JUNE 2022
CITY OF RIALTO
REPORT ON WATER QUALITY
RELATIVE TO PUBLIC HEALTH GOALS
FOR YEARS 2019, 2020, 2021
BACKGROUND:
Provisions of the California Health and Safety Code (Section 116470 (b))1 specify that larger water utilities (>10,000 service connections) prepare a special report by July 1, 2022 if their water quality measurements have exceeded any Public Health Goals (PHGs). PHGs are non- enforceable goals established by the Cal-EPA’s Office of Environmental Health Hazard Assessment (OEHHA). The law also requires that where OEHHA has not adopted a PHG for a constituent, the water suppliers are to use the Maximum Contaminant Level Goals (MCLGs) adopted by United States Environmental Protection Agency (USEPA). Only constituents which have a California primary drinking water standard and for which either a PHG or MCLG has been set, are to be addressed. This report covers the “detection” of contaminants above both PHGs and MCLGs found in the City’s water system during calendar years 2019, 2020 and 2021.
There are a few constituents that are routinely detected in water systems at levels usually well below the drinking water standards for which no PHG nor MCLG has yet been adopted by OEHHA or USEPA including Total Trihalomethanes. These will be addressed in a future required report after a PHG has been adopted.
If a constituent was detected in the City’s water supply between 2019 and 2021 at a level exceeding an applicable PHG or MCLG, this report provides the information required by law. Included is the numerical public health risk associated with the MCL and the PHG or MCLG, the category or type of risk to health that could be associated with each constituent, the best treatment technology available that could be used to reduce the constituent level, and an estimate of the cost to install that treatment if it is appropriate and feasible.
WHAT ARE PHG’S:
PHGs are set by the California Office of Environmental Health Hazard Assessment (OEHHA) which is part of Cal-EPA and are based solely on public health risk considerations. None of the practical risk-management factors that are considered by the USEPA or the California Division of Drinking Water in setting drinking water standards (MCLs) are considered in setting the PHGs. These factors include analytical detection capability, treatment technology available, benefits and costs. The PHGs are not enforceable and are not required to be met by any public water system. MCLGs are the federal equivalent to PHGs.
WATER QUALITY DATA CONSIDERED:
All of the water quality data collected by our water system between 2019 and 2021 for purposes of determining compliance with drinking water standards was considered. This data was all summarized in our 2019, 2020, and 2021 Consumer Confidence Reports and was made available online at www.rialtoca.gov.
GUIDELINES FOLLOWED:
The Association of California Water Agencies (ACWA) formed a workgroup which prepared guidelines for water utilities to use in preparing these newly required reports. The ACWA guidelines were used in the preparation of our report. No guidance was available from state regulatory agencies.
BEST AVAILABLE TREATMENT TECHNOLOGY AND COST ESTIMATES:
Both the USEPA and DDW adopt what are known as BATs or Best Available Technologies which are the best known methods of reducing contaminant levels to the MCL. Costs can be estimated for such technologies. However, since many PHGs and all MCLGs are set much lower than the MCL, it is not always possible nor feasible to determine what treatment is needed to further reduce a constituent downward to or near the PHG or MCLG, many of which are set at zero. Estimating the costs to reduce a constituent to zero is difficult, if not impossible because it is not possible to verify by analytical means that the level has been lowered to zero. In some cases, installing treatment to try and further reduce very low levels of one constituent may have adverse effects on other aspects of water quality.
CONSTITUENTS DETECTED THAT EXCEED A PHG OR A MCLG:
The City of Rialto water supply meets, with only one exception, all of the PHG and MCLG standards. The following is a discussion of the constituent that was detected in one of our drinking water sources at levels above the PHG, or if no PHG, above the MCLG.
ARSENIC:
Arsenic is a semi-metal element in the periodic table. The PHG for arsenic is 0.004 ppb. Effective January 23, 2006, the MCL for arsenic was lowered from 50 ppb to the revised standard of 10 ppb.
Arsenic test results for the City for the year 2020 from all groundwater and import sources had a range of not detected to 3.1 ppb. Arsenic was found to occur in one groundwater well. The following well had detection levels above the PHG of 0.004 ppb:
City Well 2
3.1ppb
Arsenic is a naturally occurring element that is found in combination with either inorganic or organic substances to form many different compounds. Inorganic arsenic compounds are found in soils, sediment sand groundwater. These compounds occur naturally or as a result of mining, ore smelting, and industrial use of arsenic. Organic arsenic compounds are found mainly in fish and shellfish. In the past, inorganic forms of arsenic were used in pesticides and paint pigment. They were also used as wood preservatives and as a treatment for a variety of ailments. Today, usage of arsenic–containing pesticides and wood preservatives is restricted.
People are most likely to be exposed to inorganic arsenic through drinking water and, to a lesser extent, through various foods. Unusually large doses of inorganic arsenic can cause symptoms ranging from nausea, vomiting, and diarrhea to dehydration and shock. Long-term exposure to high levels of inorganic arsenic in drinking water has been associated with skin disorders and increased risks for diabetes, high blood pressure, and several types of cancer. Inorganic arsenic and arsenic compounds are considered to be cancer-causing chemicals. Forms of organic arsenic found in seafood are not known to be toxic to humans.
Arsenic has no smell, taste, or color when dissolved in water, even in high concentrations, and therefore only laboratory analysis can determine the presence and concentration of arsenic in water. It occurs naturally in rocks, mineral deposits, and soil, water, air, and plants and animals. It can be further released into the environment through natural activities such as volcanic action, erosion of rocks and forest fires, or through human actions.
Because it occurs naturally in the environment and as a by-product of some agricultural and industrial activities, it can enter drinking water through the ground or as runoff into surface water sources.
The City water system is in full compliance with federal and state rules for arsenic.
As arsenic was detected in only a single well, any treatment considerations would need to be focused on the effected groundwater source. The most likely treatment option for arsenic removal would be Granular Ferric Oxide Resin. In studies conducted to remove arsenic via Granular Ferric Oxide Resin, (conducted by Golden State Water Co.), annualized capital and O&M costs ranged from $2.24 to $2.39 per 1,000 gallons treated. The estimated cost to treat the potential total water supplied from one water well contributing to the City’s water supply would be approximately $ 1.02 million annually.2 Treatment Technology
Source of Information
Estimated 2012 Unit Cost Indexed to 2021 ($/1,000 gallons treated) GFO/Adsorption
Golden State Water Co., Granular Ferric Oxide Resin, Arsenic removal, 600 gpm, 2 facilities, built in 2006
2.24 – 2.39
RECOMMENDATIONS FOR FURTHER ACTION:
The drinking water quality of the City of Rialto meets all State of California, DDW and USEPA drinking water standards set to protect public health. To further reduce the levels of the constituent identified in this report that are already significantly below the health-based Maximum Contaminant Levels established to provide "safe drinking water", additional costly treatment processes would be required. The effectiveness of the treatment processes to provide any significant reductions in constituent levels at these already low values is uncertain. The health protection benefits of these further hypothetical reductions are not at all clear and may not be quantifiable. Therefore, no action is proposed.
REFERENCES:
1 Excerpt from California Health & Safety Code: Section 116470(b) 2 Attachment No. 3 Table 2 Reference: Other Agencies from the Association of California Water Agencies Suggested Guidelines for Preparation of Required Reports on PUBLIC HEALTH GOALS (PHGs) to satisfy requirements of California Health and Safety Code Section 116470(b)