the impact of pervious pavements on water quality state-of

RESEARCH REPORT

VTT-R-08224-13

The impact of pervious pavements on water quality State-of-the-Art

Authors: Kalle Loimula and Hannele Kuosa

Confidentiality: Public

RESEARCH REPORT VTT-R-08224-13

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Preface

This State-of-the Art Report was created as a review of current knowledge about the impact of permeable pavements for stormwater management, with respect to stormwater and runoff quality. The report has been written as part of the Climate Adaptive Surfaces (CLASS) project (2012 – 2014) during the activities of WP 2 on Material Development. The results of this literature review are used as background when developing the laboratory testing plan for permeable materials and solutions for Finland. The knowledge is also used when assessing tools and models for designing and forecasting the impact of permeable pavement solution. The steering committee of the CLASS project has guided this work. Funding from the 16 industrial partners, VTT and Tekes is acknowledged. Participants of the steering group in the CLASS-project are:

Pirjo Sirén (chairperson), Espoon kaupunki, tekninen keskus Markus Sunela, FCG Suunnittelu ja tekniikka Oy Osmo Torvinen, Helsingin kaupunki, Rakennusvirasto Tommi Fred, Helsingin seudun ympäristöpalvelut – kuntayhtymä (HSY) Olli Böök, Kaitos Oy Pekka Jauhiainen, Kiviteollisuusliitto ry Lars Forstén, Lemminkäinen Infra Oy Pasi Heikkilä, Oulun kaupunki Mika Ervasti, Pipelife Finland Oy Tomi Tahvonen, Puutarha Tahvoset Oy Juha Forsman, Ramboll Finland Oy Tiina Suonio, RTT Betoniteollisuus Kimmo Puolakka, Rudus Oy Ab Kati Alakoski, Saint Gobain Weber Oy Ab Ismo Häkkinen, SITO Antti Auvinen, Vantaan kaupunki Angelica Roschier, TEKES Eila Lehmus, VTT

Espoo, December 2013 Kalle Loimula and Hannele Kuosa


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Summary

Urban surfaces are been covered with impermeable materials at increasing speed. This leads to increase in surface runoff as the ground is not able to take in all the water at a sufficient rate. Surface runoff transfers pollutants like heavy metals and hydrocarbons into sewer systems and natural water courses. Permeable pavements offer a solution for the problem of increased stormwater runoff and decreased stream water quality. These pavements are designed to take in sufficient amounts of water causing practically no runoff during normal storm events. Permeable pavements also act as pollution sinks because of their particle retention capacity. Impurities such as heavy metals, hydrocarbons and organic compounds are absorbed onto suspended solids and trapped inside permeable pavements. Effluent quality from permeable pavements has been found to be significantly better than typically monitored from impermeable sources in similar residential areas. Chlorides are not trapped inside the permeable structure but reduced need for winter maintenance leads to a reduction in chloride loads in sewage systems. Hydraulic properties for permeable structures remain strong in winter conditions despite of significant frost penetration.


