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356-7 Effects of Urban Karst on Performance of an Enhanced-Infiltration Stormwater Control and the Surrounding Groundwater

Session: Urban groundwater and geochemistry

Presenting Author:

Clare Robinson

Authors:

Mohamadian, Hamed¹, Power, Christopher ², Sones, Adrienne³, Hachey, Jeffrey ⁴, Robinson, Clare⁵r> (1) Civil and Environmental Engineering, Western University, London, ON, Canada, (2) Civil and Environmental Engineering, Western University, London, ON, Canada, (3) Stormwater Engineering Division, City of London, London, ON, Canada, (4) Stormwater Engineering Division, City of London, London, ON, Canada, (5) Civil and Environmental Engineering, Western University, London, ON, Canada,

Abstract:

Exfiltration storm sewer systems are a low impact development stormwater control designed to reduce stormwater runoff volumes by promoting infiltration. These systems are integrated into conventional storm conveyance systems and consist of a perforated pipe embedded in a gravel trench beneath the main storm sewer. While effective for runoff attenuation, exfiltration systems may increase the risk of groundwater contamination, including from winter de-icing salts in the study region. This study evaluates the runoff reduction performance of an exfiltration system installed in low-permeability soils, its effect on groundwater levels and quality, and the influence of urban karst preferential pathways associated with subsurface infrastructure. A 75 m section of an exfiltration system installed in low permeability soils beneath a road in London, Ontario, was monitored over 13 months, with monitoring within the sewer system and surrounding groundwater. Despite low-permeability soils and a shallow (potentially perched) groundwater table, the system achieved high runoff volume reductions (>83%). Storm-sewer chloride loads were reduced by ~99.8% via infiltration-driven volume losses, transferring chloride to the subsurface. Limited groundwater level and quality responses observed in piezometers installed in native soils, contrasted with significant groundwater level and water quality fluctuations in a downgradient piezometer installed in high permeability backfill material (i.e. urban karst zone). Data indicate that the high hydrologic performance of the exfiltration system may be due to urban karst features, which may also control the subsurface fate of infiltrated contaminants. Study findings provide insights into the effectiveness of exfiltration system for stormwater management and interactions between enhanced-infiltration stormwater controls and anthropogenic urban karst features.

Effects of Urban Karst on Performance of an Enhanced-Infiltration Stormwater Control and the Surrounding Groundwater

Description

Session Format: Oral

Presentation Date: 10/14/2026

Presentation Start Time: 03:25 PM

Presentation Room: CCC, 112

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