Willmott Dixon will extend and alter the existing swimming pool building in Rothamsted Park to provide an improved main pool, as well as new 17-metre learner pool, a sports hall, dance studios and a larger gym plus new changing rooms, a steam room, sauna and reception area.
The contractor will also transform the adjacent sports facility into Harpenden Cultural Centre with a 511-seat theatre as a replacement for the Harpenden Public Halls entertainment venue.
Work on the project, which also includes creating a 92 space car park, is expected to complete in autumn 2020.
The contract was procured via Major Works England and Northern Ireland, a part of the Scape National Construction framework.
Last year, Willmott Dixon remodelled St Albans Town Hall into a museum and art gallery. The person who led that site team, Jon Allworth, is also leading on the Harpenden project.
Chris Tredget, managing director for Willmott Dixon in North London, said: “The team are exceptionally proud of what we created in St Albans with the museum and gallery, which has been an important new attraction for the city. We are keen to make a similar impact with our work in Harpenden to expand its leisure and cultural offerings to local people.”