Moore Construction was engaged by the Marlborough Roads Recovery Team (MRRT) to undertake slip repair works at Port Underwood, focused on restoring road access through the construction of a soldier pile retaining wall and associated drainage upgrades. The works involved the design and implementation of a project-specific Traffic Management Plan (TMP) to maintain safe single-lane traffic flow throughout construction. Retaining wall benches were excavated and piling platforms formed using on-site gravel. Proof-drilling was carried out to confirm pile design, followed by the drilling and installation of 310UC97 steel piles into 600mm diameter bored shafts to 12m depth, embedded in weathered sandstone with 1.5m rock sockets. Timber lagging was installed between piles, separated from steel using malthoid DPC and packing timber. The wall was backfilled with compacted AP65 aggregate in 200mm lifts, wrapped in geotextile fabric, and underlain by a 170mm Megaflow subsoil drain with P metal surround. The drainage scope included demolition of the existing culvert and installation of a new DN500 HDPE SN8 culvert with a precast Humes inlet and cycle-friendly concrete-cast grate. Outlet protection was provided using a 6m x 4m x 300mm Reno mattress filled with durable rock. Final civil works included construction of mountable kerb and channel, full pavement reinstatement with compacted AP65 sub-base, M4/AP40 basecourse, and two-coat chip seal surfacing (Grade 3/5), followed by line marking and installation of a timber sight rail in accordance with MRRT specifications.
