HomeMy WebLinkAboutStaff Report 168-08TO:
FROM:
HONO~4BLE C!TY COUNCIL
C!TY MANAGER DEPARTMENT: UTiL!TIES
DATE:MARCH !7, 2008 CMR: !68:08
SUBJECT:PALO ALTO WATER MAIN DISTPdBUTiON SYSTEM FLUSHING
PROGRAM - STATL~S R_EPORT
This is an information report and no Council action is required.
BACKGROUND
Historically, the City of Palo Alto and approximately 85 percent of water utilities in the United
States use main flushing to improve water quality for water customers. Water utilities may flush
distribution mains for a variety of reasons: corrosion control, sediment removal, taste and odor
control, contro! of coIor, to reduce turbidity, to reduce chlorine residuals, to reduce
bacteriological grow@s, or as a response to customer complaints. The main objectives of Palo
Alto’s flushing program are to improve water quality, control bacterial growth and remove built-
up sediment.
Between 1990 and 1993, the Palo Alto Water Utility did not perform an annual main flushing
program because of the drought. During this period, customer water consumption was also
reduced, thereby accelerating sediment build-up in the mains. During 1992, numerous
complaints were received about water quality. At that time, staff took water samples in response
to these calls and found that the reduced water quality was due to the build-up of sediment in the
mains. Also, Fire Department personnel found more sediment in their equipment from the City’s
water system during 1992. Water Operations staff flushed mains every year between 1993 and
2003. Staff did not receive water quality complaints due to sediment buitd-up in the distribution
mains during that period because of the success of" the annual water distribution system flushing
program. Between 2004 and 2006, the water distribution system was not flushed on an annual
basis due to limited staff availability during that period. The water system was flushed in 2007.
The City has reallocated staffing to allow for re-initiation of the armual water flushing program.
CMR: 168:08 Page 1 of 2
DISCUSSION
Beginning April 20, 2008, and continuing tt-o:ough April 26, 2008, the City’s Water Utility
Operations Section will open tire hydrants to flush out sediment that has collected in the mains
during the past year. Flushing of the mains mav cause some slight, but temporary, reduction in
water pressure and possible water discoloration.
Residents will see fire hydrants and blow-off valves opened by staff and used as points to flush-
out the distribution system mains. Water flushed from hydrants and blow-off valves is
dechlorinated and discharged to street surfaces and storm drains, or is used to dean sanitary
sewers. It is not practical to attempt to recapture this water for re-use as litigation, filling
residential swimming pools or other purposes. The water system main flushing map and schedule
wilt be displayed in the Palo Alto Weekly, Palo Alto Daily News, City website, and scrolling
messages on the Midpeninsula Community Media Center (MCMC) community public access
charmels prior to and during the 2008 main flushing program.
ATTACHMENT
A.2008 Water SF stern Flushing Schedule and Map
PREPARED BY:BILL CHAN, Engineer
ROMEL ANTONIO Sr. Project Engineer
ROGER CWIAK,~ WGW Engineerin_,v.~ .Manager
DEPARTMENT HEAD:
CITY MANAGER APPROVAL:
Director of Utilitie~
EMILY HARRISON
Assistant City Manager
CMR: 168:08 Page 2 of 2
ATTACHMENT A