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Tataskweyak Cree Nation Environmental Remedial Actions at the Former Federal School Site

The "Former Federal School Site" (the Subject Property) is located within the community of Split Lake, at the eastern end of the peninsula that extends into Split Lake (Attachment 1: Figure 1). The Subject Property has recently been developed with four multi-tenant residential buildings. Petroleum hydrocarbon impacts have been identified at the Subject Property and remedial actions are required to address those impacts.

 

Between 1973 and 1984, the Subject Property was occupied by a Federal School (Figure 2) and the infrastructure present at the time included a school building, two temporary classrooms, a fuel-tank farm including four aboveground storage tanks (ASTs) for storage of heating-oil and a sewage treatment plant. The school building was destroyed by fire in 1987. The ASTs were removed from the Subject Property in 1995 and the same year, intrusive investigations confirmed the presence of soils with petroleum hydrocarbon parameters in excess of applicable guideline criteria at the time. Remediation was initiated, but not completed due to equipment problems and weather conditions. In 1997, a total of 1,800 cubic metres (m3) of soil was excavated and removed from the Subject Property; however, two small areas of impacted soil were left in place to the west of the former school building (southwest of the tank farm). In 2015, during construction of a residential complex at the Subject Property, hydrocarbons could be smelled indicating possible soil impacts. A Phase III Environmental Site Assessment estimated that hydrocarbon and naphthalene impacted soil was still present within the vicinity of the former school building.

 

The recommended Remedial Action Plan (RAP) for the Subject Property (the Project) includes excavation of impacted soils and off-site disposal at a locally constructed soil treatment facility (STF). Limits of the excavated soil will be determined at the time of the excavation through field observations (staining and odours), field hydrocarbon vapour testing and confirmatory laboratory samples. Shoring may need to be implemented in order to excavate the full volume of impacted material. Following excavation, the area will be fenced for safety reasons until the results of the laboratory testing show that the impacted soil has been removed. The excavation will then be backfilled with clean fill and re-graded to promote positive drainage. Compaction would be required to ensure appropriate stability for future site use.

 

Impacted soil will undergo an off-site (ex-situ) treatment which involves excavation of impacted soil from the Subject Property and transportation and disposal at a local STF to be constructed on First Nations land. Using this method of treatment will provide immediate treatment of soil impacts with respect to the Subject Property. The STF will eliminate liability by removing impacted soil from the Subject Property, is ideal for the relatively small volume of soil that will be produced by the Subject Property, and it may be used to treat soil from other local properties, if required.

 

Excavation and Off-site Disposal of Impacted Soil

The impacted area has been roughly determined; however, the limits of the impacted soil will be determined at the time of the excavation through field observations (staining and odours), field hydrocarbon vapour testing and confirmatory laboratory samples. Extra precaution will be taken to avoid damage to the monitoring wells outside of the limits of the excavation.

 

Following excavation, confirmatory soil samples will be collected to ensure that all impacted soil has been removed. If further impacted soil areas are identified during excavation, additional soil may be removed as required. When laboratory results show that all impacted soil has been removed, the excavation will be backfilled with imported clean fill from the construction of the STF, if possible. Additional clean fill may be required from local borrow sources. After the clean fill has been placed and compacted at the Subject Property, the area will be re-graded to eliminate ponded water and promote positive drainage.

 

Construction of the STF

Soil samples were gathered and analyzed from test pits excavated at the proposed STF location adjacent to the Active Community Landfill in 2018 (Figure 7). Concentrations of petroleum hydrocarbon (PHC) and polycyclic aromatic hydrocarbon (PAH) parameters for all samples were found to be below laboratory detection limits. Measured concentrations of all metal parameters were also below laboratory detection limits, or Canadian Council of Ministers of the Environment (CCME) soil quality guidelines for Residential/Parkland Land Use.

 

The STF will be designed to comply with the Federal Contaminated Sites Action Plan (FCSAP) Guidelines for Landfarming Petroleum Hydrocarbon Contaminated Soils, March 2006 (Updated 2013). These guidelines specify a maximum soil depth of 0.5 m. The excavated soil volume of 7,000 m3 will occupy an area of approximately 14,000 m2 when placed to a depth of 0.5 m in the STF. The floor of the STF will have dimensions of 120 m by 130 m, which will include a sump at the low end. The floor will be constructed with a 1% slope toward the sump.

 

The STF will be constructed by excavating the native soil with the excavated soil then used to construct perimeter berms to a minimum height of 0.5 m above original ground, to upgrade the access road and as backfill to replace the excavated impacted soil at the Subject Property. If excavation of the STF does not yield an adequate volume of soil to backfill the excavation of the impacted soil, clean fill will be acquired from another local borrow source.

