| Daly
City's Wells (Groundwater) |
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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 2000.
During
the year 2000, Daly City began a source water assessment
of its
local groundwater sources. 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 2000 nitrate testing showed detected amounts
of nitrate in excess of the MCL of 45 mg/L (ppm) at
Wells #4 (61.0 mg/L) and A Street (53.5). Nitrate
is one of the major anions in natural water, but concentrations
can be greatly elevated due to leaching of nitrogen
from fertilizers. Subsequent testing at A Street and
Well #4, located on 'A' Street east of Reiner Street
and at 799 Southgate Avenue, respectively, showed
a decreased concentration of nitrate under the MCL.
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.
Distribution
System Excess Total Coliform - May 2000
Daly
City maintains 35 sampling sites throughout the community
that are tested weekly for microbiological contaminants.
In May 2000, Daly City exceeded its 5% maximum contaminant
level for monthly positive samples of total coliform.
The May 2000 results showed 6.5% of the samples (10
out of 153) tested positive for total coliform. Six
of the ten positive samples involved a single source
area, Penhurst Court. A routine sample and two repeat
samples tested positive for total coliform.
Coliforms
are bacteria that are naturally present in the environment
and are used as an indicator that other, potentially
harmful, bacteria may be present. Coliforms were found
in more samples than allowed and this was a warning
of potential problems. However, neither fecal coliform
nor e. coli, organisms more indicative of disease
causing organisms, were detected in any of the samples
taken.
As
a result, Daly City published a public notice of the
event in June, followed by a mailed notice to all
water customers in August. In addition, a booster
pump was installed at Reservoir 5B to increase disinfection
residual within the area to lessen the chances of
additional positive sample results.
To
date, there have been no further instances of excess
levels of coliform or any adverse effects noted.
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.
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.
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.
Other
Health Related Information
Chromium 6
During the past year, the compound Chromium 6 (Hexavalent
Chromium) has come into the public eye as a result
of the popular motion picture Erin Brockavich. That
movie focused on a Southern California community water
system contaminated with extremely high amounts of
this substance as a result of illegal industrial waste
dumping. California's Department of Health Services
(DHS) conducted increased studies of this substance
and discovered new information. For years it was believed
that amounts of Chromium 6, as modeled within a water
body, comprised only a small fraction of the total
Chromium found. DHS discovered that several water
supplies tested in California had amounts of Chromium
6 that comprised a higher fraction of the total Chromium
than originally believed under the established model.
Groundwater supplies are more prone to this since
Chromium compounds are naturally occurring minerals
that exist in rock structures and can go into solution
because of the contact between the aquifer and the
rock formation of the well. Daly City's supply was
one of those sampled by DHS found to have Chromium
6 in amounts half or better of the total Chromium
detected. It must be stressed that the total Chromium
found (13.4 to 29.6 parts per
billion) is well below the established maximum contaminant
level of 50 parts per billion and does not pose any
health impacts or concerns. DHS has asked the California
Environmental Protection Agency to establish a specific
Public Health Goal (PHG) for Chromium 6 that does
not pose a significant human health risk. Establishment
of a PHG would be the first step toward development
by DHS of a state drinking water standard specifically
for Chromium 6 - the first Chromium 6 drinking water
standard in the nation.
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.
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
large 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
from the EPA, DHS required local water systems to
complete their studies. A joint effort was organized
by the SFPUC for collection and analysis of samples
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 completed
in September 1999. Lead and copper are prevalent materials
used in fixtures and pipes. There was a time in the
past when pipes themselves were made of lead. Lead
and copper can be dissolved through contact with water.
The rate or amount of material that can be put into
solution is based on the corrosivity or aggressiveness
of the water. The goal of the EPA program is to find
the best way(s) to optimize water systems to lower
the aggressiveness of the water in that system.
The results of the second Daly City study indicated
that the well water offered a buffering effect which
lowered corrosivity of the water and that blending
of SFPUC water with local well water actually lowered
the corrosivity of the SFPUC water to optimum levels.
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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. Over the next year, Daly
City is anticipating adding systems to fluoridate
the well water blended at the City's three pump stations.
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.
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