, Professor, Bioproducts and Biosystems Engineering
Robert Sykes, Former Associate Professor, Landscape Architechture
Pavements associated with roadways, highways, parking lots, and other suburban and urban infrastructures generate much higher volumes of stormwater runoff than would occur when the land is under natural or even rural/agricultural conditions. Conventional approaches for stormwater control include such features as storm sewers and constructed open channels in conjunction with stormwater holding ponds, to get rid of the stormwater as quickly as possible. These conventional approaches have been criticized because they tend to promote downstream flooding, soil erosion, reduced groundwater recharge, and water quality degradation. Alternative techniques have now been developed that enhance infiltration and treat runoff water so that groundwater recharge is enhanced, and surface water discharges are of higher quality. These techniques include bioretention (rain gardens), wet ponds, infiltration techniques, biofilter swales, curbless roads with swales, and porous pavements. However, there are questions about the possible detrimental impact of these alternative stormwater control techniques on the transportation infrastructure. It is conceived that these techniques might be the cause of increased infrastructure maintenance costs. This research investigates the potential positive and negative impacts of alternative stormwater measures on transportation infrastructure, and attempts to assess the level of acceptance of these alternative measures by decision makers.
Highway infrastructure represents a substantial portion of the total impervious areas that generate runoff water. Because of long winters in congested areas that require frequent applications of de-icing materials, much of the runoff has the potential for affecting downstream water quality. However, stormwater management techniques themselves have the potential for compromising the integrity of adjacent highways when they result in significant increases of water content in the soil beneath the roadway.
Because of impacts and the costs associated with construction and maintenance, any stormwater management system needs to be assessed before any decisions are made regarding new highway development or redevelopment. The researchers considered Best Management Practices (BMPs) as they relate to the most commonly used stormwater management approaches including dry ponds, wet ponds, infiltration trenches, infiltration basins, constructed wetlands, grassed swales, bioretention cells, sand filters, and porous pavements. This study provides a framework for considering cost of practices, negative impact on infrastructure, results from a BMP-related survey of highway design, and maintenance professionals and cost-estimation formulas for each of the most commonly used stormwater management approaches in urban Minnesota.
Researchers also conducted a survey and performed inspections to evaluate the performance of various stormwater Best Management Practices and whether they negatively impact adjacent roadways. No negative infrastructure effects were discovered.