DSpace at VNU: Stormwater quality management in rail transportation - Past, present and future

DSpace at VNU: Stormwater quality management in rail transportation - Past, present and future tài liệu, giáo án, bài gi...

and future

Phuong Tram Voa, Huu Hao Ngoa,⁎ , Wenshan Guoa, John L Zhoua, Andrzej Listowskib, Bin Duc,

Qin Weid, Xuan Thanh Buie,f

a

Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NSW 2007, Australia

b

Sydney Olympic Park Authority, 7 Figtree Drive, Sydney, NSW 2127, Australia

c

School of Resources and Environmental Sciences, University of Jinan, Jinan 250022, PR China

d

Key Laboratory of Chemical Sensing & Analysis in Universities of Shandong, School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022, PR China

e Faculty of Environment, Ho Chi Minh City University of Technology, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Viet Nam

f

Division of Environmental Engineering and Management, Ton Duc Thang University, District 7, Ho Chi Minh City, Viet Nam

H I G H L I G H T S

• Stormwater management in the railway industry focused solely on drainage

• Stringent stormwater quality standards require urgent responses from the industry

• Railway transportation generates potential sources of pollutants for runoff

• Urban retrofitting provides opportunities for railway stormwater management

a b s t r a c t

a r t i c l e i n f o

Article history:

Received 29 December 2014

Received in revised form 23 January 2015

Accepted 23 January 2015

Available online 29 January 2015

Editor: D Barcelo

Keywords:

Stormwater quality

Railway industry

Stormwater treatment

Urban retrofit

Railways currently play an important role in sustainable transportation systems, owing to their substantial carrying capacity, environmental friendliness and land-saving advantages Although total pollutant emissions from railway systems are far less than that of automobile vehicles, the pollution from railway operations should not be underestimated To date, both scientific and practical papers dealing with stormwater management for rail tracks have solely focused on its drainage function Unlike roadway transport, the potential of stormwater pollu-tion from railway operapollu-tions is currently mishandled There have been very few studies into the impact of its operations on water quality Hence, upon the realisation on the significance of nonpoint source pollution, stormwater management priorities should have been re-evaluated This paper provides an examination of past and current practices of stormwater management in the railway industry, potential sources of stormwater pollution, obstacles faced in stormwater management and concludes with strategies for future management directions

© 2015 Elsevier B.V All rights reserved

Contents

1 Introduction 354

2 Conventional approach to stormwater management in the railway industry 354

3 Stormwater quality management practices in the railway industry 355

3.1 Rationale 355

3.1.1 Recognition of non-point source pollution from the transportation sector 355

3.1.2 Contamination along railway tracks and stabling yards 355

3.2 Potential sources of stormwater pollution in the railway industry 355

3.2.1 Wooden sleepers 355

⁎ Corresponding author at: School of Civil and Environmental Engineering, University of Technology, Sydney (UTS), P.O Box 123, Broadway, NSW 2007, Australia.

E-mail addresses: ngohuuhao121@gmail.com , h.ngo@uts.edu.au (H.H Ngo).

http://dx.doi.org/10.1016/j.scitotenv.2015.01.072

Contents lists available atScienceDirect Science of the Total Environment

j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / s c i t o t e n v

3.2.2 Herbicides and pesticides 356

3.2.3 Fuels, oils and lubricants 356

3.2.4 Wear and tear 356

3.2.5 Embankments 358

3.2.6 Human waste and littering 358

3.2.7 Maintenance facilities 358

3.3 Pollution routes 358

3.4 Challenges in stormwater quality management in the railway industry 359

3.4.1 Input data 359

3.4.2 Monitoring and modelling 359

3.4.3 Treatment challenges 359

3.4.4 Regulations, policies and standards 360

4 Provisions for stormwater quality management in the railway industry 360

4.1 Source control 360

4.2 Stormwater treatment and harvesting 360

4.2.1 Stormwater treatment 360

4.2.2 Stormwater harvesting 361

4.3 Urban retrofit 361

5 Conclusion 362

Acknowledgements 362

References 362

1 Introduction

Among the many endeavours of society to promote a sustainable

transportation system, railway networks play a crucial part because of

their substantial carrying capacity A rough statistic from theWorld

Bank (2014)showed that the combined length of the world's railway

lines increased dramatically by 40% from 1990 to 2012 Compared to

roadway transport, railway is considered more environmentally

friend-ly in providing mass transporting services with less negative ecological

impact (Zimmerman, 2005) Nonetheless, the environmental benefits

from railway transportation over private vehicles are undeniable

Hence, railway networks are likely to be upgraded in order to meet

Yazici, 2014; Zhiqun and Jiguang, 2011) Although emissions from

railway systems are far less than that of automobile vehicles, the

environmental pollution from railway operations should not be

underestimated Frequently mentioned types of impact caused by

rail transportation include noise (Aasvang et al., 2007; Ali, 2005;

Trombetta Zannin and Bunn, 2014), vibration (Kouroussis et al., 2014;

Sanayei et al., 2013) and air pollution (Dincer and Elbir, 2007; Salma

et al., 2009) In contrast, there have been very few studies into the

im-pact on water courses This lack of interest does not imply that water

Osborne and Montague (2005)stated,“railway operations, both current

and in the past, have the potential to give rise to pollution, as water

drains from the railway into water courses” Yet, to date, priorities in

water management for rail tracks still solely focus on its drainage

function Hence, upon realising the significance of nonpoint source

pollution, stormwater management priorities should have been

re-evaluated This paper will provide an examination of past and current

practices of stormwater management in the railway industry, potential

sources of stormwater pollution, management obstacles and future

directions

2 Conventional approach to stormwater management in the

railway industry

Rail tracks and supporting systems attracted the most attention in

stormwater management plans for the railway industry as they were

the backbone of railway services This heightened attention was due

to the negative impact of runoff on rail tracks directly threatening rail

safety

Based on the track support systems (or substructures), rail tracks are divided into three categories: traditionally ballasted, modified ballasted and ballastless Configurations of these substructures were well pre-sented in the works ofEsveld (1997)andTeixeira et al (2009) While the latter types of rail tracks developed due to demands for high-speed trains and low maintenance frequency, ballasted railway tracks have still been employed extensively, thanks to their enormous economic advantages A typical ballasted substructure comprises of a top ballast layer (150–550 mm of single-sized rocks), a sub-ballast layer (90–450 mm of well-graded crushed rock or a sandy gravel mix-ture) and an underlying subgrade layer (natural or amended soil) Each layer performs different structural functions to ensure the durabil-ity and stabildurabil-ity of a rail track Precipitation falling on ballast quickly drains to the sub-ballast layer and then runs into drainage systems The drainage system could be either a parallel pipework network or a natural ditch, which is located along the sides of the embankment toe Similar mechanisms were found in depots or maintenance centres The influence of runoff from surrounding areas on the rail track areas

is often restricted to ensure the safety of the track bed

The effect of runoff volume on rail tracks was investigated

thorough-ly, as the saturation of water in these layers can reduce the stiffness of the track foundation (Australian Rail Track Corporation Ltd., 2006) Theflow hydraulic properties vary depending on the type and age of the track bed Drainage capacity of a track decreases over time, as sediments accumulate in its body (Burkhardt et al., 2005)

