Stormwater Volume Reduction in Combined Sewer Using Permeable Pavement: City of St. Louis

This paper describes findings from the City of St. Louis Low Impact Development Green Alley Pilot Study to reduce water quantity in the combined sewer system. Permeable pavement is one green infrastructure technique used for water quantity reduction. The effectiveness of permeable pavement in reducing the stormwater runoff to the combined sewer was tested. Monitored flow from reconstruction and postconstruction of permeable pavement are used for analysis. The separation of base flow and runoff is based on estimating the base flow in the antecedent/subsequent dry days of the rainfall events. The comparison between runoff in the reconstruction and postconstruction of the permeable pavement from three alleys showed different percentages of runoff reduction from different types of pavement (36, 13, and 46% from permeable concrete, permeable asphalt, and permeable pavers respectively). Permeable asphalt had the lowest percentage reduction, most likely due to the slope of the site and the small ratio of permeable to catchment area in this location. The permeable paver showed the highest percentage of runoff reduction.