Subsurface survey investigations and obstruction removal of abandoned petroleum, processed oil and fuel pipes were performed from 2002 to 2004 to make way for the installation of an impervious soil bentonite slurry trench cutoff wall around the perimeter of the site. Utilities, concrete, and other obstructions and debris were discovered and removed during this project. Onsite wells were decommissioned, pipeline plugs and caps were installed, utilities were relocated, and approximately 296,000 square feet of vertical barrier/soil bentonite slurry trench cutoff wall was installed.

Cross-section of soil-bentonite slurry wall.

Obstruction Removal
11/18/2004 — 10/12/2005

The Obstruction Removal Project was conducted along the southern border of the Confined Disposal Facility (CDF) site in 2005. The Contractor cleared the area free of all brush, trees, and surface obstructions and removed twelve pipes crossing the Lake George Branch of the canal. The pipes, which were located 25' below the water level underneath 15-20' of sediment, were removed in ten foot sections in order to clear a driveline for the South Cutoff Wall.

A localized braced excavation system was used in the canal to isolate the area requiring dredging and obstruction removal, as well as to prevent sloughing of sediment during operations.

System for excavating sediment and removing
pipes under the canal.

Phase 1 Dike 1
10/28/2004 — 11/5/2005

Dikes are being built of impervious clay material to contain the dredged sediments. Construction will take place in two phases: one 20 ft lift (Phase I), and another 12-14 ft lift for future capacity expansion (Phase II). The Phase I lift of the exterior dike is broken into 3 projects: Dike 1, Dike 2, and Dike 3.

Approx. 3,569 linear feet of Dike Protection System was installed in 2005 under Phase 1 Dike 1. The perimeter dike consists of a structural clay fill which provides stability for the containment of the dredged sediments and serves as a low hydraulic conductivity barrier (K=1x10-7 cm/sec or less). The dikes were constructed of native clay materials from an offsite borrow source. The exterior of the dike was designed at a 2.5 horizontal to 1 vertical slope. The interior slope is a 2 horizontal to 1 vertical slope.

Phase 1 Dike 2
7/7/2006 — 9/22/2007

This project continued the work done in 2004/2005 under the Dikes—Phase 1 project and continued construction of the perimeter dikes in the areas shown in the figure.

The perimeter dike consists of a structural clay fill which provides stability for the containment of the dredged sediments and serves as a low hydraulic conductivity barrier (K=1x10-7 cm/sec or less). The dikes were constructed of native clay materials from an offsite borrow source. The exterior of the dike was designed at a 2.5 horizontal to 1 vertical slope. The interior slope is a 2 horizontal to 1 vertical slope.

Gradient Control
5/15/2007 — 12/31/2009

88 six-inch diameter vertical extraction wells with submersible pumps were installed as part of a system to prevent potential adverse impacts to offsite groundwater. The pumps will produce and maintain a 2-foot inward hydraulic gradient around the perimeter of the Confined Disposal Facility, which, in combination with the impermeable bentonite slurry wall, will prevent contaminants from migrating offsite.

40 monitoring wells, 3 ultrasonic water level indicators, a control building, instrumentation and control system, and approximately 10,500 linear feet of 12-inch diameter gravity collection header pipe were also installed as a part of this project.

Site grading, construction of a perimeter drainage ditch, and access roads were also provided under this contract.

Interim Groundwater Treatment Plant
5/24/2007 — Present

An Interim Groundwater Treatment Plant (IGWTP) was originally installed to draw groundwater from along the southern edge of the site using well points to alleviate the pressure on the sheetpile wall. The groundwater is treated at the IGWTP to the discharge concentrations established in an NPDES permit issued to USACE by the Indiana Department of Environmental Management (IDEM). The IGWTP is designed to treat contaminants of concern in groundwater, which include, but are not limited to, organic compounds, ammonia, metals, total suspended solids, and oil and grease. The effluent from the IGWTP is discharged to the Lake George Branch of the canal.

In 2010-2011 the IGWTP will be connected to the Groundwater Gradient Control System to begin the drawdown and maintenance of the 2-foot inward gradient. The groundwater will be treated to the same NPDES permit standards issued by IDEM, and will discharge the effluent into the Lake George Branch of the canal.

South Cutoff Wall
9/5/2007 — 12/31/2009

137,000 square feet of steel sheet pile tie-back cut-off wall revetment, 48,000 square feet of steel sheet pile anchor wall, a reinforced concrete crane pad, and approximately 9,000 cubic yards of soil cap were installed to complete the South Cutoff Wall. Excavation, demolition of obstructions, and backfill placement were involved. The cut-off wall was then capped with a parapet wall constructed of approximately 1,200 cubic yards of reinforced concrete. Safety ladders, a floating dock, timber fenders were also provided under this contract.

South Cutoff Wall Construction complete.
Photo credit: NWI Times.

South Cutoff Wall during construction.
Note: Deflection in existing wall.