Evaluating the Field Performance of Permeable Concrete Pavers

Abstract

The benefits of using permeable interlocking concrete pavement systems (PICPs) have not translated into widespread adoption in Australia, where their uptake has been slow. This paper communicates the actual performance of PICPs installed in the field by providing evidence of their long-term efficiency. There are currently no Australian standards for design, specification and installation of PICPs. In this study, field measurements were conducted to determine the infiltration capacity of PICPs in Sydney and Wollongong, New South Wales, applying the single ring infiltrometer test (SRIT) and the stormwater infiltration field test (SWIFT). A strong correlation was found between the results of the two tests in a previous study, which was verified in this study. The long-term performance of PICPs is demonstrated by their high infiltration rates (ranging from 125 mm/h to 25,000 mm/h) measured in this study at field sites under a diverse range of conditions. The influences of conditions such as age of installation, slope and tree cover on infiltration rates were explored.

Full text

Citation: Nguyen, N.P.T.; Sultana, A.;
Areerachakul, N.; Kandasamy, J.
Evaluating the Field Performance of
Permeable Concrete Pavers. Water
2022,14, 2143. https://doi.org/
10.3390/w14142143
Academic Editors: Giuseppe Pezzinga
and Ioana Popescu
Received: 26 April 2022
Accepted: 30 June 2022
Published: 6 July 2022
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
water
Article
Evaluating the Field Performance of Permeable Concrete Pavers
Nam P. T. Nguyen 1, Albert Sultana 1, Nathaporn Areerachakul 2and Jaya Kandasamy 1,*
1Faculty of Engineering and IT, University of Technology Sydney, Sydney, NSW 2121, Australia;
namphuongtrinh.nguyen@alumni.uts.edu.au (N.P.T.N.); albert.sultana@alumni.uts.edu.au (A.S.)
2
Department of Safety Technology and Occupational Health, Faculty of Industrial Technology, Suan Sunandha
Rajabhat Univerity, Bangkok 10300, Thailand; nathaporn.ar@ssru.ac.th
*Correspondence: jaya.kandasamy@uts.edu.au; Tel.: +61-295142558
Abstract:
The benefits of using permeable interlocking concrete pavement systems (PICPs) have not
translated into widespread adoption in Australia, where their uptake has been slow. This paper
communicates the actual performance of PICPs installed in the field by providing evidence of their
long-term efficiency. There are currently no Australian standards for design, specification and
installation of PICPs. In this study, field measurements were conducted to determine the infiltration
capacity of PICPs in Sydney and Wollongong, New South Wales, applying the single ring infiltrometer
test (SRIT) and the stormwater infiltration field test (SWIFT). A strong correlation was found between
the results of the two tests in a previous study, which was verified in this study. The long-term
performance of PICPs is demonstrated by their high infiltration rates (ranging from 125 mm/h to
25,000 mm/h) measured in this study at field sites under a diverse range of conditions. The influences
of conditions such as age of installation, slope and tree cover on infiltration rates were explored.
Keywords: permeable pavement; infiltration rates; field measurements
1. Introduction
There has been considerable research into the operation of permeable pavements
intended to reduce runoff from urban impervious surfaces and to retain pollutants, thereby
reducing flooding and pollutant loads. Following pioneering studies in the 1990s [
1
], many
laboratory and field studies have been conducted worldwide. Several commercial products
have been developed—pervious concrete and asphalt pavements, permeable interlocking
concrete pavement (PICP) systems and grid pavement systems [2].
Permeable pavements have been widely promoted as a measure for water sensitive
urban design (WSUD) in Australia, sustainable urban drainage systems (SUDS) in the
United Kingdoms and low impact development (LID) in the Unites States of America. They
appear in many guides and lists of best management practices (BMPs) and stormwater
treatment options. PICPs have been adopted for many decades, beginning in the U.S. in
the 1970s and Europe in the 1980s.
PICPs are generally available in two types. The first type of PICPs is constructed with
non-porous pavers, where water infiltrates through the joints between pavers and into the
base layer. The second type is constructed with porous pavers, which are produced from a
no-fine concrete mixture to give a high void ratio, or using a comparable process. This type
of paver allows water to infiltrate through both the joints between pavers and through the
pavers themselves, creating a fully permeable surface.
In the case of PICPs (non-porous pavers), the gaps at joints between pavers are not
filled with sand or cement material as with conventional pavements. They are laid so
that there is sufficient space between the pavers to allow water to infiltrate into the lower
underlying layers, usually achieved through apertures fabricated into the paver’s shape.
Suitable selected material is used to fill the gaps between pavers and form the bedding
Water 2022,14, 2143. https://doi.org/10.3390/w14142143 https://www.mdpi.com/journal/water

Water 2022,14, 2143 2 of 16
layer. Pearson and Shackel [
3
] state that a fill of 2–5 mm aggregate (ASTM #9 grading)
provides the optimal compromise between high permeability and structural performance.
This study focusses on PICPs. Studies on PIPCs (both porous and non-porous) have
been undertaken globally, for example, in the U.S. [
4
–
6
]; Canada [
7
,
8
]; Europe [
9
–
13
] and
Australia [13–16]. It is evident from these studies that:
(a)
Infiltration rates through PICPs are variable, even for different test occasions at the
same location.
(b) During storm events and extended tests, infiltration rates decline with time, as systems
become saturated.
(c)
Rates are very high for laboratory tests and new field installations, but decline with
age in the field, with the main cause being blockage by fine sediments.
(d)
There can be difficulties in reversing this process through maintenance and renewal
operations.
Data from previous studies of infiltration rates of PICPs (non-porous pavers) have
been collated, primarily to assess the change in surface infiltration rate with age. The results
of the surface infiltration rates versus the age of the PICPs (non-porous pavers) are shown
in Figure 1. The general trend in the data shows a reduction in infiltration rate with age of
PICPs. However, a significant scatter is evident.
Water 2022, 14, x FOR PEER REVIEW 2 of 16
there is sufficient space between the pavers to allow water to infiltrate into the lower un-
derlying layers, usually achieved through apertures fabricated into the paver’s shape.
Suitable selected material is used to fill the gaps between pavers and form the bedding
layer. Pearson and Shackel [3] state that a fill of 2–5 mm aggregate (ASTM #9 grading)
provides the optimal compromise between high permeability and structural performance.
This study focusses on PICPs. Studies on PIPCs (both porous and non-porous) have
been undertaken globally, for example, in the U.S. [4–6]; Canada [7,8]; Europe [9–13] and
Australia [13–16]. It is evident from these studies that:
(a) Infiltration rates through PICPs are variable, even for different test occasions at the
same location.
(b) During storm events and extended tests, infiltration rates decline with time, as sys-
tems become saturated.
(c) Rates are very high for laboratory tests and new field installations, but decline with
age in the field, with the main cause being blockage by fine sediments.
(d) There can be difficulties in reversing this process through maintenance and renewal
operations.
Data from previous studies of infiltration rates of PICPs (non-porous pavers) have
been collated, primarily to assess the change in surface infiltration rate with age. The re-
sults of the surface infiltration rates versus the age of the PICPs (non-porous pavers) are
shown in Figure 1. The general trend in the data shows a reduction in infiltration rate with
age of PICPs. However, a significant scatter is evident.
Figure 1. Surface infiltration rate versus age of PICPs (non-porous), as recorded in various past
studies. (Collin et al. [6], Drake et al. [7], Boogaard et al. [10], Borgwardt et al. [11], Cipolla et al. [12],
and Sañudo-Fontaneda et al. [13]).
More recently, Boogaard and Lucke [17] conducted 17 field tests in the Netherlands
using the full-scale infiltration testing (FSIT) method where infiltration measurements
were taken when large sections of PICPs were inundated with water. All except two were
non-porous PIPCs. The results of Boogaard and Lucke [17] ranged between an infiltration
of 21–503 mm/h and PICP age of 2–8 years.
The fully permeable surface area provided by PICPs (porous pavers) can be expected
to perform as well, if not better. However few studies have been undertaken to assess the
Figure 1.
Surface infiltration rate versus age of PICPs (non-porous), as recorded in various past
studies. (Collin et al. [
6
], Drake et al. [
7
], Boogaard et al. [
10
], Borgwardt et al. [
11
], Cipolla et al. [
12
],
and Sañudo-Fontaneda et al. [13]).
More recently, Boogaard and Lucke [
17
] conducted 17 field tests in the Netherlands
using the full-scale infiltration testing (FSIT) method where infiltration measurements
were taken when large sections of PICPs were inundated with water. All except two were
non-porous PIPCs. The results of Boogaard and Lucke [
17
] ranged between an infiltration
of 21–503 mm/h and PICP age of 2–8 years.
The fully permeable surface area provided by PICPs (porous pavers) can be expected
to perform as well, if not better. However few studies have been undertaken to assess the
surface infiltration rates of PICPs (porous pavers), and how they compare against PICPs
(non-porous pavers) under factors such as age.
The adoption of PICPs in Australia has been slow [
18
], despite encouragement in
some localities. For example, the Ku-ring-gai Council in New South Wales (NSW) offers a

