Tapping into the Source City of Cambridge - Water Supply

Since the mid-1800s, the Cambridge Water Department (CWD) has provided a safe, adequate, and uninterrupted supply of the highest quality water to Cambridge residents, businesses, and universities. Through prevention initiatives such as lead pipe replacement and corrosion control programs, on-site rapid water quality testing capabilities, and watershed protection programs, the CWD has not only taken steps to protect the sources of Cambridge’s drinking water, but also to minimize the risk of lead contamination from customers’ plumbing systems.

According to the Massachusetts Department of Public Health, Cambridge is not high-risk for childhood lead poisoning. Fewer than 2% of tested Cambridge kids had elevated blood lead levels in 2014, the most recent year for which data is available. Throughout the state, the biggest source of exposure is lead paint, not drinking water. For Cambridge residents concerned about having lead water service pipes, the CWD can determine the composition of the pipes and/or provide free lead water test kits.

CWD will assist Cambridge residents concerned about having lead water service pipes by determining the composition of the pipes, and/or providing free lead water test kits.

Additionally, since 1993, the CWD has conducted annual testing for lead in the Cambridge public schools. When lead levels were close to or above action levels (15 parts per billion), the typical action is removing or replacing the drinking water bubblers or fountains.

From Source to Tap: Ensuring Water Quality

In 1991, the Environmental Protection Agency (EPA) put into law the Lead and Copper Rule (LCR) to optimize the control of lead and copper contamination from household plumbing. However, even prior the LCR’s inception, Cambridge took steps to minimize the possibility of lead entering drinking water. To help keep lead levels in the drinking water as low as possible, the CWD only purchases fittings with less than 0.25% lead content by weight. The CWD also has both a corrosion control program and a lead water pipe replacement program.

Cambridge’s “raw source” drinking water comes from our two reservoirs, Hobbs Brook and Stony Brook, and contains no detectable levels of lead. Lead in tap water typically comes from faucets, household plumbing, lead water services (the pipes that connect the water main under the street to the pipes in a building), or any fittings or fixtures made with lead content, like brass.

Cambridge's two upland reservoirs, the Hobbs Brook Reservoir in Lincoln, Lexington, and Waltham, and the Stony Brook Reservoir in Weston and Waltham, feed "raw" water to Fresh Pond.

Lead Pipe Replacement Program

Cambridge’s lead pipe replacement program encourages the replacement of lead water service lines in the public rights-of-way at no cost to the property owner, while the corrosion control program optimizes the pH of our water, thereby minimizing the introduction of lead or copper from pipes or fittings. The pipe entering a building is called a “water service” and can range in size from ¾” to 2” in diameter. The materials can be brass, steel, lead, lead-lined, or copper. Since the late 1960s, the CWD has required the installation of copper water service lines. These programs have been very effective. In 2014, the lead levels tested in 60 households throughout the City showed levels at 5 parts per billion (in the 90th percentile) at the tap (the EPA action level is greater than 15 parts per billion). Since the beginning of the lead and copper rule (1991), Cambridge water has always been in EPA compliance (below the action level).

As mentioned earlier, any Cambridge resident concerned about having a lead water service pipe can contact the CWD to determine composition of their water pipes. Additionally, free water test kits are available for lead testing for Cambridge residents. Water quality testing for any reason is also available upon request. Any residents with concerns about lead in drinking water are encouraged to flush standing water in their plumbing by running cold water before drinking or using for food preparation.

Certified Testing Lab

To further protect Cambridge’s water supply, the CWD has a certified microbiology and chemistry laboratory on site, allowing for extensive and rapid response water quality testing. The lab performs both regulatory and process control sampling and analysis, totaling over 60,000 tests per year. Since 2008, the CWD has been proactively conducting biannual non-mandated testing for pharmaceuticals and personal care products that includes over 80 compounds. In most cases, Cambridge’s water meets and exceeds all regulations and guidelines, including those for lead and copper levels, trihalomethane (THM) disinfection byproducts, and disinfection doses.

