Hydraulic Gradient Management at a Hazardous Waste Management Facility

SLR was contracted to evaluate and upgrade the hydraulic control system at a 28-acre, multi-cell, unlined hazardous waste landfill facility with over 50 years of accumulated industrial waste.

When SLR was contracted by the landfill operator, the existing hydraulic control system was failing to meet the permit requirement of a 2-foot inward gradient around the perimeter of the facility.

SLR initially determined that extra pumping capacity was required and oversaw the design and installation of additional extraction wells with paired piezometers for monitoring. The enhanced system was an improvement but still did not meet the permit requirement in all areas.

To further improve the leachate capture and to be fully compliant, SLR evaluated drawdown and capture zones for each of the 14 extraction wells surrounding the landfill. Using this data, SLR develop a MODFLOW simulation of groundwater flow across the site. Based on the MODFLOW results, SLR was able to provide the client with recommendation for estimated sustainable pumping rates, predict future capture, and determine locations for additional extraction wells.

Based on SLR’s hydrogeological investigation and modelling, the client was able to increase total leachate extraction, achieve regulatory compliance, and put in place infrastructure and system improvements necessary for long-term landfill closure.