Water 2022,14, 2143 3 of 16
rebate of up to $1000 towards the cost of replacing an impervious surface with a permeable
one [
19
]. The product is not covered in most design guidelines, practice notes or policies
prepared by councils, which means asset owners are uncertain about what needs to be
considered in the design. Approval authorities are equally unsure of how to specify a
permeable pavement and what the long-term risks of approval are, specifically clogging
leading to reduction in infiltration rate, generation of surface runoff and a loss of pavement
structural integrity that leads to uneven surfaces. Approval often depends on the views of
council engineers and their possible limited experience of success, failures and maintenance
problems. Proposals involving permeable pavements are often rejected or, if approved, are
subjected to strict conditions, which can make their use uneconomical when compared
with other BMPs.
According to Moktan [
20
], there is a reluctance to embrace PICPs in national building
standards in Australia, which can be generalized as being due to ambiguities regarding
requirements for the maintenance, quality, performance and longevity of pavers. One of the
reasons why there is limited support to back up the case for PICPs is the lack of Australian
research that can be applied to specify suitable characteristics of permeable pavers for
various conditions, most notably, pavement life.
The purpose of the field tests is to gauge the long-term in-situ performance of PICPs
and examine the results for their implications for design. Assessment of field installation of
PICPs that exist under a range of conditions such as topography, in-situ soil, vegetation and
moisture conditions, and load and operating conditions were made. There is a perception
that PICPS quickly lose their infiltration capacity and this has held back their widespread
application. The results of this study will challenge widely held notions and inform
regulatory authorities and designers of the actual situation.
This paper presents the results of field-testing of PICPs at installation sites aged be-
tween 1 and 20 years in Sydney and Wollongong. The majority of the tests were conducted
for PICPs constructed with non-porous pavers, which rely on water infiltration through
joint spaces. This current study will primarily focus on PICPs of porous pavers that create
a fully permeable surface. The results of this study augment previous studies that pro-
vide data for PICPS of non-porous pavers allowing assessment of differing performance
characteristics between these two types of pavers.
This study applied two in-situ test methods that can be performed in the field. The
first method was the SWIFT test [
14
] and the second method uses a single ring infiltrometer
test (SRIT) [
21
]. Both methods were undertaken and the results from each compared. The
results obtained using these tests were assessed against the age of the PICPs, the catchment
land use, the slope of the pavement, the presence of vegetation cover, etc.
2. Materials and Methods
2.1. Locations of Field Tests
In this study, field infiltration tests of PICPs (porous and non-porous pavers) were
performed at several locations in Sydney and Wollongong (NSW) under various conditions
(see Table S1). Figure S1 shows the locations where the field tests were performed in
relation to local government council boundaries. HydroSTON [
22
] and Ecotrihex [
23
] are
porous pavers and non-porous pavers, respectively. Most of the tests were conducted
at sites where HydroSTON pavers were installed up to 10 years prior to the tests. Field
tests were also carried out at Sydney Olympic Park where Ecotrihex pavers [
23
] were
installed. The characteristics of the pavers are shown in Figure S2. H50 (HydroSTON)
and Ecotrihex pavers are commonly used as pedestrian footpaths, and H80 (HydroSTON)
pavers are used for car parks and driveways. Figure S3 is a section view showing a typical
substructure for permeable pavers and how infiltration passes through the pavement
surface. In Table S1, the slope rating was estimated by observation on-site. Vegetation
cover was evaluated based on the presence of trees and bushes overhanging the paved
area, along with observations of vegetation debris on the pavers.

Water 2022,14, 2143 4 of 16
2.2. SRIT (Single Ring Infiltrometer Test)
The SRIT was developed by the American Society for Testing and Materials, now
ASTM International (C1781M—14a) [
21
] to measure infiltration in the field. The method is
outlined in the Supplementary Material.
2.3. SWIFT (Stormwater Infiltration Field Test)
Lucke et al. [
14
] developed a simple, quick and inexpensive field test using readily
available equipment (see Figure S4) as an alternative method for measuring the infiltration
rate of PICPs for asset managers, local councils, etc., to quickly assess and evaluate the
infiltration rates of PICPs. Lucke et al. [
14
] showed that there is a correlation between the
results of the SWIFT and SRIT tests that is evident when the results collected using these
two methods are compared graphically. The is outlined by Lucke et al. [
14
] and in the
Supplementary Material.
3. Results
3.1. Field Tests: SRIT and SWIFT Comparison
Figure 2shows comparisons between the SRIT and SWIFT test results obtained by
Lucke et al. [
14
] and in this study. Lucke et al.’s [
14
] data were collected for non-porous
PICPs. The solid line on this graph shows the overall trend of data collected in this study.
The trendline for Lucke et al.’s [
14
] data is shown as a dotted line. Both datasets show a
similar trend. Overall, the infiltration rates obtained in the two studies are high, and range
widely between 125 and 25,000 mm/h. The latter was a measurement obtained in this
study. These rates are much greater than the heaviest rainfall intensities ever experienced
in Sydney and Wollongong [24].
Water 2022, 14, x FOR PEER REVIEW 4 of 16
used for car parks and driveways. Figure S3 is a section view showing a typical substruc-
ture for permeable pavers and how infiltration passes through the pavement surface. In
Table S1, the slope rating was estimated by observation on-site. Vegetation cover was
evaluated based on the presence of trees and bushes overhanging the paved area, along
with observations of vegetation debris on the pavers.
2.2. SRIT (Single Ring Infiltrometer Test)
The SRIT was developed by the American Society for Testing and Materials, now
ASTM International (C1781M—14a) [21] to measure infiltration in the field. The method
is outlined in the Supplementary Material.
2.3. SWIFT (Stormwater Infiltration Field Test)
Lucke et al. [14] developed a simple, quick and inexpensive field test using readily
available equipment (see Figure S4) as an alternative method for measuring the infiltration
rate of PICPs for asset managers, local councils, etc., to quickly assess and evaluate the
infiltration rates of PICPs. Lucke et al. [14] showed that there is a correlation between the
results of the SWIFT and SRIT tests that is evident when the results collected using these
two methods are compared graphically. The is outlined by Lucke et al. [14] and in the
Supplementary Material.
3. Results
3.1. Field Tests: SRIT and SWIFT Comparison
Figure 2 shows comparisons between the SRIT and SWIFT test results obtained by
Lucke et al. [14] and in this study. Lucke et al.’s [14] data were collected for non-porous
PICPs. The solid line on this graph shows the overall trend of data collected in this study.
The trendline for Lucke et al.’s [14] data is shown as a dotted line. Both datasets show a
similar trend. Overall, the infiltration rates obtained in the two studies are high, and range
widely between 125 and 25,000 mm/h. The latter was a measurement obtained in this
study. These rates are much greater than the heaviest rainfall intensities ever experienced
in Sydney and Wollongong [24].
Figure 2. Comparison of PICP infiltration rates using SRIT and SWIFT tests. Data from current study
and Lucke et al. [14].
Figure 2.
Comparison of PICP infiltration rates using SRIT and SWIFT tests. Data from current study
and Lucke et al. [14].
The trendline for the data from the present study is
I = 89,951N−1.084 (1)

