Collection of Contaminated Groundwater
Storrs, CT: Leachate Interceptor Trench, University Of Connecticut Former Landfill And Chemical Pits
Geo-Con completed two leachate interceptor trenches via the bio-polymer trenching method at the University of Connecticut (UCONN) Former Landfill and Chemical Pits. The interceptor trenches were installed as part of the landfill closure, to intercept and collect and treat leachate generated from the landfill and protect the surrounding wetland areas.
The two trenches, totaling 1,465 linear feet, were installed to depths of up to 20 feet below ground surface (bgs). Bio-polymer slurry was produced in Geo-Con's high speed/high shear colloidal batch plant and piped to the trenches via high density polyethylene (HDPE) pipe. The three-foot wide trenches were excavated using a Hitachi 450 excavator and were excavated to bedrock.
The interceptor trenches included the installation of 15-foot wide overlapping HDPE liner panels on the down-gradient wall of the trench to form a continuous HDPE vapor/groundwater barrier. Geotextile was placed in the trench to completely encapsulate the 3/4-inch washed-gravel backfill.
The project faced several major challenges including:
- Work pad instability due to unconsolidated soil and layers of trash resulting in trench-wall instability. Extra care had to be taken to keep the trench completely full of fresh slurry at all times. Diligent observation of the excavation and backfill process was necessary to recognize trench-wall sloughing and implement the necessary corrective measures to ensure a high-quality end product.
- Excessive groundwater, leachate and surface runoff. Recent weather conditions caused a surcharge of groundwater, surface runoff, and highly acidic leachate to migrate toward the trenches during installation. To prevent premature slurry degradation and trench failure, slurry properties had to be constantly monitored to ensure biopolymer slurry remained viable. Geo-Con had to modify the standard chemistry of the fresh slurry to compensate for the constant influx of the acidic leachate.