ENVIRONMENTAL CONSTRUCTION AND REMEDIATION

Cutoff/Collection Trench
Streator, Illinois

Currently, Geo-Con is working on an MGP site located along the banks of the Vermillion River in the city of Streator, Illinois. The former MGP facility encompasses approximately 3 acres within a 15-acre parcel. Boundaries to the site include the Chicago and Alton Railroad right-of-way, residential properties and the Vermillion River.

Geo-Con is contracted by ThermoRetec to provide various site remediation activities at the site including:

  • Mobilization - Mobilization involves the set up of temporary Geo-Con site facilities, and the transportation of equipment to the site. This includes setting-up the batch plant pumps and hoses and mobilization of Geo-Con site personnel.

  • Site preparation - Site Preparation will include construction of temporary access roads, utility location and protection, installation of decontamination and stockpile areas, and demolition of surface structures.

  • Clearing and grubbing - Geo-Con will clear all areas, if required, within the limits of our specified scope of work. Grubbing will only be performed as deemed necessary.

  • River diversion - River diversion which will include installation of a port-a-dam system just into the river for ~ 650 linear feet. A subcontractor will be mobilized to provide and install the system.

  • De-watering - De-watering will involve drawing the water down inside the port-a-dam and on the workpad to allow for trench installation. This task will be performed with trash pumps. The initial de-watering of the port-a-dam area will be pumped back into the river. Following this initial stage, water will be pumped to an onsite treatment system provided by others and will continue to the end of the project. The de-watering will only be performed to an extent that maintains water at the top of the rock trench so that trench installation can take place with the trench full of water.

  • Installation of recovery trench and barrier wall - This task involves the installation of a recovery trench and barrier wall approximately 500 feet long and 20 feet deep to prevent impacted groundwater and NAPL from entering the Vermillion River. The trench will be installed entirely through rock. A rock-trenching subcontractor will be mobilized to excavate the trench.

  • Following excavation by the rock trencher, Geo-Con will clean out the trench utilizing a hydraulic excavator. An HDPE barrier wall will be installed into the trench. A concrete pump and extended arm will be utilized to install a 1-foot concrete plug to seal the bottom of the trench.

  • Excavation of soil and rock - Soil and rock will be excavated along the bank. Approximately 10,000 yd3 of material will be excavated. Standard construction equipment will be used for the excavation.

  • Spoils removal - The material excavated during task # 7 will be stockpiled onsite and characterized for offsite disposal. Once characterized, the excavated material will be transported for offsite disposal.

  • Cover installation - A 3-foot thick cover consisting of a HDPE liner and off-site materials including crushed stone, rip-rap, processed stone and soil will be installed on the bank after the soil and rock have been excavated and the desired grade achieved. The area above the bank will be brought to final grade and covered with import material. There will be no liner installation in this area.

  • Groundwater collection system - A ground water collection system will run from the recovery well and sumps to the ThermoRetec water treatment system. The installation will occur into the 3-foot cover on the bank and then require a three-foot trench excavation above the bank to the water treatment plant.

  • Installation of LNAPL recovery well - A subcontractor will install a LNAPL recovery well, five two-inch piezometers and extension of the existing piezometers.

  • Site restoration and demobilization - This task will include removal of port-a-dam, roads, clean up, final grading, re-vegetation, and removal of all construction equipment and temporary support facilities.
    • Start: 07/97
    • Completion: 12/08/00


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