Water 2022,14, 2143 5 of 16
where I is the infiltration rate; and N is the number of wet bricks (R
2
= 0.53). The trendline
of present study data excludes data of Trihex and Ecotrihex pavers (Table S1) that were
obtained in this study and explained later.
Lucke et al. [
14
] classified the blockage of PICPs according to infiltration rates, as
shown in Table 1. In this study, there are 10 data points that have an infiltration rate of
less than 2000 mm/h (medium blocked) and zero where the infiltration rate was less than
30 mm/h (fully blocked). The result indicated that PICPs retain their permeability very
well over extended periods under varying conditions.
Table 1. Degree of blockage of PICPS and related infiltration rates based on Lucke et al. [14].
Degree of Blockage Free of Blockage Medium Blockage Complete Blockage
Infiltration Rate (mm/h) >2000 30–2000 <30
In the present study, there were a total of 53 tests carried out at 13 locations (Table S1).
Tests at each location were carried out without cleaning the pavement surface prior to the
measurement, apart from removing large debris such as leaves that would interfere with the
testing. Of the 53 sites tested, there was only one, at the Albert de Lardes Reserve, Illawong
(Figure S1; Table S1), where the pavers appeared visibly blocked. This site is a popular
public car park, located on slightly sloping ground and with very significant tree coverage.
The site had not been subject to routine or systematic maintenance during its 7 years of use.
The three tests that were carried out at this location recorded a surface infiltration rate in
the range of 150–125 mm/h applying SRIT and wetting more than 65 pavers using SWIFT.
Figure 2shows that the trendline for the data collected in this study is different from
that of Lucke et al. [
14
]. The data of Lucke et al. [
14
] fits better to its trendline (R
2
= 0.85)
than that of the present study (R
2
= 0.53). While both trendlines have the same form, the
trendline of data of the present study shows that infiltration occurs through a smaller
number of bricks than the trendline of the data of Lucke et al. [
14
]. The data from the
present study are predominantly for HydroSTON pavers, which are porous to create a fully
permeable surface area. Lucke et al.’s [
14
] data is for non-porous pavers where infiltration
only occurs through the gaps between the pavers. Nonetheless, where the number of bricks
exceeds approximately 45 pavers, the situation appears to reverse, although this region is
not well defined with few HydroSTON data. The Trihex and Ecotrihex (non-porous pavers)
data collected in this present study fit well with the Lucke et al. [
14
] trendline, as they are
similar non-porous paver systems.
The data collected in the present study show more variability than those of Lucke
et al. [
14
], evident from the lower R
2
coefficient for the trendline of the present data. The
data of this study were collected from sites with a more heterogeneous range of conditions
(see Table S1). Apart from the predominant paver type in the study being porous pavers,
which in Lucke et al.’s study [
14
] were non-porous, other factors that could lead to the
differences in the measured infiltration rates include the slope of the pavement surface;
age of pavers; sub-grade structure including soil type, its saturation and water table
levels; quality of construction; operating conditions including size and type of clogging
materials and vegetation cover, vehicular and pedestrian loads; and frequency and quality
of maintenance. The following sections highlight differences in test conditions between the
two sets of data.
Location of testing: Lucke et al. [
14
] conducted SRIT and SWIFT tests at three sites on
the Sunshine Coast of Queensland. The SRIT test was carried out during one day, then
the SWIFT test was carried out at the exact location on another day, ensuring the same
environmental conditions were applied for each test. The tests in the present study were
carried out on the same day, one after the other at locations slightly offset to each other,
generally about 1–2 m away, i.e., the SRIT test was conducted at one location, then a few
minutes later the SWIFT test was conducted at a location within a 1–2 m radius of the SRIT

Water 2022,14, 2143 6 of 16
test location. Therefore, the base course and the surface of the pavers were not exactly the
same, yielding results that may not necessarily correlate.
Weather: Lucke et al. [
14
] stated that “replicate testing was undertaken on different
days to ensure the PICP surface was dry to allow for the number of wet bricks to be
counted.” Following the SRIT test, they waited for the pavement surface to dry to carry out
the SWIFT tests at the same location. Their study took into account the general condition of
the testing surface. The moisture conditions for the current tests were not the same for all
sites. Some sites experienced 10–30 mm of rainfall the day before testing, while other sites
were dry. The difference in moisture content at the test locations may have contributed to
the scatter in the data.
Slope: Lucke et al. [
14
] did not note the slope of the pavement at the sites where the
tests were performed. In this study, the slope of the pavements where measurements were
carried out are summarised in Table S1.
Type of pavers: Lucke et al. [
14
] carried out a similar number of tests on two PICPs
(non-porous) i.e., HydrapaveTM pavers, and Ecotrihex and Trihex pavers. The tests in this
study were carried out predominantly on HydroSTON pavers (see Figure 3). Further it was
observed that the sizes of gaps between pavers were not consistent between locations. This
can therefore affect the results of the test experiments.
Water 2022, 14, x FOR PEER REVIEW 6 of 16
ronmental conditions were applied for each test. The tests in the present study were car-
ried out on the same day, one after the other at locations slightly offset to each other, gen-
erally about 1–2 m away, i.e., the SRIT test was conducted at one location, then a few
minutes later the SWIFT test was conducted at a location within a 1–2 m radius of the SRIT
test location. Therefore, the base course and the surface of the pavers were not exactly the
same, yielding results that may not necessarily correlate.
Weather: Lucke et al. [14] stated that “replicate testing was undertaken on different
days to ensure the PICP surface was dry to allow for the number of wet bricks to be
counted.” Following the SRIT test, they waited for the pavement surface to dry to carry
out the SWIFT tests at the same location. Their study took into account the general condi-
tion of the testing surface. The moisture conditions for the current tests were not the same
for all sites. Some sites experienced 10–30 mm of rainfall the day before testing, while
other sites were dry. The difference in moisture content at the test locations may have
contributed to the scatter in the data.
Slope: Lucke et al. [14] did not note the slope of the pavement at the sites where the
tests were performed. In this study, the slope of the pavements where measurements were
carried out are summarised in Table S1.
Type of pavers: Lucke et al. [14] carried out a similar number of tests on two PICPs
(non-porous) i.e., HydrapaveTM pavers, and Ecotrihex and Trihex pavers. The tests in
this study were carried out predominantly on HydroSTON pavers (see Figure 3). Further
it was observed that the sizes of gaps between pavers were not consistent between loca-
tions. This can therefore affect the results of the test experiments.
Figure 3. Infiltration rate versus the age of PICPs with both porous and non-porous pavers.
Figure 3. Infiltration rate versus the age of PICPs with both porous and non-porous pavers.
Base course: The base course under the pavers tested in this study is noted in Table S1.
At some locations, the types of base course were not known. Lucke et al. [
14
] mentions
that two test sites used an aggregate base and one site used a sand base. Drainage through
pavers is affected by the type of base courses under the pavers, the gradation of the bedding
layer, the fill material in the joints between pavers and vegetation cover, as well as the size
of the drainage voids within the pavers themselves [25].