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Yhteenveto

Jatkuva rakentaminen aiheuttaa asuinalueiden pintojen peittymisen vettä läpäisemättömillä materiaaleilla. Tämä johtaa hulevesien määrän kasvuun, sillä maaperä ei kykene imemään sadevettä riittävän nopeasti. Hulevedet kuljettavat mukanaan saasteita, kuten raskasmetalleja ja hiilivetyjä, viemäreihin ja vesistöihin. Hulevedet aiheuttavat saastumisuhan myös maaperälle sekä pohjavesivarannoille. Rankkasateiden yhteydessä vedenpuhdistamot eivät välttämättä kykene vastaanottamaan kaikkea puhdistettavaa vettä, jolloin osa vedestä joudutaan ohjaamaan suoraan luonnon vesivarantoihin. Hulevesien laatuun sekä puhdistusmahdollisuuksiin tulee myös tästä syystä kiinnittää erityistä huomiota. Vettä läpäisevät päällysteet tarjoavat ratkaisun hulevesien määrän vähentämiseksi sekä veden laadun parantamiseksi. Läpäisevät päällysteet on suunniteltu niin imukykyisiksi, ettei valumaa pinnoilta pääse syntymään tavanomaisten sadetapahtumien yhteydessä. Läpäisevät päällysteet pystyvät myös suodattamaan monia saasteita hulevesistä ja täten parantamaan läpi virranneen veden laatua. Tutkimukset osoittavat että läpäisevät rakenteet pystyvät tehokkaasti vähentämään raskasmetallipitoisuuksia, hiilivetyjä, typpi- ja fosforiyhdisteitä, suspensoituneita kiintoaineita sekä taudinaiheuttajia läpi virranneesta sadevedestä. Kaikki läpäisevät rakenteet pystyvät tehokkaasti sitomaan veteen suspensoitunutta hienoainesta, joka puolestaan absorboi ja kuljettaa monia saasteita. Erilaisten läpäisevien rakenteiden vedenpuhdistusominaisuuksien välillä on myös paljon eroja. Läpäisevä rakenne on kokonaisuus, joka koostuu läpäisevästä päällysteestä, huokoisesta alusrakenteesta sekä mahdollisesti käytettävistä geotekstiileistä. Näillä rakenteilla on oma vaikutuksensa veden puhdistumiseen ja valitsemalla sopivat rakenteet voidaan optimoida läpäisevän rakennekokonaisuuden vedenpuhdistusominaisuudet. Läpäisevän asfaltin on todettu puhdistavan läpivirranneesta vedestä mm. moottoriöljyä, kuparia, sinkkiä sekä lyijyä. Läpäisevä päällyste voi olla myös esim. betonikivilaattaa, jossa on riittävä saumaleveys ja saumat läpäisevää materiaalia. Tällaisilla päällysteillä on hulevesistä saatu puhdistettua mm. raskasmetalleja sekä typpi- ja fosforiyhdisteitä. Saumamateriaalilla on merkitystä vedenpuhdistuksen kannalta. Ruohosaumoilla on saatu paras puhdistus raskasmetalleista. Alusrakenteella ja siinä käytettävillä kiviaineksilla on oma vaikutuksensa veden puhdistukseen. Kvartsiitin on todettu pidättävän kuparia paremmin kuin dolomiitin. Läpäisevässä rakenteessa voidaan halutessa käyttää myös geotekstiilejä, joiden puolestaan on todettu vähentävän fosforiyhdisteiden määrää läpi virranneessa vedessä. Kloridit eivät pidäty läpäisevään rakenteeseen, mutta vähentynyt tarve talvikunnossapidolle johtaa kloridimäärien vähenemiseen viemärivesissä. Tutkitut läpäisevät pinnoitteet suoriutuivat sadetapahtumista erinomaisesti imien kaiken sadeveden ilman valuman muodostumista. Hydrauliset ominaisuudet säilyivät hyvinä talviolosuhteissakin routimisesta huolimatta.


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Contents

Preface ................................................................................................................................... 2

Summary ................................................................................................................................ 3

Yhteenveto ............................................................................................................................. 4

Contents ................................................................................................................................. 5

1. Water quality introduction .................................................................................................. 6

2. Stormwater collection ........................................................................................................ 7

3. Surface runoff ................................................................................................................. 11

4. Performance in winter conditions .................................................................................... 13

References ........................................................................................................................... 15


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1. Water quality introduction

An increasing amount of urban surfaces are been covered with impermeable materials due to construction of parking lots, roads and sidewalks. These impervious surfaces have a high potential for introducing pollution for watercourses. Stormwater runoff is traditionally collected from the impervious surfaces and distributed to nearby waters or sewer systems. Contaminated surface runoff water can also be infiltrated into the underlying soil in areas used as roads or parking lots. Harmful pollutants in these surface runoff waters have the potential to pollute soil and groundwater resources where they are not sufficiently biodegraded or removed during infiltration. In 2004, The U. S. Environment Protection Agency declared urban stormwater runoff as the greatest threat to water quality in coastal estuaries, and the third greatest cause for impairment of lakes. The most important water quality variables of concern are: [Scholz & Grabowiecki 2007, USEPA 2004]

