Evaluation of the runoff water quality from a tunnel wash
Tunnels are specific sections of roads, where the rainfall runoff process does not take place. Nevertheless, they are washed out periodically mainly for traffic safety reasons. The Portuguese National Laboratory for Civil Engineering (LNEC) monitored twice (in May and December 2003) the washout process of the 1570 m long IP2 Gardunha tunnel. The objective was to evaluate pollutant accumulation in the road pavement. Due to specific requirements from LNEC the wash operation was performed without the common detergents used to enhance the cleaning process. The annual average daily traffic (AADT), in 2003, was 9923. Measurements of flow and the collection of manual samples took place at the inlet of an oil separator tank that receives all the runoff from the tunnel, and discharges it into the local creek.
The first wash (1st wash) took place over two nights, with a total duration of 345 min, and an average flow of 1.6 L s-1. The second wash (2nd wash) operation was shorter, with the duration of 103 min and an average flow of 4.2 L s-1. The annual pollutant loads for metals, total suspended solids (TSS), oil, and grease and polycyclic aromatic hydro carbon (PAH) were estimated based on wash volumes and pollutant concentrations.
Compared to other monitoring studies of highway runoff in Portugal, Gardunha tunnel wash water presented low pollutants content. Only an evaluation of the results taking into consideration the flow processes inside the tunnel atmosphere allowed an understanding of the data, being concluded that tunnel pavements accumulate much less traffic pollutants than ordinary road pavements, under similar operation conditions. Furthermore, pollutants emitted inside the tunnel will tend to build up outside, therefore increasing runoff concentrations in the road sections flanking tunnels. These results are important for the control of highway runoff impacts.
KeywordsTotal Suspended Solid Road Pavement Road Section Fire Extinguisher Road Runoff
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- 1.Rosedth R, Amundsen CE, Snilsberg P, Langseter AM, Hartnik T (2003) Wash water from road tunnels - content of pollutants and treatment options. In: Reinosdotter K (ed.) International conference on urban drainage and highway runoff in cold climateGoogle Scholar
- 2.Gabet M (1991) Pollution des eaux de lavage des tunnels routiers. Revue Générale des Routes et Aérodromes, vol. 687, pp 57-64Google Scholar
- 4.Bækken T, Åstebøl SO (1997) Tunnel wash water from the Nordby tunnel to the Årung river. Investigation of biological effects (in Norwegian). Report NIVA/Interconsult 1997Google Scholar
- 5.Barbosa AE, Antunes PB (2004) Águas de escorrência de estradas. Sistemas para minimização de impactes. Report 128/04-NRE/DHA, Laboratório Nacional de Eng. Civil, pp 66Google Scholar
- 6.Barbosa AE, Leitão T, Carvalho CR (2003) Águas de escorrência de estradas. Sistemas para minimização de impactes. Report 233/03-NRE/DHA, Laboratório Nacional de Eng. Civil, pp 130Google Scholar
- 7.Pinto da Cunha A (2002) Observação do túnel da Gardunha I (IP2). Final Report. Report 149/02 - NOS, Laboratório Nacional de Eng. CivilGoogle Scholar
- 9.Leitão TE, Barbosa AE, Henriques MJ, Ikävalko V, Menezes JT (2005) Avaliação e gestão ambiental das águas de escorrência de estradas. Final Report. Report 109/05 - NAS, Laboratório Nacional de Eng. Civil, pp 243Google Scholar
- 10.Saraiva JAG (1983) Wind effects on high rise buildings. Turbulence - Thesis, Laboratório Nacional de Eng. Civil, Lisbon, pp 262Google Scholar
- 11.Novenco (1997) Velocity and sound measurements in Tunnel Gardunha Portugal. Report Novenco, BV Nederlands, pp 18Google Scholar
- 12.Estanqueiro AIL et al. (eds.) (2005) Wind atlas of Portugal, Instituto Nacional de Eng. E Tecnologia Industrial, Lisbon, Portugal, 3 pp + CD.Google Scholar
- 13.Saraiva JAG, Barbosa AE. Shear stress induced by air flow over roads. Open roads and tunnels: a comparison (in preparation)Google Scholar