Water 2022,14, 2143 7 of 16
Trees: Lucke et al. [
14
] did not specify vegetation conditions, but photographs in the
paper show the sites to be relatively open, with only a few trees in the vicinity and none
overhanging the test location. The vegetation conditions of the tests in this study are
summarised in Table S1 and varied considerably, with overhanging trees and vegetation
cover at some locations.
Age: The variation of the age of PICPs within the three sites studied by Lucke et al. [
14
]
is not enough to properly assess the effect of age and was not considered in their analysis.
In this study, the age of the pavement is summarized in Table S1. The age was between 1
and 10 years for HydroSTON pavers, and 21 years for Trihex and Ecotrihex pavers. This
allows the impact of the age of the pavement on infiltration to be assessed and this is
discussed in Section 3.3.
3.2. Discussion on Variability
The scatter of data points in the present study is evident and may have been caused by
the different environmental conditions during measurement and factors such as slope, age,
vegetation cover, etc. To illustrate the nature of the scatter, the measurement conditions of
two points R14 and R16 are detailed.
Test R14 was conducted on a driveway at Newington College (Table S1, Figure S1)
and was located next to a tree. There was about 10 mm of rain at the site the day before
measurements were taken. Both the pavement and area around the tree had a damp surface.
The SRIT test took time to drain and the results could have been affected by the condition
of the sub-base structure. The SWIFT test could also have given an inaccurate result due
to the uneven slope (and sag point) at this test location. These reasons could explain the
lower number of wetted pavers during the SWIFT test.
The results from Test R16 were obtained at another car park at Newington College,
where the field measurements displayed a wide range. Measurements on the pavement
where cars parked gave a high infiltration rate. The Test R16 infiltration rate was obtained
on the driveway portion of the car park and was low. It was observed there were large
gaps of up to 10 mm between pavers, which could have been caused by vehicular loads.
These may have contributed to the variation in results.
3.3. Analysis of Factors Influencing the Infiltration Rate
In this section, factors that could influence the permeability of PICPs were assessed,
using data collected in this study.
Effect of paver type: The trendlines in Figure 2show infiltration occurs through a smaller
number of PICPs (porous pavers) than non-porous pavers (when the number of wet bricks
is less than 45).
Figure 2shows the surface infiltration rates of PICPs (porous pavers) obtained in
this study and that of PICPs (non-porous pavers) from previous studies, both compared
against pavement age. Trendlines show that, comparatively, porous pavers have a higher
infiltration rate relative to their age. This is expected, as porous pavers offer a significantly
more permeable surface area. There is significant scatter in this data resulting from the
influence of other in-situ factors, as previously discussed. Furthermore, the different testing
methods used in this study and the previous studies also contribute to the scatter.
Effect of age of pavement: The infiltration rate of PICPs is affected by the clogging that
typically occurs with age and by the slope of the pavement (Sañudo-Fontaneda et al. [
13
]).
Figure 4shows a plot of infiltration rates against the age of PICPs. The line shown in
Figure 4depicts the overall trend of the data. Newer PICPs give a higher infiltration rate
than older installations, as expected. However, even PICPs that are more than 20 years old
still had a high infiltration rate of about 800 mm/h. Nonetheless, the data has a large range
of vertical scatter, as discussed earlier. This could indicate the influence of other factors,
such as the slope at which the pavement was laid.

Water 2022,14, 2143 8 of 16
Water 2022, 14, x FOR PEER REVIEW 8 of 16
Figure 4 shows a plot of infiltration rates against the age of PICPs. The line shown in
Figure 4 depicts the overall trend of the data. Newer PICPs give a higher infiltration rate
than older installations, as expected. However, even PICPs that are more than 20 years
old still had a high infiltration rate of about 800 mm/h. Nonetheless, the data has a large
range of vertical scatter, as discussed earlier. This could indicate the influence of other
factors, such as the slope at which the pavement was laid.
Figure 4. Infiltration rate versus age of pavement for all field measurements conducted in this study.
Effect of usage: Infiltrations rates for PICPS used for different types of usage such as
residential driveways, pedestrian footpaths and car parks were analysed. These locations
where tests were carried out were those expected to have high pedestrian traffic or where
the pavers experienced high vehicle loads.
Figure 5 shows a comparison of infiltration rates for the different uses of PICPs. The
infiltration rate of pedestrian footpaths was slightly higher than that of residential drive-
ways and carparks.
Figure 4.
Infiltration rate versus age of pavement for all field measurements conducted in this study.
Effect of usage: Infiltrations rates for PICPS used for different types of usage such as
residential driveways, pedestrian footpaths and car parks were analysed. These locations
where tests were carried out were those expected to have high pedestrian traffic or where
the pavers experienced high vehicle loads.
Figure 5shows a comparison of infiltration rates for the different uses of PICPs.
The infiltration rate of pedestrian footpaths was slightly higher than that of residential
driveways and carparks.
To further identify the effects of traffic loads on PICPs, tests were carried out at a
car park at Newington School that had a flat slope and HydroSTON80 pavers (Table 2).
Four tests were performed at different locations at the car park. Test number R16 had been
discussed earlier. Tests R17 and R18 were carried out in the middle of a parking bay, where
high vehicle loads were not normally experienced. Tests R19 and R20 were performed on
a driveway or at a location that experiences wheel loading (near the line that demarcates
parking slots).
Table 2. Tests at different locations in Newington School car park.
Test No Number of Wet Bricks Usage Infiltration Rate (mm/h) Degree of Blockage * Age in Years
R16 18 Driveway 1362 Medium Blockage 10
R17 17 Parking bay 4772 Free of blockage 10
R18 17 Parking bay 5654 Free of blockage 10
R19 24 Driveway 3326 Free of blockage 10
R20 60 Driveway 870 Medium Blockage 10
* See Table 1for degree of blockage.

