EPA SDWIS ยท Yolo County, California ยท 218 providers profiled
Yolo County, CA Water Quality Report
Yolo County is served by 218 major public water systems on file with the EPA.
Data current as of July 2026
๐Straight from EPA
๐งชReal Lab Results
๐ Updated Quarterly
๐ Local Expertise
Results for Yolo County, CA
218 water providers on file for this county, sorted by population served.
Quick answer: Yolo County has 218 water providers profiled, sorted by population served.
Lead Summary
Nitrate
Chromium, Hex
Arsenic
Totalhaloaceticacids (HAA5)
TTHM
Chloroform
Dichloroaceticacid
Trichloroaceticacid
Fluoride
Radium-228
Combined Uranium
Gross Alpha Particle Activity
Barium
Selenium
Lead
Copper, Free
Conductivity (at 25ยฐC)
Magnesium
Silica
Sodium
Calcium
Chloride
Perfluorohexanesulfonicacid (PFHxS)
Boron, Total
Chromium
Bromoform
Dibromochloromethane
Aggressive Index
Alkalinity, Total
Alkalinity, Bicarbonate
Hardness, Total (ASCACO3)
TDS
Sulfate
Nitrate-Nitrite
Perfluoroctanesulfonicacid (PFOS)
Turbidity
pH, Field
pH
Bromide
Carbon, Total
Langelier Index (pH(s))
Gross Beta Particle Activity
Odor
Iron
Bromodichloromethane
Chlorate
Bromate
Aluminum
Manganese
Dibromoaceticacid
Orthophosphate
Vanadium, Total
Foamingagents (SURFACTANTS)
Zinc
Copper Summary
Potassium
Lithium
Carbontetrachloride
Monochloroaceticacid
PFNA
1, 2, 3-Trichloropropane
Nitrogen-Ammoniaas (N)
Combined Radium (-226 & -228)
Color
Perchlorate
Violations on file
Coliform (TCR)
Older/archived health-based violation
Found at 15 of 218 providers
Nitrate
Older/archived health-based violation
Found at 11 of 218 providers
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Selenium
Older/archived health-based violation
Found at 3 of 218 providers
Lead And Copper Rule Revisions
Currently open health violation
Found at 13 of 218 providers
Arsenic
Older/archived health-based violation
Found at 1 of 218 providers
Occurs naturally in some groundwater. Long-term exposure above the legal limit (10 ppb) has been linked to increased cancer risk and cardiovascular disease.
Contaminants found
Metals
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0.114 mg/L (ppm)
Found at 53 providers
Chromium, Hex
Detected: 41 UG/L (ppb)
Found at 40 providers
Arsenic
Detected: 13.6 UG/L (ppb)
Found at 19 providers
Occurs naturally in some groundwater. Long-term exposure above the legal limit (10 ppb) has been linked to increased cancer risk and cardiovascular disease.
Combined Uranium
Detected: 2.9 PCI/L
Found at 3 providers
A naturally occurring radioactive metal. Long-term exposure above the legal limit is associated with kidney effects and increased cancer risk.
Barium
Detected: 460 UG/L (ppb)
Found at 21 providers
Selenium
Detected: 16 UG/L (ppb)
Found at 7 providers
Lead
Detected: 180 UG/L (ppb)
Found at 9 providers
A metal that can leach from old pipes, solder, and fixtures. Current medical guidance holds there is no truly safe level of lead exposure, especially for children and pregnant women.
Copper, Free
Detected: 640 UG/L (ppb)
Found at 25 providers
Chromium
Detected: 36 UG/L (ppb)
Found at 15 providers
Occurs in two forms โ trivalent (an essential nutrient in trace amounts) and hexavalent (linked to increased cancer risk).
Iron
Detected: 800 UG/L (ppb)
Found at 6 providers
Mostly an aesthetic issue (metallic taste, staining) rather than a health concern at typical levels.
Aluminum
Detected: 220 UG/L (ppb)
Found at 2 providers
Manganese
Detected: 140 UG/L (ppb)
Found at 4 providers
Mainly a taste/staining concern at typical levels; long-term neurological research at high chronic exposure is ongoing.
Vanadium, Total
Detected: 9.8 UG/L (ppb)
5/6/2025
Zinc
Detected: 440 UG/L (ppb)
4/7/2025
Copper Summary
Detected: 1.676 mg/L (ppm)
12/31/2023
Disinfection Byproducts
Formed when chlorine used to disinfect water reacts with organic matter
Totalhaloaceticacids (HAA5)
Detected: 23 UG/L (ppb)
Found at 8 providers
TTHM
Detected: 71 UG/L (ppb)
Found at 11 providers
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: 56 UG/L (ppb)
Found at 7 providers
One of the individual trihalomethane disinfection byproducts, formed when chlorine reacts with organic matter.
