City of Thornton☆

Where the water comes from

Facility	Kind	Water
STANDLEY LAKE CLEAR CREEK	Intake	Surface water
W GRAVEL LAKES FROM LOWER CLEAR CREEK	Intake	Surface water
E GRAVEL LAKES FROM SOUTH PLATTE RIVER	Intake	Surface water

These are EPA's facility records, not DWR structures. Which decreed rights sit behind an intake is the next phase; nothing here is inferred.

Wholesale connections

Sells water to 9 systems: BRIGHTON CITY OF, AVILLA EASTLAKE, WESTMINSTER CITY OF, FRIENDLY VILLAGE OF THE ROCKIES, THE GROVE AT ALTA RIDGE, PINE LAKES RANCH, REDWOOD ESTATES, THORNTON ESTATES, WOODLAND HILLS MHC.

DWR structures that name this system

Source Probable join · fetched 2026-09-09 · matched on DWR's recorded contact or an EPA intake name; verify on the dossier

49 structures on DWR's record name this system as their contact (49). A match says who DWR lists, not who owns the water: a ditch company can own the headgate while the system owns shares, and a consultant can be the contact. The dossier holds the decree.

Compliance record

Source Register of another agency · fetched 2026-09-09 · verify at EPA ECHO ↗

EPA's own summary: violations in 2 of the last 12 quarters. In violation for, in EPA's words: 0300=Interim Enhanced Surface Water Treatment Rule.

No health-based or open violation on the federal record for this system.

What the regulator did about it

22 enforcement actions on this system's federal record. In Colorado the state is the primacy agency, so most actions are the state's; EPA acts directly on tribal systems and when it steps in.

20 most recent of 22; the rest are on the ECHO report.

Lead and copper

The latest 90th-percentile lead result is 0.0023 mg/L (sampling period ending 2025-12-31) against an action level of 0.015 mg/L, below it. 14 results on file.

The action level is not a health limit: it is the level at which the rule requires a system to act (corrosion control, public education, and in some cases replacing lead service lines). Lead mostly enters water from household plumbing, so a system-wide percentile does not tell you what comes out of one tap.

Violation, enforcement and lead/copper records are EPA SDWIS federal reporting, fetched monthly; the summary is EPA ECHO. Code names come from EPA's own REF_CODE_VALUE table. SDWIS carries violations, not routine sample results — nitrate, disinfection by-product and PFAS values are not in it, and a clean record here means nothing was reported as a violation, not that nothing was ever detected. For what was measured, ask the system for its Consumer Confidence Report.

PFAS and lithium: EPA's UCMR 5 monitoring, 2023–2025

Source Register of another agency · fetched 2026-09-09 · verify at EPA UCMR occurrence data ↗

8 samples, 210 results, 2023-02-14 to 2023-11-27. 8 of the 29 PFAS were detected at least once; lithium was measured up to 34.0 µg/L (no federal limit). PFOA measured up to 0.0071 µg/L, at or above EPA's 2024 limit of 0.004 µg/L; PFOS measured up to 0.005 µg/L, at or above EPA's 2024 limit of 0.004 µg/L.

Rows shown: every detected contaminant plus the regulated PFAS and lithium; the rest were below their reporting limits. These are UCMR monitoring samples, not compliance samples. EPA's April 2024 rule set 4.0 ng/L (0.004 µg/L) for PFOA and PFOS, the same as UCMR 5's reporting limit, so any detection of either is at or above it; the rule's compliance date and its other limits have been under revision since 2025 and are not applied here. State PFAS sampling is on CDPHE's pages ↗.

Common questions

Who provides drinking water in Thornton, Colorado?

The City of Thornton is the public water system serving 226,465 people in Adams County, from surface water. Its EPA public water system id is CO0101150.

Where does the City of Thornton get its water?

The City of Thornton reports surface water as its primary source. EPA lists its source facilities as STANDLEY LAKE CLEAR CREEK, W GRAVEL LAKES FROM LOWER CLEAR CREEK, E GRAVEL LAKES FROM SOUTH PLATTE RIVER.

Does the City of Thornton have any drinking water violations?

EPA's compliance record shows no open health-based violations for the City of Thornton at the last monthly fetch. Older and non-health-based entries, if any, are listed on this page.