An ISS Case Study at a Former MGP Facility – When the Drilling Gets Tough, the Tough Get Drilling
Dr. Paul R Lear, Technical Director, Great Lakes E&I
Great Lakes E&I provided environmental remediation services for a former MGP facility in New Jersey, including in-situ stabilization (ISS) of impacted soil. The site was pre-excavated to a depth of 10 feet in preparation for ISS work. This included the removal of asphalt pavement and concrete slabs and the excavation, transport, and off-site thermal treatment of 47,000 cubic yards of MGP-impacted soil. Obstruction (e.g., footers, foundations, pilings, etc.) encountered during the pre-excavation were size-reduced and disposed of off-site with the contaminated soils. Extensive dewatering was conducted to maintain a dry platform at the bottom of the excavation. The collected water was treated in an on-site water treatment facility prior to discharge. ISS was performed using both a crane-mounted Hain platform and a Delmag RH28 drill rig. The crane/platform assembly was supplemented with a swivel-mounted, top-feeding Kelly Bar capable of reaching a depth of 55 feet bgs and used to turn augers ranging from 6 to 10 feet in diameter. The Delmag rig used a 40 foot Kelly bar to turn augers ranging from 4 to 6 feet in diameter. A grout plant was set up and the required reagent grout was produced on-site then conveyed to the auger rigs, where it was added on a per weight basis using a pre-determined mix design of 9% by weight for Portland cement and 3% by weight for ground granulated blast furnace slag. ISS was first performed at a 10-foot-wide perimeter that was keyed 4 feet into the clay layer, followed by the interior ISS keyed 2 feet into the clay layer. The ISS-treated material met the project performance requirements >50 psi unconfined compressive strength and <1x10-6 cm/s hydraulic conductivity. During initial ISS activities, Great Lakes E&I recognized that the unconsolidated nature of the sand lithologies complicated the drilling of the ISS columns, extending the time required for the auger mixing. To address this challenge, Great Lakes mobilized a second auger rig to address shallower (>40 feet) impacted soil, while using the crane-mounted Hain platform system to treat the deeper impacts. The use of two auger rigs allowed Great Lakes E&I to recover schedule slippage. The presentation also will discuss how Great Lakes E&I overcame challenges with obstruction removal, dewatering and water treatment during the project.
Dr. Paul Lear serves Great Lakes E&I as Technical Director, providing technical expertise in support of environmental remediation, sediment remediation, and geotechnical projects throughout the U.S. He assists with business development, proposal preparation, and project execution. Dr. Lear has over 30 years of experience in hazardous waste treatment and chemical process development. He has been involved with the design and implementation of treatment systems at over 100 CERCLA and RCRA sites. His experience includes selecting and evaluating treatment alternatives, providing data for preliminary design activities and project equipment specifications, assisting project design teams, and implementing the final design. He received a B.S. degree in Soil Science from the University of Nebraska, a M.S. degree in Soil Chemistry/Mineralogy from the University of Illinois, and a Ph.D. degree in Soil chemistry/Mineralogy from the University of Illinois.