| Daly
City's Wells (Groundwater) |
|
The
SFPUC supply is made up from surface water reservoirs.
The term "surface water" refers to water
that is collected at ground level. Wells comprise
what is termed "groundwater", or water that
is stored below the earth's surface. About half of
the water served by the Daly City Water System is
from local wells. There were six wells in active service
during 2001.
During the year 2000, Daly City began a source water
assessment of its local groundwater sources that was
completed in 2001. Groundwater in many ways is a much
more protected source than surface water. We draw
water from an average depth of 300 feet below ground
from a large aquifer known as the Westside Basin that
serves a large portion of the northern San Mateo Peninsula
and extends north to Golden Gate Park in San Francisco.
Because of its protected environment and the consistency
of our monitoring results, our well water is only
required to have a disinfectant added to it prior
to being served in our system.
The disinfectant used is sodium hypochlorite, a concentrated
liquid bleach solution. It is much safer to store
and use than the pressurized containers of pure chlorine
which were used for many years. This type of disinfectant
is much safer for you and the City's staff, who operate
and maintain the system. It should be noted that the
City's wells are checked regularly for bacteriological
levels and the un-chlorinated/untreated well water
is consistently determined to have a rating of "non-detect"
for any coliform organisms. Daly City well water is
blended with San Francisco water and then distributed
throughout the community.
Results from July 2001 nitrate testing showed detected
amounts of nitrate in excess of the MCL of 45 mg/L
(ppm) at Wells #4 (59.0 mg/L) and A Street (52.0 mg/L).
Nitrate is one of the major anions in natural water,
but concentrations can be greatly elevated due to
leaching of nitrogen from fertilizers. While there
are no significant health effects of nitrate levels
in your tap water due to blending, the following information
statement is required because of the elevated findings
in the well water and is not an indicator or statement
of the quality of water distributed to you.
Nitrate:
Nitrate in drinking water at levels above 45 mg/L
is a health risk for infants of less than six months
of age. High nitrate levels in drinking water can
interfere with the capacity of an infant's blood to
carry oxygen, resulting in a serious illness; symptoms
include shortness of breath and blueness of the skin.
High nitrate levels may also affect the ability of
the blood to carry oxygen in other individuals, such
as pregnant women and those with certain specific
enzyme deficiencies. Nitrate levels may rise quickly
for short periods of time because of rainfall or agricultural
activity. If you are caring for an infant, or you
are pregnant, you should ask advice from your health
care provider.
Weekly
Water Sampling by Certified City Water Operators
Daly
City maintains 32 sampling sites located throughout
the community that are tested weekly for microbiological
contaminants. Tests are run by the City's contract
laboratory, Sequoia Laboratory in Redwood City, for
maximum contaminant levels of certain types of bacteria.
Coliforms
Coliforms are bacteria that are naturally present
in the environment and are used as an indicator that
other, potentially harmful, bacteria may be present.
In 2001, certified Water Operators collected 1,300
samples of which there were eight instances of a positive
test for coliform that equates to just 0.62 percent
of all samples taken. Upon re-sampling of the eight
locations, all tests came back negative for coliform,
and at no time did any test detect a presence of fecal
coliform or E. Coli.
Lead
and Copper
Lead in amounts in excess of established action levels
in drinking water can cause delayed physical and/or
mental development in infants and attention span and
learning deficits in children. In adults it can cause
kidney problems and possible high blood pressure.
Because of these concerns the EPA mandated in 1993
that lead and copper monitoring be conducted by all
water systems. Daly City completed the required monitoring
and corrosion study in 1994. The results of the study
were well under any action levels and met all quality
standards.
In 1998, under advisement for the EPA, DHS required
local water systems to complete their studies. A joint
effort was organized by the SFPUC for collection and
analysis by the member agencies.
Since Daly City had previously conducted the study,
an agreement was reached with DHS to do a special
water quality study to determine the aggressiveness
(corrosivity) of our well water and determine ways
to meet the requirements for corrosion control in
our water system. The study was performed in September
1999, and the results of the second Daly City study
showed results were again under any action levels
and met all quality standards.
In December 2001, lead and copper samples were collected
and this third Daly City study showed results remained
under any action levels. The results of the second
and third Daly City studies indicate that the well
water blend with Hetch Hetchy supply provided a buffering
effect, which lowered the corrosivity of the water.
Microbiological
Information
Monitoring
for bacteriological constituents in the distribution
system is required to determine the presence of microbiological
contaminants such as coliforms, fecal coliforms, and
E. Coli.
| Minimum
number of monthly samples |
108
|
| Maximum
number of positive samples allowed (MCL) |
5 |
| Yearly
number of samples taken |
1,300 |
| Highest
monthly number of positive coliform samples |
2 |
| Total
number of positive fecal coliform or E. Coli
samples |
0 |
How
Drinking Water Sources Become Polluted.
