Water Main Flushing in Various Communities
Weston & Sampson completed one of the first unidirectional flushing programs in 1989 for the Town of Winchester, Massachusetts. We have also completed unidirectional flushing programs in Chelsea, Dracut, Lexington, Pembroke, and Quincy, Massachusetts.
Unidirectional flushing, a controlled method for flushing water mains, is used in the most successful flushing programs. Water in the mains is allowed to flow in one direction only, from larger mains to smaller mains. The flow of water is controlled by closing water gate valves according to a predetermined plan. The closing of gates results in higher velocities of water being flushed through the mains and, therefore, more scouring potential to flush out sediment and debris.
A flushing program is a helpful tool in maintaining a distribution system. The largest benefit to flushing is that it promotes an increase in chlorine residual to control bacterial growth. Other benefits to customers include fewer occurrences of rusty water, taste, and odor. A unidirectional flushing program is also an excellent tool to search for closed valves in the distribution system. Following a successful flushing program, there are fewer customer complaints, which allows water departments to spend more time at other important tasks.
Residents in several areas of Quincy experienced poor water quality due to the location of the neighborhoods on unlined transmission mains a long distance from the Massachusetts Water Resources Authority (MWRA) meters. The Department of Public Works (DPW), in conjunction with Weston & Sampson, implemented an annual unidirectional flushing program in these areas in an attempt to reduce water quality complaints until these unlined transmission mains could be replaced or cleaned and lined. These flushing programs have been successful in improving water quality as well as locating closed or broken gate valves in the city.
In 1997, the Town of Lexington selected Weston & Sampson to develop a flushing program for its water distribution system. Lexington is an MWRA community located on the Northern Extra High Service Area and receives its water supply from four meters located at the southern end of the system.
After a review of the existing water distribution, the system was broken into 31 individual mini-systems, each being isolated from the rest of the system by valve operation. We recommended water main flushing within one mini-system at a time, starting nearest to the MWRA supply points and proceeding toward the system’s extremities.
The flushing program report included our recommendations for sequencing of flushing, water velocity and flow rates, and necessary valve operation associated with flushing activities. The report also contained general considerations about flushing and cleaning water mains and an opinion of probable costs.
Weston & Sampson developed a hydraulic model for a tank siting study, which was used to develop a comprehensive water flushing program. The purpose of the flushing program was to improve the water quality within the system.
Weston & Sampson developed a comprehensive unidirectional water flushing program for the Town of Winchester. To control the flow and direction of the flushing, isolated water main segments were created by the closing and opening of gate valves in the system. The program was carried out by DPW personnel and resulted in improved water quality.
MWRA Community Technical Assistance Program
The MWRA was funding $25 million annually for the Local Pipeline Assistance Program (LPAP), a 10-year interest-free loan program for rehabilitation of community water distribution systems. This program was a key part of the MWRA’s Integrated Water Supply Improvement Program to improve the water quality delivered to consumers. To qualify for LPAP funding, communities had to demonstrate to the MWRA that they followed the principles of good water distribution system management.
To help communities comply with its requirements, the MWRA established the Community Technical Assistance Program (CTAP). Weston & Sampson was selected exclusively for the CTAP with the goal that we work closely with member communities to achieve compliance.
Under the program, Weston & Sampson helped communities implement the following key components of a water distribution system management program:
Distribution System Improvements
- Identification of areas with water quality problems
- Preparation of distribution base maps
- Prioritization of water main rehabilitation programs