Frozen water is 9% lighter than regular water. That is the reason ice floats.
BWSC owns and operates a system for the distribution of potable water to approximately 88,000 active accounts throughout the City of Boston. This includes residents, schools and universities, hospitals, businesses, industries, and private and public institutions. In addition to the City's resident population of about 590,000, the daytime population nearly doubles each day by commuting workers and students, shoppers, tourists, conventioneers, hospital patients and visitors.
BWSC purchases finished water (fluoridated and disinfected) from the Massachusetts Water Resources Authority (MWRA) through 29 active metered connections located at various delivery points. The MWRA obtains its water supply from the Quabbin Reservoir, the Wachusett Reservoir and the Ware River which have a combined capacity of approximately 490 billion gallons. The Quabbin Reservoir, which is located 65 miles west of Boston, has an elevation of approximately 530 feet above the mean elevation of the City. This elevation differential creates a natural gravitational flow through most of the MWRA's waterworks system and thereby eliminates the need to pump water to BWSC's system.
The water system has been designed with redundant capacity to support most of the major distribution lines. This redundancy permits required maintenance work on discrete parts of the system without impairing the ability to provide continuous service throughout the City. The water system consists of approximately 1,018 linear miles of pipe which range in size from 4 inches to 48 inches, including 13,184 hydrants and 17,193 valves. In addition, there are four major service networks: Southern Low Service which serves the City Proper, South Boston and parts of Roxbury, Northern Low Service which serves Allston, Charlestown and East Boston, Southern High Service which serves Brighton, Dorchester, Hyde Park, Roslindale, part of Jamaica Plain, parts of Roxbury and parts of West Roxbury, and the Southern Extra-High Service which serves portions of Jamaica Plain and portions of West Roxbury and Hyde Park. An additional small area of the Orient Heights section of East Boston is served by a single connection to the MWRA Northern High Service System. Approximately 90% of the water consumed in the City is delivered through the Southern Low and Southern High Services.
BWSC follows a systematic renewal and replacement program by replacing older cast iron water pipe and rehabilitating pipe through a process of cleaning and cement lining. A minimum of 17 miles of pipe is included in each year's capital program. This program is expected to continue until the year 2010. Currently, BWSC is in the process of reassessing its entire water distribution system and operational needs through a new Water Distribution Study that is expected to be completed in early 2010.
Through aggressive leak detection and repair, and progressive metering programs, BWSC continues to reduce its unbilled and unaccounted-for-water. These programs have resulted in a reduction in unbilled water by approximately 82% from 70 mgd (millions of gallons a day) in Fiscal Year 1977 to 6.99 mgd in Fiscal Year 2008. Unbilled water is the difference between water purchased from MWRA and water sold to customers. Of the 12.5 mgd of unbilled water in 2007, it was determined that this water was used public purposes such as for fire fighting and street sweeping. BWSC continues to provide a leakage survey of the entire system each year. Leaks are repaired on an immediate basis.
Several meter programs have been initiated by BWSC. The first included meter downsizing which involves the replacement of large meters with smaller meters. Smaller meters are more effective in registering low flows, thus increasing billed water.
The second meter program involved the city-wide installation of SmartRead. SmartRead effectively reads meters by radio frequency, thereby allowing instantaneous readings of meters and eliminating estimated reading. SmartRead also allows BWSC to promptly identify accounts that may be registering in a manner not consistent with historical consumption. This program was completed in 2004 and virtually all BWSC's approximately 88,000 accounts have SmartRead installed.