The sources of drinking water (both tap and bottled)
include rivers, lakes, streams, ponds, reservoirs,
springs and wells. As water travels over the surface
of the land or through the ground, it dissolves naturally
occurring minerals and in some cases even radioactive
material. Surface waters in particular can be susceptible
to substances resulting from the presence of animals
or human activity. Contaminants that may be present
in source waters include:
Microbial Contaminants
such as viruses and bacteria that may come from septic
systems, agricultural livestock operations and wildlife.
Inorganic
Contaminants such as salts and minerals
which can be naturally occurring or result from urban
stormwater runoff, industrial or domestic wastewater
discharges, oil and gas production, mining or farming.
Organic
Chemical Contaminants including synthetic
and volatile organics which are by-products of industrial
processes and petroleum production and can also come
from septic systems, urban stormwater runoff, agricultural
chemicals such as chemical fertilizers and gas stations.
MTBE,
a gasoline additive, has become a recent water quality
concern. This organic contaminant has rapidly been
made a primary contaminant by DHS and is regularly
monitored. All test results for MTBE in the City's
wells and distribution system have been rated "non-detect".
Radioactive
Contaminants which can be naturally occurring,
or the result of oil and gas production and mining
activities.
Pesticides and Herbicides
may come from a variety of sources such as agriculture,
urban stormwater runoff and residential uses.
Unregulated
Contaminant Monitoring Helps the U.S. EPA
and the California Department of Health Services (DHS)
to determine where certain contaminants occur and
whether the contaminants need to be regulated. During
2000, the SFPUC monitored for twelve unregulated contaminants
including MTBE, perchlorate, herbicides, and pesticides.
These contaminants were not detected in any of Daly
City's or SFPUC's supplies.
How
Do We Know Our Water is Safe?
In
order to insure that tap water is safe to drink, the
U.S. EPA and the California Department of Health Services
(Department) prescribe regulations, which limit the
amount of certain contaminants in water provided by
public water systems. Department regulations also
establish limits for contaminants in bottled water
that must provide the same protection for public health.
Drinking
water, including bottled water, may reasonably be
expected to contain at least small amounts of some
contaminants. The presence of contaminants does not
necessarily indicate that water poses a health risk.
| For
more information about contaminants and potential
health effects, call the U.S. EPA's Safe Drinking
Water Hotline at
1-800-426-4791. |
Some
people may be more vulnerable to contaminants in drinking
water than the general population. Immuno-compromised
persons such as persons with cancer undergoing chemotherapy,
persons who have undergone organ transplants, people
with HIV/AIDS or other immune system disorders, some
elderly, and infants can be particularly at risk from
infections. These people should seek advice about
drinking water from their health care providers. EPA/Centers
for Disease Control guidelines on appropriate means
to lessen the risk of infection by Cryptosporidium
and other microbial contaminants are available from
the Safe Drinking Water Hotline (800-426-4791) or
on the U.S. EPA's website www.epa.gov/safewater/hfacts.html.
Operator
Certification
New
regulations required that in 2002 Water Operators
not only needed a water treatment certificate but
also a distribution certificate. As of December 2001,
Daly City received interim Distribution certification
for all of our Water Operators good until 2005. After
this date, the Operators must take a test to receive
a permanent Distribution certificate. The increased
regulations also include that to maintain certification,
employees must complete 16 to 24 contact hours of
education during a span of two years.
We have always taken pride in technical knowledge
of our Water Operators and water distribution system
crews and, with the increased regulations, staff will
gain a greater educational advantage to better serve
you the customer.
Source
Protection is the primary barrier to water
pollution. A contaminant that does not get into the
water source does not need to be removed. SFPUC maintains
a comprehensive watershed control and management program
to protect source water. The water from Hetch Hetchy
Reservoir in Yosemite National Park is so well protected
that the Hetch Hetchy water supply is one of only
six major water supplies in the country that is exempt
from filtration. SFPUC controls activities on the
watershed lands around their east bay reservoirs,
limiting activities to those compatible with maximum
protection of the water quality.
Daly
City, through proper design, construction, operation,
maintenance and source control monitoring, achieves
the same high level of source protection at the six
active wells. The quality of the water supplied by
local wells is high enough so as to not require further
treatment other than disinfection for your protection.
The City is committed to providing the highest quality,
safe water from its system to our customers.
Water
Treatment is the next protective barrier.
Water from the remote Hetch Hetchy reservoir and our
wells is unfiltered because it meets all state and
federal requirements without filtration. Water from
the other Bay Area watersheds near populated areas
is filtered to meet standards for clarity. All of
our water is disinfected with either chlorine or sodium
hypochlorite (concentrated bleach) to meet state and
federal quality standards.
