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FAQ For Drinking Water

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Published on March 27, 2017. Last modified on September 24, 2019

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Frequently Asked Questions

Public Water

The drinking water that is supplied to our homes comes from either surface water or ground water. Surface water collects in streams, rivers, lakes, and reservoirs. Ground water is water located below the ground where it collects in pores and spaces within rocks and in underground aquifers. We obtain ground water by drilling wells and pumping it to the surface.

Public water systems provide treated water from surface and ground water for public use. Water treatment systems are either government or privately-held facilities that withdraw water from the source, treat it, and deliver it to our homes.

A private well uses ground water as its water source. Owners of private wells and other individual water systems are responsible for ensuring that their water is safe from contaminants. (Information from CDC)

A. The presence of certain contaminants in our water can lead to health issues, including gastrointestinal illness, reproductive problems, and neurological disorders. Infants, young children, pregnant women, the elderly, and immunocompromised persons may be especially at risk for becoming ill after drinking contaminated water. For example, elevated levels of lead can cause serious health problems, especially for pregnant women and young children. Federal law requires that systems reduce certain contaminants to set levels, in order to protect human health. However, the presence of contaminants when tested does not necessarily indicate that the water poses a health risk. (Information from CDC)

A. There can be many sources of contamination of our water systems. Here is a list of the most common sources of contaminants:

  • Naturally occurring chemicals and minerals (for example, arsenic, radon, uranium)
  • Local land use practices (fertilizers, pesticides, livestock, concentrated animal feeding operations)
  • Manufacturing processes
  • Sewer overflows
  • Malfunctioning wastewater treatment systems (for example, nearby septic systems)


A. The United States has one of the safest public water supplies in the world. However, if you are concerned about contaminants in your home’s water system, contact your state drinking water certification officer to obtain a list of certified laboratories in your state. Depending on how many contaminants you wish to test for, a water test can cost from $15 to hundreds of dollars. The Safe Drinking Water can give you information on testing methods.

A. A change in your water's taste, color, or smell is not necessarily a health concern. However, a change could be a sign of serious contamination problems. If you notice a change in your water, call you public water system company. If you want to test your water, your local health department should assist in explaining any tests that you need for various contaminants. If your local health department is not able to help you can contact a state certified laboratory to perform the test. To find a state certified laboratory in your area call the Safe Drinking Water Hotline at (800) 426-4791.

A. In order to disinfect your drinking water during a boil water advisory, you should boil your water at a rolling boil for at least one minute (at altitudes greater than 6,562 feet (> 2000 meters), boil water for 3 minutes). Boiling your water for at least one minute at a rolling boil will inactivate all harmful bacteria, parasites, and viruses from drinking water.

Although chemicals (for example, bleach) are sometimes used for disinfecting small volumes of drinking water for household use, chemical disinfection is generally not recommended for commercial establishments because of the lack of on-site equipment for testing chemical residuals. Furthermore, the parasite, Cryptosporidium is poorly inactivated by chlorine or iodine disinfection. Cryptosporidium can be removed from water by filtering through a reverse osmosis filter, an "absolute one micron" filter, or a filter certified to remove Cryptosporidium under NSF International Standard #53 for either "cyst removal" or "cyst reduction." See "A Guide to Water Filters." However, unlike boiling or distilling, filtering as just described will not eliminate other potential disease-causing microorganisms, such as bacteria and viruses. Ultraviolet light treatment of water is not effective against Cryptosporidium at normally-used levels.

Well Program

A. Hire a licensed C-57 contractor and complete the applicable application. The application must be signed by both the property owner (or authorized representative) and contractor. The application must be complete and accompanied by the appropriate fee.

A. EHB maintains a list of contractors that have worked in Monterey County. If a contractor wants to be added or removed from the list, he/she may contact EHB at (831) 755-4507

A. All well constructed, repaired, reconstructed, or destroyed in Monterey County must be done in conformance with the California Well Standards Bulletin Nos 74-81 and 74-90, and Monterey County Well Ordinance (Chapter 15.04 of the Monterey County Code)

A. If sewage disposal is or will be by an on-site waste disposal system and the lot can be served by a water system, the property must be at least 2.5 acres in order to obtain a permit to construct.

A. The depth of the well is determined by the applicant and contractor. EHB will not tell you how deep to drill the well.

A. The depth of the well is determined by the applicant and contractor. EHB will not tell you how deep to seal the well, but must approve the seal depth before it is installed. As per 15.04.120 of the Monterey County Code, the seal is required to:

    • Restore, as far as feasible, the controlling hydrological conditions that existed before the well was drilled and constructed, including the elimination of physical hazards.
    • Prevent pollution of groundwater.
    • Conserve the yield and hydrostatic head of aquifers.
    • Prevent intermingling of desirable and undesirable waters In order to obtain seal depth approval, the contractor is required to submit a descriptive log to EHB. Properties within a water management agency are required to submit both a descriptive log and an electric log for review by the water management agency.


