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MWRA's Drinking Water Test Results
For 2010 - Published June, 2011

Massachusetts Water Resources Authority

HTML Version- Metro Communities

Below are MWRA's 2010 Drinking Water Test Results for Metro Boston and Metro West communities.

Results for Chicopee, South Hadley and Wilbraham are available in a separate report [PDF].

This report includes the results of those tests for 2010. This report is required under the federal Safe Drinking Water Act Public Law 104-12, Section 1414 (C), PWS ID #6000000.

More Information
cover of report
Back to MWRA 2010 Annual Drinking Water Test Results Main Page
Download a PDF of this report (Metro Version)
Download a PDF of this report (CVA Version)
Annual Water Quality Report Archive
All MWRA water quality tests
Table of Contents
Message from MWRA Executive Director Fred Laskey
Where your water comes from
Map of the MWRA water system
How your water is treated
Improvements to the system
Test results
Information about lead
Important Information from EPA and DEP
Special notice for the immuno-compromised
Facts about sodium
Information about cross connections
Information on the May 1, 2010 Boil Water Order
Water conservation
Where to go for more information
Contact us
Additional information from your city or town water department

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Message from MWRA Executive Director Fred Laskey

Dear Customers,

This report contains the 2010 test results on your drinking water. Hundreds of thousands of tests confirmed that the quality of your water is excellent. For 2010, MWRA met every federal and state drinking water standard. System-wide, we have been below the Lead Action Level for the past seven years. Please see your community's letter for more information on your local system.

Two upcoming projects will enhance the quality and safe delivery of our water. Soon we will be begin building ultraviolet disinfection facilities at our Carroll Water Treatment Plant. Together with ozone, this will give us two forms of powerful disinfection. Then, we will be constructing a water tank and pumping station in Stoneham to provide storage for six communities, and redundancy for 21 communities in case of emergency.

You may have heard press reports about a chemical called Hexavalent Chromium, or Chromium 6. Although there are no federal standards for this substance, MWRA has begun voluntary testing for it as recommended by the EPA. In response to the Japanese earthquake, we have also tested for and found no traces of radioactive iodine or cesium. As more information becomes available, we will share it with you on

Please take a moment to read this important information. We want you to share our confidence in your drinking water.

Frederick A. Laskey
Executive Director

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Where Does Your Water Come From?

The Green Choice
As water travels eastward directly to your faucet, clean hydro-energy is produced. MWRA also has wind turbines and solar panels at our Carroll Treatment Plant. Tap water is delivered straight to your home without trucking or plastic waste. Drink tap water and be green!

Your water comes from the Quabbin Reservoir, about 65 miles west of Boston, and the Wachusett Reservoir, about 35 miles west of Boston. These reservoirs supply wholesale water to local water departments in 51 communities.The two reservoirs combined supplied about 200 million gallons a day of high quality water to consumers in 2010.

Quabbin and Wachusett watersheds are protected naturally with over 85% of the watersheds covered in forest and wetlands. To ensure safety, the streams and reservoirs are tested often and patrolled daily by the Department of Conservation and Recreation (DCR).

Rain and snow falling on the watersheds - protected land around the reservoirs - turn into streams that flow to the reservoirs. This water comes in contact with soil, rock, plants, and other material as it follows its natural path to the reservoirs.

While this process helps to clean the water, it can also dissolve and carry very small amounts of material into the reservoir. Minerals from soil and rock do not typically cause problems in the water. But, water can also transport contaminants from human and animal activity. These can include bacteria, viruses, and fertilizers - some of which can cause illness. The test data in this report show that these contaminants are not a problem in your reservoirs' watersheds.

The Department of Environmental Protection (DEP) has prepared a Source Water Assessment Program report for the Quabbin and Wachusett Reservoirs. The DEP report commends DCR and MWRA on the existing source protection plans, and states that our “watershed protection programs are very successful and greatly reduce the actual risk of contamination.” The report recommends that we maintain present watershed plans and continue to work with residents, farmers, and other interested parties to maintain the pristine watershed areas. Your water also comes from local supplies that have separate reports.