CWD operates a 2,500 square foot laboratory that is responsible for providing lab services, both chemical and biological. The laboratory is fully equipped with the traditional instrumentation and more specialized equipment for micro-bacteriological testing, metals analysis, and organic analysis.

Water Distribution System

The City’s comprehensive Water Main Replacement Program aims to replace all of the old unlined cast iron water mains with cement-lined ductile iron pipe. Through collaboration with the Department of Public Works, the City has been replacing over two miles of pipe per year.

Cambridge’s transmission and distribution system consist of 180 miles of underground pipes ranging in size from 6” to 63” in diameter, more than 4,500 valves, 1,700 hydrants, and 14,000 water services. The system provides water to over 105,000 residents.

The CWD uses brass water works materials containing less than 0.25% lead content by weight. Examples of these materials include water meters, couplings, and sidewalk shutoff valves.

How is Your Water Treated?

Before water is delivered to your home or business, source waters of the Cambridge reservoir system undergo extensive treatment at the Walter J. Sullivan Water Purification Facility at Fresh Pond Reservation. The water is treated to exceed all local, state, and federal drinking water standards.

The Walter J. Sullivan Water Purification Facility at Fresh Pond
  1. Pretreatment: The first steps in the treatment process combine pre-oxidation with ozone, coagulation and dissolved air flotation (DAF) to remove manganese, natural color, sediment and particles, algae, protozoa, viruses and bacteria.
  2. Ozone Disinfection: Fine bubbles of ozone are dissolved into the water to kill bacteria, viruses, and protozoa.
  3. Filtration: The water passes through granular activated carbon (GAC) to remove organic compounds. Filtration also acts as a “polishing step” to remove additional particles, color and protozoa.
  4. Disinfection: Free Residual Chlorine is used to provide the second step of disinfection for redundancy in the overall process and monochloramine is used to maintain a disinfectant residual throughout the distribution system.
  5. Post Treatment: The pH of the water is adjusted for corrosion control and fluoride is added for dental health.

The CWD’s state-certified laboratory continuously monitors the effectiveness of the treatment process and makes adjustments to ensure the highest quality water.

Lead Exposure Risk: Paint vs Water

According to the Massachusetts Department of Public Health, Cambridge is not a high-risk community for childhood lead poisoning. Of the nearly 2,400 Cambridge children tested for lead in 2014, five had elevated blood lead levels (10-24 µg/dl) and no child met the criteria for lead poisoning (> 25 ug/dl).

While the current national discussion is focused on lead exposure from drinking water, the great majority of lead poisoning cases in the Massachusetts are linked to lead paint in older homes. To protect children from lead poisoning, the Massachusetts Lead Law requires the removal or covering of lead paint hazards in pre-1978 homes where children under 6 live. In Cambridge, 87% of housing units were built prior to the 1978 ban on lead paint.

Older homes have lead paint on the inside and the outside of the building. When old paint cracks and peels, it creates lead dust. Lead dust can enter a child’s body when he puts his hands and toys in his mouth. Young children are especially vulnerable during home renovation projects that can disturb lead paint and generate substantial amounts of lead dust.

In addition to lead paint, children are also susceptible to lead in the soil or perhaps a family member who inadvertently brings home lead dust from their worksite (e.g., house painting job, auto body shop), and certain imported spices.

In addition, a 2008 EPA law requires lead-safe work practices for firms performing renovation, repair, and painting projects that disturb lead-based paint in pre-1978 homes, child care facilities, and preschools.

In short, the best approach to reducing lead exposure in young children in Cambridge is to focus on the largest source of lead exposure—lead paint.

Could What Happened in Flint Happen in Cambridge?

In Flint, the water source was changed and treatment was not adjusted effectively. The new source contained high levels of microbial contamination, so larger amounts of disinfectants were used to treat the water, which resulted in the formation of disinfection byproducts and water quality violations. Flint’s effective corrosion control was not used to treat the new water source, thereby causing the release of lead from household plumbing systems.

