New technologies may be used at ‘state superfund’ site near Darby

After expanding its water sampling activities in 2019 related to the environmental contamination at the old S&W Sawmill site north of Darby, International Paper is moving forward in the development of a Feasibility Study Work Plan which will serve as the roadmap for evaluating cleanup operations at the site. Environmental contamination from the historic sawmill is being regulated as a Comprehensive Environmental Response, Compensation & Liability Act (CECRA), or “state superfund,” facility. Currently, IP, the lead liable party at the site, is conducting the investigation and cleanup under the oversight of the Montana Department of Environmental Quality (DEQ). IP also plans on testing out some new technology for containing and potentially disposing of the toxic materials.

Historically, ditches located near the operations area of the facility drained north and combined with the Waddell Ditch north of Bunkhouse Road. During historical investigations between 2011 and 2012, limited soil and sediment samples within and adjacent to the Waddell Ditch were collected and analyzed for PCP and dioxins/furans. 

However, while evaluating the available information in response to questions and concerns from irrigation ditch users, it became apparent that the Waddell Ditch conditions had changed since the original sampling was performed and there was also a need to investigate other nearby ditches and seeps. This resulted in DEQ requiring IP to perform additional sampling in the ditches and to investigate whether there is interaction between the contaminated groundwater associated with the facility and irrigation ditches further from the former sawmill properties, along the direction of groundwater flow. According to the company’s latest update, the focus of the investigation is determining whether groundwater (now present at higher levels than it historically was) is coming into the ditches as surface water or is surfacing and running into the ditches as surface water via overland flow. 

In 2019, necessary ditch survey work and sampling activities were conducted on the Waddell, Overturf, and Tiedt­Nicholson (TN) ditches. Based on the results, additional sampling activities were performed in 2020 on the Overturf Ditch, the TN Ditch, and a seep adjacent to the Overturf Ditch to investigate ditch conditions up- and down-stream of the facility. Any new contaminants and contaminant concentrations discovered as part of the recent sampling will be added to existing documents describing conditions at the facility to ensure they are appropriately accounted for in site-specific cleanup level calculations. The new information and site-specific cleanup levels will be integrated into the Feasibility Study documents.

In 2020, IP installed additional groundwater monitoring wells at the facility to more accurately locate the eastern extents of the dioxins/furans plume, on the east side of US Highway 93. IP continues to evaluate the groundwater plume twice a year through the sampling of 31 groundwater monitoring wells. Two of these wells are residential drinking wells east and north of the facility. Samples are collected both when the groundwater table is at its annual high and at its annual low levels. According to the company’s report, the dioxin/furan contamination exceeding groundwater standards in shallow groundwater extends off the former sawmill property to the east-northeast, to approximately the vicinity of the TN Ditch. PCP contamination exceeding the groundwater standard is located within the boundary of the IP-owned properties west of US 93 and does not extend past those properties.

IP recently identified its desire to further evaluate one of the technologies in the FSWP, and has submitted a work plan for a technology study, which DEQ has reviewed. The technology, known as “in-situ soil solidification,” can be used to physically bind contaminants into a solidified mass, which can reduce the mobility of the contaminant in the environment. As part of the technology study, samples will be collected at the facility and analyzed in a laboratory. The analyses will help determine whether the technology is viable for the contaminants at the facility, and pro­vide justification for whether the technology is appropriate to be considered further as an option for cleanup of the facility.

DEQ expects this study to occur concurrently with the ongoing irrigation ditch investigation, so results of the study can be incorporated into the feasibility study as needed. This helps to keep the Superfund process moving forward after the irrigation ditch investigation caused a bit of an unexpected, although necessary, slow-down. 

DEQ anticipates that IP will complete the FS report in mid-2021 (including integration of new irrigation ditch information), at which point DEQ will prepare the Proposed Plan. The Proposed Plan will identify DEQ’s preferred remedy for cleaning up the facility, and will be presented for public comment. DEQ anticipates completion of the Proposed Plan and the associated public comment period at the beginning of 2022. 

Upon completion of the Proposed Plan and public comment period, DEQ will evaluate public comments received, make any necessary changes to final remedy decision, and issue the Record of Decision (ROD). The ROD is DEQ’s final selection of the remedy for cleaning up the facility, which IP will be required to implement. After the release of the ROD, IP will prepare document(s) outlining the implementation strategy and specific engineering design work needed to implement DEQ’s selected remedy.