The plant is located at the town lines of Marlborough, Northborough, and Southborough, Massachusetts.

CWTP is named after John J. Carroll, an original member of the Massachusetts Water Resources Authority (MWRA) board of directors.

[citation needed] In addition to water treatment, CWTP has five concrete contact chambers capable of storing 11.3 million US gallons (43 million litres).

[4][2] A 500 kW photovoltaic array is used to harness solar energy, reducing operational cost.

[2] As of February 2019[update], water treatment performed at CWTP consists of:[2][5] Water for CWTP comes from the Wachusett Reservoir, primarily via the Cosgrove Tunnel, with the Wachusett Aqueduct as a standby backup.