Rushton and Ghataora (2014)observed that greater impact occurred when water accumulated in the sub-ballast and subgrade layers, where finer grains were predominant Under the load of moving trains, trapped water became pressurised, drawing clay or silt from the subgrade upward to the ballast layer, known as the“clay pumping” phe-nomenon (Rushton and Ghataora, 2009) Together with the depositing

of dust and abrasive materials on the ballast surface, clay pumping can cause ballast fouling (Indraratna et al., 2011) The fouled ballast further degraded the drainage capacity of the track support system and led to structural deformation Due to its high risk of rail track structural deformation, stormwater was a critical problem for rail operation Stormwater runoff had subsequently been perceived as a nuisance that must be drained as quickly as possible

For modified ballasted systems (with a bituminous or geotextile layer working as the sub-ballast layer) and ballastless systems, the ef-fects of stormwater on the foundation structure are less severe.EAPA (2003)pointed out three main reasons for this improvement Firstly,

an asphalt layer distributed train loadings more uniformly, hence

eliminated the“clay pumping” phenomenon in the upper ballast layer.

Secondly, a dense layer of asphalt moved water away quickly to protect

the top layer Finally, the impermeable bituminous layer can act as a

barrier to block the upward movements of silt materials from the

subgrade (or foundation) layer

Due to drainage being the focus of stormwater management

systems, only hydraulic profiles were considered in design Collected

stormwater from the drainage systems were then discharged into

natu-ral water bodies, including rivers, streams, creeks or even drinking

water catchments, while its effects on the basin were completely

ignored No quality consideration was found in any official technical

guidance for drainage systems in the railway industry (Australian Rail

Track Corporation Ltd., 2013; U.S Army Corps of Engineers, 2004)

3 Stormwater quality management practices in the railway industry

3.1 Rationale

The above perception remained unchanged until recent years when

stormwater management objectives were re-assessed due to the

following reasons

3.1.1 Recognition of non-point source pollution from the transportation

sector

An abundant number of papers have highlighted the existence of

pollution from diffuse sources over the last 40 years (Clark and Pitt,

stormwater then became one of the largest non-point pollution sources

contributing to the degradation of surface water resources (National

Research Council, 2008) Unlike effluent discharges with relatively

sta-ble characteristics, there is wide variation in stormwater quality and

quantity Attempts to build roadway runoff profiles were accomplished

universally While an insignificant concentration of biological oxygen

demand (BOD5), bacteria and nutrients are found in stormwater, it is a

substantial source of heavy metals and polycyclic aromatic

hydrocar-bons (PAHs) (Barbosa et al., 2012) These constituents were often

et al., 2012)

To reduce the negative impacts of runoff, several countries set up

regulations for stormwater pollution control, such as the National

Pol-lutant Discharge Elimination System Stormwater Program (1990) in

Union A few states in the US even issued more stringent industrial

stormwater permits As a result, the railway industry must comply

with these new requirements An understanding of stormwater quality

from railway operations is a prerequisite for applying effective

pollution-reduction measures required to fulfil these tightening

regula-tions (Kayhanian et al., 2012) Despite the practical needs to understand

stormwater quality profiles, available literature has shown little

infor-mation pertaining to this issue It imposed a large burden on the old

Weiner (2011)argued, stormwater management turns out to be one

of the largest struggles that the railway industry has to overcome in

the coming years

3.1.2 Contamination along railway tracks and stabling yards

Railway is an important means of freight transport over long

dis-tance at reasonable cost It is the preferred choice for transporting

crude oil This, consequently, has caused the environmental risks

associ-ated with rail to increase As evidence of this, more than 4350 m3of oil

was released into the environment due to rail incidents in America in

2013, which was equal to 150% of past four decades put together

(Tate, 2014) Although clean-up activities could reduce the harmful

ef-fects to some extent, the accumulated oil in the soil could pollute

stormwater in much later years, as in the case of Osborn Yard in

Louis-ville, Kentucky (Kurzanski et al., 2013) Signs of oil pollution appeared in

the stormwater run-off as a result of diesel spillage incidents that occurred 20 years ago

Apart from incident-related causes, daily railway operations were also proven to affect the soil quality along rail tracks and supporting infrastructures.Malawska and Wiłkomirski (2001)surveyed concentra-tions of nine metals (Co, Cd, Cr, Cu, Fe, Hg, Mo, Pb, Zn) and 14 priority PAHs in soil samples taken from four railway locations– the siding, the main track within the platform, the cleaning bay and the loading ramp– at the Iława Głowna junction (Poland) Most of the substances tested for, except Mo, were at substantially higher concentrations than

in the control sample The largest concentrations of pollutants were found near the platform and railway siding areas where trains spent long periods of time at low speeds Metals detected at high

dry weight) 13 years later, the authors executed comparative research

at the same locations PAHs had significantly increased by 8–25 times, which turned the soil from“slightly polluted” class to “polluted” and

“heavily polluted” classes, with reference to Polish and Dutch regula-tions (Wilkemirski et al., 2011) To a lesser extent, metal levels had also magnified by 1.2 to 2 times The investigation of heavy metals along rail tracks in Qinghai–Tibet railway (Zn, Cd and Pb) and Suining railway station (Pb and Cd) provided similar results (Chen et al., 2014; Zhang et al., 2012)

Even though the movement of these pollutants from soil to water environment has not been studied in great detail, soil pollution in rail track areas could potentially result in stormwater contamination (Burkhardt et al., 2008)

3.2 Potential sources of stormwater pollution in the railway industry Emission sources from the railway industry can be divided into two groups— those associated with daily operation (i.e affected by the frequency of trains) and those independent of rail traffic volume (i.e supporting infrastructures) The main sources of pollutants from daily operation include: (1) wooden sleepers, (2) herbicides for vegetation control, (3) fuelling and lubrication, (4) wear-and-tear processes and corrosion-resistant poles, (5) embankment materials and (6) human activities The pollution from incidents such as oil spillage that were briefly presented in the previous section is not the focus of this paper 3.2.1 Wooden sleepers

The most significant source of organic compounds in railway runoff comes from creosote-impregnated wooden sleepers Creosote is a fu-sion mixture of more than 162 compounds including PAHs (69%), nitro-gen heterocyclics (11%) and other aliphatic hydrocarbon (Utley, 2005)

It has been used as a fungicide to enhance the lifespan of wooden sleepers (Brooks, 2001) Although the toxicity of creosote is low (Chakraborty, 2001), it is identified as a potential carcinogen due to its PAH components In Switzerland, creosote-loaded sleepers accounted for 43% of annual stock (Kohler et al., 2000) Nevertheless, the country with the highest demand for wooden sleepers is the US For instance, the US required approximately 17 million new sleepers in the year

for the popularity of wooden sleepers come from their impressive abil-ity in the dynamic attenuation of loadings, their light weight, their ease

to install and maintain, and most importantly, their economic viability The average loss rate of creosote in rail sleepers was about

