Wastewater has begun to flow in Council’s new 1.45km trunk main that takes Ashburton’s sewerage and dirty household water to the Wilkins Road treatment plant.

The trunk main is part of a $2.33 million project that is the final phase of a big upgrade of the town’s wastewater network.

Infrastructure and Open Spaces Group Manager Neil McCann said the new 800mm diameter trunk main replaces the old 600mm diameter pipeline, and is designed to cope with urban growth in the future.

“The project also involved replacing an ageing structure at Trevors Road known as a grit chamber, which caught stones and other non-biodegradable objects in the system.”

The open-top concrete grit chamber was installed in the 1940s to collect sewerage from the town, and direct it to Milton Road and then under the Ashburton River to the Wilkins Road treatment plant.

Mr McCann said the new, larger trunk main no longer crosses private property on its way to Milton Road, and he was pleased to see it come online last week.

“It hooks up with the upgraded river crossing and the new additional relief sewer, both big projects completed in the past couple of years. The town’s original network of sewer pipes dates back to the 1920s and while we still have a few earthenware pipes we are systematically replacing the old with the new.”

Two old concrete wastewater tanks near the old grit chamber will also be removed eventually. Back in the 1950s, the tanks were used for the primary treatment of raw sewerage by separating solids from liquids.

Mr McCann said wastewater treatment had come a long way since then, and was heavily monitored to protect both people and the environment.

“The new trunk main is made of special plastic and there are seven manhole points along it.

“Ashburton has nearly 9200 wastewater connections and all the wastewater is collected at the Wilkins Road oxidation ponds, treated and then piped to Ocean Farm, where is it sprayed onto farmland near the coast.

“While ACL manages the day-to-day operations, it is Council’s responsibility to ensure the whole scheme runs safely and effectively.”

ACL was also the contractor for the grit chamber project.

Below: One of the new manholes along the new sewer trunk main from Trevors Road to Milton Road.