Marwell Tar Pit

• The Marwell Tar Pit was officially designated a Yukon Contaminated Site in 1998, pursuant to the Environment Act and the Contaminated Sites Regulation.

History• The CANOL

(Canadian Oil) Project was conceived during the WW2 when the Allied Forces were losing.

• Fuel supplies to support the war effort were threatened.

• Official U.S. Navy Photograph, National Archives Collection

Marwell Tar Pit

The sludge or “tar” from the tanks was deposited in the tank berm creating the Marwell Tar Pit.

Where is the Tar Pit ?

TakhiniArena

North of the 2 mile hill.

At the ends of Jasper and Quartz Roads

In the Marwell Industrial area of Whitehorse

Quartz Rd

AIRPORT

Site Location

Marwell Tar Pit Project

Project Initiation and Planning

• The Government of Canada and the Yukon Government have agreed to jointly fund the project. (70%-30% split)

• The Site Assessment and Remediation Unit (SARU) which is tasked with identifying, assessing and remediating Yukon Government contaminated sites, has been tasked with implementing and managing the Project.

Phase 1: Preliminary Activities

Phase objective: to acquire a completeunderstanding of the site characteristics.

• Identify the types of and area impacted by contamination.• Identify and quantify the impacts to the environment.• Identify and evaluate “clean up” options.• Identify Risks and Impacts of the project.• Test remediation technologies as and if required.

Phase 2: Remedial Activities

Phase objective: to remediate the site.

• Remedial Action Plan identification and Approval. • Environmental Screening (YESAA).• Regulatory Regime and Permitting. • Contracting and Construction Work.• Risk Assessment / Management.• Reporting, review and approval.• Monitoring Program design, review, and approval.

Phase 3: Post Remedial Activities

Phase objective: To Close out the project.

• Rehabilitation of the site, such as contouring and seeding if appropriate.

• Initiation of post remedial monitoring program.• Regulatory review of monitoring outcomes.• Application for a certificate of compliance.

Ultimate Project Goal• To manage this hydrocarbon impacted site and meet

Contaminated Sites Regulations. (CSR Industrial Standards, Risk Management)

• To manage human and environmental exposure to and impacts from site contaminants.

Borehole and Well Drilling

Soil Sampling

Water Sampling

Key Findings From Assessment• Contamination mostly oil 

related – similar to heating oil and roofing tar.  

• ~3500 dump trucks of material (~50,000 tonnes)

• PCBs and solvents not found.• Contamination is not leaving 

the site.• Groundwater is not 

discharging into streams.

Where is Contamination Found?• Bulk of contamination in circular, 

former tank basin... “hockey puck”

• In soil and groundwater (not vapour)

• Down to an average depth of 4‐5 m

• Deeper groundwater impacts only under the “hockey puck”.

• In silts/sands and clay, but also as “oily goop” in pockets of gravel, and minor pockets of wood debris.

Profile of Tar Pit

Human Health & Ecological Risk Assessment

• Risk assessors identified risks to humans and the environment.

• Importantly for our purposes, they derived site‐specific remediation targets (SSRTs) to support development and implementation of remediation/risk mitigation plans. 

Remedial Objectives

• Protect human health and environmental health

• Make the site safe for industrial use

• Decrease financial liability related to contamination

Remediation Is Challenging

What are the challenges?• Typical approaches not possible given 

mixed soils ‐ irregular silt/clay and sandier layers and pockets of lower and higher contamination.

• Whitehorse climate – shorter field season.

• Digging and stockpiling of multiple waste level soils in a tight area.

• Neighbours/community interests.• Silts and clays with heavier oils.• Funding

Remedial ApproachesThese are approaches to remediation and not actual technologies:

1) Cover the Surface

2) Remove or treat > SSRTs in the top 1.25 m.

3) Remove or treat > SSRTs in the top 1.25 m and remove all product (oily “Goop”) found deeper in the pit

4) Remove or treat > SSRTs in the top 1.25 m as well as remove product and >Special Waste from below (down to base)

5) Remove or treat > SSRTs in the top 1.25 m as well as remove product and >Special waste and >SSRTs down to the base.

6) Remove or treat all materials >Industrial Std levels within the pit

Conclusions• All approaches will protect human health and the environment.• Approaches that treat or remove the majority of the contamination 

provide the best bang‐for‐the‐buck.• Approaches that leave contamination behind, leave more than the 

financial liability shown.  Reduced remediation results in ongoing costs of monitoring & maintenance program required to ensure compliance with any risk‐based management permit.

• Importantly, overall risks remain high when greater concentrations of contaminants are left behind or when large volumes of moderate levels of contamination are left behind. Uncertainties (risks) remain and include potential regulatory changes to standards, including risk standards and risk management conditions; limitations on future land use and development; public perceptions; orders or other triggers to clean up; accidents; unplanned migration of contamination etcetera.