Lake Oswego tap water, in plain English

• Health-based Lead and Copper Rule: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded once in January 2000. The EPA record for these does not include a measured level. All have since returned to compliance, per EPA records.
• Monitoring Consumer Confidence Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times between July 2024 and July 2025. All have since returned to compliance, per EPA records.
• Monitoring Bromate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2019. All have since returned to compliance, per EPA records.

• Monitoring 1,2,4-Trichlorobenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring cis-1,2-Dichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Xylenes, Total: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring DICHLOROMETHANE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring o-Dichlorobenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring p-Dichlorobenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Vinyl chloride: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring 1,1-Dichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring trans-1,2-Dichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring 1,2-Dichloroethane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring 1,1,1-Trichloroethane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Carbon tetrachloride: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring 1,2-Dichloropropane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Trichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring 1,1,2-Trichloroethane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Tetrachloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring CHLOROBENZENE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Benzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Toluene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Ethylbenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Styrene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Glyphosate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Di(2-ethylhexyl) adipate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Di(2-ethylhexyl) phthalate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring 2,4-D: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring Benzo(a)pyrene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2023. EPA records do not show all of these as returned to compliance.
• Monitoring COLIPHAGE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 9 times between January 2017 and January 2020. All have since returned to compliance, per EPA records.
• Monitoring E. COLI: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in September 2012. All have since returned to compliance, per EPA records.
• Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between January 1994 and July 1994. All have since returned to compliance, per EPA records.

• Monitoring Consumer Confidence Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 7 times between July 2003 and October 2024. All have since returned to compliance, per EPA records.
• Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 8 times between July 1994 and October 2022. All have since returned to compliance, per EPA records.

• Monitoring COLIPHAGE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2025. EPA records do not show all of these as returned to compliance.
• Monitoring Consumer Confidence Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 5 times between October 1999 and July 2024. All have since returned to compliance, per EPA records.
• Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times between January 2003 and October 2017. All have since returned to compliance, per EPA records.
• Monitoring E. COLI: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in November 2010. All have since returned to compliance, per EPA records.

• Monitoring Consumer Confidence Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times between July 2023 and July 2025. All have since returned to compliance, per EPA records.
• Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 4 times between October 1995 and October 2017. All have since returned to compliance, per EPA records.

• Health-based Coliform (TCR): a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded once in March 2016. The EPA record for these does not include a measured level. All have since returned to compliance, per EPA records.
• Monitoring Consumer Confidence Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times between July 2023 and July 2025. All have since returned to compliance, per EPA records.
• Monitoring Revised Total Coliform Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in November 2022. All have since returned to compliance, per EPA records.
• Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 4 times between April 2001 and October 2017. All have since returned to compliance, per EPA records.
• Monitoring Endrin: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring BHC-GAMMA: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Methoxychlor: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Toxaphene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Dalapon: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Diquat: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Endothall: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Glyphosate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Di(2-ethylhexyl) adipate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring OXAMYL: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Simazine: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Di(2-ethylhexyl) phthalate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Picloram: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Dinoseb: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Hexachlorocyclopentadiene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Carbofuran: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Atrazine: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring LASSO: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Heptachlor: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Heptachlor epoxide: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring 2,4-D: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring 2,4,5-TP: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring HEXACHLOROBENZENE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Benzo(a)pyrene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Pentachlorophenol: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Total Polychlorinated Biphenyls (PCB): a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring 1,2-DIBROMO-3-CHLOROPROPANE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring ETHYLENE DIBROMIDE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Chlordane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring 1,2,4-Trichlorobenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring cis-1,2-Dichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Xylenes, Total: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring DICHLOROMETHANE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring o-Dichlorobenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring p-Dichlorobenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Vinyl chloride: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring 1,1-Dichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring trans-1,2-Dichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring 1,2-Dichloroethane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring 1,1,1-Trichloroethane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Carbon tetrachloride: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring 1,2-Dichloropropane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Trichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring 1,1,2-Trichloroethane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Tetrachloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring CHLOROBENZENE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Benzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Toluene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Ethylbenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Styrene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
• Monitoring Public Notice: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in May 2016. All have since returned to compliance, per EPA records.

• Health-based Lead and Copper Rule: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 2 times between March 2019 and July 2019. The EPA record for these does not include a measured level. All have since returned to compliance, per EPA records.
• Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 5 times between July 2018 and October 2024. All have since returned to compliance, per EPA records.
• Monitoring Consumer Confidence Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 10 times between October 1999 and July 2023. All have since returned to compliance, per EPA records.
• Monitoring Nitrite: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Barium: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Cadmium: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Chromium: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring CYANIDE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Fluoride: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Mercury: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Nickel: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Sodium: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Antimony, Total: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Beryllium, Total: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Thallium, Total: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Selenium: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in January 2020. EPA records do not show all of these as returned to compliance.
• Monitoring Combined Uranium: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between April 2018 and October 2018. All have since returned to compliance, per EPA records.
• Monitoring Combined Radium (-226 and -228): a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between April 2018 and October 2018. All have since returned to compliance, per EPA records.
• Monitoring Gross Alpha, Excl. Radon and U: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between April 2018 and October 2018. All have since returned to compliance, per EPA records.
• Monitoring TTHM: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in October 2018. All have since returned to compliance, per EPA records.
• Monitoring Total Haloacetic Acids (HAA5): a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in October 2018. All have since returned to compliance, per EPA records.
• Monitoring Revised Total Coliform Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in December 2016. All have since returned to compliance, per EPA records.

As of June 2026, EPA records show no reported violations for this system in the period covered. This is not a guarantee about every substance, or about the water inside your home's plumbing.