JG Afrika and Leomat Construction jointly devised an innovative approach to swiftly and cost-effectively replace a treated-process water pipeline from Tugela Mill to a discharge point on the Tugela River that had reached the end of its design life.
Tugela Mill’s treated-process water pipeline was previously transferred via a 1m-diameter underground pipeline over 3,5km to the effluent discharge point on the Tugela River, while also passing through the suburbs and parallel to the Mandeni Stream.
The existing pipeline had to remain operational until the new infrastructure was completed to avoid any production disruptions at the mill. The transition from the old to the new infrastructure would then have to be finalised within a nine-hour shutdown period.
Moreover, the new pipeline had to follow the existing route as closely as possible to comply with environmental requirements. This is in addition to being constructed within 3m of the existing infrastructure to ensure that all the construction works were undertaken within the current 8m-wide servitude.
It also needed to be sized to accommodate a flow rate of 50Ml of treated effluent per day.
The new pipeline was first completely constructed and commissioned above ground and laid within the servitude. This permitted the treated effluent to be transitioned from the old to the new infrastructure in a very short timeframe.
The Class 10 high-density polyethylene pipeline (HDPE) pipe was butt-welded in 12m-long sections to create robust and durable joints. This enabled the pipe to be pressure tested and commissioned in only six months versus an estimated 18 months that it would have taken using conventional trenching methods.
The old pipe trench was then re-excavated to remove and recycle the existing steel pipe. Thereafter, the new pipeline was lifted and relayed into the trench.
This approach provided significant cost savings considering that all of the rock had already been removed when the original pipeline was constructed, while the bedding and blanket placed under and around the old pipeline could also be reused.