Former MGP Site: Shallow Soil Mixing
Geo-Con recently completed the remediation of a former MGP site located in the Southern United States. Geo-Con was contracted on behalf of a confidential southern utility company to complete the remediation on the site, which was the location of a manufactured gas plant that was operational during the late 1800's and early 1900's.
Geo-Con performed in-situ soil mixing of 16,290 cubic yards (CY) of soil, by the large diameter-auger method, to stabilize and solidify the existing contaminated soils and prevent the off-site migration of contaminants. Soil mixing was accomplished using Geo-Con's custom-made Calweld drill platform mounted on a Manitowoc 3900 crawler crane. Soil mixing was performed up to 26-feet deep, 5-feet into the existing saprolite-clay confining layer. Soil was blended with a cementitious grout consisting of Portland cement, Ground Granulated Blast Furnace Slag Cement, and Bentonite. Grout was produced on site in Geo-Con's custom made batch plant and pumped to the soil-mixing rig where it was blended with the in-situ soils to create a homogeneous soil mix that passed strict quality control requirements for Unconfined Compressive Strength, Permeability, and Wet/Dry Durability.
Geo-Con also served as the prime contractor on this project, which entailed site preparation and setup, demolition of existing fencing and structures, installation and maintenance of traffic controls, and eventual site restoration. Support of the soil-mixing operation involved the pre-excavation and stockpiling of clean overburden soils, handling and off-site disposal of impacted soils and soil-mix spoils, impacted water management, treatment, and disposal, as well as odor control using stockpile covers and odor-control foaming agents. Real-time air monitoring was performed during all intrusive activities.
The site was located in a high-visibility urban area and included remediation in city-owned right-of ways, which created unique challenges to project completion. Site controls, public health and safety, and odor controls were paramount during construction.