Water 2022,14, 2143 9 of 16
Water 2022, 14, x FOR PEER REVIEW 9 of 16
Figure 5. Infiltration rate of pavers under different usage.
To further identify the effects of traffic loads on PICPs, tests were carried out at a car
park at Newington School that had a flat slope and HydroSTON80 pavers (Table 2). Four
tests were performed at different locations at the car park. Test number R16 had been
discussed earlier. Tests R17 and R18 were carried out in the middle of a parking bay,
where high vehicle loads were not normally experienced. Tests R19 and R20 were per-
formed on a driveway or at a location that experiences wheel loading (near the line that
demarcates parking slots).
Table 2. Tests at different locations in Newington School car park.
Test No
Number of Wet Bricks
Usage
Infiltration Rate (mm/h)
Degree of Blockage *
Age in Years
R16
18
Driveway
1362
Medium Blockage
10
R17
17
Parking bay
4772
Free of blockage
10
R18
17
Parking bay
5654
Free of blockage
10
R19
24
Driveway
3326
Free of blockage
10
R20
60
Driveway
870
Medium Blockage
10
* See Table 1 for degree of blockage.
Table 2 demonstrates how the type of traffic and load can affect the infiltration rate.
The tests performed where there was higher traffic/load had a lower infiltration rate than
those locations with less traffic/load (see Table 2). The lowest infiltration rate collected at
locations under heavy loads and that were more highly trafficked was still relatively high
at 800 mm/h.
At Sydney Olympic Park E8, E9, E10 and E11 (Figure S1) had lower infiltration rates
because the paver type was PICPs (non-porous) and were 21 years old. PICPs here also
Figure 5. Infiltration rate of pavers under different usage.
Table 2demonstrates how the type of traffic and load can affect the infiltration rate.
The tests performed where there was higher traffic/load had a lower infiltration rate than
those locations with less traffic/load (see Table 2). The lowest infiltration rate collected at
locations under heavy loads and that were more highly trafficked was still relatively high
at 800 mm/h.
At Sydney Olympic Park E8, E9, E10 and E11 (Figure S1) had lower infiltration rates
because the paver type was PICPs (non-porous) and were 21 years old. PICPs here also
experienced high pedestrian traffic loads. Despite this the PICPs still had a relatively high
infiltration rate of 600–700 mm/h.
These measured data provide support for the use of PICPs as car park and pedestrian
pavements. Indeed, several government planning guides promote the use of a permeable
pavement for car parks [
26
–
29
]. Beyond this, these documents fail to provide technical
specifications or design parameters that can support their design and installation.
Effect of slope of pavement: Figure 6plots the infiltration of PICPs against the slope of
the pavement. Note that the slope was measured by eye-estimate and given a rating that
ranged from flat/gentle (rating = 1), medium (rating = 2) and steep (rating = 3), a form of
classification that may have exacerbated the scatter. In addition, 4–7 year old pavements
were selected for this plot because this was the range where the amount of data was the
largest. In the figure, the callout labels show the age of the pavers. The figure shows that
infiltration is higher where the slope is medium/steep compared with a flat/medium slope.
This may be explained by a self-cleaning effect where debris that would otherwise clog
pavements are more easily washed/blown away off steeper slopes.

Water 2022,14, 2143 10 of 16
Water 2022, 14, x FOR PEER REVIEW 10 of 16
experienced high pedestrian traffic loads. Despite this the PICPs still had a relatively high
infiltration rate of 600–700 mm/h.
These measured data provide support for the use of PICPs as car park and pedestrian
pavements. Indeed, several government planning guides promote the use of a permeable
pavement for car parks [26–29]. Beyond this, these documents fail to provide technical
specifications or design parameters that can support their design and installation.
Effect of slope of pavement: Figure 6 plots the infiltration of PICPs against the slope of
the pavement. Note that the slope was measured by eye-estimate and given a rating that
ranged from flat/gentle (rating = 1), medium (rating = 2) and steep (rating = 3), a form of
classification that may have exacerbated the scatter. In addition, 4–7 year old pavements
were selected for this plot because this was the range where the amount of data was the
largest. In the figure, the callout labels show the age of the pavers. The figure shows that
infiltration is higher where the slope is medium/steep compared with a flat/medium
slope. This may be explained by a self-cleaning effect where debris that would otherwise
clog pavements are more easily washed/blown away off steeper slopes.
Figure 6. Infiltration rate versus slope of pavement. The age of the pavement is between 4 and 7
years old. The call-out boxes show the age of the pavement.
Effect of vegetation overhang: Vegetation overhanging a pavement could influence the
infiltration through the pavement as more debris maybe expected to fall on the pavement.
While testing in the field, vegetation overhang was estimated based on the number of
surrounding trees and whether leaves were observed on the pavers and between the gaps
in the pavers. It was rated as 1 for no/light overhang, through to 3 for heavy vegetation
overhang.
Figure 6.
Infiltration rate versus slope of pavement. The age of the pavement is between 4 and 7 years
old. The call-out boxes show the age of the pavement.
Effect of vegetation overhang: Vegetation overhanging a pavement could influence the
infiltration through the pavement as more debris maybe expected to fall on the pavement.
While testing in the field, vegetation overhang was estimated based on the number of
surrounding trees and whether leaves were observed on the pavers and between the
gaps in the pavers. It was rated as 1 for no/light overhang, through to 3 for heavy
vegetation overhang.
The result plotted in Figure 7shows that vegetation also affects the infiltration rate of
PICPs, which is higher for lightly covered pavements. It should be noted that the infiltration
rates are high despite the presence of overhang, with locations with heavy overhang of
vegetation recording up to 6000 mm/h.
Effect of saturation: One of the concerns of PICPS is the expected reduced infiltration
rate over periods of extended rainfall. This can occur as the subgrade, base course and
bedding layer, and ground beneath the PICPs becomes saturated. The infiltration rate of
PICPs decreased over time during extended infiltration testing and continuous rainfall
(Razzaghmanesh and Beecham [
30
]). Infiltration testing conducted by Borgwardt [
11
]
applied a modified SRIT method with sprinklers to simulate rainfall of constant intensity.
The results showed a characteristic trend of high values at the beginning of the test, a
non-linear reduction over time and an asymptotic constant infiltration rate towards the
end, corresponding with the system under fully-saturated conditions.
In this study a series of test were carried out in order to assess how infiltration rates
reduce over an extended period, to assess the impact of substructure saturation. These
tests were carried out using the SRIT method at 8 locations where HydroSTON PICPs are
installed. At each site, the SRIT test was carried out at the same spot five consecutive times
at 30-min intervals apart.