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Map of the MWRA Water System

mwra water map

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How Your Water Is Treated

What is Ozone?
Ozone consists of 3 atoms of oxygen. It is created by applying an electrical current to pure oxygen in a specially designed chamber. Ozone provides better disinfection than chlorine alone, especially against Cryptosporidum and other hard to kill germs. It also reduces the amount of potentially harmful disinfection byproducts.

From the Reservoir to Your Home

The water you drink is treated at the John J. Carroll Water Treatment Plant in Marlborough. The first treatment step is disinfection of reservoir water. MWRA’s licensed treatment operators carefully add measured doses of ozone gas bubbles to the water to kill any pathogens (germs) that may be present in the water. Fluoride is then added to reduce cavities. Next, the water chemistry is adjusted to reduce corrosion of lead and copper from home plumbing. Last, we add mono-chloramine, a mild and long-lasting disinfectant combining chlorine and ammonia, which protects the water while it is in the local pipelines.

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Improvements to the System

MWRA’s Improvements to the Water Supply

2010 marked the 25th anniversary of the MWRA. In that time, MWRA and our community partners have made improvements to the entire water system: from the watersheds, to the aqueducts and tunnels, to treatment plants and to MWRA and local pipelines. These are the largest investments in the water system since the 1930s. MWRA and our community partners continue to make the necessary investments to maintain and upgrade our facilities. Take a look at our 25th Anniversary Report [PDF] on

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2010 Test Results

Tests Before Treatment

Test results show few contaminants are found in the reservoir water. The few that are found are in very small amounts, well below EPA's standards. Turbidity (or cloudiness of the water) is one measure of overall water quality. There are two standards for turbidity: all water must be below 5 NTU (Nephelometric Turbidity Units) and can only be above 1 NTU if it does not interfere with effective disinfection. MWRA met both of these standards. Typical levels at Wachusett Reservoir are 0.4 NTU and were below the 1 NTU 99.99% of the time. The highest level was 1.69 NTU, but this did not interfere with effective disinfection. MWRA also tests reservoir water for pathogens such as fecal coliform, bacteria, viruses, and the parasites Cryptosporidum and Giardia. They can enter the water from animal or human waste. All test results were well within state and federal testing and treatment standards.

Test Results - After Treatment

EPA and state regulations require many water quality tests after treatment to check the water you are drinking. MWRA conducts tens of thousands of tests per year on over 120 contaminants. A complete list is available on For results on your local water supply, please see your community's letter. The only contaminants found are listed below, and all levels met EPA's standards. The bottom line is that the water quality is excellent.

Test Results After Treatment
The only contaminants found are listed below and all levels met EPA's standards. The bottom line is that the water quality is excellent.
(We found) Detected
Range of
How it gets in the water
Common mineral in nature
Water disinfectant
Additive for dental health
Nitrate ^ ppm
Atmospheric deposition
Nitrite ^
Byproduct of water disinfection
Byproduct of water disinfection


Byproduct of water disinfection


Byproduct of water disinfection
KEY: MCL=Maximum Contaminant Level - The highest level of a contaminant allowed in water. MCLs are set as close to the MCLGs as feasible using the best available technology. MCLG=Maximum Contaminant Level Goal - The level of contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety. MRDL=Maximum Residual Disinfectant Level. The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants. MRDLG=Maximum Residual Disinfectant Level Goal. The level of a drinking water disinfectant below which there is no known or expected health risk. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contamination. ppm=parts per million ppb=parts per billion nd=not detected ns=no standard ^As required by DEP, the maximum result is reported for nitrite, not the average.

Tests in Community Pipes

MWRA and local water departments test 300 to 500 water samples each week for total coliform bacteria. Total coliform bacteria can come from the intestines of warm-blooded animals, or can be found in soil, plants, or other places. Most of the time, they are not harmful. However, their presence could signal that harmful bacteria from fecal waste may be there as well. The EPA requires that no more than 5% of the samples in a month may be positive. If a water sample does test positive, we run more specific tests for E.coli, which is a bacteria found in human and animal fecal waste and may cause illness.