A. Water Quality will be required on the newly constructed well if it is for domestic use. Source capacity testing may be required as well.


A. Fertilizers such as potassium Nitrate and ammonium Nitrate are a primary source of Nitrates in drinking water. When applied to fields, Nitrates easily leach into soil and ultimately into water aquifers. In areas of heavy fertilizer usage, as in the strawberry fields of northern Monterey County and parts of the Salinas Valley, Nitrate contamination of aquifers is of serious concern. Also, in areas of concentrated below ground sewage disposal, Nitrate-rich seepage from septic systems is a significant contributor to the problem of groundwater pollution.

Because they do not evaporate, Nitrates are likely to remain dissolved, and to concentrate, in groundwater.

A. In 1974, Congress passed the Safe Drinking Water Act. This law requires the Environmental Protection Agency (EPA) to determine safe levels of chemicals in drinking water that may cause health problems. These drinking water standards, and the regulations for ensuring these standards are met, are called National Primary Drinking Water Regulations. All public water supplies must abide by these regulations.

A Maximum Contaminant Level (MCL) for each chemical found in drinking water is determined, based on possible health risks and exposure. The MCL for Nitrates has been set at 45 mg/l or 45 ppm (tested as Nitrates), and 10 mg/l or 10 ppm (tested as nitrogen). The EPA believes, given present technology and resources, this is the lowest level to which water systems can reasonably be required to remove this contaminant.


  • Excessive Nitrates in drinking water can interfere with the oxygen-carrying capacity of the blood. This condition (methemoglobinemia) can be so acute that health deteriorates rapidly over a period of days. Symptoms include shortness of breath and blueness of the skin. Infants under six months of age are especially at risk of developing serious health problems.
  • Because of changes in body chemistry when a woman becomes pregnant she is particularly susceptible to methemoglobinemia and should be sure that the water she drinks has an acceptable Nitrate level.
  • According to the EPA, a lifetime exposure to Nitrates at levels above the MCL has the potential to cause diuresis (excessive urination) and hemorrhaging of the spleen.


A. A public water system is required to collect water samples at least once a year and analyze them to find out if Nitrates are 50% or more of the MCL. If Nitrates are present above 50% of the MCL, the water system must continue to monitor the contaminant level every 3 months. If Nitrate levels are found to exceed the MCL, the water system must notify the water users and must take steps to reduce the amount of Nitrates so that they are consistently below that level. Additional actions, such as providing alternative drinking water supplies, may be required.

If drinking water comes from a private well it should be tested at least once each year. The Monterey County Health Department certified laboratory provides sampling containers and can test the water sample, or the Division of Environmental Health can refer you to a commercial certified laboratory that can test your water for Nitrate. These tests cost about $20.

  • If the Nitrate level is close to the MCL:
    Do not use well water to make formula for infants under six months old, and do not drink it if you are pregnant
  • If the Nitrate level exceeds the MCL:
    Use bottled water for drinking and cooking.
Boiling the water does not help —this will actually increase the concentration of Nitrates.


A. The continued use of bottled water for household consumption is never a permanent solution to the problem of high Nitrates.

  • Nitrates in drinking water can be reduced by the use of treatment methods such as ion exchange or reverse osmosis. These techniques require a significant investment and have continuing costs related to maintenance. Information about these and other treatments can be obtained from the Certified Residential Water Treatment Devices website of the California Department of Public Health.
  • Drilling a deeper well is expensive and may not succeed in producing water with a lower Nitrate contaminant level. Retrofitting an existing well is rarely a feasible alternative.
  • As a permanent solution to high Nitrates in drinking water, the Division of Environmental Health encourages users relying on individual wells to connect to a public water system, and recommends that impacted water systems consolidate with other water systems that can supply water that meets the drinking water standards for Nitrates. The economy of size—many residents addressing the issue of high Nitrates together—offers the best prospects of successfully maintaining a healthy water supply.
Note that a water system may not alter a water source, or use treatment of any kind, without prior approval from the Health Department’s Environmental Health Division.



A. Prior to January 23, 2006, the Federal and State MCL for Arsenic were 50 parts per billion(ppb). On January 23, 2006, the U.S. Environmental Protection Agency (E.P.A.) adopted a more stringent Federal maximum contaminant level (MCL) of 10 ppb for Arsenic. On November 28, 2008, the State of California followed by also adopting the MCL standard of 10 ppb into the California Code of Regulations. The current legal MCL for potable water in California is 10 ppb.

A. The California Department of Health and Federal EPA lowered the MCL for Arsenic from 50ppb to 10 ppb based on research indicating that ingestion of Arsenic at levels equal to or above 10 ppb increased the risk of bladder and lung cancer.