210 mg/m2·day for 20–30 years in service, of which PAHs accounted for 20 mg/m2·day (Kohler et al., 2000) Despite this, the asserted pos-sibility of creosote leakage into water was considered debatable.Brooks (2004), in his 18-month study to investigate the seepage of creosote from railway sleepers to adjacent environments, suggested that leakage

of creosote via stormwater was negligible The authors argued that cre-osote loss was accompanied mostly with vaporisation, weathering and deposition in railway ballast.Thierfelder and Sandström (2008)also

stated that creosote-impregnated wooden sleepers used for

embank-ments would expose no risk to the water environment, albeit no

evidence was given for this conclusion

On the other hand,Kang et al (2005)explored the migration of 16

priority PAHs from impregnated wooden sleepers in fresh water

under differentflow-rate regimes in one week Seven lower molecular

fluorene, phenanthrene and pyrene) were detected in the leakage

water in all cases.Chakraborty (2001)also studied three different

mechanisms of creosote loss– bleeding, leaching and vaporisation –

for eight light PAHs (the 7 previously mentioned PAHs and

acenaph-thylene) It was found that the main mechanism for PAHs loss was

leaching (more than 50%), rather than vaporisation and bleeding

In addition,Becker et al (2001)explored the leaching behaviour of

creosote in treated wood in three media— deionised water, buffered

so-lution at pH 4.7 and humic mixture liquid In their research, nitrogen

heterocyclics and several PAH compounds were leachable in all media

Heterocyclic nitrogen substances (quinoline, isoquinoline, indole and

2-methyl-quinoline) were leaked with a higher rate than that of PAHs

The highest leaching rate was quinoline with 1050 mg/kg of wood

after 24 h of submerging in water The leaching rate for PAHs such as

naphthalene, dibenzofurane, phenanthrene and pyrene was much

were minor compared to its extractable quantities (0.1–3.0%) by using

Soxhlet extraction method with toluene solvent

It could be concluded that heavier PAHs tend to attach to organic

matters and sediments whereas lighter PAHs are able to dissolve with

a low concentration into stormwater, normally much lower than its

solubility (Table 1)

3.2.2 Herbicides and pesticides

Weed-growth on roadbeds or embankments is strictly controlled as

they may (1) impede a driver's ability to see signals, (2) impede staff

members working in rainy weather, (3) impede inspectors examining

track damage or (4) becomefire hazards (Victorian Rail Industry

Envi-ronmental Forum, 2007) Although different methods of weed control

have been considered, chemical herbicide spraying appears to be the

most economically feasible (Torstensson et al., 2005).Table 2

summa-rises several toxicological parameters of typical herbicides applied in

the railway industry

Among these herbicides, diuron has been prohibited since the late

1990s in the railway industry because it is toxic and highly mobile Its

strong mobility resulted in the destruction of a vast majority of pine

trees along the rail corridors in Sweden (Torstensson et al., 2002)

Nevertheless, diuron has still been used for weed control in numerous countries due to its long-lasting effectiveness Glyphosate then emerged

as a safer alternative Compared to other herbicides, glyphosate has higher water solubility but lower toxicity (Schweinsberg et al., 1999)

In an investigation of pesticide application in the UK,Croll (1991)

discovered a disproportionate amount of triazine concentration in surface water compare to the amount utilised in agriculture Croll suspected that a substantial part of this type of pesticide originated from weed control for railway and roadway A similar observation was made bySkark et al (2004) Indeed, the average application rate of herbicides per area for railroads was claimed to be six times higher than that being applied in agriculture (Schweinsberg et al., 1999) Some papers discovered the existence of herbicides in surface water in railway territories The concentration of herbicides exceeded the drink-ing standard of 0.1μg/L in the surface water near the railway lines (Cooker, 1996; Schweinsberg et al., 1999) They accumulated in the drainage ditch of a disused railway section at levels as high as

800μg/L (Heather and Hollis, 1999)

Besides these contaminants, the arsenic level in soil along aban-doned rail tracks in South Australia was measured to be within the

(Smith et al., 2006) as a consequence of the use of As-based herbicides 3.2.3 Fuels, oils and lubricants

Leakages of petroleum products from fuel storage tanks,filling sta-tions, locomotives and transformers are also frequent sources of water pollution Risks from oil leaks are directly proportional to the share of diesel locomotives in the railway industry The conversion from diesel-powered trains to electric trains in railway networks is underway worldwide, but has encountered various unfavourable hurdles More than two-thirds of locomotives in the railway industry are currently powered by diesel (World Bank, 2007) The fraction of diesel locomo-tives is extremely high in regions where freight transportation over long haulage distances is predominant, for instance North America (99%), Latin America (97%) and Australia (95%) (World Bank, 2007) This is because freight trains only need simple infrastructure and low levels of electrification spanning over long sections In contrast, passen-ger trains require higher levels of electrification because they run through and connect multiple high-density metropolitan areas Thus, currently, railway electrification efforts are chiefly accelerated in popu-lated metropolitan regions or in ambitiously developing countries such

as India and China (Juhasz et al., 2013)

Furthermore, oil and grease are also commonly used for lubricating curves, gears and engines Despite this, information relating to oil leakage in railway operation is incredibly scarce Only one Swedish survey exists on this topic, presenting the oil leakage rates of various transformers The rates for large transformers, booster transformers and auxiliary transformers are 10, 3 and 0.5 L/year, respectively (Gustafsson et al., 2007) In a recent study on the stormwater runoff profile from railway bridges,Gil and Im (2014)found the concentra-tions of oil and grease in a concrete road-bed and a gravel road-bed were 0.20–2.90 and 0.61–6.70 mg/L Oil leakages contain a high concen-tration of carcinogenic PAHs Some organic compounds, even in small amounts, can cause odour and aesthetic problems Highly mobile hy-drocarbon components pose higher risks to the receiving water bodies 3.2.4 Wear and tear

The largest source of heavy metal emissions originated from friction processes— rolling stock braking (73%), rail (21%), wheel (5%) and then power line (1%) (Burkhardt et al., 2008) Both embankments and sur-rounding areas of the railroad were contaminated with metals (Bukowiecki et al., 2007; Gustafsson et al., 2007) Iron accounted for the highest portion of metal emission in the braking and abrasion pro-cesses, followed by Mn, Cr and trace amounts of Ni, Mo, V and Pb Mean-while, power line abrasion contributed the biggest quantity of Cu while

Zn was emitted from galvanised poles at a quantity of 140 g/pole/year

Table 1

Leaching rates for priority PAHs from impregnated wood in different types of water.

Experiment

conditions

Kang et al.

(2005)

Becker et al (2001)

+Medium Fresh water Deionised

water

Buffer solution

Humic solution +Temperature 12–13 °C – – –

+Time 7 days 120 h 120 h 120 h

Substance Unit

μg/cm 2

·day mg/kg wood mg/kg wood mg/kg wood Naphthalene N/A 77 ± 12 108 ± 14 105 ± 31

Acenaphthene N/A 49 ± 6 37 ± 1 31 ± 1

Fluorene N/A 42 ± 10 30 ± 3 31 ± 3

Phenanthrene 0.2–0.5 44 ± 2 44 ± 5 60 ± 27

Fluoranthene N/A 22 ± 1 6 ± 2 27 ± 19

Pyrene N/A 14 ± 2 4 ± 2 21 ± 16

Quinoline – 2450 ± 180 1890 ± 180 1760 ± 170

Isoquinoline – 427 ± 18 205 ± 21 354 ± 35

Indole – 706 ± 23 374 ± 33 544 ± 66

2-Methyl-quinoline – 354 ± 38 150 ± 5 254 ± 26

Dibenzofuran – 46 ± 6 57 ± 3 41 ± 1

(Burkhardt et al., 2008) Most metals were bound with particles while

some were released in the dissolved phase (Zn, Cu and Ni) The

distribu-tion of metals depends on spatial and temporal scales which have not

been studied

Three studies reported the existence of metals in railway runoff

(Gil and Im, 2014; Gill, 2012; Larsson, 2004) Apparently, it is dif

fi-cult to compare between railway runoff and highway runoff quality

due to data for the former group being both lacking and inadequate Thus,Table 3was given as a rough guide to locate the ratio of

and benchmark values The benchmark values for stormwater

(2009b)were used to represent the“level of concern” to receiving water quality

Table 2

Representative herbicides used in railway industry.

