LSA Funnel and Reactive Gate
CSX Transportation Waycross Railyard
Waycross, GA
Significant Project Features:
Funnel and gate project using a one-pass trenching and Large Diameter Auger (LDA) methods.
- One-pass trenching 30’ deep utilizing either bentonite or Portland cement in designated areas.
- One-pass trenching the entire length of the funnel and gate wall.
- LDA soil removal of contaminated soils for gate construction.
- Installation of thirty-inch diameter, 30’ casing to perform soil removal, backfill with sand and Zero Valent Iron (ZVI) mixture, and casing extraction.
- Generation of ZVI and sand backfill with prescribed reagent percentages using a redi-mix concrete mixer.
- On-site management, preparation, and load-out of contaminated spoils for disposal.
- Completion of approximately 37 LDS soil removal locations. GSI excavated soil to a maximum depth of 28’ below ground surface.
- Complete removal of contaminated soils.
Background:
The site was used as the former mechanical operations of the CSX Transportation railyard located in Waycross, GA in Ware County. Several projects have been completed to manage the groundwater contamination on this site.
Project Objectives:
The project was designed to cut off groundwater flowing off the CSX property and funnel the contaminated groundwater to a permeable reactive barrier gate wall.
Description of Work
GSI installed ~450 linear feet of bentonite funnel wall and ~250 linear feet of low strength cement gate wall. A total of 21,000 VSF of trench was installed at an average depth of 30 feet. GSI completed the funnel and gate wall installation using the one-pass trenching method. After the completion of the initial one-pass trenching construction, GSI utilized LDA soil removal techniques and processes to excavate contaminated soils for disposal. GSI installed the 30” casing, extracted the casing, and backfilled with the sand/ZVI mixture. GSI completed the soil excavation with a drill bucket attached to a Comacchio CH650. After the contaminated soil was excavated, GSI managed and prepared the contaminated site soils to an on-site soil stockpile for load-out and disposal at an approved landfill facility. Approximately 37 caissons were installed and excavated to an average depth of 28 feet. The 30” diameter caissons were replaced with a sand and zero valent iron (ZVI) mixture. After the gate was installed, a low strength flowable fill was used to cap the gate elements.
Key Project Objectives
Ensure all contaminated soils are removed to design depths and extents.
- Maintain the integrity of the design of the permeable reactive gate.
- Provide quality control ensuring the ZVI/sand backfill has the prescribed amount of each reagent per caisson location.
Project Challenges
- GSI managed all angles of friction from both the ZVI/sand backfill and external soils to extract the casing from each location.
- Saturated soil conditions were encountered during Caisson installation and excavation.
- Generating a stream bypass to allow the funnel and gate wall to cross an existing site stream.
