OTTAWA -- Overnight construction work on the Trillium Line expansion is set to begin Tuesday.

River Ward Coun. and transit commissioner Riley Brockington shared two memos on Twitter Monday afternoon outlining the work that is set to begin.

The first memo describes work where the Trillium Line and Via Rail tracks intersect between Mooney's Bay and Walkley stations. A bridge is being built in the area to allow Via trains to safely bypass the Trillium Line. The work is expected to last one month.

Construction work will begin at 10 p.m. each night and end by 6 a.m. each morning. Efforts will be made to keep lights facing away from residences. Sound levels are not expected to exceed 85 decibles—approximately as loud as a lawnmower—but the memo says that sound level should be greatly reduced by about 30 metres away.

Construction work on the future South Keys Trillium Line transfer station is also set to begin Tuesday night.

Excavation work is scheduled to take place each night from 11 p.m. to 7 a.m. Aug. 4 to Aug. 23.

The memo says nearby residents should not be troubled by lights, as they will be facing away from residential areas. There will be some noise, at a level not expected to exceed 65 decibels. For comparison, the sound of a vacuum cleaner is commonly used to refer to a level of 70 decibels.

The work is part of the Stage 2 expansion of the north-south Trillium Line, which is scheduled to be complete in 2022. The Trillium Line will remain closed until the expansion is complete. The expansion will extend the line from its southern terminus at Greenboro Station to Riverside South and the Ottawa Airport. 

The SNC-Lavalin backed "TransitNext" group is building the Trillium Line expansion.