Herbicide unit LD 50a(g/kg) ADI (mg/kg) RfD (mg/kg per day) LC 50 (mg/L) DT 50 Notes

Phenoxy-carboxylic acids

2,4-D 0.4 0.3 a

0.01 f

0.01 a

100 e b7 days e – 2,4,5-T 0.5 0.03 a 0.01 a 0.54–0.77 h – –

MCPA 0.7 0.00015 a

0.01 f

0.0005 a

0.0044 g

232 e 1–10 days e – Dichlorprop 0.8 0.03 f – 521 e 21–25 days e –

Triazines

Atrazine 2.0 0.0007 a

0.005 f

0.035 a 176 h 19–120 days k Germany: used until 1991 a

Hexazinone 1.7 0.1 f

0.035 a – 8–92 days k

Germany: used until 1989 a

Simazine N5.0 0.005 a

0.005 a

5 h

(rat) 27–216 days i – Terbuthylazine 2.0 0.003 f – 10–36 days k –

Propazine 0.02 f

0.02 a

2.04 m

131 days m – Urea derivatives

Bromacil 5.2 0.1 f

0.1 g – 12–46 days k

Germany: using from 1989 a

Chlorotoluron N10.0 0.0005 a

Diuron 3.4 0.00003 a

0.007 f

0.002 g – 12–48 months d Germany: used until 1996 a

Holland: used until 1999 Sweden: used between 1974 and 1993 b

UK: used until 2008

Miscellaneous

Amitrole N5.0 0.001 l

1.13 g

0.439 (rat) l

50 days l

Germany: used until 1989 a

Picloram 3.8 0.07 f

0.2 g

26 e 30–90 days e

Germany: used until 1989 a

Imazapyr – 2.5 f – N100 e 2–6 months d

EU: used until 2004 e

Glyphosate 4.5 0.3 a

0.1 a

86 e 2–5 months d

3–174 days e

Germany: using since 1987 a

Sweden: using since 1986 c

Notes:

ADI: acceptable daily intake.

LD 50 : lethal dose for rat (oral).

RfD: reference dose for chronic oral exposure.

LC 50 : lethal concentration for fish.

DT 50 : disappearance time for 50% of substance.

a

Adapted from Schweinsberg et al (1999)

b

Adapted from Torstensson et al (2005)

c

Adapted from Gustafsson et al (2007)

d

Adapted from Torstensson et al (2005)

e Adapted from Britt et al (2003)

f Adapted from Bending and Rodriguez-Cruz (2007)

g

Adapted from Department of Health — Office of Chemical Safety (2014)

h

Adapted from Dikshith and Diwan (2003)

k

Adapted from Directorate-general health and consumer protection (2001)

i

Adapted from Gunasekara et al (2007)

j

Adapted from Hayes and Kruger (2014)

l Adapted from Sarmah et al (2009)

m Adapted from University of Hertfordshire (2013)

Table 3

Metal concentrations in runoff from highway and railway.

Component (μg/L) Zn Cu Cd Pb Cr Fe Source of data

Railway

Railway bridge – 25–270 0.015–3.1 2–63 – – Gil and Im (2014)

Stabling yard 23–180 25–92 b0.1 9.3–16 2.9–5.3 Larsson (2004)

Highway 63–1784 5.5–11.7 9.4–350.6 5.64–1860 0.056–16.6 334–89,000 Kayhanian et al (2012)

Benchmark value 117 63.6 15.9 81.6 – 1000 USEPA (2009b)

Compared to highway runoff, the concentrations of Cd, Cr and Pb

were relatively low whereas Zn and Cu were typically high The

concen-tration of Cu in railway runoff was significantly greater than the amount

in roadway runoff, in some cases, up to 20 times higher Iron content in

railway runoff has not been studied in existing research; however, its

content in the environment is expected to be much higher than other

metals (Wilkemirski et al., 2011)

The toxicity of these metals has been widely studied Despite Cu, Mn

and Zn being less harmful than Pb and Cr, they are more soluble, and so

tend to have a greater impact on the water environment (Osborne and

Montague, 2005) While the toxicity of iron is low, it can affect water

colour and taste

3.2.5 Embankments

3.2.5.1 Soil erosion Erosion of rail embankments can result in a washing

out of sediments These sediments themselves could be a source of

pol-lution, depending on their particle size Furthermore, heavy metals and

organic compounds tend to attach to particles As a result, particles may

act as a medium for transporting pollutants into the water environment

3.2.5.2 Substitute materials for ballasts Steel furnace slags are often used

as a substitute for natural rocks in the ballast layer Originating as a

by-product of the iron or steel processing industry, slag is a fused

non-metallic mixture which is rough surfaced and angular in external

shape Steel slag is also highly resistant to physical and electrical forces

These characteristics make steel slag a perfect candidate for railroad

bal-last Most practitioners consider slag to be an inert and safe material

Yet,Piatak et al (in press)warned about the risks of slag usage Most

no-tably, the content of Al, As, Cd, Cr, Pb and Mn content in iron and steel

slag often exceeds the US EPA standards for residential and industrial

soil Therefore, after interacting with air or water, derivative weathering

products from slag can release trace metal elements such as Cd, Cr and

Pb, especially under rainfall conditions This is the case when the quality

of slag is not controlled

3.2.6 Human waste and littering

In many developing countries, open carriage toilets are still being

utilised in train cars Human excrement and garbage are discharged

di-rectly onto rail tracks and surrounding areas This waste often contains

pathogens, nutrients and organic matter They are deposited and then

accumulate in the environment without any treatment Representative

cases can be found in many developing countries For example, with

over 14 million people being transported via India's rail network every

day, it was estimated that about 3980 MT of human waste were

Auditor General of India, 2013) Moreover, railway corridors, which

are commonly viewed as vacant land, become an attractive

environ-ment for illegal discharges of sewage and domestic waste

3.2.7 Maintenance facilities

Maintenance activities take place at all railway depots Common

contaminants in runoff water from these areas are oil and grease,

chlo-rinated and non-chlochlo-rinated solvents, phenols, antifreeze, detergents,

Montague, 2005) These pollutants have resulted from different

processes in maintenance centres: metal processing, fuelling, repair of

machines and batteries, maintenance of rolling stocks, train cleaning

and so on Apart from a study byGill (2012), information on the runoff

quality from these areas is totally lacking

3.3 Pollution routes

From the above analysis, the main pollutants in railway industries

are PAHs, herbicides and heavy metals The possibility of runoff

pollu-tion is determined by numerous factors, such as precipitapollu-tion regimes,

runoffflow dynamics, substance properties and its interaction with surrounding soils (Fig 1)

