The Little Long Hydroelectric site, built in the 1960s, is the first of a series of four sites developed along the Mattagami River.
The Little Long Dam Safety Project is underway to increase the discharge capacity at this spillway structure to comply with updated requirements established by the Province of Ontario. The company is in the process of adding four new sluiceway passages, which control water levels and flow rates in rivers, at the Adam Creek Sluiceway Structure. The owner Ontario Power Generation (OPG) is also making reliability improvements to the existing Little Long (2) and Adam Creek (8) sluice gates.
Location
The Little Long Dam Safety Project site is located in Northeastern Ontario, 70 km North of Kapuskasing, Ontario on the Little Long headpond
Scope of work
Bauer was awarded the contract to construct two temporary cofferdams. The cofferdams would allow for the construction of four additional sluiceways, thereby increasing the overall discharge capacity at the Adam Creek spillway structure. The main scope of work included the following:
On each side of the Adam Creek Sluiceway Structure, approximately 25 to 30 piles – out of 64 – were drilled through the top layer of the dike core and overburden soil that consisted of clay, sand and boulders above bedrock.
Away from this area, the piles were starting well in bedrock with a layer of boulders on top ranging from 200 mm to 800 mm in size. As per design, rock socket of 3.5 m to 4.5 m was achieved on the project with 3.5 m being in the area of existing overburden and dike core, (i.e.: closer to the dam face and away from the existing sluicegates).
Geology
The bedrock was identified as metasediment bedrock (Biotite Gneiss) with some quartz veins, typically consisting of slightly weathered to fresh weathering, in a non-porous and medium to strong condition. On the basis of the recorded RQD values, the rock quality is estimated to be generally “Fair” to “Excellent”. The average RQD value of approximately 92 % was observed suggesting a rock of generally “Excellent” quality. The UCS of the tested samples (intact rock of suitable core length) ranged from 55.8 to 169.5 MPa.
Equipment
Construction period
Phase 1 – East Cofferdam
Phase 2 -West Cofferdam
Miscellaneous
Pile installation of the project was executed in extreme winter conditions with temperatures well below -30 degrees Celsius.