Success with pressure sewerage scheme at Grovetown

Grovetown is a community of approximately 300 people situated in flat and low lying land 5 km north east of Blenheim. The area suffers from difficult ground conditions including poor drainage and a high water table, conditions which had led to the failure of many of the household septic tanks. Several options were considered for upgrading Grovetown’s on-site wastewater systems and incorporating conveyance of effluent from the nearby Spring Creek oxidation pond. Marlborough District Council decided to install a pressurised sewer system using grinder pump systems on each individual property, and a common pressure main from Spring Creek to the existing Blenheim Sewage Treatment Plant (STP).

The design and implementation of the system involved unusual and sometimes difficult considerations including Council’s ownership of facilities on private land, and installation in a way that was agreeable to each landowner. Pipelines were sized for the ultimate estimated population, so flushing points had to be added around the reticulation where initial velocities would be low. A pump station was installed at the Spring Creek STP to convey effluent to Blenheim STP, collect the Grovetown GPS discharges, and to provide a means of flushing the line to prevent solids build up from low velocities.