2023 CONSUMER CONFIDENCE REPORT
The PHGs Report Detected One
Contaminant Above the Public
Health guidelines:
ARSENIC
What is ARSENIC?
• Arsenic is a semi-metal element in the periodic table. It is a naturally occurring element that is found in combination with either inorganic or organic substances, and are found in soils, sediment, and sand groundwater.
• The Public Health Goal ( PHG) for arsenic in drinking water is 0.004 ppb (parts per billion). • The Maximum Contaminant Level (MCL) for arsenic is 10 ppb. • Therefore, safe levels of arsenic in drinking water is any level under 10ppb, zero being the safest. • Arsenic was found to occur in only one groundwater well – City Well 2, and not in any other wells. • It should be noted that City Well 2 water is blended with additional water sources that contain no detection levels of arsenic.
FACTS!
CITY OF RIALTO
SAFE LEVELS OF ARSENIC
HAS BEEN DETECTED IN OUR
DRINKING WATER
SINCE 2015
Public Health Goal (PHG) for Arsenic is .004 ppb
Maximum Contaminate Level (MCL) for Arsenic is 10.0 ppb Detection Levels
Note: 2023 sample @9.7 ppb taken on March 22nd was 1 day after the well was brought online after being offline for approximately 3 months, which is what lead to the high arsenic hit.
Root Cause Analysis
In March 2023, the 3 year sample for arsenic was due. At that time, City Well #2 (“Well”) was offline and out of service for approximately 3 months for repairs. The Well was repaired and placed back online on March 21, 2023 and the sample was taken the next day on March 23rd.
• It appears from the level reported that the well should have ran to waste for a longer duration because the arsenic had concentrated due to it being offline for 3 months. • A longer duration of running to waste would have provided a representative sample. • Based on historical and subsequent quarterly samples taken the 9.7 ug/l in 2023 was an anomaly as running to waste longer would have provided a representative sample.
Action(s) Taken
• Quarterly samples were taken, which stabilized to historical averages of 5.0 ug/l. • An arsenic field test kit is being utilized prior to placing the well online in the event the well was out of service for any duration of time.
Levels of arsenic can vary based on the dynamics of the aquifer that is supplying the water in Lytle Creek (and to the well).
QUESTIONS?