Water Treatment Plant History
The Tewksbury water system began circa 1941 mainly to service the state hospital and the surrounding homes near Long Pond. Remnants of the old pump house can still be seen on Pond Street. As the Town grew and the demand for water increased, new wells were added to meet the demand for water and to start the water system. The original wells were located mainly in the southern section of the Town with two wells located just outside the center of town near the Great Swamp. All of the wells were high production, overburden wells that drew water from the sand and gravel strata from between 50 to 100 feet deep. The underground water, moving in a river-like fashion, travels northeast towards the Merrimack and Shawsheen Rivers and eventually out to the ocean. As the wells aged, reduced water output and increasing iron and manganese levels forced the shutdown of many of the 15 wells that were built in Town. In 1992, the last well house was closed and the Town relied on producing its own water from the new water treatment plant.
The first storage tank stood on Ames Hill and its foundation can still be seen. This old tank has since been replaced by two underground storage tanks, which were built circa 1951 and 1958. Both of these storage tanks are still in use today and each tank can hold up to 500,000 gallons of water. The most visible water storage tank decorates the horizon of the Tewksbury skies towards the northwest. The Astle Street tank (a.k.a. elevated tank) was constructed in 1971 and was just recently refurbished and painted a respectable blue color. The Astle Street tank can store up to 1,000,000 gallons of water. The interesting shape used is called a torus and is designed to trap sediment particles in the bottom round shape and add structural stability. The top of the tank stands 135 feet above the ground level and the overflow pipe is at the same altitude as the Ames Hill storage tanks. The newest tank is the Colonial Street tank, which is partially underground and holds 5 million gallons. Since Tewksbury is remarkably flat the elevated tank design was needed to develop the 'hydraulic head' or water pressure to run the water system. At the base of the tank, the water pressure can reach up to 58 pounds per square inch.
The Tewksbury water system is a large maze of pipes measuring in diameter from as small as 2" to as large as 36". The water distribution system consists of approximately 150 miles of pipe. To help keep this water system clean, annual flushing usually scheduled for the fall is performed where crews from the Water and Sewer Division open water hydrants around Town. When flushing pipes, water from the hydrants can reach heights above 50 feet as the pressure removes sediment and scrubs the pipelines clean. This process can consume over 10 million gallons, but is considered a basic maintenance procedure that all water systems perform on an annual basis.
Since many lower areas have water pressures over 80 pounds per square inch, reducing valves are used to protect household devices, such as water heaters, from experiencing too much water pressure. Please do not remove such devices as they are designed to protect your internal water system.
The Tewksbury Water Treatment Plant was built back in the late 1980s and operates 24 hours a day, 7 days a week with a staff of nine Department of Public Works employees to address the Town's demand for water. The water plant draws water from the Merrimack River, which is considered one of the best raw water sources in the area. The water drawn from the river undergoes many treatment processes that remove particulate matter, disinfects, and polish the water before transmission to the populace. Please find below a brief description of the water plant's capabilities.
- Plant Flow - 7.0 Million Gallons Per Day (MGD).
- Primary Disinfection - Chlorine Dioxide, a powerful disinfectant/oxidant. This chemical is generated on-site and is dosed into the water at about 1 to 2 milligrams per liter (mg/L).
- Secondary Disinfection - Sodium Hypochlorite, bleach is used as a secondary disinfectant to help remove ammonia and oxidize certain forms of manganese. Sodium Hypochlorite is used twice, once in the pretreatment and again in the finished water just as it leaves the plant. The free chlorine dose is controlled at about 0.7 mg/L and the success of this triple disinfectant program is reflected in the zero bacterial detection rate since 1988.
- Rapid mixing/coagulation - Two stages, utilizing vertical shaft radial mixers. The coagulant chemical is aluminum sulfate (alum).
- Flocculation - Two stages, having a total of 15 minutes detention time and utilizing vertical-shaft, axial-flow flocculation.
- Filtration - Four automatic backwash filters (ABF) having a design filtration rate of 2.37 GPM/square foot. Filter media consists of 36 inches of activated carbon over 12 inches of sand. ABF is able to stay in operation while backwashing.
- Corrosion control - pH adjustment using sodium hydroxide (NaOH), followed by an application of a blended zinc orthophosphate corrosion inhibitor.
- Final Disinfection - Sodium Hypochlorite.
- Fluoride source - Hydrofluosilicic acid. Controlled dosage at 1 mg/L (we call it Silly acid).
- Treated water storage - Two 1-million-gallon storage tanks and one 5-million gallon tank.
The water pumped into the system is evaluated and tested every four hours. The facility runs 24 / 7 and is manned by licensed certified operators. Strict rules enforced by the Department of Environmental Protection (DEP) and the Environmental Protection Agency (EPA) require notification of the public if any part of the drinking water regulations are violated. Please click here for the EPA or call. Our water system number is 329-5000. If you have any questions, please feel free to contact us.