SWMU 55 – Administration Building

Proposed Remedial Measure

The proposed remedy for SWMU 55 is demolition of the existing structures, excavation and off-site disposal for contaminated soils and demolition debris material. The SWMU 55 remedy will be addressed by Sunflower Redevelopment, LLC in accordance with the KDHE Consent Order  No. 05-E-0111.

Groundwater beneath SWMU 55 is not a media of consideration for SWMU 55 because the groundwater was addressed during the RFI for SWMU 60, which is located within the footprint of SWMU 55. SWMU 60 indicated that site-specific COCs for groundwater (including lead) were below the TMDLs, as indicated by samples collected from monitoring well 060MW003 (Tetra Tech, 2021).


Justification

Historical soil sampling activities were conducted as part of the RFI at SWMU 60 (Old Photographic Laboratory) from 2008 to 2010. The majority of SWMU 60 is located within the SWMU 55 boundary (Tetra Tech, 2021). SWMU 60 includes the eastern-most portion of Administration Building 2 and the surrounding area. Soil samples were collected for lead along the outside walls of the east wing of Building 214, from the east, west, and south sides of the ammonia tank building (attached to the south wall of the east wing of Building 214), from the drainage ditch originating from the southeast corner of Building 214, and from the interior subfloor from beneath the photographic laboratory (Tetra Tech, 2021). Detected values were below the Residential TMCL for lead of 400 mg/kg (Tetra Tech, 2021).

As part of the SWMU 55 RCRA Facility Investigation Report, January 2020, a field investigation was conducted to determine if lead concentrations in soils adjacent to SWMU 55 buildings exceed Residential or Non-Residential TMCL criteria (BMcD, 2020). Soil samples were collected from a depth of 0 to 0.5 ft bgs and analyzed for lead (BMcD, 2020). Sample locations included soils from the perimeter of Buildings 140, 141, 200, 214, 234, 565, and the drainage area about three feet from the exterior walls of Buildings 140, 200, 214 and 565 (BMcD, 2020).

Analytical results from the RFI demonstrated that lead was detected in all 143 surface soil samples collected, indicating that SWMU 55 soils were impacted by lead (BMcD, 2020). It is likely that the deterioration of lead-based paint used on the SWMU 55 buildings impacted perimeter soils. There were 19 samples in which lead concentrations exceeded the Residential TMCL for lead of 400 mg/kg (BMcD, 2020). Of these 19 samples, lead concentrations exceeded the Non-Residential TMCL of 1,000 mg/kg in three samples (BMcD, 2020). None of the soil samples collected from the drainage areas exceeded TMCLs for lead.

The Army conducted a streamlined health risk evaluation by comparing RFI data to the approved TMCLs for the site. KDHE believes that proper employment of the KDHE (2021) RSK Manual values result in risk-based remediation that is consistent with federally promulgated standards, including the Safe Drinking Water Act, 42 U.S.C. §300f – 300j-26, and is protective of human health as required by Resource Conservation and Recovery Act, 42 U.S.C. §6901 et seq., including the Hazardous and Solid Waste Amendments (HSWA) and 40 CFR Part 264.101. KDHE Tier 2 risk-based cleanup goals represent concentrations at which the contaminants pose an acceptable human health risk to receptors, including sensitive groups (e.g., children or the elderly), over a lifetime.

Cleanup goals were developed for two general categories of receptors: residents and non-residents, according to the appropriate land-use designation, exposure frequency, and exposure duration. According to the Johnson County Rural Comprehensive Plan Resolution No. 079-98. Conceptual Land Use Plan, Sunflower Army Ammunition Plant. July 23, 1998 the area encompassing SWMU 55 is proposed to be a Business Center, consisting of mixed office, research and development, and technology uses. Based on this land-use, the potential current and future receptors include:

  • Current: Construction and excavation workers.
  • Future: Construction workers, business center employees and visitors.

The RFI identified lead as a COC at SWMU 55 based on exceedances of the residential soil TMCLs, therefore, the exposure pathway for soil was considered during the assessment (BMcD, 2020). Evaluated exposure pathways include incidental ingestion and inhalation of airborne particulates (dusts). Based on comparison of the RFI results to TMCLs, which identified exceedances and therefore pose a potentially unacceptable health risk, the following corrective action objectives (CAOs) were established for surface soil SWMU 55:

  • Mitigate risk to human health via direct contact with impacted surface soil with COC concentrations above TMCLs.
  • Mitigate the potential future migration of contaminants from impacted surface soil to surface drainage pathways.

Additional evaluation of groundwater in the area will occur when work on GWOU-#4 is done.