Total Coliform Results
Highest % of positive samples and month
Violation of EPA's 5% Limit?
2.5% (May)
4.3% (August)
0.7% (May)
1.1% (August)
1.9% (March)
2.6% (November)
1.7% (May)
7.0% (November)
3.1% (October)
0.8% (August)

The table reports test results from 30 communities that receive all of their water from MWRA. Total coliforms were found in nine communities. No E. coli was found in any MWRA community in 2010. *Residents of Somerville should read their community letter for more information.

Research for New Regulations

MWRA has been working with EPA and other researchers to define new national drinking water standards by testing for unregulated contaminants. To better understand the drinking water, MWRA has voluntarily been testing for Cryptosporidium and Giardia prior to treatment. No Cryptosporidium was detected in 2010.

Measurement Units
cysts per 100L
MWRA's disinfection is designed and operated to kill Giardia.
nanograms per liter (ng/l)

* The result is from 2009. The DEP guidance value for NDMA is 10 ng/l.

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What You Need to Know about Lead in Tap Water

MWRA water is lead-free when it leaves the reservoirs. MWRA and local pipes that carry the water to your community are made mostly of iron and steel and do not add lead to the water. However, lead can get into tap water through pipes in your home, your lead service line, lead solder used in plumbing, and some brass fixtures. Corrosion or wearing away of lead-based materials can add lead to tap water, especially if water sits for a long time in the pipes before it is used.

In 1996, MWRA began adding sodium carbonate and carbon dioxide to adjust the water's pH and buffering capacity. This change has made the water less corrosive, thereby reducing the leaching of lead into drinking water. Lead levels found in sample tests of tap water have dropped by over 90 percent since this treatment change.

MWRA Meets Lead Standards in 2010

Under EPA rules, each year MWRA and your local water department must test tap water in a sample of homes that are likely to have high lead levels. These are usually homes with lead service lines or lead solder. The EPA rule requires that 9 out of 10, or 90%, of the sampled homes must have lead levels below the Action Level of 15 parts per billion (ppb).

All 14 sampling rounds over the past seven years have been below the EPA standard. Results for the 450 samples taken in September 2010 are shown in the table. 9 out of 10 houses were below 7.03 ppb, which is below the Action Level of 15 ppb. Some individual communities had more than one home test above the Action Level for lead. If you live in one of these communities, your community's letter will provide you with more information.

September 2010 Lead and Copper Results
Lead (ppb)
90% Value
90% Value
(Target) Action Level

(Ideal Goal) MCLG

# Homes above AL/# Homes Tested
Copper (ppm)
ppb = parts per billion. ppm = parts per million. AL=Action Level-The concentration of a contaminant which, if exceeded, triggers treatment or other requirements which a water system must follow. MCLG=Maximum Contaminant Level Goal The level of contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety.


90th Percentile Lead Levels for
MWRA Communities: 1992-2009
9th percentile graphic


What can I do to reduce exposure to lead in drinking water?

  • Run the tap until after the water feels cold. To save water, fill a pitcher with fresh water and place in the refrigerator for future use.
  • Never use hot water from the faucet for drinking or cooking, especially when making baby formula or other food for infants.
  • Ask your local water department if there are lead service lines leading to your home.
  • Check your plumbing fixtures to see if they are lead-free. Read the labels closely.
  • Test your tap water. Call the MWRA Drinking Water Hotline (617-242-5323) or visit our website for more tips and a list of DEP certified labs that can test your water.
  • Be careful of places you may find lead in or near your home. Paint, soil, dust and some pottery may contain lead.
  • Call the Department of Public Health at 1-800-532-9571 or EPA at 1-800-424-LEAD for health information.

Important Information from EPA about Lead

If present, elevated levels of lead can cause serious health problems, especially for pregnant women and young children. Lead in drinking water is primarily from materials and components associated with service lines and home plumbing. MWRA is responsible for providing high quality drinking water, but cannot control the variety of materials used in plumbing components. If your water has been sitting for several hours, you can minimize the potential for lead exposure by flushing your tap for 30 seconds to 2 minutes before using water for drinking or cooking. If you are concerned about lead in your water, you may wish to have your water tested.

