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How the MWRA Water System Works
Massachusetts water Resources Authority

 

The MWRA Water System
map of water system - mwra

WHERE YOUR WATER COMES FROM

MWRA supplies wholesale water to local water departments in 48 communities: 42 in greater Boston and the MetroWest areas and three in Central Massachusetts. MWRA also provides a back-up water supply in three other communities.

 

HOW WATER GETS TO YOUR TAP

Protected Reservoirs

MWRA's water comes from the Quabbin Reservoir, about 65 miles west of Boston, and the Wachusett Reservoir, about 35 miles west of Boston. The two reservoirs combined supplied an average of 214.21 million gallons per day to consumers in 2007. The Quabbin alone can hold a supply of 4-year supply of water.

The reservoirs are filled naturally. Rain and snow fall onto watersheds (protected land around reservoirs) and eventually turn into streams that flow into reservoirs. This water comes into contact with soil, rock, plants and other material as it follows its path. This process helps to clean the water, and it can also dissolve and carry very small amounts of material into the reservoir.

The Quabbin and Wachusett Reservoirs are protected. Over 85% of the watershed lands that surround the reservoirs are covered in forest and wetlands. About 75% of the total watershed land cannot be built on. The natural undeveloped watersheds help to keep MWRA water clean and clear. Also, to ensure safety, the streams and the reservoirs are tested often and patrolled daily by the Massachusetts Department of Conservation and Recreation (DCR). Because they are well-protected, the water in the Quabbin and Wachusett Reservoirs is considered to be of very high quality.

Generating Power as it Goes

Quabbin water enters the Wachusett Reservoir at Oakdale and circulates for eight months before being drawn off in Clinton. Electric power is generated as the water both enters and leaves the reservoir and at two other stations in the system.

Tested Each Step of the Way

MWRA tests over 1,500 water samples per month, from the reservoirs all the way to household taps. Annual and monthly test results are posted on mwra.com.

Treatment

MWRA's licensed treatment operators treat drinking water according to strict state and federal regulations.

Water Treatment Steps for Metro West and Metro Boston Communities
Water for most MWRA communities (except Chicopee, South Hadley Fire District #1 and Wilbraham) is treated at the new John J. Carroll Water Treatment Plant at Walnut Hill in Marlborough. Water from the Quabbin and Wachusett reservoirs enters the plant through the Cosgrove or Wachusett Aqueduct. The treated water leaves leaves the plant through the MetroWest Water Supply Tunnel.
Treatment
Current Dose
Purpose
Ozone 2.2 mg/l To achieve 2 log crypto inactivation (except during half plant); Primary disinfectant
Sodium bisulfite 0.2 mg/l To remove ozone
Sodium hypochlorite 3.7 mg/l Residual disinfection
Sodium hydrofluorosilicic acid 0.9 mg/l For dental health
Sodium carbonate 35.5 mg/l To raise the alkalinity of the water for pH buffering; to minimize lead and copper corrosion in home plumbing.
Aqueous ammonia 0.8 mg/l To combine with free chlorine residual to form monochloramine; residual disinfection
Carbon dioxide 6 mg/l To reduce pH; to minimize lead and copper corrosion in home plumbing

 

Water Treatment Steps for Chicopee Valley Area Communities
Water for Chicopee, South Hadley Fire District #1 and Wilbraham is treated at the Quabbin Disinfection Facility in Ware, Massachusetts. Water from the Quabbin Reservoir enters the facility through the Quabbin Aqueduct. Treated water leaves the plant through the Chicopee Valley Aqueduct. Each community further treats the water to reduce the chances that metal particles from home plumbing could dissolve into tap water.
Treatment
Current Dose
Purpose
Chlorine   Primary disinfection


Toward Your Community

For MetroWest and Metro Boston Communities - treated water is sent through the MetroWest Water Supply Tunnel and is stored in covered tanks. From there it is drawn into distribution mains and many smaller community pipes. Water meters log the water entering each community.

Chicopee Valley Area Communities - treated water is sent through the Chicopee Valley Aqueduct to local distribution mains and smaller community pipes. Water meters log the water entering each community.

Into Your Home

Local pipes serve each street and eventually carry water into buildings. Meters installed by the local community measure the amount of water delivered to each home or business.

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Updated August 13, 2013