suspended solids,

heavy metals,

nutrients (nitrogen and phosphorus),

hydrocarbons and

faecal pathogens. Permeable pavement systems (PPS) offer one solution for the problem of increased stormwater runoff and decreased stream water quality. Permeable pavements can function as pollution sinks because of their particle retention capacity during infiltration. This retention capacity is an important feature in PPS because many of the harmful pollutants such as polycyclic aromatic hydrocarbons, heavy metals, phosphorus and organic compounds are absorbed onto suspended solids. Geotextiles are used in PPS to enhance their fine particle retention capacity. Tota-Mahraj et al. (2012) identified geotextiles as one of the most important components within PPS. Research has shown that the PPS structure itself can also be used as an effective in-situ aerobic bioreactor. Petroleum contamination reduction in the effluent to 2.4% of the oil applied was reported by Pratt et al. [Pratt 1989]. If there is any concern about the pollutants migrating to groundwater, PPS should be constructed with an impermeable membrane, and the treated stormwater should be discharged into a suitable drainage system. [Scholz & Grabowiecki 2007, Coupe et al. 2003, Tota-Maharaj et al. 2012] Porous pavements are prone to clogging within 3 years after installation. Clogging of the voids leads to a loss of porosity and a decrease in PPS performance. There are three main causes for clogging. Firstly, sediment can be ground into the porous pavement by traffic. The second cause is waterborne sediment, which drains onto pavements and clogs the pores. Finally, shear stress caused by numerous breaking actions of vehicles at the same spot, which results in collapse of pores [Scholz & Grabowiecki 2007, Stenmark 1995]. However, Booth & Leavitt (1999) evaluated four commercially available PPS and after 6 years of daily parking usage they showed no signs of wear.


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2. Stormwater collection

Effluent quality from PPS has been found to be significantly better than typically monitored from urban, impermeable highway sources in similar residential areas, and there exists the opportunity for the design of construction and choice of materials to effect quality enhancement. The reduced effluent discharge, combined with lower pollutant concentrations, means much reduced pollutant loads are passed to receiving waters. Discharge form PPS typically have lower concentrations of zinc (Zn), lead (Pb), copper (Cu), cadmium (Cd), suspended solids, motor oil, nutrients (nitrogen and phosphorus) and microbial pollutants. Hardness and conductivity typically have higher values in the subsurface infiltrate compared to the surface runoff. Note that metal toxicity criteria are determined not only by the concentration of the constituent but also by hardness, as hardness increases allowable concentrations for metals also increase. [Benjamin et al. 2002, Pratt et al. 1989, Bean et al. 2007] Benjamin et al. (2002) investigated the performance of 4 commercial PPS for 6 years, while traditional impervious asphalt was used as a reference. Basically all rainwater infiltrated through the permeable pavements with almost no surface runoff. The highest rainfall intensity observed during the study period was 7.4 mm/h. Motor oil was detected in 89 % of samples from the asphalt runoff but not in any water sample infiltrated through the permeable pavement. The infiltrated water also had significantly lower levels of Cu and Zn than the surface runoff from the asphalt area. In another study, Legret et al. (1996) concluded that the filtration effect of runoff waters by the reservoir in PPS can decrease the pollutant concentrations of about 64 % for suspended solids and 79 % for lead. Bean et al. (2007) monitored the performance of 4 PPS in North Carolina for up to 26 months. The discharge from permeable pavement cells had lower concentrations of Zn than the adjacent asphalt runoff. Exfiltrate concentrations of total phosphorus from the permeable pavement were also significantly less than asphalt runoff concentrations. Total phosphorus concentrations from a permeable pavement exfiltrate and asphalt runoff samples are represented in Figure 1.

Figure 1. Total phosphorus concentrations from a permeable pavement exfiltrate and an adjacent asphalt runoff samples. [Bean et al. 2007]

Tota-Maharaj & Scholz (2010) investigated PPS for the removal of urban runoff pollutants under varying environmental conditions. The medium term study was made both indoors and outdoors in the University of Edinburgh area. The study showed high removal efficiencies for


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ammonia-nitrogen and orthophosphate-phosphorus. Practically all microbial pollutants were removed or degraded within each system. Mean removal efficiencies for total coliforms, E. coli and fecal streptococci were 98.6 %. Mean removal efficiencies for nutrients are represented in Figure 2.

