2023-07-28_REVISION - M1977170 (2)

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Corporate rters �� Lakewood, • :� Inn , :, 303.980.0089 Environmental,Inc. July 28, 2023 Mr. Lucas West Environmental Protection Specialist Colorado Division of Reclamation, Mining and Safety lucas.west@state.co.us Subject: Revision I to Stockpile Sampling Plan, Butala Sand and Gravel, 9000 CR 152, Salida, Colorado 81201 Dear Mr. West: In accordance with your request, please accept this document as Revision I to Butala Sand and Gravel's (Butala's) Stockpile Sampling Plan (the Plan). The Plan will be implemented as soon as practical following the Colorado Division of Reclamation, Mining and Safety(DRMS) approval. The purpose of this Plan is to evaluate possible impact of stockpiled materials at the Butala facility with constituents of concern (COCs) from the Smeltertown Superfund Site, Former Koppers Wood Treating Site, Salida Colorado (also known as Operable Unit 2 or OU2). According to the Record of Decision (ROD) for OU2, the COCs for soil are: polyaromatic hydrocarbons (PAHs) (specifically benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, dibenzo(a,h)anthracene, indeno(1,2,3-ed)pyrene); pentachlorophenol (PCP); and dioxin compounds (specifically dibenzo-p-dioxin (HpCDD), hexachlorodibenzo-p-dioxin (HxCDD), hexachlorodibenzofuran (HxCDF), and octachlorodibenzodioxin (OCDD)). The dioxin compounds were evaluated during the OU2 remedial investigation and were analyzed in samples that contained detectable concentrations of PCP. The results were then evaluated as part of the Smeltertown sitewide Human Health Baseline Risk Assessment (RA) prepared by CH2M Hill, dated April 1995. The RA evaluated a long list of potential COCs including 17 PAH compounds, PCP, 7 dioxin compounds, 22 polychlorinated biphenyl (PCB)/pesticide compounds, and 23 different metals. The ingestion of the PAH compound benzo(a)pyrene was shown to contribute to the overall surface soil cancer risk.Arsenic was also a major contributor to the risk and hazard indices in the exposure pathways evaluated; however, studies conducted since this RA have suggested that the arsenic in soil at and near the Butala property is naturally occurring, is within common background levels in Colorado, and is not associated with spills or releases that occurred on OU2. As part of other ongoing soil sampling work being conducted by Butala on the adjacent Vista Del Rio Subdivision (VDR), the Environmental Protection Agency (EPA) and the Colorado Department of Public Health and Environment(CDPHE) required analysis of the above referenced PAH compounds and PCP but did not require analysis of the dioxin compounds. That study, and a study of drainage ditches on the Butala property found no significant or wide-spread metals concentrations in near surface soil and sediment. For these reasons,the dioxin compounds and metals are not included as part of this Plan and the required analytical work will focus on the PAH compounds.