Safe Drinking Water Quality

Safe drinking water is essential for daily life. It is also one of the world’s most valuable resources. How often do you think about your tap water quality? The Town of Gilbert takes it seriously and consistently makes sure it is safe and available to you when you turn on the faucet.

Consumer Benefits:

1. Safe, Convenient, affordable
2. Public health protection
3. Economic support and development

Water quality control involves the use of the best available technology within economic limits from the protected raw water source to the required treatment and to the distribution system leading to the ultimate consumer’s tap.

Drinking Water Quality Standards and Guidelines

The Safe Drinking Water Act (SDWA) is the main federal law that ensures the quality of Americans' drinking water. Under SDWA, U.S. Environmental Protection Agency (EPA) sets standards for drinking water quality and oversees the states, localities, and water suppliers who implement those standards. The U.S. EPA has set standards for more than 80 primary contaminants that may occur in drinking water and pose a risk to human health. These standards, called maximum contaminant levels, are the safety limits established for safe drinking water.

Monitoring Drinking Water Quality

The Town of Gilbert Water Quality staff performs up to 100 tests daily in the drinking water you receive at your home or business. These tests ensure that your water meets every health and safety standard set by the state and federal government. The Town of Gilbert has a State certified laboratory that analyzes daily process, distribution and regulatory compliance samples. For complete in-depth analyses, we also use commercial state certified labs. Our staff works to ensure compliance with all drinking water regulations and helps with new rule implementation.
Town of Gilbert meets the following water quality standards:

• Federal (U.S. EPA) Drinking Water Standards
• State (ADEQ) Water Quality

Testing Requirements and Results for Lead and Copper:

The Town of Gilbert is required to collect and test water samples from 50 homes every three years. Historically low levels of lead and copper have resulted in reduced monitoring requirements. Test for lead and copper was last completed in July 2022. Under the EPA’s lead and copper rule, testing of customer residences is selected based on criteria that makes them more likely to have plumbing in their homes which may contain lead solder or are more likely to have lead service lines. The lead and copper rule requires that water systems maintain lead concentrations of less than 15 ppb in more than 90% of samples collected from customer taps. During Gilbert's last sampling event, 51 homes were tested for lead with all homes either being non-detectable or far below the EPA’s action level.

Per- and Polyfluoroalkyl Substances (PFAS) Testing

Per- and Polyfluoroalkyl Substances, also known as PFAS, are a widely used group of man-made chemicals that have been in production since the 1940s.

Gilbert has been actively engaged in planning for the upcoming regulations surrounding PFAS and is aware of the various treatment and remediation options for PFAS. As an example, Gilbert’s North Water Treatment plant is currently under complete reconstruction which includes the addition of Granular Activated Carbon (GAC) contactors which are an effective method for removing PFAS in the water.

In November 2023, Gilbert began our Unregulated Contaminant Monitoring Rule (UCMR 5) testing, as required by the EPA. As a part of that testing, all of our water sources were tested for 25 different PFAS compounds. During testing, Gilbert detected PFOA, PFOS, PFPeA and PFBS at three separate locations. These locations were at two well sites and the North Water Treatment Plant. Further investigations are ongoing at all of these locations to try and determine the source of those detects.

A summary of the UCMR 5 testing to date is shown in the following table:

Testing Results
Location	Sample Date	Results (ppt)	Compound Type	Proposed MCL (ppt)
North Water Treatment Plant	11/8/2023	10.0	PFBS	2000
Well 7	11/14/2023	3.9	PFOA	4.0
Well 7	11/14/2023	5.6	PFOS	4.0
Well 7	11/14/2023	3.4	PFPeA	1.0 (unitless) Hazard Index
Well 25	11/7/2023	7.9	PFBS	2000

 

The Town of Gilbert takes the matter of PFAS seriously.  While there are currently no regulated amounts for PFAS as the regulations are still in the proposal phase, the Town has been and continues taking proactive measures to meet any future regulations.  Currently, the PFAS detection is restricted to only a few sites and not found townwide. Of the affected sites, Well site 7 was immediately taken offline as a precautionary measure.

It is important to note that testing under the EPA’s 5^th Unregulated Contaminant Monitoring Rule (UCMR5) is in the first round of sampling, and additional sampling and testing are ongoing. As required under Arizona state law, the results will be published in the annual Consumer Confidence Report to be released before July 1, 2024 which can be found at gilbertaz.gov/water-quality-report and Gilbert will continue to provide updates from the most recent testing on this website. 