Figure 2. Mean removal efficiencies for nitrate-nitrogen, ammonia-nitrogen and orthophosphate-phosphorus with respect to the (a) indoor and (b) outdoor PPS. Sample number = 67; bar graphs with error bars indicating standard deviation. [Tota-Maharaj & Scholz 2010]

Tota-Maharaja et al. (2010) examined also the influence of geotextile membranes to filtration effects within the permeable pavement systems. Water quality analysis indicated that the absorption capabilities of the geotextile membrane provide higher removal efficiency for typical contaminants in urban runoff when compared to PPS without the geosynthetic layer. Mean monthly inflow and outflow concentrations of phosphorus in inflow stormwater and 3 different PPS are represented in Figure 3. Influent phosphorus is removed via mechanical filtration and biological treatment.


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Figure 3. (a) Mean monthly inflow and outflow concentrations of ortho-phosphate-phosphorus; (b) Mean monthly inflow and outflow concentrations of total phosphates. [Tota-Maharaja et al. 2010]

Myers et al. (2011) investigated the influence of the type of reservoir basecourse aggregate on the quality of stored water. They used reservoirs filled with dolomite aggregate or quartzite aggregate or control reservoirs with no aggregate and monitored the water quality for up to 144 hours. Both dolomite and quartzite significantly reduced the concentrations of colour and UV254-absorbing compounds, total Kjeldahl nitrogen (TKN), total phosphorus (TP), total copper, total lead and total zinc. Total suspended solids (TSS) and turbidity were initially higher than in controls but ultimately decreased to levels lower than in controls after 144 hours. Figure 4 presents the variation of concentration for zinc, lead and copper with residence time for PPS with dolomite aggregate, quartz aggregate or control with no aggregate.


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a) b) c)

Figure 4. Variation of concentration for a) total zinc, b) total lead and c) total copper with residence time for PPS with dolomite aggregate, quartz aggregate or control with no aggregate. [Myers et al. 2011]

Dierkes et al. (2002) tested permeable pavement systems for their retention capability of dissolved heavy metals. Four different types of pavers were tested, a paver with open joints, a porous paving-stone, a paver with large greened apertures and a porous paver with greened apertures. They prepared a synthetic runoff with heavy metals with a pH of 5 to be used in the tests. The heavy metal concentrations were chosen from literature data and multiplied by 10 in order to study the structures under the worst case scenario. A total of 4000 mm of rain was simulated reflecting 5 years of rain in Germany. The load of heavy metals for one square-meter over a period of 50 years is presented in Figure 5. The left column shows the total input mass of metals and the right columns show the mass of metals that left the different types of permeable pavements. The most heavy metals in exfiltrate were found where the infiltration was carried out only though the joints. Blocks with greened areas seem to be very efficient at trapping metals. Pb and Cu were retained more effectively than Zn and Cd in the structure. [Dierkes et al. 2002]

Figure 5. Heavy metal retention of four different permeable pavements. [Dierkes et al. 2002]


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3. Surface runoff

Usually permeable pavement systems are designed in a way that no surface runoff occurs and all rainwater infiltrates though the surface. This indeed seems to be the case as reported in several studies. Benjamin et al. (2002) concluded that virtually all rainwater infiltrated through the permeable pavements forming no surface runoff from a total of 15 distinct precipitation events. Booth & Leavitt (1999) made similar observations reporting that a surface runoff of approximately 0.1 % of the total rainfall was recorded from the surface of permeable pavement. This recorded runoff was more likely a result of observed leaks in the covering over the collection gutter than actual runoff. Comparison of normal asphalt and permeable pavement (Turfstone®) runoff is represented in Figure 6.

