and
loggers (model CR1000X).
Row
1
2
3
Surface
Pavers
Porous Concrete
Porous Asphalt
T East (°C)
7.7
5.6
7.1
T West (°C)
-1.7
6.8
7.8
23
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Table 2. Location and results of January 2010 surface infiltration measurements.
Distance
Distance from
J2 from North
E Curb edge
water used
E
o
O
o
Q.
E
1 * 1
C£ I _J
L2
E A1
0 A2
L1
W L2
L3
L1
E L2
1 A1
L2
W L3
A2
L2
E L3
A1
L1
W L2
A1
L2
E L3
A2
L1
W L3
A1
Ft
53
24
53
11
43
26
44
29
50
30
12
37
61
41
11
4
42
9
17
11
6
34
53
42
In.
8
4
8
5
11
2
6
7
8
6
6
7
1
10
0
0
9
11
3
5
6
7
10
3
Ft
18
15
3
13
18
16
35
30
30
23
15
9
6
6
1
19
23
3
11
19
25
23
32
7
In.
3
6
6
10
9
10
6
6
7
6
9
9
5
8
0
1
2
10
11
2
2
1
2
9
CL
7.0
11.8
6.5
11.7
8.2
6.8
10.2
8.2
6.9
9.8
7.5
9.3
7.6
7.5
7.1
6.6
5.3
7.8
102.8
191.8
104.3
36.6
20.1
42.2
O)
1
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
3.6
3.6
3.6
3.6
18.0
3.6
1
H
31.6
65.9
22.6
55.1
21.6
30.0
38.8
38.5
30.9
54.9
31.3
42.3
19.8
22.0
21.6
27.2
20.8
30.4
187.8
293.2
233.2
72.6
153.9
76.9
£ ^ $ ° a
t 8 I £ £
1115
535 1070 514 48%
1559 Y
640
1632 1149 496 43%
1175
908
915 988 132 13%
1141
642
1126 Y 867 244 28%
833
1780 Y
1600 Y 1670 96 6%
1632
1296 Y
1694 Y 1383 278 20%
1159
38
24 31 7 22%
30
97
229 139 78 56%
92 Y
-§->
i
10.4
15.8
8.3
7.8
16.5
8.6
16.0
9.9
The average surface temperature recorded by thermistors embedded in each surface listed from
08:00 through 16:00 EST the day of measurement (January 14, 2010) for rows 1 through 3 is
below. Row 0 does not have embedded thermistors. The average air temperature for the same
period was 3.2 °C.
Row
1
2
3
Surface
Pavers
Porous Concrete
Porous Asphalt
T East (°C)
2.3
-2.9
4.6
T West (°C)
4.9
-1.1
1.4
24
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Table 3 Locations and results for February 2010 surface infiltration measurements.
-9 Distance
=s from
Curb
Distance
from
North
edge
-J2.
E
O O)
o
Ct
t g
g
lo
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Table 4. Locations and results for March 2010 surface infiltration measurements.
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Table 5. Locations and results for April 2010 surface infiltration measurements.
O
5
6
0
1
2
3
-U
E
g
M- ^0
ro 8
X _l
L1*
E A1*
A2*
L2*
W A1*
A2*
L2*
E A1*
A2*
L1*
W L3*
A2*
L1*
E L2*
A2*
L2*
W L3*
A1*
L1*
E L2*
A2*
L1*
W L3*
A1*
Distance
from curb
Ft
57
66
10
4
20
6
44
52
35
43
32
68
27
31
31
52
3
6
12
51
10
57
3
10
In.
1
1
12
4
10
10
9
10
2
3
5
10
4
0
2
3
11
1
2
1
7
0
2
1
Distance
from
North
edge
Ft
2
11
5
18
4
12
20
22
34
23
14
13
23
37
29
8
20
25
31
4
25
15
3
26
In.
12
3
1
0
3
3
2
4
3
5
4
4
7
2
1
3
11
3
9
8
4
2
1
2
E
P
"5
CL
5.7
8.7
4.9
5.7
5.1
6.5
10.0
9.4
9.6
9.1
7.7
7.5
9.4
8.2
5.6
5.3
6.5
5.4
43.6
57.5
38.0
83.2
56.4
68.4
1
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» ,
24.6
13.4
16.1
22.8
22.8
33.3
39.3
39.6
40.6
39.9
29.6
29.3
17.1
19.1
18.0
20.5
27.5
27.8
65.8
134.4
80.8
169.8
106.1
129.8
- E c "°
= 3. o < 55
1433
2630 2084 606
2189 Y
1546
1546 Y 1383 281
1058
897
890 885 15
868
883
1191 1092 181
1203
2057
1845 Y 1953 106
1958
1719
1282 1423 257
1268
107 Y
52 82 28
87
42
66 54 12
54
Q
CO
r±
29%
20%
2%
17%
5%
18%
34%
23%
cL
E
-------
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