Rainfall is indeed a crucial factor in the environmental fate of contaminants It determines the movement of pollutants through rail tracks and embankments In general, ballast and subballast layers have much higher permeability than the subgrade Contaminants will be transported downward and normally retained at the interface between the subballast layer and the subgrade At low rainfall intensity (under

15–20 mm), rain water may accumulate inside the track bed The infil-tration and evaporation rate might account for up to 75% of

(Burkhardt et al., 2005) Under high intensity rainfall, contaminants will be either washed out into drainage systems or infiltrated into adja-cent soil Consequently, the retention time of pollutants in rail tracks fluctuates significantly, from half a day to three months from site to site (Osborne and Montague, 2005) Thefirst flush effect was detected

at locations that experienced great variation in wet and dry weather conditions (Gil and Im, 2014), but in places where the rainfall regime

et al., 2007)

Secondly, the discharge of a contaminant into runoff is dependent not only on its sources and characteristics, but also on its interactions with the soil environment The unsaturated soil near the track bed

(Burkhardt et al., 2005) Flow dynamics in soil is determined on one hand by soil texture and structure, on the other hand, by soil water content and tension Two key mechanisms for the mass transfer of heavy metals and organic compounds are degradation and adsorption/ desorption

Heavy metals are neither biologically nor chemically degraded They will accumulate in the track bed or in the surrounding environment Heavy metals tend to attach to silt materials in natural soil The adsorp-tion of heavy metals on silt particles is influenced by pH Alkaline soil provides conditions advantageous for the adsorption of heavy metals, whereas acidic soil is favourable for desorption This typically increases the toxicity of the metals and their complexes For example, the low soil

showed the changes in Cd's mobile capacity (Liu et al., 2009) An inter-esting fact is that whereas most of the heavy metals in railway runoff are toxic, Fe and Mn could act as absorbents for attaching heavy metals and

Emission sources

Substances (Amounts, patterns, characteristics) Runoff

(Track proile, drainage system)

Mobility/ losses (Soil, track proile):

Iniltration Degradation Sorption/ desorption

Precipitation (Intensity, frequency, volume)

Runoff pollution

Fig 1 The pollution pathway in rail track areas.

Modified from Burkhardt et al (2008)

anionic compounds such as glyphosate (Burkhardt et al., 2005)

None-theless, their sorption capacities have not yet been investigated

In contrast, organic compounds will degrade over time Their

degra-dation is characterised by disappearance time (DT50) which varies

greatly in relation to different types of environment In the case of rail

tracks, the biodegradation of PAHs and herbicides is extremely low As

Burkhardt et al (2005)observed, the microbial biomass in a track area

is only one tenth of those in agricultural soil This could be explained

by the coarse texture, low organic and nutrient contents of ballast and

embankment materials Therefore, PAHs and herbicides used in railway

embankments usually had better mobility and prolonged persistence

(Cederlund et al., 2007) Many of these organic compounds are attached

to organic matters in soil In favourable conditions, contaminants can

be reactivated and released slowly over long periods of time The

stormwater runoff then acts as a pathway to transport the contaminants

from the soil into surface water bodies (Osborne and Montague, 2005)

3.4 Challenges in stormwater quality management in the railway industry

Huge challenges have been encountered from the implementation

of stormwater quality management in the railway industry Apart

from common issues of stormwater management which were clearly

addressed byLangeveld et al (2012)andBarbosa et al (2012), the

railway industry experienced some particular struggles worth noting

3.4.1 Input data

A lack of data is encountered as the most significant problem In

reality, albeit the necessity of a thorough investigation on drainage

systems both quantitatively and qualitatively, it is a tough task for any

railway manager Not only is railway runoff quality data frequently

un-available, but documentation for stormwater drainage systems has also

been inadequate (Singaraja et al., 2012) Historical modifications in

storm drains were not recorded properly This is particularly

problemat-ic when it comes to predproblemat-icting the movement of pollutants because they

may distribute and end up at various unknown receptors

The co-mingled effects of runoff between railway land-use and

sur-rounding land-uses are another troublesome issue, especially under

pressures of obtaining stormwater permits and abiding by surface

water standards Some storm drain lines for the railway industry receive

both stormwater falling on its own assets and from other facilities in the

same watershed Furthermore, cross connections between different

stormwater networks or between drainage and sewage systems make

the situation more challenging (Dunning, 2012)

3.4.2 Monitoring and modelling

Monitoring is a necessary step to determine baseline conditions,

levels of contamination, treatment methods and management

mea-sures Key considerations for a stormwater monitoring program include

monitoring locations and safety, parameters and frequency, analytical methods, precision and accuracy as well as cost-effectiveness (Fig 2) Stormwater monitoring is more challenging than effluent monitor-ing due to the irregular nature of runoff, along with a substantial discrepancy of effluent throughout a rain event or time of discharge The number of events, the time and method of sampling during an event may lead to a striking contrast in results (Lee et al., 2007)

flow-weighted composite sampling Although grab sampling is simple and cheap, it may distort the result of runoff quality, depending on the time of collecting samples (Lee et al., 2007) In contrast, flow-weighted composite sampling gives a more precise outcome However,

it is more complicated, costly and requires more training for tioners Selection of the monitoring method should be based on practi-cal conditions Nevertheless, grab sampling is still preferential in the railway industry To minimise the error in sampling,Leecaster et al (2002)suggested that the frequency for sampling be seven storm events per year, 12 samples per event using volume-weighted ratio Further discussion on the stormwater monitoring program could be seen inLee et al (2007) The sampling of track drainage systems is

clas-sified as a high-risk task Safety issues may arise from either “adverse climatic conditions” or the potential harm of being struck by running trains The deficiency of clearly designated stormwater drains makes their monitoring even more troublesome (Copeland and Lefler, 2013) With regards to the lack of monitoring data on stormwater quality, a mathematical model is necessary for the prediction of its discharges

on the environment (Barbosa et al., 2012) Several sophisticated stormwater quality management models have been incorporated with the consideration of treatment methods (Elliott and Trowsdale, 2007) Unfortunately, little information is available for movement kinetics of pollutants through rail tracks The application of available models for modelling railway runoff, therefore, needs further study in order to fine-tune and calibrate

3.4.3 Treatment challenges Besides uncertainties in stormwater quantity and quality, the selection of treatment methods faces various challenges First, space constraints are encountered in many types of railway infrastructures Railway corridors are often narrow but they accommodate a wide range of crucial infrastructures for daily operations such as power lines, communication cables, signalling systems, accesses, barriers and drainage systems This is also the case for many stations and stabling yards The restricted availability of land in the areas results in the limitation of treatment alternatives

Maintenance frequency of treatment systems must follow the oper-ational procedures of railways In fact, maintenance is a key issue for rail operations as anything within 3 m of a live track can only be accessed during a possession This is when a section of the track must be officially