Figure 6. Comparison of normal asphalt and permeable pavement (Turfstone®) runoff, storm of November 27, 1996. [Booth & Leavitt 1999]

Sometimes no reservoir structure is used beneath the PPS and the infiltrate is collected by e.g. an impervious membrane and discarded into a suitable drainage system. Pervious asphalt can be used this way as road surfacing material. Splashing is avoided and the runoff water is discharged at the road edge. Pagotto et al. (2000) investigated the effect of porous asphalt on runoff water quality when compared to conventional asphalt. The research was performed at a French highway. Runoff water quality was improved for the main pollutants of runoff water. Heavy metal loads discharged into the environment were reduced from 20 % (Cu) up to 74 % (Pb), solids were retained at a rate of 87 % and hydrocarbons intercepted at an even higher rate (90 %). Pollutant contents of runoff waters from both a conventional pavement and a porous pavement are represented in Figure 7. It is mainly the retention of fine particulate pollution by porous pavement filtration that explains the reduction amount of hydrocarbons and metals. However, other mechanisms may also be at work, namely the retention of coarse particulate pollution by filtration and the retention of certain dissolved metals, such as Zn and Cd, by adsorption. [Pagotto et al. 2000]


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Figure 7. Pollutant contents of runoff waters from both a conventional pavement and a porous pavement. [Pagotto et al. 2000]


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4. Performance in winter conditions

If permeable pavements are considered to be used in cold climates their winter performance has to be considered. Winter conditions expose the pervious pavement structure to additional stress in the form of freeze-thaw and frost penetration. A snowflake is also a greater collector of atmospheric pollutants compared to an equal mass raindrop due to the larger specific surface area and slower falling speed [Westerlund 2007]. This leads to a possibility of increased pollutant loads compared to summer conditions. Literature regarding these issues is reviewed in this chapter. Roseen et al. (2012) studied the hydrologic performance and water quality treatment performance of permeable asphalt in winter conditions. The test lasted from 2004 to 2008 and took place in New Hampshire where 6 months of subfreezing temperatures typically occur. Hydrologic performance was impressive despite the cold-climate challenges. Porous pavements are believed to be more resistant to freezing than standard pavements because of their disconnection to subsurface moisture and because they thaw more rapidly as a result of the rapid infiltration of meltwater [Bäckström 2000]. Significant frost penetration was observed up to 71 cm without any declines in hydrologic performance or noticeable frost heave. The life span of permeable pavements is expected to exceed that of typical pavement applications in northern climates because of the absence of adverse freeze-thaw effects, such as heaving. Water quality treatment performance was also found to be impressive for petroleum hydrocarbons, zinc and total suspended solids. Moderate removal was observed for phosphorus. [Roseen et al. 2012] In another study by Roseen et al. (2009) seasonal variations for stormwater management systems in cold climate conditions were investigated. Frost penetration was observed but they concluded that it does not necessarily equate to filter media permeability as frozen media may still have significant porosity and permeability. Rainwater quality was measured for 2 summers and 2 winters. Analyses were made for total suspended solids (TSS), total petroleum hydrocarbons-diesel (TPH-D), dissolved inorganic nitrogen (DIN), total phosphorus (TP) and total zinc (TZn). Porous asphalt had good winter performance having equal removal efficiency compared to summer for TSS, TPH-D and TZn. Removal of TP was more efficient during winter and removal of DIN was not observed during winter or summer. Overall seasonal variance was minimal. Annual and seasonal influent and effluent concentrations for a porous asphalt parking lot is represented in Figure 8.


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Figure 8. Annual and seasonal influent and effluent event mean concentrations for a porous asphalt parking lot; box and whisker plots indicate maximum, minimum, 75th, and 25th percentiles and median. Annual-In = annual influent, Annual-Eff = annual effluent, Summer-In = summer influent, Summer-Eff = summer effluent, Winter-In = winter influent, Winter-Eff = winter effluent. [Roseen et al. 2009]

Chloride penetration to groundwater resources might be a concern when applying permeable pavements to areas that require winter maintenance. Hogland et al. (1987) monitored water-quality treatment performance of several pervious asphalt sites with snowmelt and reported a 650% increase in chloride content. The increase in chloride content originates from salts used for de-icing purposes. A common guideline for constructing permeable pavement structures is that the structure should be constructed with an impermeable membrane if there is any concern about pollutants migrating to groundwater. The filtrate should then be discharged into a suitable drainage system thus not having an adverse effect on groundwater resources. Cahill et al. (2003) reported that pervious asphalt parking lots required less snow-removal plowing and that snow and ice melted faster compared to regular parking lots. 75% reduction in salt application was possible according to University of New Hampshire (2007). In conclusion, the use of permeable pavements could result in reduced chloride loads in sewage systems and reduced winter maintenance costs compared to traditional pavements.


