Manx Utilities says it will be ready to partially reopen the Old Castletown Road tomorrow morning.
Work at White Hoe has progressed well and ahead of programme, with key construction stages completed.
MUA said: “The works involve replacing a large access cover above a deep underground valve chamber that forms part of the wastewater main between Douglas and Meary Veg.
“The cover must be reinstated in precisely aligned sections, with new concrete requiring controlled curing to ensure long‑term structural integrity. During this period, the works will move to a single‑lane arrangement.
From Thursday morning, Old Castletown Road will reopen to allow one‑way traffic into Douglas.
Subject to successful concrete curing and routine safety checks, the road remains on schedule to fully reopen on March 25.