Manto Sipi Remediation of Former Band Tank Farm Site

The Manto Sipi Cree Nation inhabits the God's River Reserve 86A located on the north shore of God's Lake at the inlet of God's River. This community is situated in central-east Manitoba, approximately 585 km northeast of Winnipeg, Manitoba, and 262 km southeast of Thompson, Manitoba. The former band tank farm site is located in an area that has been partially developed for industrial type use in the western portion of the community. (See Figure 1, attached.) This former fuel compound site was abandoned at some point following the construction of a new fuel storage facility for the community in 2013. The site currently consists of a former roadway/ parking area through the centre of the site, a row of seven parallel, interconnected aboveground fuel storage tanks (ASTs) along the eastern boundary of the site, and two ASTs on the southern boundary of the site. The ASTs include a mix of single and double walled tanks of various age and manufacturers. Each of the ASTs has a volume capacity of approximately 50,000 L; however, all are currently empty. Previous intrusive Phase II/ III environmental site assessments (ESAs) were undertaken by in 2010 and in 2017, and identified the presence of petroleum hydrocarbon (PHC) impacted surficial and subsurface soils in two portions of the site. One area is located in the vicinity of the eastern ASTs and has an estimated lateral area of 384 m2 and depths extending from near surface to approximately 4.5 meters below grade (mbg). The second area of impacted soil is located in the southern portion of the site, in the vicinity of the two remaining ASTs. This area of impact has an estimated lateral area of 324 m2 and depths extending from near surface to approximately 3.2 mbg. In total, there is an estimated 2770 m3 of soil impacted with PHCs at concentrations exceeding the Canadian Council of Ministers of the Environment (CCME) Environmental Quality guidelines considered applicable to this site (i.e., Tier I values for fine grained soil in residential land use area with eco-soil contact and vapour inhalation receptor pathways). Review of shallow groundwater conditions in the low permeability, fine grained soil found discontinuous perched groundwater conditions with dissolved hydrocarbon impacts over only a limited area within the limits of the defined soil impacts. The proposed remediation of the former band tank farm site will comprise the following activities:

· Decommissioning of the remaining ASTs: The nine on-site ASTs will be decommissioned by a licensed petroleum technician. This will include the disconnection and removal of all fuel tanks and associated piping. The materials will be transported out of the community via winter road to a licensed facility in Thompson or Winnipeg.
· Rehabilitation of the community land farm site: As part of previous environmental site remediation projects in the community, a land farming soil treatment facility has been developed to the north of the community, near the community landfill. (See Figure 1.) The land farm was originally constructed by Manitoba Hydro in 2003 following approval of the associated remediation action plan by Manitoba Environment (now Manitoba Conservation and Climate) and was decommissioned in 2006. The land farm was rehabilitated for use in 2008 for a separate site remediation program, based on the remediation plan approved by Manitoba Environment and ISC, and then again decommissioned in 2012. This facility consists of a graded open area surrounded by an earthen berm to allow for the placement of the hydrocarbon impacted soil in a contained area and treatment through aeration and nutrient amendment. Rehabilitation will consist of repairs to the berm which had been breached to allow for drainage during non-use, installation of a geosynthetic liner to improve the impermeability of the base, reinstallation of a water treatment system for precipitation runoff control, and mobilization of the applicable soil overturning equipment. Upgrades to the access road to the site will also be undertaken to accommodate the haul truck traffic.
· Excavation of the petroleum hydrocarbon contaminated soils: All contaminated soil from the designated areas will be excavated using convention practices and transported to the land farm site. Soil samples will be collected form the walls and base of the resulting excavation for confirmation that the limits of impact have been attained. Any limited groundwater and precipitation that accumulates in the excavation will be pumped out and transport to the land farm and then sprayed over the soil awaiting treatment. The two excavation areas will then be backfilled with local fill material and compacted to allow for site redevelopment.
· Treatment of the contaminated soils: The soil in the land farm area will initially be spread out into an approximately 0.9 m thick layer across the base of the land farm. The upper 0.3 m layer will be overturned using a mechanical disker on a regular basis during the spring to fall treatment period. Representative soil samples will be collected near the end of the treatment period to confirm that the residual petroleum hydrocarbon concentration in the soil had dissipated to below applicable guideline values. The treated soil will then be removed from the land farm for reuse as general fill/ cover material at the community landfill. This process will be repeated for the two subsequent soil layers. Once all formerly impacted soil has been removed from the land farm the facility will be decommissioned accordingly.