The Additional and Uncharacterized Sites Operable Unit (AUS OU) was created in the late 1990s to address areas of known or potential contamination not included in previously established operable units. The AUS OU consists of 32 individual sites ranging from approximately 1 acre to over 500 acres.

Shannon & Wilson provided data collection services for the Phase II Remedial Investigation of the AUS OU, which is a Comprehensive Environmental Response, Compensation, and Liability (CERCLA) site. As such, strict oversight by federal agencies and stringent Standard Operating Procedures were required. The lead regulatory agency is the U.S. Fish and Wildlife Service (FWS) of the U.S. Department of the Interior (DOI) with additional assistance from the U.S. Environmental Protection Agency (EPA), and the Illinois Environmental Protection Agency (IEPA) and the USACE Louisville District.

All Shannon & Wilson personnel working on this site had HAZWOPER 40-hour training, underwent medical surveillance, completed project-specific training, and were required to maintain detailed documentation of site activities. The initial project scope included:

• The installation and development of 168 monitoring wells, including bedrock wells installed using sonic drilling technology 
• The utilization of direct push technology for more than 400 soil borings to collect stratigraphy and environmental samples 
• The collection of over 1,800 soil and groundwater samples
• Test pits to determine the vertical and horizontal extent of suspected disposal sites
• The collection of two rounds of water levels at more than 400 wells spread across the site
• Two rounds of groundwater sampling using low-flow technology at 250 wells
• The installation of 13 sub-slab vapor monitoring points and collection of sub-slab and ambient air samples at six buildings at the refuge.

Shannon & Wilson assisted the client by coordinating all work and interfacing between the client and regulatory oversight. Work requirements included Munitions and Explosives of Concern (MEC) avoidance in approximately half the operable units, coordinating work with the Illinois Ordnance Plant which had active operations on seven operable units, managing impacts to wildlife habitat on the refuge, and implementing strict decontamination procedures. 

In addition to soil, groundwater, and soil vapor sampling, subsequent work included characterization of potential asbestos contamination in soil. This work was performed in a MEC area and required a geophysical study to map metallic targets within the project area prior to performing the characterization. The asbestos characterization included a combination of surficial sampling on a grid system and targeted test pits. Due to the presence of significant metallic targets all sampling was performed in close coordination with MEC avoidance or removal activities, as necessary.