Information on lead in drinking water, testing methods, and steps you can take to minimize exposure is available from the Safe Drinking Water Hotline at 1-800-426-4791 or

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Important Information from EPA and DEP

Drinking Water and People with Weakened Immune Systems

Some people may be more vulnerable to contaminants in drinking water than the general population. Immuno-compromised persons such as persons with cancer undergoing chemotherapy, persons who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly, and infants can be particularly at risk from infections. These people should seek advice about drinking water from their health care providers. EPA/CDC guidelines on appropriate means to lessen the risk of infection by Cryptosporidium and other microbial contaminants are available from the EPA's Safe Drinking Water Hotline (1-800-426-4791).

Contaminants in Bottled Water and Tap Water

Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants.The presence of contaminants does not necessarily indicate that water poses a health risk. More information about contaminants and potential health effects can be obtained by calling the EPA’s Safe Drinking Water Hotline (1-800-426-4791) or MWRA.

In order to ensure that tap water is safe to drink, the Massachusetts DEP and EPA prescribe regulations which limit the amount of certain contaminants in water provided by public water systems. Food and Drug Administration (FDA) and the Massachusetts Department of Public Health regulations establish limits for contaminants in bottled water which must provide the same protection for public health.

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Facts About Sodium

Sodium in water contributes only a small fraction of a person's overall sodium intake (less than 10%). MWRA tests for sodium monthly and the highest level found was 35.3 mg/l (about 9 mg per 8 oz. glass). This would be considered very low sodium by the Food and Drug Administration.

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Information about Cross Connections

Massachusetts DEP recommends the installation of backflow prevention devices for inside and outside hose connections to help protect the water in your home as well as the drinking water system in your town. For more information on cross connections, please call 617-242-5323 or visit

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Information on the May 1st Boil Water Order

On May 1 2010, a major pipe break caused a disruption in water service, and the activation of a back-up water supply. MWRA has several back-up supplies throughout the service area for emergencies. This back-up supply did not meet the high standards of our normal reservoirs, and therefore a precautionary boil water order was needed. After repairs and many tests, normal water service was back within 72 hours. If MWRA were to have another emergency, you would be notified via radio, television, newspapers, state and local government, health officials and MWRA.

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Water Conservation

Wasting water can add up quickly. On average, each person uses about 65 gallons of water each day. More efficient water use can reduce the impact on the water supply and on your wallet. For ways to make your home and your habits more water efficient, contact the MWRA at 617-242-SAVE or visit our web site for tips on saving water indoors and in your backyard.

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Where to Go for More Information

Web Sites and Telephone Numbers
Mass. Department of Conservation and Recreation
Source Water Assessment and Protection Reports
Information on Water Conservation

Public Meetings
Water Supply Citizens Advisory Committee

Contact Us

If you have questions or comments about this report, please contact us. Call (617) 242-5323, e-mail, or write to: MWRA, Charlestown Navy Yard, Building 39, Boston, MA 02129.

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Additional Information from Your City or Town Water Department

Read your community letter [PDF] for important information about your water from your city or town water department.

Fully Supplied Communities
These communities receive all of their drinking water from MWRA.
The water is treated at the Carroll Water Treatment Plant
and transmitted via the MetroWest Tunnel.
Lexington Nahant Somerville
Lynnfield W.D. Newton Southborough
Boston Norwood Stoneham
Brookline Quincy Swampscott
Chelsea Reading Waltham
Everett Revere Watertown
Saugus Weston


Partially Supplied Communities
These communities receive some of their drinking water from MWRA.
The MWRA water is treated at the Carroll Water Treatment Plant
and transmitted via the MetroWest Tunnel.
Canton Northborough Winchester
Residents of Peabody, Stoughton and Wellesley: please contact your local water department for your report.

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Updated June 9, 2011