Site Redevelopment Former Monsanto/Solutia Chemical Plant

ATON was retained by Opus Development and Faultless Healthcare Laundry to perform oversight activities associated with construction of new commercial buildings on the site.

Completion Date: Nov. 30, 2019


ATON was retained by Opus Development to perform contractor oversight and air monitoring during excavation activities associated with construction of a new office building on the site.

ATON was also retained by Faultless Healthcare Laundry to design and oversee the installation of a vapor mitigation system (VMS) beneath the proposed new commercial/industrial laundry building consisting of a vapor barrier membrane with an active sub-slab depressurization system (SSDS).


The former Monsanto Chemical Works (later Solutia Inc.), John F. Queeny Plant was in operation from 1901 until 2006. The facility manufactured over 200 products including industrial chemicals, chemical intermediates, herbicides, pesticides, food additives, and pharmaceuticals. A variety of hazardous wastes were produced as part of the facility operations. The 38 acre site is regulated by an Administrative Order on Consent (Consent Order) between the EPA Region 7, the Missouri Department of Natural Resources (MDNR) and the former property owner, and has undergone RCRA Corrective Action for prior hazardous waste management activities.


The project included review of previously collected soil vapor sampling data at the project site. During excavation activities, ATON used a photoionization detector (PID) as well as Draeger chemical detection tubes to ensure that constructions workers were not exposed to volatile organic chemicals (VOCs) at concentrations in excess of the United States Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs). ATON also performed asbestos inspections and air monitoring during the removal of previously unforeseen buried piping throughout the site.


Excavator digging trench.

Excavation work was conducted on schedule without any VOC exposure to construction workers. ATON conducted air monitoring activities to evaluate the risk of exposure to VOCs and documented all data with daily project reports including diagrams of air monitoring results and locations.