Alwen Water Scheme (nprn 85178) was constructed for the Corporation of Birkenhead between 1911 and 1921 to provide a water supply and comprises Alwen Reservoir, Dam and Filter House (nprn 85183). Various housing is associated with the scheme: a manager's house (nprn 408482), terrace of workers? housing (nprn 85249) and barracks (nprn 85248) for the construction workers.
Curved on plan and approximately 157m long, the dam is built of reinforced concrete and rock-faced concrete blockwork. At the foot of the dam is a turbine house providing hydro electricity.
B.A.Malaws, RCAHMW, 17 November 2008.