BioPolymerTrench

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BIO-POLYMER DRAIN TRENCHES
CASE HISTORIES

DEEPWOODS LANDFILL
Dallas, Texas

Remedial Construction Services, L.P. (RECON) used the Biopolymer (BP) trench slurry method to install a hanging curtain groundwater and landfill gas recovery trench at a municipal solid waste facility in Dallas, Texas.

Biopolymer Trenching
BP Trenching is a variation of the "slurry trench" technique, which involves excavating a narrow trench that is kept full of BP slurry. The slurry exerts hydraulic pressure against the trench walls and acts as shoring to prevent collapse. BP slurry is biodegradable and does not reduce the final permeability of the in-situ soil or backfill materials.

Some advantages of the BP slurry trench method for this project included:
Eliminating the need for shoring;
Enhancing safety -- the workers did not have to enter the excavation and the slurry helped to suppress harmful vapors;
Eliminating the need for dewatering and associated treatement and disposal;
Accommodating the need for design flexibility during the installation of the filter fabric, liners, and recovery pipes;
Constructing the trench with a limited work area; and
Installing activities were completed quickly.

Trench Installation
The Deepwood trench was approximately 2,300 feet long and was excavated to the top of a confining layer with a maximum depth of 35 feet. The trench design required the installation of filter fabric on the sides of the trench excavation; double 40-mil high density polyethylene (HDPE) curtains on the down graident side of the trench; horizontal gas recovery pipes 5 feet above the groundwater table; and horizontal groundwater recovery pipes 6-inches from the bottom of the trench. Risers were connected to the groundwater and the gas recovery pipes every 100 feet.

VERNON POWER AND LIGHT
Vernon, California

Vernon Power and Light had a 30,000-gallon diesel fuel release from an aboveground storage tank. Due to the sandy soils, the diesel moved quickly and traveled downward 40 feet below ground surface to a confining layer. At that depth, the diesel began moving laterally. Remedial Construction Services, L.P. (RECON) was retained on a "fast-track" contract to install a recovery trench around the perimeter of the diesel plume in effort to recover the free-phase diesel.

Recovery Trench
The recovery trench was installed to a depth of 40 feet below grade. Lateral perforated piping was placed in the bottom of the trench, along with vertical risers set on 30-foot centers.

A groundwater treatment system was installed in combination with the recovery trench. This system included vacuum extraction, an oil/water separator and carbon treatment. Approximately 2,000 gallons of free-phase diesel was recovered and recycled, and an additional 200,000 gallons of water was treated in the groundwater treatment system and released into the sanitary sewer system.

Dig and Haul
As part of the remedial action. RECON excavated the highly saturated soils. Approximately 5,000 tons of diesel-impacted soil was excavated and transported offsite to a licensed soil recycling facility.

After removal of the impacted soils, the base of the excavation was backfilled with permeable gravel. Water injection lines were installed to enhance the hydraulic conditions and accelerate the free product recovery. The remaining balance of the excavation was backfilled with previously excavated "clean" soil and imported backfill.

SKULL CREEK OIL SEEPS
Cushing, Oklahoma

Remedial Construction Services, L.P. (RECON) was contracted to perform an interim remedial measure at former refinery in Cushing Oklahoma. This work was performed as part of an ongoing refinery closure under the regulatory of the State of Oklahoma. In order to divert the flow of a creek impacted with oily wastes, RECON was selected to convert a portion of an existing meander into a interceptor/treatment trench. This action allowed waters to bypass the impacted creak meander.

Channel Construction
The initial phase included creating a new channel; approximately 300 feet in length with 3:1 slopes and bottom grades to meet the creek flow modeling requirements. Work included:

Surveying and laying out the channel location;
Clearing and grubbing the work area;
Excavating approximately 14,000 cubic yards of soil to create a new channel;
Sloping and stabilization of banks and the bottom of the channel; and
Installing diversion wing walls to route the water down the new channel.

The wing walls were installed with close detail to radius and obstruction, so as not to diminish the natural flow of the creek and minimize future erosion. RECON contoured the wing walls and covered them with 18-inch riprap armor and a 3:1 slope.

Interceptor Trench Installation
In order to install the interceptor trench, RECON meticulously removed approximately 4,000 cubic yards of oily waste from the meander using a 300 series track mounted excavator and off-road articulated dump trucks. The excavated soils were dewatered by segmenting and depositing in a frac tank and transferred to the onsite waste staging area.

Subsequent actions included:

The placing and compacting of 16,000 cubic yards of interceptor trench soils in the creek meander.Mixing and placing bio-augmented solution consisting of compressed cow manure, gypsum, wood chips and limestone cobbles in the trench. In order to promote good aerobic activity, the solution was covered with limestone.Installing of a weir structure and sump on downstream side of the trench.
Finish grading of treatment area.

Restoration
To complete the project, RECON planted 422 trees at numerous locations around the work area and seeded the site with native grasses as part of an agreement with the US Army Corps of Engineers, who manages the creek.

Despite an abnormal amount rain, this project was completed on time and on budget