Deine study type

Determine study scope (Spatial boundaries, scale and duration) Consider sampling design

issues Field

sampling sites

Spatial variablity Frequency

Precision and accuracy

Measurement parameters

Cost effective-ness

Fig 2 Framework for stormwater monitoring.

shut down for works Because of this, maintenance requirements for

drainage should not be any more frequent than yearly

3.4.4 Regulations, policies and standards

As stormwater quality management in the railway industry is a

newly emergingfield, there is still debate as to whether railway runoff

should be integrated into a general urban stormwater management

scheme or be solely managed on its own On one hand, the inclusion

of railway runoff into the general stormwater management program

can reduce the cost of management and treatment On the other hand,

it can be argued that each industry has to eliminate its own pollution

and railway is not an exception It is necessary to reduce the level of

metals and organic compounds which are specific in the industry

Moreover, unlike other industrial sources, which have clear

bound-aries as well as outfalls for their assets, railway is mostly a line source

(except at stabling yards or depots) which runs over different territories

with various discharge regulations Every territory has its own permits,

which poses a great challenge for a general control of stormwater

qual-ity in the industry, even though operational activities between different

regions are similar

Bench-mark standards for stormwater management are also

sub-jected to a number of critiques as they are ineffective in controlling

stormwater quality (National Research Council, 2008) Thus, a new

methodology of allocating pollutant loads for different sectors in a

catchment has recently been proposed to assist the enforcement of

bench-mark standards (Rogne, 2012) The new calculation method is

based on Total Maximum Daily Loads (TMDLs) for a catchment The

rail-way industry is accordingly required to employ an integrated system of

monitoring programs, stormwater control measures, appropriate

modelling and treatment methods to adhere with this new approach

(Schultz and Godlewski, 2012)

In short, the accountability of stormwater management programs is

often low With ambiguous understandings of the nature of pollutants

in the railway environment, it is more challenging for rail companies

to appraise whether their runoff water meets the given standards or

not

4 Provisions for stormwater quality management in the railway

industry

4.1 Source control

The pollution prevention measures are preferable in stormwater

quality management in the railway industry To minimise the causes

of pollution is more cost-effective than treating its consequences

down-stream as simple changes could lead to long-term positive results

Com-mon practices have been proposed to reduce pollutants at the source

and prevent contact between stormwater and potential contaminants

in the rail industry (US EPA, 2009a) However, these practices

concen-trated mainly on maintenance facilities and depots, rather than

pollu-tion along rail tracks, stabling yards and embankments Therefore, the

following solutions are suggested for controlling potential sources of

stormwater pollution for these areas

As wooden sleepers are of most concern in relation to PAHs sources,

they should be replaced by less harmful materials.Gustafsson et al

(2007)investigated the replacement of wooden sleepers with concrete

sleepers Through their experiments, concrete sleepers were proven to

be ecologically safe The only additive in concrete that attracted

environmental concerns was sulphonate naphthalene With a

concen-tration of 1‰ in the concrete, it showed an insignificant leaching rate

(Gustafsson et al., 2007) Switching from wooden sleepers to concrete

sleepers and composite sleepers (a new type of sleeper) becomes

increasingly popular

The application of herbicides in weed control practices should be

carefully planned with regards to types of weed, time and amount of

application, weed resistance capacity to herbicides and treatment

locations The substitution of persistent and toxic herbicides for alterna-tives with quickly-degradable active ingredients is highly

recommend-ed A new technique of applying herbicides in the railway is to use low-speed swiping trains These trains distribute herbicides directly onto specific weed-ridden areas at speeds of 5–8 km/h rather than spraying over entire areas, as is the present conventional method

AsHansen and Clevenger (2005)argued, the disruption to natural soil conditions along railway edges promoted the invasion of exotic plant species Therefore, an additional method for controlling weeds that can be utilised is the re-plantation of indigenousflora (Victorian Rail Industry Environmental Forum, 2007) The preservation of natural vegetation on railway corridors also helps to reduce embankment ero-sion by increasing slope stabilities and eliminating water logging at the track toes In addition, mulches (organic and inorganic) could be utilised to reduce the growth of weeds

A large quantity of metal deposits originated from abrasion

process-es of brakprocess-es, rails, wheels and power linprocess-es The magnitudprocess-es of deposits caused by these abrasion processes vary according to the type of materials involved; for instance, composite brakes and wheels emitted the least amount of metals, compared to cast-iron and sintered iron The substitution of cast-iron and sintered iron brakes by composite brakes could eliminate the emission of metals by approximately 90% (Gustafsson et al., 2007)

As mentioned earlier, pollution along railway tracks is mainly accompanied withfine fractions It means that removing fine particles could reduce high fraction of impurities Therefore, increasing the fre-quency of ballast cleaning can reduce the accumulation of contaminants onto track beds

4.2 Stormwater treatment and harvesting 4.2.1 Stormwater treatment

Although source control measures are effective in reducing pollution potentials, they alone cannot fulfil the requirements of stormwater dis-charge permits (Dunning and Weiner, 2011) In this case, a treatment system is necessary Unfortunately, the railway industry has not paid a great attention to stormwater treatment The judgement of selecting treatment methods must be based on understandings of quantity and quality characteristics of stormwater, treatment objectives, local condi-tions and possibilities for incorporating with educational or aesthetical purposes (Barbosa et al., 2012).National Research Council (2008)and

Scholes et al (2008)provided systematic comparisons of different alter-natives for stormwater treatment

It is obvious that no single treatment method would be effective for removal of all pollutants Learning from experiences of highway runoff treatment, the conventional treatment chain often serves these functions: (1) trapping litter and large objects, (2) detaining coarse sed-iments, (3) settlingfine sediments, and (4) treatment of dissolved solids and other contaminants In the case of the railway industry, space constraints and maintenance requirements are important factors in the selection of treatment methods.Table 4reviews different methods

in stormwater treatment and their applicability in the railway industry Constructed wetlands and detention basins, two common methods

in urban stormwater treatment, would rarely be used due to limited space availability at railway areas Initial sizing of wetlands should be based on pollution reduction targets, but in reality, other factors such

as topography may mean that excessive land area is required Sedimen-tation basins as a part of a wetland may have design particle sizes

dictat-ed by the catchment management authority The trapping offine clay and silt particles makes basin size prohibitively expensive

Simple methods such as buffer strips and grass swales are helpful in the removal of several pollutants The removal of contaminants by

buff-er strips is dependent on slope, length, runoff velocity, topography and vegetation type Buffer strips are suitable for removing coarse sediments

Stagge et al (2012)reported high removal efficiency for grass swales

in treating highway runoff (50–60% of sediment, 46–81% of Zn, 27–75%

Stormwater BMP Database roughly supports thefigures byWong et al

(2000)with the exception of generally lower rates for TSS removal in

swales Grass swales were very effective in removing zinc from runoff

Stagge et al (2012)emphasised that in the cases of physical limitation

as in railway corridors, the application of grass swales (about 200 m

length) can significantly improve the effluent water quality However,

finer sediments deposited during smaller flows may be remobilised

during larger events Vegetation types must be carefully selected to

prevent harmful effects on track foundation

Infiltration systems often achieve moderate levels of pollutant

re-moval due to the close contact between the runoff and substrate surface

during the infiltration of the runoff through the media (Scholes et al.,

2008), but they can have high failure rates Cleaning time is an essential

factor in the design of these systems

Wong et al (2013)advocated the use of biofiltration systems

with a submerged zone for urban stormwater treatment The

biofilters showed high removal efficiencies of TSS (N90%), pathogens

(1–3 log for Clostridium perfringens, Escherichia coli, and F-RNA

et al., 2008; Li et al., 2012; Lim et al., 2015; Zhang et al., 2014)