Effective
Operation & Maintenance
of the distribution system assures that the water
maintains its quality as it travels through the system
to your tap. Minimal chlorine residual is maintained
in the distribution system to prevent any regrowth
of organisms during storage and transmission of the
water as it travels to you. Active flushing of water
mains and rotation of stored water supplies also keeps
the water fresh and limits growth of organisms. Daly
City conducts continuous water quality monitoring
and testing to assure your drinking water is safe
and healthy. Daly City, working with the San Mateo
County Health Dept., maintains an active cross-connection
control program to prevent the intrusion of potentially
harmful materials into the drinking water system.
Cross-connection control is done by isolating hazards
(boilers, cooling towers, fire sprinklers, etc.) from
the drinking water supply by requiring and overseeing
the installation of approved backflow prevention devices,
which are annually inspected and certified by trained
staff to insure their continued effectiveness.
Arsenic
New regulations for reporting arsenic levels have
been established at less than 10 ug/l. Staff has completed
preliminary testing of its groundwater at two local
wells. Current testing standards detect arsenic at
1 ug/l and A Street Well tested at 1.3 ug/l while
Jefferson Well tested non-detect. While results are
below the standard, Daly City will provide an informational
statement if for any reason sampling exceeds 5 ug/l
(one-half of the new standard) as this testing program
is implemented.
Other
Health Related Information
Cryptosporidium
and Giardia
Cryptosporidium, a parasitic microbe found
in most surface water supplies, can pose a potential
health threat. If swallowed, it may produce cryptosporidiosis,
with symptoms of diarrhea, stomach cramps, upset stomach,
and slight fever. Some people are more vulnerable
to Cryptosporidium than others and should seek
advice about types of drinking water from their health
care providers.
The
SFPUC tests for Cryptosporidium in both source
and treated water supplies at least quarterly. The
SFPUC occasionally (about 19 percent of the time)
detects low levels of Cryptosporidium in the
Hetch Hetchy, East Bay, and San Francisco Peninsula
source (untreated) waters at an overall average level
of 37 Cryptosporidium/100 liters of water.
Giardia, a parasitic microbe found in most
surface water supplies, can pose a potential health
threat. If swallowed, it can produce the same symptoms
as does Cryptosporidium. The SFPUC tests for
Giardia in both source and treated water at
least quarterly. The SFPUC occasionally (about 23
percent of the time) detects low levels of Giardia
in the Hetch Hetchy, East Bay, and San Francisco Peninsula
source (untreated) waters at an overall average level
of 12 Giardia/100 liters of water.
Drinking water, including bottled water, may reasonably
be expected to contain at least minute amounts of
some contaminants including Cryptosporidium
and Giardia. The presence of small amounts
of contaminants does not necessarily indicate that
water poses a health risk. More information about
contaminants and potential health effects can be obtained
by calling the Environmental Protection Agency's Safe
Drinking Water Hotline (800)-426-4791.
Please note that Cryptosporidium and Giardia are associated
with surface water supplies and are not commonly detected
in groundwater. Daly City's wells in previous years
have never had a detected level of either of these
microbes.
Important
Definitions for Understanding This Water Quality Report
Public Health Goal (PHG): The level of a contaminant
in drinking water for which there is no known or expected
associated health risk. PHG's are non-enforceable
targets set by the California Environmental Protection
Agency (Cal EPA).
Maximum
Contaminant Level Goal (MCLG): The level of a
contaminant in drinking water for which there is no
known or expected health risk. MCLG's are set by the
U.S. Environmental Protection Agency (U.S. EPA).
Maximum
Contaminant Level (MCL): The highest level of
a contaminant that is allowed in drinking water. Primary
MCL's are set as close to the PHG's and MCLG's as
is economically and technically feasible. Secondary
MCL's are set to protect odor, taste and appearance
of drinking water.
Primary
Drinking Water Standard: MCL's for contaminants
that affect health along with their monitoring and
reporting requirements and water treatment requirements.
Variances
and Exemptions: State or EPA permission not to
meet an MCL or a treatment technique under certain
conditions. Daly City and the SFPUC have no variance
or exemption for MCL's.
Treatment Technique: A required process intended
to reduce the level of a contaminant in drinking water.
Regulatory
Action Level: The concentration of a contaminant
which, if exceeded, triggers treatment or other requirements
which a water system must follow.
Waiver:
Permission from the State Department of Health Services
(DHS) to decrease the frequency for a particular contaminant.
This decision is based on previous monitoring indicating
a firm belief that the contaminant does not exist
in the system. Waivers are for defined periods of
time and require an application for extension.
THM
& HAA5
Trihalomethane
(THM) and Haloacetic acids (HAA5) are naturally occurring
by-products of the disinfection process.
