To ensure the effective collection and transport of our customers’ wastewater to the MWRA regional sewer system, to protect the public’s health and safety by minimizing sewer system backups and overflows, and to remove infiltration and inflow from the sewer system.
Weymouth, Massachusetts is primarily a residential suburb located 12 miles southeast of Boston. Weymouth has a total area of 21.61 square miles and a population of approximately 55,000 people. Weymouth is surrounded by several towns, two rivers, and a bay. To the north, Weymouth is bordered by Hingham Bay and the Fore & Back Rivers, to the south by Abington and Rockland, to the east by Hingham and to the west by Braintree and Holbrook.
The Town of Weymouth has approximately 1,054,975 linear feet of gravity sewer pipe, excluding building service connections, and approximately 4,880 sanitary sewer manholes. Gravity sewer pipe sizes range from 4-inches to 42-inches in diameter. The town has approximately 600,000 linear feet of building connections and approximately 42,600 linear feet of sewer force mains and pressure sewers that range from 4-inches to 18-inches in diameter. The Town is divided in to six interceptor sub-basins, each containing smaller sub-areas. The six interceptor sub-basins are Lower Central, Old Swamp River, Southeast, Landing Interceptor, Mill River and North Weymouth.
The majority of the Weymouth sewer system was built between 1947 and 1980. This system contains approximately 320 miles of sewer lines that are operated and maintained by the Sewer Division. Currently, the wastewater flow that is produced in the town’s system goes into the MWRA system at 11 different locations. Once the flow enters into the MWRA system, it travels through Nut Island and then continues onto the Deer Island Wastewater Treatment Plant. The Weymouth sewer system contains 11 pump stations, 17 ejector stations, 3 submersible stations and more than 5,000 manholes. Approximately 97% of the Town is sewered, while the remaining portion is on septic systems. The Weymouth DPW estimates that in 2015 there were only 468 homes not connected to their sewer system. Based on an average of 3.5 people per home, this would represent a total of 1,638 people that are unsewered.
The size of the sewer line that gets installed in the system is based upon the amount of flow the line will receive. The more flow the line receives, the larger the line must be. The flow that enters the line is based upon the town population. As the population increases, the flow that enters the lines increases. Most of the town’s sewer lines were installed as the town was being developed. With the tremendous town’s growth over the past half-century, the existing sewer system has certain areas unable to handle the additional demands. The Insufficient capacity of these lines, results in backups and overflows, which present a public health hazard and compromise Weymouth’s sensitive ecosystem.
The Weymouth DPW began working on this problem in 1985, when it commissioned an Infiltration/Inflow (I/I) analysis to identify if rainwater and groundwater material were entering into the sewer system. The results of the analysis showed that the town had a larger amount of I/I (rainwater and groundwater) entering it’s system. Between 1986 and 1993 the town worked hard at eliminating the major I/I problem and by 1994, the Town had completed removing the major identified I/I sources from the sanitary sewer.
Despite these efforts, the sewer system was still greatly over-taxed. In 1998, the DPW and the DEP signed a consent order calling for a reduction in sewer demand, tying any new demand for sewer capacity into a corresponding reduction in I/I. At the same time, the DPW initiated a multi-year, comprehensive sewer repair program aimed at preventing millions of gallons a day from entering the system while addressing sewer capacity deficiencies.
This project was known as the Town of Weymouth Capital Improvement Program (CIP), a sewer system improvement project.
The recommended CIP included construction of a new pump station on Libbey Industrial Parkway and a new force main to divert flow back into the Lower Central Interceptor where the existing interceptor now crosses Washington Street; conversion of the existing pressure sewer on Pleasant Street and between Pleasant Street and the Route 3/Route 18 Cloverleaf to a gravity sewer; and construction of a new gravity sewer in the Landing to divert flow from Commercial Street to the MWRA sewer at Smelt Brook.
The CIP was designed to alleviate the chronic sanitary sewer overflows that Weymouth’s existing wastewater collection system experiences. The CIP was implemented under five contracts: Contract No. 1 – Lower Central Interceptor Sewer Replacement-Winter Street to Essex Street; Contract No. 2 – Lower Central Interceptor Sewer Replacement – Commercial Street to Old Country Way; Contract No. 3 – Pump Station and Influent Gravity Sewer; Contract No. 4 – Force Main; and Contract No. 5-Landing Area Gravity Sewer.
In the last several years several field investigative programs have been completed for the Town of Weymouth. These programs are continuous flow monitoring, flow isolation; groundwater monitoring, rainfall monitoring, manhole physical survey, television inspection and sewer cleaning, smoke testing, dye testing and dyed water flooding.
The objective of the town’s I/I investigations is to assess the quantity of I/I that is entering Weymouth’s sanitary sewer system in the Lower Central, Old Swamp River, Southeast, Landing Interceptor, Mill River and North Weymouth sub-basins.