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Water Quality Monitoring

Monitoring of the imported Hetch Hetchy supply is conducted by the SFPUC.  The SFPUC treats the Hetch Hetchy supply by lime addition at Rock River for corrosion control and chlorination at Tesla Portal for disinfection, but does not filter prior to delivery.  Bay Area reservoir waters receive complete treatment of filtration and disinfection at either the Sunol or the Harry Tracy filtration plants.  Filtered water from these treatment plants may be co-mingled with unfiltered Hetch Hetchy water in bay area transmission pipelines.  The SFPUC and the agencies that serve water from the SFPUC Hetch Hetchy supply previously applied for and were granted filtration avoidance for that supply under the Federal regulations.  The Department adopted revisions to the Surface Water Treatment Regulations ("SWTR"), Chapter 17, Title 22, Califomia Code of Regulations that include criteria and requirements for avoiding filtration for public water systems that serve water from a surface water supply.  With the adoption of the revisions, which became effective July 8, 1998, those public water systems serving water from the Hetch Hetchy supply must demonstrate to the Department of Health Services that the supply meets the state's criteria for filtration avoidance.  In accordance with Citation Order Number 02-051 issued to the City of Redwood City on April 2, 1997, within 120 days of the effective date of the amendments to the state SWTR, the City applied to the Department for certification that the Hetch Hetchy supply it distributes will be in compliance with the state criteria for filtration avoidance.

The City routinely monitors water quality within the distribution system.  The water quality meets primary and secondary drinking water standards.  The City has had no recent bacteriological problems.  While the City should be able to meet the recently adopted 80 µg/L total trihalomethanes ("TTHM") standard of the Enhanced Surface Water Treatment Regulation, the City in association with the SFPUC should work to reduce TTHM levels.  The lead action level was exceeded in consumer tap samples taken in 1992 and 1993.  The City is continuing lead and copper tap sampling, water quality parameter monitoring, and public education as required by the Lead and Copper Rule. The City has not exceeded the Action Level for lead and copper since the testing program in 1993.  Should the City exceed the lead action level after the implementation of regional treatment, the City will have to install optimal corrosion control treatment on its own.

  • Bacteriological Quality.  The City has an approved bacteriological sample plan, dated August 2000, that makes use of a series of dedicated sampling stations located at key points within the distribution system. City personnel routinely collect 23 samples per week for bacteriological analysis. The 23 samples are selected from 28 sites designated for even weeks and 28 sites designated for odd weeks.
  • Disinfection Residual.  The City collects samples for free chlorine residual monitoring at the same time and same location as the bacteriological monitoring as required by the state Surface Water Treatment Regulation.
  • General Physical.  The City collects 24 samples per month for color, odor, turbidity, pH, and temperature measurements.
  • Trihalomethanes.  As required, the City collects four samples from the distribution system per quarter for trihalomethane monitoring.  Analysis is performed at the SFPUC certified laboratory in Millbrae.
  • Asbestos.  Due to the presence of asbestos-cement pipe, the system is vulnerable to asbestos contamination from leaching.  The City submitted sample test results to the DOHS demonstrating compliance with state requirements and was granted permission to reduce the testing cycle to once every nine years.
  • Lead and Copper.  Under the state Lead and Copper Regulation, the City of Redwood City is a large-size water system.  This designation requires the City to perform corrosion control treatment steps.  Since the City obtains all of the drinking water from the SFPUC and provides no further treatment, the City is piggybacking onto the  SFPUC's corrosion control studies.  The City conducted two six-month rounds of initial sampling at consumer taps for lead and copper.  The lead action level was exceeded in both rounds.  The reports are dated December 1992 and May 1993.  The City provides public education materials within the annual water quality report that is distributed to its customers.  The City has performed some water quality parameter monitoring in the past.  The City has an approved sampling plan for lead, copper, and water quality parameter monitoring on file with the Department of Health Services dated November 3, 1998.  During two six-month rounds, ending July 31, 1999, the City conducted monitoring in conjunction with the SFPUC and the other public water systems that serve water from the SFPUC supply.  The City is required to conduct two six-month rounds of lead and copper monitoring at consumer taps, two six-month rounds of water quality parameter monitoring at taps in the distribution system, and bi-weekly water quality parameter monitoring at points of entry to the distribution system.  The water quality samples are to be analyzed for pH and Langelier Index. The SFPUC use the data generated to determine optimal corrosion control treatment appropriate for the SFPUC transmission system.  Should any suburban agency continue to exceed the lead action level after the implementation of regional treatment, the individual agency will have to install optimal corrosion control treatment on its own.
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