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References

Bäckström, M. 2000. Ground temperatures in porous pavement during freezing and thawing. Journal of transportation engineering, Vol. 126, pp. 375-381.

Bean, E. Z. et al. 2007, Evaluation of four permeable pavement sites in eastern north Carolina for runoff reduction and water quality impacts, Journal of irrigation and drainage engineering, Vol. 133, pp. 583-592.

Benjamin, O. et al. 2002, Long-term stormwater quantity and quality performance of permeable pavement systems, Water research, Vol. 37, pp. 4369 - 4376.

Booth, D. B. & Leavitt, J. 1999. Field evaluation of permeable pavement systems for improved stormwater management. Journal of the American planning association, Vol. 65, pp. 314 - 325.

Cahill et al. 2003. Porous asphalt: The right choice for porous pavements. Hot mix asphalt technology. pp. 26-40.

Coupe, S. J. et al. 2003, Biodegradation and microbial diversity within permeable pavements. Euro. J. Protistol., Vol. 39, pp. 495 - 498.

Dierkes, C. et al. 2002. Pollution retention capability and maintenance of permeable pavements. Global Solutions for Urban Drainage, Proc. of the Ninth Int. Conf. on Urban Drainage, Sept 8 – 13, 2002, Portland, OR, pp. 1 – 13.

Hogland et al. 1987. The unit superstructure during the construction period. Science of the total environment. Vol. 59, pp. 411-424.

Legret, M. et al. 1996. Effects of a porous pavement with reservoir structure on the quality of runoff water and soil. The science of the total environment, Vol. 189/190, pp. 335 - 340.

Myers, B. et al. 2011. Water quality with storage in permeable pavement basecourse’, Water management, Vol. 164, pp. 361 - 372.

Pagotto, C. et al. 2000. Comparison of the hydraulic behaviour and the quality of highway runoff water according to the type of pavement. Wat. Res., Vol. 34, pp. 4446 - 4454.

Pratt, C. J. et al. 1989. Urban stormwater reduction and quality improvement through the use of permeable pavements. Wat. Sci. Tech., Vol. 21, pp. 769 - 778.

Pratt, C. J. et al. 1999. Mineral oil bio-degradation within a permeable pavement: long term observations. Wat. Sci. Tech., Vol. 39, pp. 103 - 109.

Roseen, R. M. et al. 2009. Seasonal performance variations for storm-water management systems in cold climate conditions. Journal of environmental engineering, Vol. 135, pp. 128-137.

Roseen, R. M. et al. 2012. Water quality and hydrologic performance of a porous asphalt pavement as a storm-water treatment strategy in a cold climate. Journal of environmental engineering, Vol. 138, pp. 81-89.

Scholz, M. & Grabowiecki, P. 2007. Review of permeable pavement system. Building and environment, Vol. 42, pp. 3830 - 3836.


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Stenmark, C. 1995. An alternative road construction for stormwater management in cold climates. Wa. Sci. Tech., Vol. 32, pp. 79 - 84.

Tota-Maharaj, K. & Scholz, M. 2010. Efficiency of permeable pavement systems for the removal of urban runoff pollutants under varying environmental conditions’, Environmental progress & sustainable energy, Vol. 29, pp. 358 - 369.

Tota-Maharaj, K. et al. 2012. The performance and effectiveness of geotextiles within permeable pavements for treating concentrated stormwater. Sixteenth International Water Technology conference, Istanbul, Turkey, pp. 1 – 13.

USEPA 2004, ‘Nonpoint source pollution: the nation’s largest water quality problem’, EPA841-F-96-004A.

Westerlund, C. 2007. Road runoff quality in cold climates. Doctoral thesis. Luleå University of Technology.

UNHSC, Roseen, R. et al. 2007. UNH Stormwater Center 2007 Annual Report. University of New Hampshire, Cooperative Institute for Coastal and Estuarine Environment Technology, Durham, NH.

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