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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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