Utilities Department Water Division
Triennial Water Quality Report
June 17, 2025
ATTACHMENT 2
Drinking Water Report
• Maximum Contaminant Level (MCL) vs Public
Health Goal (PHG)
• Report on Napa Water 2022-2024
ATTACHMENT 2
Drinking Water Standards
• MCL: Maximum Contaminant Level
– Analytical detection
– Treatment technology available
– Benefits
– Health effects
– Costs
– Practical implementation
• Napa met all MCLs
ATTACHMENT 2
Drinking Water Standards
• PHG: Public Health Goal
• OEHHA: CA Office of Environmental Health Hazard
Assessment
• CA Health and Safety Code Section 116470
– Idealistic targets
– Emerging data (human or non-human)
– Non-factors
• Analytical detection levels
• Available treatment
• Benefits
• Costs
ATTACHMENT 2
Napa Report 2022 - 2024
• Napa met Public Health Goals (PHGs) for 93 of 95
PHG standards
• Napa did not meet PHGs as follows:
Triennial
PHG MCL Avg
– Bromate (ppb) 0.1 10 3.0
– Copper (Action Level) (ppm) 0.3 1.3 0.49
ATTACHMENT 2
Napa Report 2022 - 2024
No action is recommended to modify water treatment
processes.
• Bromate – can form as a result of the reaction of ozone and bromide. Bromide is detectable during episodes of
challenging water quality due to winter storms.
• Copper – our water is well below the action level of 1.3 ppm. Changes to the optimized corrosion control does
not guarantee reduction as these low levels and could
introduce other adverse water quality effects.
ATTACHMENT 2
Recommended Action
• Receive Triennial Report on Water
Quality relative to Public Health Goals pursuant
to CA Health & Safety Code Section 116470.
ATTACHMENT 2