How-ever, the biofilters were not effective in removing the triazine

herbi-cides This was due to the short hydraulic retention time (3–5 h) of

the biofilters (Zhang et al., 2014), which was insufficient for

biodeg-radation of these herbicides Thus, there is a tendency to seek out

patho-gens, arsenic and micropollutants as herbicides

For stabling yards, drainage systems have to move water away from

the track formation quickly, denying the possibility of retention for

fil-tering or sedimentation However, some stabling yards run in parallel

to an access road, which may allow for the possibility of long narrow

options such as grass swales, bioretention pits, and underground in

fil-tration trenches For most depot sites, parking lots and stations, which

are mostly impervious surfaces,filtration tanks could be located

under-neath In addition, bioretention could be reserved for landscaped garden

beds in these areas

4.2.2 Stormwater harvesting

To fulfil the goals of a sustainable transportation system, the railway industry aims to investigate opportunities for harvesting stormwater (Transportation for NSW, 2013) Compared to wastewater reuse, stormwater harvesting receives less public objections While most stations would not be able to incorporate any water storage under plat-forms due to structural elements and amount of services present, many would have space on the platforms for above-ground water tanks to capture rainwater from the station roofs In addition, a spacious area under stabling yards becomes an attractive opportunity for storing stormwater Australia is a pioneering country in this area, having constructed the largest underground stormwater storage system in a railway area Being constructed at Auburn station (Sydney) in 2011, the underground structure stores and treats more than 11,000 m3of stormwater

4.3 Urban retrofit Urban retrofit is an innovative planning and design approach that considers the resilience of urban water that is aimed at developed or brownfield areas It fosters the incorporation of stormwater into the

Railway corridors are a promising candidate for urban designers to look for opportunities to incorporate natural elements and transform

“vacant” space into liveable space AsPenone et al (2012)discussed, railway could bear an ecologically functional connectivity in the fragmented urban context, especially when it runs across densely pop-ulated areas An example is the conversion of rail spaces to the green recreational belt“Green Rail Track” in Amersfoort (Utrecht, Holland)

well-planned application of vegetated treatment methods along the tracks serves multiple purposes— reducing pollutant flux, providing structural connectivity for plant communities and integration of greenery into the grey infrastructure These outcomes look promising, not only in regards

to its corridors, but also its green track application Green tracks for light railways have been very common in the UK, Germany, Netherlands and France In the study ofTapia Silva et al (2006), they assessed the ability

Table 4

Comparison of different stormwater treatment methods.

Modified from NSW Environment Protection Agency (1997)

Types of

treatment

Targeted pollutants Scale of

catchment

Space constraint

Environmental and community amenity

Operational and maintenance requirement

Primary treatment

Litter pits, baskets and racks Litter and gross pollutants b1 ha Low Low Simple maintenance

Sediment traps Coarse sediments 8–20 ha Low Low Simple maintenance

Gross pollutant traps Litters, coarse sediments 8–20 ha Low Low Simple maintenance

Oil/grit separators Oil, coarse sediments N1 ha Low Low Simple

Secondary treatment

Buffer (filter) strips Litter and gross pollutants, coarse sediments,

suspended solids (SS), total phosphorus (T-P), total nitrogen (T-N), bacteria

b1 ha Moderate Moderate–high Simple maintenance

Slope of the strip b 5%

Maximum flow depth = 12 mm Grass swales SS, T-N, T-P, organic matters, oil and grease,

bacteria

b2 ha Moderate Moderate–high Simple maintenance Sand filters SS, T-N, T-P, bacteria 1–6 ha Low Low Moderate maintenance due to sediment build-up

May require pre-treatment Infiltration trenches and basins SS, T-N, T-P, organic matters, bacteria b6 ha High Moderate–high Mostly suitable for sandy loam to loam soil

type with the infiltration rate of 13–25 mm/h Extended detention basins Coarse sediments, SS, bacteria N6 ha High Moderate Simple maintenance

May require pre-treatment Tertiary treatment

Biofilters SS, T-N, T-P, organic matters, bacteria N/A Low Moderate Moderate to complex

May require pre-treatment Constructed wetlands Coarse sediments, SS, T-N, bacteria N6 ha High High Moderate to complex

evaporation Nevertheless, the development of ballastless rail tracks

provides a good opportunity for incorporation of green turf on the

sur-face of concrete slabs

5 Conclusion

stormwater management practices in the railway industry This paper

points out the changes in perception of stormwater management

systems, from a drainage system (in the past) to a quality control (in

the present) and a resource in urban areas (in the future) To date, the

contamination of stormwater in railway areas has not been properly

studied From the limited literature available, this paper tries to analyse

potential sources of pollutants and their pollution pathways However,

stormwater pollution and management levels vary from country to

country Some pioneering countries, such as the US, the UK and

Australia, have already issued relevant regulations and guidelines

for controlling pollution from the railway industry This paper also

addresses the managerial challenges and provides provisions for future

management of stormwater quality in the railway industry

From this study, we have found that there are many gaps in thisfield

that are open to further research:

– To survey stormwater quality from different assets of railway

infra-structures such as rail tracks and embankments, stations, stabling

yards and depots;

– To model the transport behaviours and mass balance of pollutants

through various types of track bed and embankments;

– To explore the environmental fates of contaminants (PAHs,

herbi-cides and heavy metals) under real railway conditions;

– To investigate particle size distributions along rail tracks and their

effects on the selection of treatment methods for stormwater;

– To study different methods for treating stormwater in the railway

industry

Acknowledgements

Waste-water treatment and Reuse Technologies, the Centre for Technology in

Water and Wastewater (CTWW), the School of Civil and Environmental

Vietnam International Education Development Scholarship

References

Aasvang, G.M., Engdahl, B., Rothschild, K., 2007 Annoyance and self-reported sleep

dis-turbances due to structurally radiated noise from railway tunnels Appl Acoust 68,

970–981.

Ali, S.A., 2005 Railway noise levels, annoyance and countermeasures in Assiut, Egypt.

Appl Acoust 66, 105–113.

ANZECC, ARMCANZ, 2000 Australian Guidelines for Water Quality Monitoring and

Reporting Australian Water Association, Artarmon.

AREMA, 2008 M/W budgets to climb in 2008 Rail Tracks and Structures 104

Simmons-Boardman Publishing Company, New York.

Australian Rail Track Corporation Ltd., 2006 Track Drainage — Inspection and

Mainte-nance Australian Rail Track Corporation Ltd., Australia.

Australian Rail Track Corporation Ltd., 2013 Track Drainage — Design and Construction.

Australian Rail Track Corporation Ltd., Australia.

Barbosa, A.E., Fernandes, J.N., David, L.M., 2012 Key issues for sustainable urban

stormwater management Water Res 46, 6787–6798.

