Construction considerations for wick drain ground improvements Due to the large quantities required, both Titan TE-BXC30 biaxial geogrid composite and Mirafi HP370 reinforced woven geotextile were used at different locations. The first noted geosynthetic is made of biaxial polypropylene geogrid heat bonded to nonwoven polyester geotextile. A minimum 1 foot (0.30 m) thick granular drainage blanket was installed over the geosynthetic reinforcement layer. The drainage blanket primarily consists of sand and gravel-sized particles and has less than 5% fines. Loading, hauling, spreading and nominal compaction of drainage blanket material was carried out and the final surface of the drainage blanket was checked to be consistent with the required design grades. Some construction activities were carFIGURE 4 Dozer grading drainage blanket surface FIGURE 5 Wick drain rig completing a wick drain trial ried out during the winter. These activities included foundation soil cut, geosynthetic placement and drainage blanket placement (Figure 4). During the winter, the earthworks design was altered to use cut only; no fine-grained foundation fill placement was allowed over this period. Wick drains installation Wick drains were installed through the drainage blanket in a triangular pattern with 7-foot (2-m) spacing. The selected spacing was verified by means of a test fill (Etezad et al. 2019). The wick drains were generally pushed through the cohesive soil units to refusal in the lower granular till layer above the bedrock, thus providing double drainage for wick drains. The installed wick drains were MebraDrain MD-88, which consist of a 4-inch (100 mm) wide fishbone profile polymer core wrapped in a nonwoven filter jacket. The installed wick drains were anchored at their base with a steel plate. The wick drains were installed using six hydraulic wick drain rigs mounted to tracked excavators of varying sizes and installation depth capacities. Wick drain installation 22 Geosynthetics | August September 2022