Ontario orders further action on Hamilton’s ‘Sewergate’


In the wake of four years of sewage leaking undetected into a City of Hamilton creek, Ontario has ordered the city to undertake targeted dredging after local officials decided not to undertake additional, comprehensive remediation.

The November 20 Provincial Officer’s Order from the Ministry of the Environment, Conservation and Parks, recommends mitigation measures to improve water quality in Cootes Paradise and dredge Chedoke Creek. Due to the incorrect operation of a combined sewage overflow (CSO) tank valve, and the malfunction of a second gate valve without detection, an open bypass gate leaked approximately 24 billion litres of combined sewage into the creek.

The creek in turn outlets at the south shore of Cootes Paradise Marsh, part of a nature reserve owned and managed by the Royal Botanical Gardens.

“[…] I am of the view, after having consulted with ministry experts, that the spill caused or may cause impairment to the system and therefore the items identified in the Order are required and more work is needed,” stated Shelley Yeudall, a provincial water inspector for the Hamilton region.

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A consultant’s report addressed in spring 2019 advised City of Hamilton officials not to remediate the areas in question. There was a recommendation of “no action”. It was also determined that it was not possible to attribute environmental impacts experienced in these areas exclusively to the leaked sewage.

“[…] A ‘no action’ recommendation by the city does not discharge its obligation to restore the natural environment nor does it address or prevent potential adverse effects, or may impair or continue impairment of the natural environment, including waters,” Yeudall added.

City officials suggested in a November 20 statement that they have already taken significant efforts to clean up the creek and removed 242,000 litres of “floatable material” from the surface and edge of the creek.

Explained: Combined sewer overflow and the Chedoke Creek spill


In terms of what the province is concerned about happening to the environment, it states that the sediment has been identified as having a moderate to high risk for some organisms due to polycyclic aromatic hydrocarbons. Additionally, high ammonia and nitrite levels in the water will continue to contribute to the eutrophication of the system, all of which may continue to impact organisms in the water and sediment. Phosphorus may add nutrient loading to the entire system and continue to increase the risk in the frequency and size of algal blooms that may impair the water for its use or cause injury as a result of the blooms.

The City of Hamilton runs both the Dundas and Woodward wastewater treatment plants. It also operates approximately nine CSO tanks, designed to hold a portion of sewage and stormwater during rain events that exceed the capacity of the plants.

The spill wound up being dubbed “sewergate” in local media after Hamilton officials failed to publicly disclose the full extent of the problem.

“We apologize to the residents of Hamilton for the failure to publicly disclose the volume and duration of the discharge of stormwater runoff and sanitary sewage into Chedoke Creek when it first became known to the Council in 2018 and at subsequent Committee and Council meetings,” Hamilton Mayor Fred Eisenberger said in a December 2019 statement released to media.

On March 13, 2020, Hamilton’s Royal Botanical Gardens (RBG) staff expressed concerns regarding ecological damage and contamination to Cootes Paradise Marsh, which is owned by RBG. It requested a robust analysis of the spill impact and future remediation efforts.


  1. Electro Kinetics may be a solution for remediation and not require dredging. It has been used for remediation of organics such as hydrocarbons and blue-green algae in surface water ponds. It works by generating oxygen and hydroxyl radicals that break down the contaminates.


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