Water 2022,14, 2143 11 of 16
Water 2022, 14, x FOR PEER REVIEW 11 of 16
The result plotted in Figure 7 shows that vegetation also affects the infiltration rate
of PICPs, which is higher for lightly covered pavements. It should be noted that the infil-
tration rates are high despite the presence of overhang, with locations with heavy over-
hang of vegetation recording up to 6000 mm/h.
Figure 7. Infiltration rate versus vegetation cover.
Effect of saturation: One of the concerns of PICPS is the expected reduced infiltration
rate over periods of extended rainfall. This can occur as the subgrade, base course and
bedding layer, and ground beneath the PICPs becomes saturated. The infiltration rate of
PICPs decreased over time during extended infiltration testing and continuous rainfall
(Razzaghmanesh and Beecham [30]). Infiltration testing conducted by Borgwardt [11] ap-
plied a modified SRIT method with sprinklers to simulate rainfall of constant intensity.
The results showed a characteristic trend of high values at the beginning of the test, a non-
linear reduction over time and an asymptotic constant infiltration rate towards the end,
corresponding with the system under fully-saturated conditions.
In this study a series of test were carried out in order to assess how infiltration rates
reduce over an extended period, to assess the impact of substructure saturation. These
tests were carried out using the SRIT method at 8 locations where HydroSTON PICPs are
installed. At each site, the SRIT test was carried out at the same spot five consecutive times
at 30-min intervals apart.
Figure 7. Infiltration rate versus vegetation cover.
The greatest reduction in PICP infiltration rates occurred at the residential driveway of
186 Wooloware Roadd, Burraneer, with a change of 1571 mm/h between the first and fifth
repetition, or a 12% reduction (Figure 8). The greatest percentage reduction was found at
the footpath entrance of Newington College, Stanmore, with a 63% reduction in infiltration
rate observed. These results are consistent with the conclusions presented by Boogaard
et al. [
17
], Razzaghmanesh and Beecham [
30
], and Borgwardt [
11
], that the PICP infiltration
rates decline with time during extended testing due to saturation of the system. The test
shows that the drop in infiltration can be high, and possibly explain some of the scatter
observed in Figure 2.
All locations tested showed a similar trend and the reduction in infiltration rates can be
represented by the nonlinear regression trendline. The high R
2
shows the trendline fits the
data well. It can be seen that there are differences in the rate of change between most of the
sites. This is due to the differing substructure and subgrade properties at the sites. Sites that
showed little change (such as Alice Street, Turramurra) were likely constructed over open
or uniformly graded base layers over a well-draining subgrade. Sites that show significant
early changes (such as both Newington College sites) are likely more densely graded. The
Concrete Masonry Association of Australia [
31
] advises the use of open-graded bases for
PICPs trafficked by cars and uniformly graded for pedestrian-only traffic. Therefore, it is
more likely that the infiltration rate changes observed at the Newington College sites are
the result of a low permeability subgrade, as both test locations were built for different
loadings (one site is a car park and the other a footpath) and installed several years apart.

Water 2022,14, 2143 12 of 16
An analysis of the pavement’s substructure would be required to evaluate these findings,
which is beyond the scope of this current study.
Water 2022, 14, x FOR PEER REVIEW 12 of 16
The greatest reduction in PICP infiltration rates occurred at the residential driveway
of 186 Wooloware Roadd, Burraneer, with a change of 1571 mm/h between the first and
fifth repetition, or a 12% reduction (Figure 8). The greatest percentage reduction was
found at the footpath entrance of Newington College, Stanmore, with a 63% reduction in
infiltration rate observed. These results are consistent with the conclusions presented by
Boogaard et al. [17], Razzaghmanesh and Beecham [30], and Borgwardt [11], that the PICP
infiltration rates decline with time during extended testing due to saturation of the sys-
tem. The test shows that the drop in infiltration can be high, and possibly explain some of
the scatter observed in Figure 2.
Figure 8. Infiltration rate verses the number of SRIT tests carried out.
All locations tested showed a similar trend and the reduction in infiltration rates can
be represented by the nonlinear regression trendline. The high R2 shows the trendline fits
the data well. It can be seen that there are differences in the rate of change between most
of the sites. This is due to the differing substructure and subgrade properties at the sites.
Sites that showed little change (such as Alice Street, Turramurra) were likely constructed
over open or uniformly graded base layers over a well-draining subgrade. Sites that show
significant early changes (such as both Newington College sites) are likely more densely
graded. The Concrete Masonry Association of Australia [31] advises the use of open-
graded bases for PICPs trafficked by cars and uniformly graded for pedestrian-only traf-
fic. Therefore, it is more likely that the infiltration rate changes observed at the Newington
College sites are the result of a low permeability subgrade, as both test locations were built
for different loadings (one site is a car park and the other a footpath) and installed several
years apart. An analysis of the pavement’s substructure would be required to evaluate
these findings, which is beyond the scope of this current study.
The results of the repeated SRIT method conducted in this study show a similar char-
acteristic trend as Borgwardt [11], although no asymptotic constant infiltration rate was
observed because the saturation point had not been reached. It is expected that PICPs will
be in a fully saturated condition during a storm event. Therefore, the saturated infiltration
rate, obtained through continuous or repeated infiltration tests, gives a more realistic ap-
praisal and should be considered when designing PICPs.
3.4. Prediction Limits
Prediction limits were derived based on the data collected in this study and by Lucke
et al. [14]. These were determined by assuming that (a) the data can be fitted with a power
function (equivalent to a straight-line fit on the logarithms of the data points), and (b) the
distribution of points about the fitted line is normal. A total of 90% and 95% of measure-
ments of infiltration rates and wetted bricks, respectively, should fall above the two pre-
diction lines shown in Figure 9.
Figure 8. Infiltration rate verses the number of SRIT tests carried out.
The results of the repeated SRIT method conducted in this study show a similar
characteristic trend as Borgwardt [
11
], although no asymptotic constant infiltration rate was
observed because the saturation point had not been reached. It is expected that PICPs will
be in a fully saturated condition during a storm event. Therefore, the saturated infiltration
rate, obtained through continuous or repeated infiltration tests, gives a more realistic
appraisal and should be considered when designing PICPs.
3.4. Prediction Limits
Prediction limits were derived based on the data collected in this study and by Lucke
et al. [
14
]. These were determined by assuming that (a) the data can be fitted with a
power function (equivalent to a straight-line fit on the logarithms of the data points), and
(b) the distribution of points about the fitted line is normal. A total of 90% and 95% of
measurements of infiltration rates and wetted bricks, respectively, should fall above the
two prediction lines shown in Figure 9.
Figure 9relates the infiltration rates to the number of wet bricks, which in turn is
related to the area of the paved surface. If a suitable infiltration rate of PICPS for design
purposes is defined, then, based on the 90% or 95% limits, the paved area can be determined.
Furthermore, if there is an adjoining catchment that flows onto the paved surface, then the
required infiltration rate can be adjusted to allow the infiltration of runoff from both the
catchment and paved surface.
This raises the question about an infiltration rate suitable for the design of PICPs and
if it can be derived from all of the data collected. Tests show that all of the sites provide
very high infiltration rates, with the lowest being approximately 125 mm/h for both the
current study and the study of Lucke et al. [
14
]. This, at least, provides an empirical basis
for choosing an infiltration rate for the design of PICPs. Further guidance on the infiltration
rate for design can be obtained by exploring the probability of exceedance of the data, see
Figure 10. Taking the infiltration rate that is exceeded in 90% of cases, the data collected in
this study gives a value of 700 mm/h and Lucke et al.’s [
14
] data gives 400 mm/h. Both
of these are high infiltration rates. Based on this, the lower value of 400 mm/h could be
assumed for design purposes, based on field measurements in the Sunshine Coast, Sydney
and Wollongong.