 

The side slopes of the STF will be constructed with side slopes of 3H:1V, and the floor and side slopes will be compacted to 98% of Standard Proctor Density. The liner system will consist of a layer of 1.5 mm high density polyethylene (HDPE) geomembrane placed on the prepared ground surface, followed by a layer of 407 g/m2 non- woven geotextile placed above the HDPE. The geotextile and geomembrane layers will be anchored in a trench at the top of the berms, and will be covered by a 0.3 m thick layer of mulch from the clearing and grubbing stockpile at the site, to protect the geotextile and geomembrane from damage during the placement of impacted soil. The impacted soil from the Subject Property will be placed on the protective soil layer and spread to a maximum thickness of 0.5 m.

 

Operation of the STF

A comprehensive Operation Manual will be developed to direct treatment activities at the STF. The manual will include the activities required to efficiently treat the impacted soil and will describe soil and groundwater sampling requirements to determine treatment effectiveness and to monitor any potential seepage of impacted groundwater from the STF.

 

Water management at the STF will involve periodic inspection of the water levels in the sump. Water that collects in the sump will likely be impacted with PHC and will not be allowed to enter the environment surrounding the STF. The water will be pumped from the sump onto the impacted soil using a submersible trash pump and hoses. Aeration of the soil in the STF will be accomplished by tilling the soil using an agricultural tiller pulled by a tractor. Aeration will be done twice per month (or more frequently) when the soil is unfrozen, typically starting in June and finishing in October each year.

 

Samples of the impacted soil in the STF will be collected twice per year, in August and October for analysis by an environmental laboratory for PHC parameters. The number of samples will be determined by the requirements of the Manitoba Guideline for the Treatment and Disposal of Contaminated Soil (2016). When the treated soil meets the federal guidelines for Industrial land use, the soil can be removed from the STF and used as cover material at the Active Community Landfill.

 

Monitoring of Residual Hydrocarbons in Groundwater

Monitoring wells outside the Subject Property excavation area should be left intact and available for future monitoring and sampling. Six (6) additional wells will be installed within the area of excavation, once backfilling has occurred. In order to confirm that the source of impacts has been removed and to verify the presence/absence of residual hydrocarbon impacts in the groundwater, all monitoring wells left intact and the new monitoring wells will be monitored approximately six months to one year following remediation of the Subject Property. Provided residual impacts are not identified, this should be followed by monitoring well decommissioning and closure. If any groundwater impacts above applicable criteria are identified at the Subject Property, additional remediation should be considered.

 

Environmental Description

The Former Federal School Site is located on a peninsula surrounded by Split Lake (approximately 100 m to the north, west and south). The Potential STF Site is located inland, approximately 800 m north of Split Lake. The community of Split Lake is located within the Hayes River Upland Ecoregion in the Boreal Shield ecozone. Canadian Climate Normals data from the closest weather station (Thompson, approximately 145 km southwest) indicates an approximate mean annual precipitation of 510 mm, with the heaviest precipitation occurring within the summer months.

 

Surficial geology mapping indicates that the overburden in the area ranges in thickness from 1 m to 20 m thick. There are three main types of surficial deposits in the Split Lake area including clay, silt, and minor sand with low relief massive and laminated deposits. Low-lying relief generally characterizes the Split Lake area, including the two locations of the investigation.

 

The major surface water body closest to the areas of investigation is Split Lake. Split Lake drainage is directed in a northeast direction through the Hayes, Stuart and Nelson rivers. Veneer bogs, flat bogs and gently sloping clayey glaciolacustrine blankets and veneers occupy large areas of the region. Groundwater in the region is confined to generally thin, low permeability deposits with very localized flow systems. The groundwater flow direction at the remediation site, as indicated from previous studies, is to the northeast.

 

The Hayes River Upland Ecoregion is characterized by medium to tall stands of black spruce and jack pine with some paper birch. Shrubs are primarily ericaceous shrubs, willow and alder. Mosses, lichens, low ericaceous shrubs and some herbs provide ground cover. Wildlife includes a number of small to large mammals and numerous bird species are also found in the ecoregion.


Disclaimer

This map is for illustrative purposes. The markers represent the approximate locations based on available data. More than one marker may be identified for a given assessment.

 

Latest update

03/20/20 – The public comment period on the project is closed. – Indigenous Services Canada is considering comments received to help inform its determination on whether the carrying out of the project is likely to cause significant adverse environmental effects. .

Contacts

Indigenous Services Canada
Shelly Johnson, Environmental Specialist
365 Hargrave Street
Winnipeg, MB R3B 3A3
Telephone: 204-984-0709
Email: shelly.johnson@canada.ca


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