Understanding Randle Reef

Hamilton Harbour is home to the largest and
most contaminated site within the Canadian
side of the Great Lakes – Randle Reef.

Hamilton Harbour is the western tip of Lake Ontario, separated naturally from the lake by a sandbar known as the Beach Strip. It is the largest naturally protected harbour on western Lake Ontario. Industry, commerce and residential areas, along with private and public open spaces share its 45-kilometre shoreline. The Harbour’s watershed covers more than 500 square kilometres and is drained by three major tributaries – Grindstone, Spencer and Red Hill creeks. The cities of Hamilton and Burlington, with a combined population of 785,000 people, are located within and around the watershed. In 1987, the Harbour was identified as an Area of Concern under the Canada–United States Great Lakes Water Quality Agreement due to significant impairment of water quality, loss of fish and wildlife habitat, and contaminated sediment and fish and wildlife populations. While many improvements have been made to reduce pollution in the Harbour, the legacy problem of contaminated sediment remains.

Located in the southwest corner of Hamilton Habour, the Randle Reef site is approximately 60 hectares (or about 120 football fields) in size. The site contains approximately 615,000 cubic metres of sediment contaminated with polycyclic aromatic hydrocarbons (PAHs) and other toxic chemicals. It is the largest PAH-contaminated sediment site on the Canadian Great Lakes. The contamination is often described as “a spill in slow motion” due to the continuing slow spread of contaminants across the Harbour floor and uptake into the food chain of the Harbour ecosystem. PAH contamination at Randle Reef is a legacy of a variety of past industrial processes dating back to the 1800s. There were multiple sources of contamination including coal gasification, petroleum refining, steel making, municipal waste, sewage and overland drainage.

The site was identified as a principal target of Harbour restoration objectives in the late 1980s. Studies were conducted over several years to determine options for cleaning up the site. In 2002, a Project Advisory Group reached an agreement to explore the idea of containing and capping the sediment. An environmental assessment, project designs, and the quest to secure funding soon followed.

The Randle Reef sediment remediation project involved constructing a 6.2 hectare engineered containment facility (ECF) on top of a portion of the most contaminated sediment, then dredging and placing the remaining contaminated sediment in the facility. The facility was made of double steel sheet pile walls with the outer walls being driven to depths of up to 24 metres into the underlying sediment. The inner and outer walls were sealed creating an impermeable barrier. The sediment will then be covered by a multi-layered environmental cap.

Cleaning up Randle Reef is one of the most significant steps remaining to remediate Hamilton Harbour and remove it from the list of Areas of Concern. The project will reduce the amount and spread of contaminants through the Harbour, significantly improving water quality and fish and wildlife habitat. The Harbour will also experience economic and social benefits: enhancement of shipping and port facilities, increased recreational opportunities, and the promotion of the Harbour community as a clean and progressive place to live and work.

STAGE 1, Construction of the ECF structure and dredging between the double sheet pile walls [COMPLETE]

• The seawall at Pier 15, at the foot of Sherman Avenue, was over 100 years old and in a state of disrepair. It was rebuilt in 2015 as part of this project to allow dredging to occur adjacent to the wall without compromising its integrity.
• Double steel sheet pile walls were installed during 2016 and 2017 to create the perimeter of the ECF structure. Construction was completed prior to dredging activities. The outer wall provides structural stability, and the inner wall provides isolation of the contaminated sediment from the surrounding Harbour environment. The interlocks between sheet piles on the inner wall were sealed creating an impermeable barrier.
• The sediment between the ECF’s inner and outer walls was mechanically dredged and moved inside the ECF. The space between the walls was sampled to confirm contaminant removal and then filled with clean crushed rock to provide structural stability.
• Before closing out Stage 1, the ECF was tested to verify the integrity of the seals on the inner wall.

STAGE 2, Dredging of the contaminated sediment located outside of the ECF, 2018-2021 [COMPLETE]

• Production dredging (of sediment beyond the footprint of the ECF). A cutter suction hydraulic dredge made multiple passes along the bottom of the Harbour to reduce the possibility of leaving behind contaminants. Areas that exceeded a predetermined PAH value after dredging were managed by a second pass of dredging and/or covered by a thin layer of sand. A discharge pipeline carried the dredged sediment from the dredge pump into the EFC. The pipeline was submerged under water in the EFC to reduce the possibility of toxins transferring from the sediment into the air.
• As the ECF filled with sediment, the excess contaminated water was treated by an on-site water treatment system to remove any remaining sediment or dissolved contaminants. Treated water was thoroughly tested and safely discharged into Hamilton Harbour.