System Overview
The Pawtucket Water Supply Board (PWSB) is a water supplier that serves a population of over 100,000. The retail service area includes the Cities of Pawtucket and Central Falls and the Valley Falls section of the Town of Cumberland. The PWSB owns and operates the water systems in Pawtucket and Valley Falls, and the City of Central Falls.
The water resources of the PWSB consist of both surface water and groundwater within the Abbott Run watershed, a tributary of the Blackstone River. The watershed lies within the Town of Cumberland in Rhode Island and the Towns of Wrentham, Plainville and Attleboro in Massachusetts. The PWSB owns about 10% of the Abbott Run watershed.
The PWSB has decommissioned its 1938 water treatment facility in Cumberland and has been producing potable water at its new state-of-the-art treatment facility since March 19, 2008.
The new treatment facility includes a new raw water pump station capable of pumping 26 million gallons per day (mg/d) through eight (8) Johnson intake screens. The raw water pump station and the treatment facility have standby power that will support 100% of their loads.
The treatment plant has 4 up-flow clarifiers that will operate at 4,000 gallons per minute (gpm), and 8 filters that operate at 2,000 gpm. The facility is capable of producing up to 25 mg/d. The water treatment processes are (in order): up-flow clarifiers, deep bed granulated/activated carbon filters (6 feet), and ultra-violet (UV) disinfection. Finished water is stored in two tanks: 1.4 mg and 5 mg. The facility has 4 high-lift pumps capable of pumping up to 35 mg/d to the distribution system. All finished water entering the distribution system gets treated with hypochlorite (chlorine), hydrated lime (PH control), fluoride, and orthophosphate (a corrosion inhibitor). Click here if you're interested in reading about orthophosphate (a link to a FAQ page written by the people who supply water to the City of Arlington, VA.)
After treatment, water leaves the pump stations
through a network of 12, 16, 20, 24 and 36 inch diameter water transmission
mains to all parts of the PWSB system, much like the spokes on a wheel. Smaller
distribution mains distribute the water to all areas of the PWSB system. In
all, there are approximately 240 miles of transmission and distribution water
mains in the PWSB system.
The pipelines installed before 1958 are
constructed of unlined cast iron. Pipe lined with cement was not manufactured
until after 1958. These unprotected older mains are subject to rusting on the
inner surface, resulting in rust particles settling to the bottom of the main
and causing discolored water when the flow of water is disturbed. The PWSB has
accelerated the program of renovating these older mains by cleaning them to
bare metal and applying a cement coating to prevent further rust problems.
Mains older than 1920 and all mains less than 6" are being replaced. Over 100
miles of main renovation and replacements have been completed, with
approximately 100 miles of main scheduled for renovation by 2012 to complete
the system.
There are a number of appurtenances within the distribution
system. The system has approximately 1700 fire hydrants and 6,000 line valves.
These are replaced as needed with the main renovation program.
The
distribution storage facility of the PWSB is comprised of two storage tanks.
Earth Tech will be adding 5 million gallons of additional storage at the new
water treatment plant. The two tanks on the west side of the system are
connected to the transmission and distribution grid through two 24 inch
diameter water lines. The original storage structure at this location was
constructed in the 1870s as an open air 22 million gallon reservoir and was
replaced with a 10 million gallon tank in 1994.
There are approximately
22,200 customer service connections in the PWSB distribution
system. Each service connection has a service line, curb stop
and meter. In the PWSB system, the PWSB owns and is responsible for the repair
and replacement of the portion of the service line within the public right of
way, generally up to and including the curb stop. (The PWSB has partnered with
Aquarion Corporation to provide the option of a customer protection plan for
the portion of the service owned by the customer.) The PWSB
owns all of the water meters which are two inches or smaller.
The PWSB has a staff of 53
employees that perform all of the operations and maintenance for the
organization. The PWSB owns and operates its own fleet of vehicles.
The
PWSB has a Board of Directors and is a semi-autonomous extension of the City of
Pawtucket. It is an enterprise fund agency; no subsidization exists between the
City and the PWSB. Rates are determined by the PWSB Board and are subject to
the approval of the RI Public Utilities Commission (PUC) after a thorough
examination and review by the Division of the PUC and the State Attorney
General's office which acts as an advocate for the rate payer. The PUC has
approved rates for pay-as-you-go funds for capital projects, and for debt
service for the financing of the major capital projects.
Financing for
the water treatment facilities and the water main projects is obtained through
the State of Rhode Island Clean Water Finance Agency. The agency provides
subsidized funding through the federal State Revolving Fund Loan Program (SRF)
for drinking water. The SRF is administered through the State Department of
Health.