Pending final determination of Southern Water’s ‘Water for Life’ Business Plan, this initial contract is expected to be worth £325m to the joint venture in an equal share over the five-year period.

Under the extended contract from AMP6, the joint venture will bring together its consultancy, design, digital, construction and commissioning skills to maintain and improve Southern Water’s water supply and wastewater treatment.

The AMP 7 contract will begin in April 2020 and will see Costain collaborating with Southern Water ensuring they optimise innovation and efficiency throughout AMP7 delivery. 

Alex Vaughan, chief executive officer of Costain, said: “Having now worked with Southern Water through the previous four regulatory AMP cycles, this contract extension is further testimony to the value of our long-term, strategic relationship.”

Neil Colman, director of engineering and construction, Southern Water said: “We fully expect the delivery of our PR19 programme to be challenging and require large efficiency gains.

“Only with partners as committed as we are to delivering smart solutions can we be sure of securing a resilient water future for the South East.”