A. Demonstrating compliance with the Arsenic standard is based on the average of four quarterly samples. Therefore, your system must collect three more quarterly samples beginning the next quarter (Quarters are January-March, April-June, July-September, and October- December). The results of each quarterly sample must be submitted to the Monterey County Environmental Health Division (EHD). If EHD determines that the average of the four quarterly samples exceeds the MCL, the system will be required to come into compliance with Arsenic standards. However, if the initial sample exceeds the MCL for Arsenic, the system may forego the quarterly sampling and immediately take steps to come into compliance.

A.A. Some people who drink water with Arsenic in excess of the MCL of 10 ppb over many years may experience skin damage, circulatory system problems and may have an increased risk of cancer and the enhancement of cancer progression. Arsenic also appears to act as endocrine disrupter to block glucocorticoid action which may contribute to the incidence of diabetes, hypertension, and cancer.

More specifically, a variety of human cancers are associated with Arsenic ingestion such as, but not limited to, lung, bladder, prostate, skin, and liver cancer. At the cellular level, Arsenic can also inhibit chromosomal repair and mitochondrial respiration. In addition, Arsenic can also cause circulatory system and neurological damage and promote diabetes. Therefore all users of water from wells and other sources with Arsenic levels over 10 ppb are required to drink and cook with potable bottled water.

A. The primary Arsenic exposure route is oral through ingestion of food and water. Incidence of respiratory uptake from air exposure is negligible. Skin uptake may be possible from contact with contaminated soil, but uptake from dilute water solutions such as from showering or hand washing is unlikely.

A. No! Studies have indicated there is no health risk from skin contact at levels typically found in drinking water. However, ingestion of Arsenic may cause dermal symptoms such as skin damage.

A. When you become aware that your water system is over the MCL for Arsenic, you should first assure that all other members of your water system are informed. Everyone on the system should immediately begin using potable bottled water for drinking and cooking. An Arsenic Quality Standard Failure notification form (English) (http://www.co.monterey/health/EnvironmentalHealth/WaterProt/pdf/21-PUBLIC_NOTIFICATION_ARSENIC.pdf) (Spanish) (http://www.co.monterey/health/EnvironmentalHealth/WaterProt/pdf/22-PUBLIC_NOTIFICATION_Arsenic-Spanish.pdf) must be distributed to all users of the water system. The responsible contact person or operator for a water system must provide a copy of the completed Proof of Notification for MCL failure form (http://www.co.monterey/health/ EnvironmentalHealth/WaterProt/pdf/20-generic_proof_of_notification.pdf) to the Monterey County Health Department, Environmental Health, at 1270 Natividad Rd., Salinas Ca. 93906,Attn: Drinking Water Protection Services.

A. Practical treatment technology for Arsenic has only recently evolved. There are some existing Arsenic treatment systems that are installed on larger water systems in Monterey County. These systems are currently being evaluated for long term effectiveness and feasibility for application to smaller water systems. As Arsenic removal technology improves more cost effective treatment systems should be available in the future.

Responsible persons or operators of small water systems that are out of compliance with the MCL for Arsenic should immediately consult with a licensed engineer to evaluate treatment options and the associated ongoing operation and maintenance costs of the various treatment options. It is required by code that all plans for treatment are submitted to and approved by the Monterey County Health Department, Environmental Health Division prior to installation.

A. Yes, in accordance with Monterey County Code, Chapter 15.04.

A. You should begin by determining whether any of your neighbor’s wells are in compliance with the MCL for Arsenic. If so, the Monterey County Environmental Health Division recommends consolidating your water system with a compliant neighboring well or water system when it is feasible.

Drilling a new well is another alternative. However, as a cautionary note, be aware that Arsenic is a naturally occurring chemical in some geological formations, such as granitic formations. Therefore a new well may also be high in Arsenic if it is drilled to a similar depth and in the same geological formation as the old well.

A. Funding may be available through the California Department of Public Health (CDPH). However funding tends to be focused on larger systems serving 15 or more connections, but because funding rules may change over time, small water system operators should still contact CDPH to explore potential current or future funding opportunities. For information on outside funding sources and opportunities for Arsenic treatment, the CDPH has suggested referencing the following:

For more information on types of treatment available for Arsenic removal, the following listing may be helpful:
  • CA Code of Regulations, Title 22, Chapter 15, Article 12 – Best Available Technologies (BATs)Please be advised that any plan to use a BAT as treatment requires plans to be designed and stamped by a licensed engineer.
  • Isolux Technology - An Arsenic removal treatment system manufactured by Isolux Technology is currently operational for a public water system in Monterey County. For more information regarding this Arsenic removal treatment system, contact Isolux Technology at (800) 366-4850.


Have a question that was not answered here?

You may also call the Health Department’s Environmental Health Division’s Drinking Water Protection Services at 755-4507.