Project Description

Iqaluit is located in the southeast part of Baffin Island in the Arctic territory of Nunavut above the tree line at N63°45′ and W68°31′ and approximate Elev. 202masl. Formerly known as Frobisher Bay, Iqaluit is at the mouth of Frobisher Bay between the Hall and Meta Incognita Peninsula overlooking Koojesse Inlet. The Iqaluit area is part of the Jordan River tectonostratigraphic domain in the southern extension of the Cumberland batholith which is one of the largest plutonic belts in the northeastern Canadian Shield (1.86 billion years old). The plutonic rocks comprise massive to foliated orthopyroxene biotite monzogranite that may contain horneblende, pyroxene and garnet. The granite is massive and coarse grained. It contains tonalite, quartz diorite and metasedimentary rock inclusions. There are xenoliths of quartzite, amphibolite, and marble with quartzite. The surficial sediments comprise small localized till, outwash, deltaic gravel and sandy alluium deposits. The terrain contains permafrost to significant depths of up to 100m, and the seasonal freezing and thawing in the active zone has caused microcracking of the bedrock surface to approximately 1 to 3m (3 to10ft.) depth.

The bedrock at the tower site located approximately 3km northeast of Iqaluit is described as fair to good quality gneissic granite. Bedrock outcrops are generally smooth without visible fractures. The regional geology appears to be dominated by major jointing, striking in the northwest to southeast direction dipping at about 45 degrees northeast. At the site the major joints strike in the northwest to southeast direction dipping at 48 degrees southwest. Most visible fractures or joints are closed and the joint spacing is 2m or greater. GPR surveys showed massive, relatively sound rock, overlain by 0 to 2m of overburden comprised mainly of sand interspersed with unsorted rocks of boulder and cobble sizes.

The 25 MPa concrete tower footings were designed and constructed using controlled blasting and rock excavation methods to specified sound rock levels obtaining a bearing pressure of 1400kPa. Sixteen vertical rock anchors were drilled into gneissic granite with a total drilled length of 10.5m, a tendon diameter of 26mm, a bond length of 5.0m, and a free length of 5.0m. The anchor holes were inspected using a borehole camera. The rock anchor holes were redrilled immediately before installing high early strength cold temperature grout which yielded 28 day laboratory compressive strength test results exceeding 50MPa. Early onsite grout cube testing was performed to confirm a minimum strength of 20MPa after about 40 hours and prior to anchor testing. All anchors were tested to a maximum load of 170kN or 250% of the specified working load. All anchors were locked off in accordance with a revised specification at 130 kN or 190% of the specified working load of 68kN. A granular hardstand was constructed using compacted OPSS Granular B Type 1 aggregates to connect to the existing hillside access roadway.