Water 2022,14, 2143 13 of 16
Water 2022, 14, x FOR PEER REVIEW 13 of 16
Figure 9 relates the infiltration rates to the number of wet bricks, which in turn is
related to the area of the paved surface. If a suitable infiltration rate of PICPS for design
purposes is defined, then, based on the 90% or 95% limits, the paved area can be deter-
mined. Furthermore, if there is an adjoining catchment that flows onto the paved surface,
then the required infiltration rate can be adjusted to allow the infiltration of runoff from
both the catchment and paved surface.
Figure 9. The data obtained in the present study fitted with a power distribution together with 90%
and 95% prediction limits.
This raises the question about an infiltration rate suitable for the design of PICPs and
if it can be derived from all of the data collected. Tests show that all of the sites provide
very high infiltration rates, with the lowest being approximately 125 mm/h for both the
current study and the study of Lucke et al. [14]. This, at least, provides an empirical basis
for choosing an infiltration rate for the design of PICPs. Further guidance on the infiltra-
tion rate for design can be obtained by exploring the probability of exceedance of the data,
see Figure 10. Taking the infiltration rate that is exceeded in 90% of cases, the data col-
lected in this study gives a value of 700 mm/h and Lucke et al.’s [14] data gives 400 mm/h.
Both of these are high infiltration rates. Based on this, the lower value of 400 mm/h could
be assumed for design purposes, based on field measurements in the Sunshine Coast,
Sydney and Wollongong.
Evaluating the performance of PICPs has been a subject of debate and contributed to
the lack of an Australian standard. In this study field measurements were conducted to
determine the infiltration capacity of PICPs. The infiltration rate of PICPs collected from
field tests varied over a relatively high range from 125 to 25,000 mm/h under various con-
ditions. The latter was a measurement obtained in this study. Field test results obtained
Figure 9.
The data obtained in the present study fitted with a power distribution together with 90%
and 95% prediction limits.
Water 2022, 14, x FOR PEER REVIEW 14 of 16
indicated that PICPs retain their permeability effectively over extended periods. Age,
slope and vegetation affect the infiltration of PICPs and display expected trends despite
scattering in the data. Although the difference in infiltration rates for different type of
usage were noted, PICPs still perform well under high traffic loads.
Figure 10. Probability of the infiltration rate being exceeded based on all data collected in this study
and data from Lucke et al. [14].
4. Conclusions
In the past, measurement of field infiltration rates has been problematic due to diffi-
culties in applying proper methods of testing, access to laboratories to perform tests, and
time and cost constraints on tests. The study shows that SWIFT and SRIT results correlate
reasonably well, validating the use of the simpler SWIFT method. SWIFT tests can be per-
formed easily, providing a simple and cost-effective way of estimating infiltration. Prop-
erty owners or council staff can easily perform this test and obtain an instant estimation
of the condition of pavers and, if desired, determine maintenance.
Repeated infiltration testing over a short period supports the characteristic trend that
the rate of infiltration through PICPs decreases non-linearly as the system becomes satu-
rated. This change in infiltration rate is dependent on the gradation of the base/sub-base
layer and condition of the subgrade. In the extreme case, the infiltration rate was observed
to decrease by more than 50% over the course of the repeated testing. Therefore, the infil-
tration rate under fully saturated conditions should be considered when designing PICPs.
Figure 10.
Probability of the infiltration rate being exceeded based on all data collected in this study
and data from Lucke et al. [14].

Water 2022,14, 2143 14 of 16
Evaluating the performance of PICPs has been a subject of debate and contributed to
the lack of an Australian standard. In this study field measurements were conducted to
determine the infiltration capacity of PICPs. The infiltration rate of PICPs collected from
field tests varied over a relatively high range from 125 to 25,000 mm/h under various
conditions. The latter was a measurement obtained in this study. Field test results obtained
indicated that PICPs retain their permeability effectively over extended periods. Age, slope
and vegetation affect the infiltration of PICPs and display expected trends despite scattering
in the data. Although the difference in infiltration rates for different type of usage were
noted, PICPs still perform well under high traffic loads.
4. Conclusions
In the past, measurement of field infiltration rates has been problematic due to diffi-
culties in applying proper methods of testing, access to laboratories to perform tests, and
time and cost constraints on tests. The study shows that SWIFT and SRIT results correlate
reasonably well, validating the use of the simpler SWIFT method. SWIFT tests can be per-
formed easily, providing a simple and cost-effective way of estimating infiltration. Property
owners or council staff can easily perform this test and obtain an instant estimation of the
condition of pavers and, if desired, determine maintenance.
Repeated infiltration testing over a short period supports the characteristic trend
that the rate of infiltration through PICPs decreases non-linearly as the system becomes
saturated. This change in infiltration rate is dependent on the gradation of the base/sub-
base layer and condition of the subgrade. In the extreme case, the infiltration rate was
observed to decrease by more than 50% over the course of the repeated testing. There-
fore, the infiltration rate under fully saturated conditions should be considered when
designing PICPs.
In summary, the use of PICPs is one of the effective approaches to improve runoff water
quality, reduce surface runoff in urban catchments and help mimic the natural hydrological
cycle impacted by urbanization, and PICPs are suggested in many documents issued by the
NSW Government and councils. This paper has focused on evaluating the infiltration rate
and parameters that affect the long-term performance of PICPs. The study focused on the
greater Sydney region. Similar data from more regions around the world will better define
and consolidate the findings in this study. The effects of clogging and quality maintenance
programs, the characteristics of the sub-grade and how extended periods of rainfall might
influence the infiltration rate of PICPs, while conducted in this study in a limited sense,
should be assessed in more detail through further research.
Supplementary Materials:
The following are available online at https://www.mdpi.com/article/
10.3390/w14142143/s1, Figure S1: Testing locations shown on local council boundaries, Figure S2:
Types of pavers used; HydroSTON [
22
] and Ecotrihex [
23
]; Figure S3: Substructure of PICPs, HydroS-
TON, [
22
]; Figure S4: SWIFT method and equipment used for on-site tests; Table S1: Location and
characteristics of test sites. References [14,21–23,32] are cited in the Supplementary Materials.
Author Contributions:
Conceptualization, J.K.; methodology, J.K.; formal analysis, N.P.T.N., A.S.;
investigation, N.P.T.N., A.S.; resources, J.K.; data curation, N.P.T.N., A.S.; writing—original draft
preparation, N.P.T.N., A.S.; writing—review and editing, N.A., J.K.; supervision, J.K.; project adminis-
tration, J.K. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Data Availability Statement: Data collected in this study are available at PICPS Test Data.xlsx.
Acknowledgments:
The authors would like to thanks UTS BE students who undertook the collection
of data in this study as part of their BE capstone project. They are Roel Ten Cate, Andy Vo and Edwin
Wong. We also thank Wiebke Benze von Fritz from HydroCon for her assistance.
Conflicts of Interest: The authors declare no conflict of interest.

