North Drumheller Flood Improvements Project

Project Highlights

The Town of Drumheller (the Town) is a community where major floods have occurred in 1902, 1915, 1932, 1954, 1991, 2005, 2013, and 2018. While some areas in Drumheller have existing flood mitigation infrastructure, additional work is needed to improve upon Drumheller’s level of flood mitigation and resiliency. To this end, the Drumheller Resiliency and Flood Mitigation Office (DRFMO) was established in 2019 to administer funds received through the Government of Canada’s Disaster Mitigation and Adaptation Fund, the Government of Alberta’s Community Resiliency Program, and from the Town of Drumheller.

KWL was assigned the engineering services contract for the design and construction of the North Drumheller Flood Improvements Project (NDFIP) and the Grove Plaza Berm. NDFIP consists of two new berms along the left bank of Red Deer River and the right bank of Michichi Creek, and the upgrade of an existing berm along left banks of Red Deer River and Michichi Creek. The Grove Plaza berm consisted of the upgrade of an existing berm along the left bank of the Red Deer River.

Michichi Siphon Realignment Assessment

The Town of Drumheller had a 250 mm diameter sewer pipe crossing Michichi Creek above the creek invert. The pipe had experienced operational issues over its service life and the existing pipe installation did not meet current design standards. Given the planned realignment of nearby berms designed by KWL, the Town retained KWL to design a new sanitary crossing of Michichi Creek.

To accommodate the depressed sewer profile needed to cross beneath Michichi Creek, a siphon design was initially considered to replace the existing sanitary crossing. The design of the siphon included a double barrel HDPE siphon beneath the creek. Two construction methodologies were explored: open cut with temporary creek bypass and horizontal directional drilling. Factors that were considered included the subsurface conditions, property ownership, and the environmental risk to the creek. Michichi Creek needed to be bypassed and temporarily dewatered for other berm realignment work, so an open cut construction was recommended.

A double barrel siphon was recommended to maintain flushing velocities during low flow periods and meet target capacities during higher flows. This design included an inlet and outlet chamber on either end of the siphon with recommended odour control.

However, after a further review of the limited available flow data and a review of the expected inflows from the catchment area, the siphon was eliminated as a design option. Upstream infrastructure was limited resulting in periods of very low flows making it difficult to maintain flushing velocities through any combination of pipe sizing. As a result, a pumped forcemain creek crossing was selected with a lift station on the upstream end of the creek crossing.

Michichi Pump Station

The installed lift station consists of a prefabricated FRP submersible wet well and a below grade valve chamber. The sanitary station is a duplex station designed to convey sewage of nearby residential homes to a downstream station and has a capacity of approximately 30L/s. The wet well was over 7 m in depth to match the required force main crown which needed to be below the Michichi Creek scour depth.

The incoming sewer alignment and tie ins were reconfigured and rerouted to the lift station. The forcemain replaced the existing sewer creek crossing. To reduce excavation requirements, approximately 60 m of force main was horizontally directionally drilled.

The lift station was commissioned and began operation in late 2024.