Significant Project Features:
- Soil mixing to establish a containment wall through lignite seams carrying creosote and creosote impacted groundwater offsite
- Previous work completed at this Superfund site by Geo-Solutions included installation of a soil-bentonite cutoff wall and shallow soil mixing for creosote impacted soil stabilization.
Project Background:
Geo-Solutions was subcontracted to complete an additional component of the specialty geotechnical construction portion of the American Creosote Works (ACW) Superfund site remediation. Geo-Solutions’ involvement in the work at this site started back in 2012 and 2013 when it was subcontracted to install a soil-bentonite cutoff wall and to stabilize creosote impacted soils using shallow soil mixing with Portland cement. The containment wall work scope included the installation of a 40 feet deep, 1,350 foot long barrier wall with a minimum width of feet. The containment wall was designed to have a maximum permeability of 1×10-6 cm/s to prevent the migration of creosote and creosote impacted groundwater offsite through lignite seams. Geo-Solutions installed the containment wall with its Delmag RH-18 drill rig fitted with a 7 foot diameter auger. Geo-Solutions’ column to column spacing was selected to ensure the minimum wall width was achieved even when the auger deviated in opposite direction in adjacent columns.
Description of Work:
- Installation and excavation of three test columns.
- Sonic coring of the test columns
- Installation of 347 seven (7) foot diameter soil mixed columns.
- Maximum depth of 43 feet.
- Soil mix zone ranged in length from 20 feet to 23 feet.
- Bentonite added to reduce permeability
- Achieved permeability values in the low 10-7 / high 10-8 cm/s range which was well below specified maximum.
- Work completed over 12 weeks, including 2 weeks of setup / tear down and a holiday shutdown period of 2 weeks.
Key Project Objectives:
- Ensure that the permeability of the target treatment zone, from 20 feet to 40 feet below ground surface, was below 1×10-6 cm/s.
Project Challenges:
- Drilling adjacent to soft columns. Geo-Solutions is used to drilling adjacent to cured columns (w/ cement). Drilling at this site required adjustments to normal procedures
- Drilling through hard lignite seams
- Winter weather
