MONTARA WATER AND SANITARY DISTRICT Water Quality Report
Serving roughly 6,078 people in San Mateo County, California.
Data current as of July 2026
🔍Straight from EPA
🧪Real Lab Results
📅Updated Quarterly
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Results for MONTARA WATER AND SANITARY DISTRICT
1 water provider directly on file, serving roughly 6,078 people in San Mateo County, California.
Quick answer: MONTARA WATER AND SANITARY DISTRICT has no violations on file. One reading is worth knowing about: Nitrate was measured at 8.6MG/L, among the highest of the 113 providers on file in this area. It's the most notable figure in this system's record among its 113 local peers.
Lead Summary
Copper Summary
Totalhaloaceticacids (HAA5)
TTHM
Chloroform
Bromoform
Bromodichloromethane
Dibromochloromethane
Dichloroaceticacid
Trichloroaceticacid
Dibromoaceticacid
Nitrate
Aggressive Index
Langelier Index (pH(s))
Magnesium
Calcium
Sodium
Alkalinity, Total
Alkalinity, Bicarbonate
Hardness, Total (ASCACO3)
TDS
Chloride
Sulfate
Fluoride
Gross Alpha Particle Activity
pH
Manganese
Trans-1, 2-Dichloroethylene
Cis-1, 2-Dichloroethylene
Perchlorate
Barium
Arsenic
Zinc
Conductivity (at 25°C)
Carbon, Total
Turbidity
Iron
Aluminum
Color
Utility MONTARA WATER AND SANITARY DISTRICTPopulation served 6,078Owner Local government
No violations on file
Contaminants found
Metals
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0 mg/L (ppm)
12/31/2023
Copper Summary
Detected: 2.6 mg/L (ppm)
12/31/1999
Manganese
Detected: 81 UG/L (ppb)
8/27/2025
Mainly a taste/staining concern at typical levels; long-term neurological research at high chronic exposure is ongoing.
Barium
Detected: 30 UG/L (ppb)
8/13/2025
Arsenic
Detected: 7.2 UG/L (ppb)
8/13/2025
Occurs naturally in some groundwater. Long-term exposure above the legal limit (10 ppb) has been linked to increased cancer risk and cardiovascular disease.
Zinc
Detected: 23 UG/L (ppb)
8/13/2025
Iron
Detected: 210 UG/L (ppb)
8/11/2025
Mostly an aesthetic issue (metallic taste, staining) rather than a health concern at typical levels.
Aluminum
Detected: 200 UG/L (ppb)
8/11/2025
Disinfection Byproducts
Formed when chlorine used to disinfect water reacts with organic matter
Totalhaloaceticacids (HAA5)
Detected: 9.6 UG/L (ppb)
8/6/2025
TTHM
Detected: 29 UG/L (ppb)
8/6/2025
A group of disinfection byproducts formed when chlorine reacts with organic matter. Long-term exposure above the legal limit has been linked to increased cancer risk in some studies.
Chloroform
Detected: 4.5 UG/L (ppb)
8/6/2025
One of the individual trihalomethane disinfection byproducts, formed when chlorine reacts with organic matter.
Bromoform
Detected: 6.8 UG/L (ppb)
8/6/2025
Bromodichloromethane
Detected: 6.4 UG/L (ppb)
8/6/2025
Dibromochloromethane
Detected: 11 UG/L (ppb)
8/6/2025
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Nitrate
Detected: 8.6 MG/L (ppm)
9/25/2025
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Chloride
Detected: 43 MG/L (ppm)
8/13/2025
Sulfate
Detected: 12 MG/L (ppm)
8/13/2025
Fluoride
Detected: 0.58 MG/L (ppm)
8/13/2025
Often added deliberately for dental health; can also occur naturally.
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 3.5 MG/L (ppm)
8/13/2025
Calcium
Detected: 30 MG/L (ppm)
8/13/2025
Sodium
Detected: 25 MG/L (ppm)
8/13/2025
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
Langelier Index (pH(s))
Detected: -1.5 LANG
8/11/2025
Hardness, Total (ASCACO3)
Detected: 89 MG/L (ppm)
8/13/2025
Gross Alpha Particle Activity
Detected: 2.68 PCI/L
8/13/2025
pH
Detected: 7.5 PH
8/13/2025
A measure of how acidic or basic the water is (7 is neutral). Affects taste and plumbing, not a direct health measure.
VOCs (Volatile Organic Compounds)
Industrial solvents and fuel-related chemicals that evaporate easily
Cis-1, 2-Dichloroethylene
Detected: 2.3 UG/L (ppb)
2/3/2025
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 80 MG/L (ppm)
8/13/2025
Other
Additional substances tested that don't fit neatly into the categories above
Dichloroaceticacid
Detected: 2.7 UG/L (ppb)
8/6/2025
Trichloroaceticacid
Detected: 3.3 UG/L (ppb)
8/6/2025
Dibromoaceticacid
Detected: 3.6 UG/L (ppb)
8/6/2025
Aggressive Index
Detected: 11.2 AGGR
8/13/2025
Alkalinity, Total
Detected: 80 MG/L (ppm)
8/13/2025
TDS
Detected: 200 MG/L (ppm)
8/13/2025
Trans-1, 2-Dichloroethylene
Detected: 0.69 UG/L (ppb)
2/3/2025
Perchlorate
Detected: 2 UG/L (ppb)
8/27/2025
Can occur naturally or from industrial/military sources; may interfere with thyroid function at elevated levels.
Conductivity (at 25°C)
Detected: 320 UMHO/CM
8/13/2025
Carbon, Total
Detected: 0.67 MG/L (ppm)
8/11/2025
Turbidity
Detected: 1.4 NTU
8/11/2025
A measure of water cloudiness from suspended particles.
Color
Detected: 5 UNITS
8/11/2025
Filtration considerations: See the table below for how whole-house carbon, under-sink reverse osmosis, and under-sink carbon systems compare against what's actually on file here. These are general system types, not a specific product recommendation.