Gilbert is fortunate to have a diversified water portfolio and can take affected well sites temporarily offline while still maintaining system demand. This built-in redundancy will allow the Town to fully investigate and implement the best solutions for treatment. The Town of Gilbert is committed to maintaining high water quality standards and producing safe clean drinking water, while also keeping the rate payers in mind. 

Proposed MCL/MCLG
Compound	MCLG	MCL
PFOA	0 ppt	4 ppt
PFOS	0 ppt	4 ppt
PFNA	1.0 (unitless hazard index)	1.0 (unitless hazard index)
PFHxS	1.0 (unitless hazard index)	1.0 (unitless hazard index)
PFBS	1.0 (unitless hazard index)	1.0 (unitless hazard index)
HFPO-DA (GenX)	1.0 (unitless hazard index)	1.0 (unitless hazard index)

 

Legend
MCL	Maximum Contaminant Level
MCLG	Maximum Contaminant Level Goal
HAL	Health Advisory Level
HBWC	Health-Based Water Concentration
PPT	Parts Per Trillion
PFAS	Polyfluoroalkyl substances
PFBS	Perfluorobutane sulfonate

 

Proposed PFAS National Primary Drinking Water Regulation

To learn more about PFAS, its health effects and PFAS testing in drinking water systems visit https://www.epa.gov/pfas and https://www.epa.gov/pfas/pfas-explained.

Drinking Water Source

Surface water is a primary water source for the Town of Gilbert. Surface water is supplied via canal system from the Salt River Project (SRP) and Central Arizona Project (CAP). SRP manages several dams and reservoirs on the Salt and Verde rivers. Water collected from these rivers into reservoirs is released into SRP canals. CAP's 336 mile long system carries Colorado River water from Lake Havasu, through Phoenix, to south of Tucson.

Where Does Our Drinking Water Come From?

• SRP - snow and rain runoff from the watersheds in Arizona. For more information, please visit SRP Canals and Dams
• CAP - water from the Colorado River watershed – Please visit CAP Water Quality
• Groundwater - water pumped from underground wells

Water Treatment - The Town of Gilbert has two drinking water treatment plants:

North Water Treatment Plant (NWTP): Called NWTP due to its location on the north side of the town. The NWTP is situated on the eastern canal receiving water from the SRP (mixture of salt river and verde river). Water delivered from the NWTP is treated using the conventional methods of coagulation, flocculation, sedimentation, and filtration. The NWTP can produce as much as 45 million gallons of water per day (MGD) and has a 16 million gallon (MG) reservoir onsite for water storage.

North Water Treatment Plant Brochure

Santan Vista Water Treatment Plant (SVWTP): Called Santan Vista because of the stunning view of the Santan moutains from the plant control room. This plant is receiving water from CAP (Colorado river watershed). From CAP turnout, water is brought to the plant through approximately 14 miles of 48” ductile iron pipeline. This plant is built and operating in partnership with City of Chandler. Initial capacity for this plant is 24 MGD; 12 MGD for the town and 12 MGD for the City of Chandler. This plant is treating the water using ballasted flocculation and average process time is 20-25 minutes. Onsite reservoir capacity is 6 MGD.

Santan Vista Water Treatment Expansion Project

Santan Vista Water Treatment Plant Brochure

Groundwater

Groundwater availability from wells is nearly 44 MGD, not including reservoir storage, and is also delivered to the customers via the distribution system that uses chlorine as disinfectant. Groundwater is pumped from 17 wells located throughout the town. Groundwater is used to meet the high demand and during canal dry outs for maintenance. Groundwater can be pumped directly in the distribution systems or can be used to fill a reservoir. In total, the Town of Gilbert can produce approximately 101 MGD and has storage capacity of just over 45 MG and can more than meet the demands from the community which has now grown to over 205,000 residents.

Disinfection

Water is disinfected before it enters the distribution system to ensure that dangerous microbial contaminants are killed. Ozonation and chlorination are used as the means of disinfection for drinking water from the water treatment plants. Water is then delivered to the community through the distribution system of over 700 miles of pipe line at a pressure of 60-80 pound per square inch (psi).