The ammunition depot sits on a hillside that faces Halifax Harbour. Due to its location on the hillside, concrete blast walls are required in front of each ammunition bunker to absorb any blast that might occur to shield the harbour and surrounding area from the force of the blast. New regulations require the blast walls to be constructed of a material that would not fragment into pieces larger than 19 mm if hit by an explosive blast.
The criteria that had to be met were: maximum particle size of 19mm when exposed to blast, economics, a design life of 20 years, ease of construction and material availability. After careful evaluation, a geotextile-wrapped wall was chosen. This geotextile option allowed for the face and reinforcement to be of a single material. If exposed to a blast, the maximum particle size would be limited by the gradation of the contained granular backfill which was (19 mm). It would be easy to construct using temporary forms, and by spraying the exposed geotextile face with an asphalt emulsion after completion, UV stability would not be an issue. In addition, the new blast walls would have to be freestanding, thus requiring four exposed sides.
TenCate Mirafi® PET 100 polyester geotextile met all the technical specifications and requirements of the design. In accordance with the contract documents, TenCate Geosynthetics provided a qualified technician, experienced in the construction of these types of wall systems, to provide on site technical support to the contractor. Each blast wall is 72 m x 9 m x 6 m high and was constructed of 11 lifts of TenCate Mirafi® PET100 geotextiles.