Cambridge strictly regulates its water for disinfection byproducts and organic removal. The City applies corrosion control treatment, including maintaining a stable, slightly alkaline pH.

While some water pipes, fittings, and fixtures in Cambridge homes do contain lead, the CWD has detected only tiny amounts of copper and lead in the many water tests it conducts every year for residents. These levels are well below the EPA guidelines. In short, your water is safe to drink.

The Cambridge Water Department: a History of Quality

The CWD’s mission is to provide a safe, adequate, and uninterrupted supply of the highest quality water to its citizens. The City purchased its water system in the mid-1800s, expanded the system in the late 1800s and early 1900s to add the Hobbs Brook and Stony Brook Reservoirs, and then built a 7-mile conduit to bring water to Fresh Pond from those “upcountry” reservoirs. The first water treatment plant came online in 1923 and was replaced in 2001.

Images from the former Water Treatment Facility replaced in 2001 (Photo Credit: Gaylen Morgan)

Today, the Cambridge watershed is 24 square miles, consisting of the Fresh Pond, Hobbs Brook, and Stony Brook Reservoirs, two dams, three gatehouses, and 12 United States Geological Survey certified gauging stations. The stations monitor flows, basic water chemistry, and reservoir elevations. Because Cambridge owns and operates its water system and has established an “enterprise fund” for the water department, the water rates pay for all of the operating, capital, and debt service of the CWD, and all monies are dedicated to the water system.

The City of Cambridge gets its drinking water from a 24 square mile watershed located in the Towns of Lincoln, Lexington, and Weston and the City of Waltham. Cambridge owns and maintains lands and infrastructure to better manage water quantity and quality brought everyday (via gravity) to the Fresh Pond Reservoir in Cambridge.

Sources of Cambridge's Drinking Water

The Cambridge Water System extends across four towns and includes four bodies of water. The Hobbs Brook Upper Reservoir flows into the Hobbs Brook Lower Reservoir and connects with the Stony Brook Reservoir. The water then flows to the Fresh Pond Reservoir through an underground aqueduct. The Stony Brook Reservoir watershed extends from Weston north into the Town of Lincoln. The watershed for the Hobbs Brook Reservoirs includes areas of Waltham, Lexington, and Lincoln. The watershed for the Fresh Pond Reservoir is completely within the City of Cambridge. Storm drainage modifications were implemented to divert street runoff away from Fresh Pond Reservoir. The contributing watershed area is the first step in a multi-barrier program to protect our drinking water. The combined capacity of the Hobbs Brook and Stony Brook reservoir system is 3.1 billion gallons; an additional 1.3 billion gallons of water is stored in Fresh Pond Reservoir.

Fresh Pond Reservation consists of 162 acres of open space surrounding and protecting the 155 acre Fresh Pond Reservoir. Fresh Pond Reservoir is a vital part of Cambridge's drinking water supply system.

Our water supply is backed up by interconnections to the Massachusetts Water Resources Authority (MWRA) system.

Water Source Protection Program

In 2011, the Watershed Division of the CWD updated its comprehensive Source Water Protection Program. The major components of the program, to ensure a continuous supply of high quality water, include the following:

  1. Extensive monitoring: sampling and analysis of water chemistry.
  2. Hazardous materials emergency response planning: reducing the potential for contamination in the watersheds.
  3. Partnership development: building relationship swith other parties in the watershed with common goals.
  4. Proactive site review and monitoring: minimizing potential impacts on the watershed from construction.
  5. Stormwater management: insuring that Best Management Practices are implemented.
  6. Community outreach: engaging in public relations and education.

The Cambridge Water Department will continue its mission of providing the highest quality water to Cambridge residents, businesses, and universities well into the future.

Publication of the City of Cambridge

City Manager's Office

795 Massachusetts Avenue

Cambridge, MA 02139


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