Town of Cobourg staff would like to advise residents that the cleanup of drilling mud that entered Brook Creek is almost finished, and the work is expected to be completed by Wednesday December 10, 2025.
Background
On November 18, 2025, pressurized drilling mud used in the micro-tunnelling process of a Town project to install trunk sanitary sewer entered the east tributary of Brook Creek approximately 350m north of the railway tracks at Brook Road North. Since the accidental discharge, the Town and their consultants have been working with the Ganaraska Region Conservation Authority, the Ministry of the Environment, Conservation and Parks, and the Department of Fisheries and Oceans on a remediation plan.
Since the incident, the drilling mud has settled and measures have been put in place to prevent spread throughout the creek. The remediation plan includes vacuuming of the drilling mud from the creek, ongoing monitoring, and other various efforts as required. As remediation work begins, the mud will temporarily be disrupted causing the creek to appear milky in some locations. This is anticipated and expected to clear up within a few days of the work being completed.
What is Drilling Mud
Drilling mud is a pressurized fluid used in the micro-tunnelling construction method. The
tunneling equipment and carry away the soil that is removed as the tunnel is constructed
(drilled). The drilling mud being used on Brook Road North is an inert, non-hazardous product
that is certified to NSF/ANSI 60 (drinking water standards) and consists of bentonite clay and
water.
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