Beginning
in January 2002, new regulations on these by-products
require a more extensive sampling program. Before
THM's were sampled quarterly at four strategic locations.
Now, a total of sixteen samples locations have been
included throughout the water distribution system.
Also
beginning in 2002, HAA5 testing has been included
into this amended sampling program. This testing involves
five compounds and is reported as a total number to
DHS as part of the City's quarterly reports.
The
THM standard changed from 100 parts per billion (ppb)
to 80 ppb. Daly City, along with other suburban agencies
that receive water from the Hetch Hetchy Regional
Water System, received a waiver from the EPA and DHS
on this standard until the end of 2003. The waiver
was granted to Daly City as a result of its water
quality sampling program and the scheduled disinfection
conversion to chloramination.
This
disinfection conversion will result in a significant
decrease in the disinfection by-products and will
better assure a safe and clean water supply for the
future. The conversion process is being planned in
coordination with the San Francisco Public Utilities
Commission.
An
operational consideration associated with the use
of chloramination is to avoid stagnant water within
the system. Chloramination retains a modal contact
time of up to 28 days. Stagnant water increases the
possibility of taste and odor complaints associated
with nitrification.
Part
of the City's response to the chloramination conversion
will involve a citywide flushing program to begin
this fall. The flushing program will clear out naturally
occurring sediment from water mains. Crews flush the
system by exercising fire hydrants throughout local
neighborhoods. Residents will receive advanced flyers
announcing when flushing will occur in their area.
In addition to clearing water lines, the flushing
program enables staff to better assess the condition
of water valves in the system and fire flows throughout
the community.
To
better assure water circulation, operational parameters
on filling and draining reservoirs will be modified.
A major capital improvement is slated for Reservoir
5B on Margate Court to improve circulation within
this 10.3 million gallon storage facility. Crews will
also be installing blow offs along dead-end mains
to improve circulation and water quality. Finally,
the City has cleaned all of its reservoirs and has
instituted an annual cleaning program.
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Future
Changes
Fluoridation
SFPUC
has fluoridated their treated water for almost 50
years. Depending on your location in Daly City, you
may receive only SFPUC supplied water and have the
optimum level of fluoride content which is only 1
mg/L (parts per million). In other areas receiving
blended well and SFPUC water, since we do not fluoridate
our well water, you may be receiving water with fluoride
levels as low as 0.3 mg/L. By year end 2003, Daly
City is anticipating adding systems to fluoridate
the well water blended at the City's three pump stations
to meet the optimum standard throughout the entire
community.
Chloramination
One of the current goals of the EPA and DHS is to
lower disinfection byproducts in drinking water. These
are organic compounds formed by the breakdown of chlorine
as it oxidizes microbial material and breaks down.
To reduce the level of these compounds, a small amount
of ammonia can be added which forms Chloramines. These
chloramines optimize the effect of the chlorine by
allowing it to exist longer in the water and break
down less than chlorine alone. The SFPUC is making
the switch within the next few years. The anticipated
date for this conversion is the summer of 2003. At
that time Daly City will make the same modification
to the local system to maintain a uniform disinfection
process between the SFPUC water and our blended well
water.
There will be some changes necessary for aquarium
owners, as chloramines are toxic to fish. Aquarium
owners will need to fully de-chlorinate tank make-up
water. Also, people on dialysis or with other specific
health needs may need to alter water use when the
change to chloramination takes place. There will be
public notices with the necessary information distributed
preceding the actual change. And the City will work
with the Medical Community to fully inform those residents
at risk to adverse effects prior to the change. This
information will be sent out in a timely manner, allowing
you ample time to make any changes if you are one
of the few customers that will be affected by the
change. Switching to chloramines has been very successful
across the country and the positive benefits far exceed
the known potential problems.
Conjunctive
Use Aquifer Recharge Study
As part of ongoing efforts to preserve the Westside
Basin Groundwater Aquifer for drinking water purposes,
Daly City amended its Water Supply Contract with the
San Francisco Public Utilities Commission to conduct
an aquifer recharge study. The purpose of the study
is to jointly assess available groundwater storage
capacity within the Westside Basin.
Conjunctive Use refers to balancing the use of available
surface water supplies with that of groundwater. During
certain years, when supplemental surface water is
available, Daly City agrees to buy that supplemental
water at a discount price in lieu of extracting groundwater
from its local wells. The purpose of the study is
to assess the impact within the groundwater basin
on aquifer storage and whether the basin can be used
to enhance aquifer recharge. It is hoped that improved
basin recharge and storage will provide additional
water to the region that can be utilized during drought
conditions. Local impacts, if any, once the program
is implemented may involve some residents noticing
a slightly different taste in their water from the
higher amount of surface water blend from the reduction
of groundwater. It is expected that this impact will
be minimal.
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