Evaluating the Hydrologic Performance of Permeable Articulating Concrete Blocks over Silty Clay Soil in Maryland

A permeable articulating concrete block (P-ACB) pavement (area=218 m2, storage depth=1.2 m) was installed in April 2021 in Colmar Manor, MD. This 1.5-year study analyzed the volumetric stormwater reduction and subsurface infiltration performance for 50 rainfall events at this site. Subsurface infiltration rates were calculated by fitting linear and exponential decay models to depth sensor data. Site soil boring data revealed a heterogenous soil composition, including hydrologic soil group (HSG) A, B, and D soils. The local permitting agency classified soils per the lowest HSG (D), which is not recommended for infiltration-based best management practices. Nonetheless, exponential models revealed a mean subsurface infiltration rate of 2.35±1.88 cm/h, despite the presence of D soil with low hydraulic conductivity. Balances of rainfall and storage volumes reveal that the pavement fully captures rainfall from a 873 m2 drainage area, 8% greater than anticipated in design stages (809 m2). Study results predict that the P-ACB pavement system is able to fully capture rainfall from storms up to 10.44 cm without reaching overflow into a mid-drain, based on trends from observed data and assuming static volumetric storage with 40% porosity. Considering continuous exfiltration from the storage bed, an additional 0.58 cm can be managed during a 4-h rainfall, for a total capture of 11.02 cm.