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Chattanooga Creek Remediation
Chattanooga, Tennessee
Envirocon was awarded a contract for the remediation of 1.9 miles of the Middle Reach of Chattanooga Creek in
Tennessee. The Chattanooga Creek was contaminated with coal tar from a former coking facility. This project is being performed as
part of a Superfund site remediation program.
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| Sectional restoration of creek |
Envirocon and our teaming partner have formed an integrated team to provide turn-key design and remedial action services for the removal of impacted sediments from the creek. Our teaming partner, with assistance from Envirocon, performed the remedial design during the initial phase of the project.
The second phase of the project includes all remedial activities planned for the creek. Envirocon's approach for diversion of the creek, which is 40- to 70-feet wide, includes a series of pumps and piping systems to divert the main channel flow and while maintaining the footprint of the diverted creek bed from minor groundwater and run-on infiltration. The creek is being dammed using earthen dams to stop the flow of main channel. Damming the creek is performed in sections or "reaches" providing two dewatered reaches at one time, thus allowing for optimal use of the equipment and work area. By drying two areas at once, the process provides a dried area to proceed with excavation while the pumping system is reconfigured allowing excavation to continue without stoppage.
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| Excavation of sediments from Chattanooga Creek |
Approximately 100,700 tons of coal tar sediments are being excavated from the 1.9-mile span of the creek. Two load-out areas have been set up, each consisting of two excavators, both of which are capable of maneuvering in the soft creek bottoms. The first excavator is used for locating, excavating, and stockpiling coal tar material for loading by the second excavator. Following excavation of the coal tar, the sediments are transported to a pre-constructed 200-foot by 200-foot drying bed. The drying bed was constructed with a 10-foot berm to prevent run-on, a layer of sand, 40-mil PVC geosynthetic liner, and another layer of sand. The final sand layer was topped with gravel to facilitate drainage and promote drying. The drying bed includes a leachate system where liquid will be collected by pumping to a water treatment system. The coal tar is then treated in the drying bed with 10% lime kiln dust (LKD) to stabilize the material. The LKD is mixed with the coal tar using a SS250 which blends the material and promotes drying.
Envirocon developed the mix design with plans to use a local source for the LKD. The two major performance criteria to be verified and tested under our QA/QC program include passing TCLP and the paint filter test.
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| Pumping of non-aqueous phase liquid (NAPL) from creek bottom |
Upon completion of the stabilization activities, the dried/stabilized materials are moved to a temporary staging area to be sampled prior to loading. If necessary, additional stabilization will take place, or the material is loaded into haul trucks and transported to a Subtitle D landfill.
Once EPA approval has been obtained, bank stabilization will occur. It is anticipated that approximately 9,000 cubic yards of backfill material will be placed. The majority of the creek bed will not require any import of backfill material.
Following completion of all remedial activities, restoration of the site will include revegetation, restoration of impacted creek banks, seeding with native grasses, placement of rip rap, and removal of all dam materials.
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