Infiltration-Exfiltration System for Stormwater Control: A Full Scale Test

Abstract

The traditional approach of storm water management on collecting, conveying and discharging runoff is becoming impractical on the current growing urbanization scenario and altered precipitation patterns, with high intensity events being observed more frequently. The contaminants present on runoff after washing off surfaces are an important cause of rivers and streams pollution. To avoid saturation of the urban drainage system and improve water quality the currently strategies for storm water management acts on management water on its source and encouraging systems that also function on water treatment. These systems are often referred as SUDs (sustainable urban drainage systems), green infrastructures, BMPs (best management practices), LIDs (low impact developments). This approach is already mentioned on public policies on urban drainage and land use, specially by limiting the discharge and requiring detention or retention tanks. \nApplication of these strategies for stormwater control may be difficult, especially in fully developed urban areas. Retrofitting of such areas is usually more expensive and may be limited to few urban spaces. One of the more feasible and effective interventions is the change of traditional road, pavement and parking surfaces with permeable ones. \nHowever, this change is limited by the need to find a trade-off between good infiltration performances and sufficient strength to traffic loads. That’s the reason for which this solution is often applied only to roads with low traffic loads. \nAn alternative is to limit the adaptations to road gutters, that are less stressed by dynamic loads. The use of an infiltration-exfiltration system as street gutters, consisting of a porous concrete surface with a gravel base, may achieve several goals. First, stormwater runoff to be discharged into the sewer network is reduced. Second, peaks of stormwater flow into the sewer network are reduced, due to the temporary storage inside the porous layers of the part of stormwater runoff that can’t be infiltrated. Third, the porous surface acts as filter, promoting load removal from runoff. \nAn infiltration-exfiltration system for road gutters is proposed. Test results from an experimental site are also presented. The system was installed on a 15 meters length gutter of a parking lot, with a catchment area of 400 square meters. A comparison with a traditional road gutter with the same dimensions was also performed, by simulation with a hydrologic-hydraulic numerical model.