Utilities
Department
Water Division
Triennial Water
Quality Report
June 21, 2022
ATTACHMENT 2
Drinking Water Report
• Max Contaminant Level (MCL) vs Public
Health Goal (PHG)
• Report on Napa Water 2019-2021
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 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 2019-2021
• Napa met PHGs for 91 of 95 PHG standards
• Napa did not meet PHGs as follows:
Triennial
PHG MCL Avg
Bromate (ppb) 0.1 10 1.0
Coliform Bacteria (MCLG) 0 <5.0% 1.3%
Copper (Action Level) (ppm) 0.3 1.3 0.33
Total Trihalomethanes (ppb) 0.0005 0.08 0.07
ATTACHMENT 2
Napa Report 2019-2021
No action is recommended to modify water
treatment processes.
• Bromate – can form as a result of the reaction of ozone and bromide. Bromide is only detectable during episodes of challenging water quality due to winter storms.
• Coliform Bacteria – are found everywhere in nature and generally not harmful. They are analyzed as surrogate indicators for potential pathogens, hence the PHG is zero and does not take into account laboratory analytical limitations.
• Copper – our water is well below the action level of 1.3. Changes to the optimized corrosion control does not guarantee reduction as these low levels and could introduce other adverse water quality effects. • Total Trihalomethanes (THMs) – THMs can form as a result of the reaction of chlorine and naturally-occurring organic matter.
Chlorine is legally required and helps to prevent serious illness from organisms in water that produce disease.
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