Bromoform
Detected: 17.4 UG/L (ppb)
Found at 3 providers
Dibromochloromethane
Detected: 3.2 UG/L (ppb)
Found at 8 providers
Bromodichloromethane
Detected: 11 UG/L (ppb)
Found at 6 providers
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Nitrate
Detected: 21 MG/L (ppm)
Found at 52 providers
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Fluoride
Detected: 0.7 MG/L (ppm)
Found at 21 providers
Often added deliberately for dental health; can also occur naturally.
Chloride
Detected: 92 MG/L (ppm)
Found at 11 providers
Boron, Total
Detected: 1500 UG/L (ppb)
Found at 2 providers
Sulfate
Detected: 100 MG/L (ppm)
Found at 10 providers
Nitrate-Nitrite
Detected: 21 MG/L (ppm)
Found at 11 providers
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 71 MG/L (ppm)
Found at 10 providers
Sodium
Detected: 76 MG/L (ppm)
Found at 10 providers
Calcium
Detected: 74 MG/L (ppm)
Found at 11 providers
Potassium
Detected: 3.1 MG/L (ppm)
Found at 3 providers
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
Gross Alpha Particle Activity
Detected: 4.66 PCI/L
Found at 8 providers
Hardness, Total (ASCACO3)
Detected: 470 MG/L (ppm)
Found at 9 providers
pH, Field
Detected: 7.5 PH
8/13/2025
pH
Detected: 8.2 PH
Found at 13 providers
A measure of how acidic or basic the water is (7 is neutral). Affects taste and plumbing, not a direct health measure.
Langelier Index (pH(s))
Detected: 0.87 LANG
Found at 10 providers
Orthophosphate
Detected: 1.1 MG/L (ppm)
Found at 2 providers
PFAS & Emerging Contaminants
Human-made "forever chemicals" and other substances not yet fully regulated
Lithium
Detected: 45.9 ยตg/L (ppb)
Found at 4 providers
Occurs naturally in some groundwater. Not currently federally regulated in drinking water.
PFNA
Detected: 0.0042 ยตg/L (ppb)
8/14/2023
VOCs (Volatile Organic Compounds)
Industrial solvents and fuel-related chemicals that evaporate easily
Bromide
Detected: 0.015 MG/L (ppm)
9/3/2025
Carbontetrachloride
Detected: 0.51 UG/L (ppb)
9/23/2025
1, 2, 3-Trichloropropane
Detected: 0.015 UG/L (ppb)
5/22/2025
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 512 MG/L (ppm)
Found at 12 providers
Other
Additional substances tested that don't fit neatly into the categories above
Dichloroaceticacid
Detected: 19 UG/L (ppb)
Found at 7 providers
Trichloroaceticacid
Detected: 11 UG/L (ppb)
Found at 7 providers
Radium-228
Detected: 1.17 PCI/L
Found at 2 providers
Conductivity (at 25ยฐC)
Detected: 1300 UMHO/CM
Found at 18 providers
Silica
Detected: 30 MG/L (ppm)
Found at 3 providers
Perfluorohexanesulfonicacid (PFHxS)
Detected: 3 NG/L (ppt)
4/2/2025
Aggressive Index
Detected: 12.9 AGGR
Found at 11 providers
Alkalinity, Total
Detected: 470 MG/L (ppm)
Found at 12 providers
TDS
Detected: 770 MG/L (ppm)
Found at 12 providers
Perfluoroctanesulfonicacid (PFOS)
Detected: 4.4 NG/L (ppt)
3/11/2025
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
Turbidity
Detected: 6.3 NTU
Found at 9 providers
A measure of water cloudiness from suspended particles.
Carbon, Total
Detected: 1.3 MG/L (ppm)
Found at 2 providers
Gross Beta Particle Activity
Detected: 8.14 PCI/L
4/2/2025
Odor
Detected: 17 TON
Found at 10 providers
Chlorate
Detected: 110 UG/L (ppb)
10/1/2025
Bromate
Detected: 99 UG/L (ppb)
10/1/2025
Dibromoaceticacid
Detected: 1.2 UG/L (ppb)
8/13/2025
Foamingagents (SURFACTANTS)
Detected: 0.083 MG/L (ppm)
4/7/2025
Monochloroaceticacid
Detected: 2.1 UG/L (ppb)
1/8/2025
Nitrogen-Ammoniaas (N)
Detected: 0.71 MG/L (ppm)
8/7/2025
Combined Radium (-226 & -228)
Detected: 1.13 PCI/L
8/7/2025
A naturally occurring radioactive element found in some groundwater.
Color
Detected: 2 UNITS
2/20/2025
Perchlorate
Detected: 1 UG/L (ppb)
2/25/2025
Can occur naturally or from industrial/military sources; may interfere with thyroid function at elevated levels.
Filtration considerations: General system types, not a specific product recommendation.