Becker, L., Matuschek, G., Lenoir, D., Kettrup, A., 2001 Leaching behaviour of wood treated

with creosote Chemosphere 42, 301–308.

Bending, G.D., Rodriguez-Cruz, M.S., 2007 Microbial aspects of the interaction between

soil depth and biodegradation of the herbicide isoproturon Chemosphere 66,

664–671.

Bratieres, K., Fletcher, T.D., Deletic, A., Zinger, Y., 2008 Nutrient and sediment removal by

stormwater biofilters: a large-scale design optimisation study Water Res 42,

3930–3940.

Britt, C., Mole, A., Kirkham, F., Terry, A., 2003 The Herbicide Handbook: Guidance on the

Use of Herbicides on Nature Conservation Sites English Nature, Yorkshire, the UK.

Brooks, K.M., 2001 The Environmental Risks Associated with the Use of Pressure Treated Wood in Railway Rights-of-way Railway Tie Association, Fayetteville, GA.

Brooks, K.M., 2004 Polycyclic Aromatic Hydrocarbon Mitigation from Creosote-treated Railway Ties into Ballast and Adjacent Wetlands United States Department of Agri-culture, Madison, WI.

Bukowiecki, N., Gehrig, R., Hill, M., Lienemann, P., Zwicky, C.N., Buchmann, B., et al., 2007.

Iron, manganese and copper emitted by cargo and passenger trains in Zürich (Switzerland): size-segregated mass concentrations in ambient air Atmos Environ.

41, 878–889.

Burkhardt, M., Rossi, L., Chevre, N., Boller, M., Steidle, L., Abrecht, J., et al., 2005.

Gewässerschutz an Bahnanlagen - Emittierte Stoffe im Normalbetrieb der SBB sowie Grundlagen zu deren Umweltverhalten Eawag, Dubendorf.

Burkhardt, M., Rossi, L., Boller, M., 2008 Diffuse release of environmental hazards by rail-ways Desalination 226, 106–113.

Cederlund, H., Börjesson, E., Önneby, K., Stenström, J., 2007 Metabolic and cometabolic degradation of herbicides in the fine material of railway ballast Soil Biol Biochem.

39, 473–484.

Chakraborty, A., 2001 Investigation of the Loss of Creosote Components From Railroad Ties Graduate Department of Chemical Engineering and Applied Chemistry Master

of Applied Science (University of Toronto, Toronto, Canada).

Chen, Z., Ai, Y., Fang, C., Wang, K., Li, W., Liu, S., et al., 2014 Distribution and phytoavailability of heavy metal chemical fractions in artificial soil on rock cut slopes alongside railways J Hazard Mater 273, 165–173.

Clark, S.E., Pitt, R., 2012 Targeting treatment technologies to address specific stormwater pollutants and numeric discharge limits Water Res 46, 6715–6730.

Comptroller and Auditor General of India, 2013 Performance Audit of Environment Man-agement in Indian Railways International Centre for Environmental Audit and Sus-tainable Development, India.

Cooker, J., 1996 Monitoring of Pesticides by the NRA in Connection With the Spraying of Railway Lines to Control Weed Growth Environment Agency Report, Australia.

Copeland, E., Lefler, D., 2013 Negotiations and challenges to revise NPDES permit limit for copper and ammonia 2013 Railroad Environmental Conference University of Illinois, Urbana-Champaign, Illinois, p 9.

Croll, B.T., 1991 Pesticides in surface waters and groundwaters Water Environ J 5, 389–395.

Department of Health — Office of Chemical Safety, 2014 Acceptable Daily Intakes for Ag-ricultural and Veterinary Chemicals The Office of Chemical Safety (Office of Health Protection, Department of Health), Canberra.

Dikshith, T.S.S., Diwan, P.V., 2003 Industrial Guide to Chemical and Drug Safety A John Wiley & Sons, Inc., Publication, New Jersey.

Dincer, F., Elbir, T., 2007 Estimating national exhaust emissions from railway vehicles in Turkey Sci Total Environ 374, 127–134.

Directorate-general health & consumer protection, 2001 Review Report for the Active Substance Amitrole (Unit E1— Legislation Relating to Crop Products and Animal Nu-trition) European Commission, Belgium.

Dunning, R., 2012 All of your storm drain maps are wrong 2012 Railroad Environmental Conference University of Illinois, Urbana-Champaign, Illinois, p 9.

Dunning, R., Weiner, J.L., 2011 Hope is not an approved BMP — lessons in Railroad Stormwater Management from the West Coast 2011 Railroad Environmental Confer-ence University of Illinois, Urbana-Champaign, Illinois, p 28.

Elliott, A.H., Trowsdale, S.A., 2007 A review of models for low impact urban stormwater drainage Environ Model Softw 22, 394–405.

Esveld, C., 1997 Low-maintenance ballastless track structures Rail Eng Int Ed 3, 13–16.

European Asphalt Pavement Association (EAPA), 2003 Asphalt in Railway Track Breukelen, European Asphalt Pavement Association, The Netherlands.

Gil, K., Im, J., 2014 Analysis of non-point source characteristics of heavy metals and oil and grease at railway bridge area with various land uses Desalin Water Treat 1–7.

Gill, G., 2012 Development of Stormwater Quality Profiles and Treatment Strategies for Selected Railway Infrastructure School of Civil and Environmental Engineering, Fac-ulty of Engineering and IT Bachelor of Engineering (University of Technology, Syd-ney, UTS).

Gunasekara, A.S., Troiano, J., Goh, K.S., Tjeerdema, R.S., 2007 Chemistry and Fate of Sima-zine vol 189 Springer, The US.

Gustafsson, M., Blomqvist, G., Håkansson, K., Lindeberg, J., Nilsson-Påledal, S., 2007.

Järnvägens föroreningar — källor, spridning och åtgärder: En litteraturstudie (Rail-way Pollution — Sources, Dispersion and Measure: A Literature Review) VTI (Statens väg- och transportforskningsinstitut), Sweden.

Hansen, M.J., Clevenger, A.P., 2005 The influence of disturbance and habitat on the pres-ence of non-native plant species along transport corridors Biol Conserv 125, 249–259.

Hayes, A.W., Kruger, C.L., 2014 Hayes' Principles and Methods of Toxicology Sixth Edition CRC Press, London.

Heather, A.I.J., Hollis, J.M., 1999 Agency E Losses of Six Herbicides From a Disused Railway Formation Environment Agency.

Hoofwijk, H., Stobbelaar, D.J., Gestel, Dv., 2013 Een Groen Spoor door Amersfoort Wageningen UR Science Shop Amersfoort.

Indraratna, B., Salim, W., Rujikiatkamjorn, C., 2011 Chapter 8 — track drainage and use of geotextiles In: Rujikiatkamjorn, C (Ed.), Advanced Rail Geotechnology — Ballasted Track CRC Press, London, UK, pp 203–217.

Juhasz, M., Princz-Jakovics, T., Vörös, T., 2013 What are the real effects of railway electri-fication in Hungary? European Transport Conference 2013 40 AET, Franfurt, Germany.

Kamga, C., Yazici, M.A., 2014 Achieving environmental sustainability beyond technologi-cal improvements: potential role of high-speed rail in the United States of America Transp Res Part D: Transp Environ 31, 148–164.