He worked at Masterton District Council until 2006 and then alongside Carterton District Council as a utilities manager until moving on to work at South Wairarapa in 2010.
"I think I have been able to, in my own way, contribute to the council going forward."
Chief executive officer Paul Crimp said Mr Sloan had made a significant contribution "with his professional and calm personality and his vast experience".
He said Mr Sloan had played a significant hand in advancing the wastewater consents in Featherston, Martinborough and Greytown.
"This is a major body of work that has taken the best part of four years."
Mr Crimp said the council was keen to retain Mr Sloan's capability in a part-time role once the consents were granted, as there would be a lot of implementation work required.