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Excavation and Disposal

Commerce City, CO: Rocky Mountain Arsenal Site Remediation

Geo-Con was contracted at the Rock Mountain Arsenal in Denver, Colorado to complete a soil remediation project. The project consisted of the remediation of material in former disposal pits that contained waste from the manufacture of chemical weapons on the Arsenal. The material in the pits was excavated and combined with the clean soil surrounding the pits. This mixture was then fed through a pugmill plant where it was mixed with cement and water to produce a stabilized end product.

The primary contaminants treated were heavy metals such as arsenic, lead and mercury, with the maximum mercury concentration in soil equaling 94.0 mg/kg. The 6% cement in the mixture was designed to bind the metals and reduce the leachability, achieving TCLP criteria. The treated material was then hauled to the on-post landfill. Initially, Geo-Con completed trial batches at various cement contents to determine what would be used during full scale production. As with all Geo-Con projects, the Health and Safety of the workers is of paramount importance on this project. The entire project was performed under Level "B" protection.

Additionally, in order to minimize the possibility of vapors being released during the pumill mixing, Geo-Con designed and custom built a vapor extraction and treatment system that was attached to the pugmill mixing chamber. Proper blending of the pit material and the clean surrounding material was achieved with a system of screens and belts equipped with belt scale system. The belt scales were connected to a CPU, which constantly monitored and adjusted the belt speeds to ensure the proper blending ratio. The clean-up at the Rocky Mountain Arsenal was a multi-contractor effort under the direction of the Program Management Contractor. This project was Geo-Con's fourth contract at the Arsenal and was the first project at the Arsenal that involved the direct treatment of soil.


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