Effect of Setback Distance on Ability of Gravel Trenches to Intercept Contaminated Groundwater

Abstract

Computer simulations tested the ability of gravel interceptor trenches to capture a plume of contaminated groundwater. The plume had a maximum length and width of 87 and 19 m, respectively. In alternate simulations, one-meter wide trenches were located 5, 10, 20, and 50 m downgradient of the plume. A minimum trench length and time required to capture the plume was determined for each location (setback). The plume was considered captured if it passed entirely through a trench. A 21 m-long trench captured the plume at setbacks of 5 and 10 m. Minimum trench length increased to 23 and 25 m at setbacks of 20 and 50 m, respectively. Increased contaminant spreading with distance traveled dictated longer trenches at larger setbacks. Results of this study suggest that, at settings where contaminant plumes are carefully monitored and spatially defined, passive interceptor trenches should be close to a plume's leading tip and slightly longer than the maximum width of the plume.

Contaminated Groundwater Flow Control Across an Inverted Groundwater Divide With Three Groundwater Control Systems

“…One of the simplest and most effective configurations for a passive interceptor trench is a linear trench, installed perpendicular to groundwater flow, spanning the maximum width of a hydraulically up gradient contaminant plume (Hudak, 2005). The pumping trench is backfilled with sand or gravel (McMurtry and Elton, 1985), and groundwater that collects in the trench is pumped to a treatment plant.…”

“…Avci (1992) determined that the use of simulations and models were a quick way to establish initial interceptor trench effectiveness using assumptions regarding boundary conditions, but field tests are required to determine how actual boundary conditions will influence the interceptor trench. Hudak (2005) looked at the most effective size and set back distance of an interceptor trench. The further the interceptor trench is from the contaminated area, the wider the trench size and longer the time period necessary to capture the contaminant plume.…”

“…The further the interceptor trench is from the contaminated area, the wider the trench size and longer the time period necessary to capture the contaminant plume. Hudak (2005) suggests that interceptor trenches oriented perpendicularly to regional groundwater flow should be located close to the leading tip of a contaminant plume and be slightly wider than the maximum width of the plume. This trench configuration is not always feasible due to the arrangement of local topography or the contaminant plume.…”

“…Or, if a contamination source is too wide, installation of an interceptor trench may be prohibitively expensive. Hudak (2005) determined that because wider trenches and farther setbacks increased capture time, quicker recovery was possible if a shorter setback distance could be implemented.…”

Performance assessment of hanging funnel‐and‐gate structures designed by reverse particle tracking for capturing polluted groundwater

“…Such effects may enlarge a plume, causing mass to migrate around an undersized interceptor structure. Others have simulated mass transport or geochemical processes near interceptor structures Hudak, 2005;Mayer et al, 2001). This study builds upon previous work, using a mass transport model to investigate potential errors in designing hanging funnel-and-gate structures with particle tracks.…”