The Phase I ESA identified Recognized Environmental Conditions (RECs) associated with the historical use of the property. The existence and subsequent demolition of 12 residential properties with basements was identified as a REC in the Phase I ESA; documentation did not exist or was not identified for the fill material that was used to bring the former residential properties up to the existing land surface elevation for the construction of the credit union building and parking lot.

Compounding the issue was the known use of foundry spoils and the existence of non-native industrially-purposed sand used on adjacent parcels as fill material. SWI recommended additional investigative work to determine if the RECs identified in the Phase I ESA resulted in potential human health and environmental risks. Subsequently, SWI completed a Phase II ESA, followed by a Wis. Admin. Code ch. NR 716 Site Investigation (SI) at the property. SWI ultimately submitted a ch. NR 722 Remedial Action Plan and ch. NR 726 Case Closure request to the Wisconsin Department of Natural Resources (WDNR) and the case was subsequently closed by the WDNR.

The Phase II ESA and SI worked to define the nature and extent of the subsurface contaminants of concern (COCs) at the property via soil borings and the installation of temporary groundwater monitoring wells. Soil and groundwater samples were collected and analyzed for Resource Conservation and Recovery (RCRA) program metals, polycyclic aromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs). Toxicity Characteristic Leaching Procedure (TCLP) testing was also completed on a select group of soil samples to determine the potential toxicity of the impacted soil. Benzene, RCRA metals, and PAHs were detected in soil samples above the WDNR soil residual contaminant levels (RCLs) protective of human health and groundwater quality, and above established background threshold values (BTVs). Most of the impacted soil appeared to be associated with the imported non-native soil materials. Furthermore, groundwater samples collected from temporary monitoring wells had ch. NR 140 enforcement standard (ES) exceedances for barium, arsenic, and chrysene (PAH).

After defining the nature and extent of the COCs on the property, Shannon & Wilson recommended and implemented an engineered cap and cap maintenance plan to eliminate the direct contact exposure pathway and prevent infiltration of precipitation from mobilizing contaminants from soil to groundwater at the property. 

Project Highlights

• Shannon & Wilson was efficient in identifying and defining the extent of impacts to soil and groundwater with minimal mobilizations.

• Shannon & Wilson successfully petitioned the WDNR for case closure; argued that remaining impacts were low risk and could be addressed with existing infrastructure (cap) and not a more costly excavation.