Water 2022,14, 2143 15 of 16
References
1.
Pratt, C.; Mantle, J.; Schofield, P. UK Research Into the Performance of Permeable Pavement, Reservoir Structures in Controlling
Stormwater Discharge Quantity and Quality. Water Sci. Technol. 1995,32, 63–69. [CrossRef]
2.
Eisenberg, B.; Lindow, K.; Smith, D. (Eds.) Permeable Pavements, Permeable Pavements Task Committee; American Society of Civil
Engineers: Reston, VA, USA, 2015.
3.
Pearson, A.R.; Shackel, B. Concrete segmental pavements aesthetic and performance solutions. In Proceedings of the 5th
International Conference on Concrete Block Paving, Tel-Aviv, Israel, 23–27 June 1996; pp. 669–678.
4.
Bean, E.Z.; Hunt, W.F.; Bidelspach, D.A.; Smith, J.E. Evaluation of Four Permeable Pavement Sites in Eastern North Carolina for
Runoff Reduction and Water Quality Impacts. J. Irrig. Drain. Eng. 2007,133, 583–592. [CrossRef]
5.
Winston, R.; Al-Rubaei, A.; Blecken, G.; Hunt, W. A Simple Infiltration Test for Determination of Permeable Pavement Maintenance
Needs. J. Environ. Eng. 2016,142, 06016005. [CrossRef]
6.
Collins, K.A.; Hunt, W.F.; Hathaway, J.M. Hydrologic Comparison of Four Types of Permeable Pavement and Standard Asphalt
in Eastern North Carolina. J. Hydrol. Eng. 2008,13, 1146–1157. [CrossRef]
7.
Drake, J.; Bradford, A.; Marsalek, J. Review of environmental performance of permeable pavement systems: State of the
knowledge. Water Qual. Res. J. 2013,48, 203–222. [CrossRef]
8.
Valeo, C.; Gupta, R. Determining Surface Infiltration Rate of Permeable Pavements with Digital Imaging. Water
2018
,10, 133.
[CrossRef]
9.
Dierkes, C.; Kuhlmann, J.; Kandasamy, J.; Angelis, G. Pollution Retention Capability and Maintenance of Permeable Pavements.
In Proceedings of the 7th International Conference on Urban Drainage, Portland, OR, USA, 8–13 September 2002.
10.
Boogaard, F.; Lucke, T.; van de Giesen, N.; van de Ven, F. Evaluating the Infiltration Performance of Eight Dutch Permeable
Pavements Using a New Full-scale Infiltration Testing Method. Water 2014,6, 2070–2083. [CrossRef]
11.
Borgwardt, S. Long Term In-Situ Infiltration Performance of Permeable Concrete Block Pavement. In Proceedings of the 8th
International Conference on Concrete Block Paving, San Francisco, CA, USA, 8–11 September 2015.
12.
Cipolla, S.; Maglionico, M.; Stojkov, I. Experimental Infiltration Tests on Existing Permeable Pavement Surfaces. CLEAN—Soil Air
Water 2015,44, 89–95. [CrossRef]
13.
Sañudo-Fontaneda, L.; Andres-Valeri, V.; Costales-Campa, C.; Cabezon-Jimenez, I.; Cadenas-Fernandez, F. The Long-Term
Hydrological Performance of Permeable Pavement Systems in Northern Spain: An Approach to the “End-of-Life” Concept. Water
2018,10, 497. [CrossRef]
14.
Lucke, T.; White, R.; Nichols, P.; Borgwardt, S. A Simple Field Test to Evaluate the Maintenance Requirements of Permeable
Interlocking Concrete Pavements. Water 2015,7, 2542–2554. [CrossRef]
15.
Beecham, S.; Pezzaniti, D.; Myers, B.; Shackel, B.; Pearson, A. Experience In The Application of Permeable Interlocking Concrete
Paving in Australia. In Proceedings of the 9th International Conference on Concrete Block Paving, Buenos Aires, Argentina,
Argentinean Concrete Block Association (AAHB), Buenos Aires, Argentina, 18–21 October 2009; Argentinean Portland Cement
Institute (ICPA) Small Element Paving Technologists (SEPT): Buenos Aires, Argentina.
16.
Shackel, B. The Design, Construction and Evaluation of Permeable Pavements in Australia. In Proceedings of the 24th ARRB
Conference: Celebrating 50 years of Road and Transport Research 2010, Melbourne, VIC, Australia, 12–15 October 2010.
17.
Boogaard, F.; Lucke, T. Long-Term Infiltration Performance Evaluation of Dutch Permeable Pavements Using the Full-Scale
Infiltration Method. Water 2019,11, 320. [CrossRef]
18.
Johnson, T.; King, R. Experience with Pervious Paving. In Proceedings of the 6th Australian National Conference on Urban Water
Management: New Frontiers into the Next Decade, Virtually, 13–16 April 2021.
19.
Ku-ring-gai Council. Current Projects and Priorities, Water Smart Rebates. 2018. Available online: https://www.kmc.nsw.gov.au/
Current_projects_priorities/Key_priorities/Environment_sustainability/Our_community_programs/Water_Smart/Water_
Smart_rebates (accessed on 20 May 2019).
20.
Moktan, B. Understanding the Design and Approval Process of Permeable Pavements in Australia, Engineering Graduate Project; University
of Technology: Sydney, Australia, 2018; pp. 6–10.
21.
C1781/C1781M-14a; Standard Test Method for Surface Infiltration Rate of Permeable Unit Pavement Systems. ASTM International:
West Conshohocken, PA, USA, 2014.
22.
HydroSTON 2016, Designs and Specification, Sydney. Available online: https://hydroston.com.au/specifications/ (accessed on
4 April 2019).
23.
Adbri Masonry. Types of Pavers: Ecotrihex, Sydney. 2019. Available online: https://www.adbrimasonry.com.au/commercials/
paving/industrial-paving/ecotrihex-2 (accessed on 4 April 2019).
24.
Current Results. Sydney-Extreme Daily Rainfall for Each Year. Current Results Weather and Science Facts (2022). Available
online: https://www.currentresults.com/Yearly-Weather/Australia/NSW/Sydney/extreme-annual-sydney-precipitation.php
(accessed on 8 June 2022).
25.
Brown, C.; Chu, A.; van Duin, B.; Valeo, C. Characteristics of Sediment Removal in Two Types of Permeable Pavement. Water
Qual. Res. J. 2009,44, 59–70. [CrossRef]
26.
NSW Department of Planning and Environment. Apartment Design Guide; NSW Department of Planning and Environment:
Sydney, Australia, 2015; ISBN 978-0-7313-3676-0.

Water 2022,14, 2143 16 of 16
27.
NSW Department of Planning and Environment. New England North West Regional Plan, Sydney, Australia. 2018. Avail-
able online: https://www.planning.nsw.gov.au/Plans-for-your-area/Regional-Plans/New- England-North-West/Draft-
New-England-North-West-Regional-Plan/Protected-water-environment-and-heritage?acc_section=direction_5_1_-_manage_
water_resources_for_a_growing_economy_and_environmental_sustainability (accessed on 28 August 2018).
28.
City of Botany Bay. Development Control Plan 2013, Stormwater Management Technical Guidelines, Sydney, Australia. Available
online: https://www.bayside.nsw.gov.au/sites/default/files/2018-01/Part-10-Stormwater-Mgmt-Tech-Guidelines_Amd8_A090
81_E050917.pdf (accessed on 3 June 2019).
29.
Blacktown City Council, Water Sensitive Urban Design (WSUD) Standard Drawings, Plan & Build, Stage 2—Plans and Guidelines,
Developers Toolkits for Water Sensitive Urban Design (WSUD). 2017. Available online: https://www.blacktown.nsw.gov.
au/Plan-build/Stage-2-plans- and-guidelines/Developers-toolkit-for-water-sensitive-urban-design-WSUD/Water-sensitive-
urban-design-WSUD-standard-drawings (accessed on 3 November 2019).
30.
Razzaghmanesh, M.; Beecham, S. A Review of Permeable Pavement Clogging Investigations and Recommended Maintenance
Regimes. Water 2018,10, 337. [CrossRef]
31.
Concrete and Masonry Association of Australia. Permeable Interlocking Concrete Pavements—Design and Construction Guide; Concrete
and Masonry Association of Australia: Sydney, Australia, 2010.
32.
NSW Roads & Maritime Services. Test Method T377, Water Permeability of no Fines Concrete (Falling Head Laboratory Permeameter);
RMS NSW Government: Sydney, Australia, 2016.