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Ongoing Groundwater Monitoring, Plant Effluent and River Sediment Sampling, Cascades Pulp and Paper Mill

XCG was retained by Cascades Container Board Packaging – Trenton to conduct an annual groundwater, surface water, sediment, and plant effluent monitoring program at the Cascades Trenton Plant property (Site). The monitoring program began in response to requests made by the Ministry of the Environment (MOE, or the Ministry), beginning in 2004. XCG has been completing groundwater monitoring at the site beginning in 2004, with the annual monitoring program beginning in 2010 at the Trenton site.

The purpose of the monitoring program is to sample 65 monitoring wells on the property, a groundwater interceptor trench, plant effluent, and sediment from the Trent River.

Initial investigations identified three aquifers on the site: shallow aquifer, deep aquifer, and a perched aquifer in a closed landfill area in the central part of the site. The groundwater flow direction in all aquifers is generally to the west toward the Trent River.

The following work plan was originally developed in 2007 through consultation with the MOE and XCG, with additional investigations added to the program as required between 2007 and 2023:

1. Installation of a groundwater monitoring network adjacent to the Trent River to supplement existing monitoring wells onsite. This was completed by XCG in 2009 and included 11 pairs of monitoring wells installed in the shallow and deeper aquifers adjacent to the east side of the Trent River.

2. Groundwater, surface water, and plant effluent monitoring is completed twice a year to include potential season fluctuations.

3. Sediment sampling of near shore sediments is completed in areas of potential impacts from surface water runoff.

4. Inspections of the river shoreline to investigate potential groundwater seeps above the water line that may flow into the Trent River. This is completed by utilizing a canoe for river access due to shallow waters and areas of inaccessible shoreline from land.

5. Analysis of potential groundwater exfiltration impacts to the Trent River through contaminant loading calculations for key exceeding parameters. This included monthly 7Q20 low flow calculations for the Trent River to assess the potential worst-case situation. This was completed in 2011.

6. River bottom sediment sampling adjacent to the site and upstream to investigate potential impacts to river sediments from site operations and/or upstream contributions. This was completed in 2020. The work was completed using a small aluminum boat with two XCG personnel, with sample collection completed by using a mini-ponar sediment grab sampler.

On a yearly basis, XCG completes a report summarizing the year’s work program, site conditions, groundwater flow direction, tabulated analytical results for groundwater, sediment, and plant effluent. Each yearly report includes all historic analytical data and the findings of any additional work included such as river sediment sampling and groundwater exfiltration calculations. Conclusions and recommendations are made on a yearly basis in each report. The Ministry completes a review of each yearly monitoring report and may provide comments to Cascades. If additional monitoring activities are requested XCG discusses the requested changes with the Ministry and Cascades and incorporates them into the following years work program.

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