The Shabomeka Lake Dam has been the subject of several geotechnical and structural reports since the last rehabilitation in 1989. In 2019, a Class EA was completed that recommended reconstructing the concrete control structure and rehabilitating the two adjacent earth embankments.
The site must be dewatered before work can begin. The concrete control structure will be demolished and rebuilt with an electrical bascule gate. A soil-cement-bentonite cut-off wall will be installed in the existing earth embankments. In addition, the north embankment will have an emergency overflow channel installed. At the end of the work, all soils will be stabilized, and the site will be restored to its original condition.
An early drawdown of the lake is required before work can begin. The drawdown timeline will be optimized to minimize recreational and ecological impacts while meeting the requirements for construction. It's critical to the success of the project that the lake is at its minimum target by mid-September.
The drawdown will begin the week of August 23rd, 2021. The lake will drop 5-10 cm per day before reaching a minimum of 269.30 MASL by September 15, 2021. The tentative project schedule is provided below:
|Dates||Proposed Works||Target Levels|
|July 26th – Aug. 22nd||Site clearing, water levels gauge removed.||271.10 – 270.90|
|Aug. 23rd – 29th||Drawdown begins. The lake will drop 5-10 cm per day.||270.90 – 270.20|
|Aug. 30th – Sept. 6th||Drawdown continues.||270.40 – 269.50|
|Sept. 7th – 14th||Drawdown finishes. Access to the structure is restricted.||269.90 – 269.30|
|Sept. 15 – 30th||Staging area set up, cofferdam and access road are installed. Demolition of existing control structure.||269.40 – 269.30|
|Oct. 1st – 31st||Excavation of SCB trenches, construction of the new control structure. Embankment crest heightening, placement of rip rap on the upstream face.||269.40 – 269.30|
|Nov. 1st – 30th||Installation of the bascule gate.||269.40 – 269.30|
|Dec. 1st -24th||Testing and commissioning of new structure.||269.40 – 269.30|
Access to the north shore will be provided downstream of the worksite for the duration of the project. By completing the work in the fall, we will be able to return to seasonal water levels in the spring.
The new structure will help mitigate extreme water conditions and protect the lake in a changing climate. The inconvenience of an early drawdown will pay dividends to all stakeholders for many years into the future.
Thank you for your patience and support as we complete this important project!