B
84

Record-only indicator: B

Not a safety rating. Missing or old measurements can produce a high score.

Coverage: 8/8 mapped systems have a dated lead result; 0/8 have copper results; 6/8 have UCMR monitoring.

Longmont, CO 80504

Weld County · Population served: 102,866 · SDWIS 2026-07-21 · UCMR5 August 2026

Service-area evidence: EPA service-area records associate the listed system with this ZIP. Boundaries may still overlap or change.

Water Systems Serving This Area

🏔
LONGMONT CITY OF
Surface water · Pop. 102,866

Lead: 1.6 ppb; period end 12/31/2025. Copper: not available ppb; period end unknown.

PWSID: CO0107485
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FIRESTONE TOWN OF
Surface water · Pop. 27,798

Lead: 3.6 ppb; period end 12/31/2024. Copper: not available ppb; period end unknown.

PWSID: CO0162476
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LITTLE THOMPSON WD
Surface water · Pop. 25,654

Lead: 9.0 ppb; period end 12/31/1996. Copper: not available ppb; period end unknown.

PWSID: CO0135477
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LEFT HAND WD
Surface water · Pop. 20,280

Lead: 1.0 ppb; period end 12/31/2025. Copper: not available ppb; period end unknown.

PWSID: CO0107471
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FREDERICK TOWN OF
Surface water · Pop. 17,173

Lead: 2.9 ppb; period end 12/31/2025. Copper: not available ppb; period end unknown.

PWSID: CO0162288

Reported lead and copper results

ContaminantReported value or boundHistorical comparison valueInterpretationStatus
Lead
9.0 ppbPeriod end: 12/31/1996
15 ppb Largest reported value or bound among mapped systems; not necessarily the largest actual concentration. At/below comparison value

PFAS / Forever Chemicals

1 detected 1 above comparison value

UCMR5 occurrence results are screening information, not a finding of regulatory compliance or noncompliance. PFAS rules and compliance dates are evolving.

CompoundLevelEPA MCLInterpretationStatus
PFOA4.8 ppt4 ppt4 pptAbove comparison value

Violation History (Last 5 Years)

4Total (5yr)
0Health-Based
2Major

Public-record summary

Understanding Your Water in Longmont

Record-only indicator — incomplete or old records can produce a high score. A score of 100 is not a safety finding. Coverage: 8/8 mapped systems have a dated lead result; 0/8 have copper results; 6/8 have UCMR monitoring. Tap water quality in Longmont, Colorado (80504) receives an record-only indicator of B (Moderate-low record-based concern) with a score of 84 out of 100, based on analysis of EPA compliance data, contaminant testing, and violation history. This is 16 points above the Colorado state average of 68. The area is served by 8 water systems providing water to approximately 102,866 people, using surface water sources. Notably, 1 PFAS compound exceeds the EPA final MCL value used for comparison — a significant concern given the persistent nature of these chemicals.

Record-only score 84/100 B
vs State ▲ 16 pts above Colorado avg (68)
Comparison limits No national safety ranking: coverage and service areas overlap.

What a Grade B Means

Grade B summarizes the records available to this model, not household safety. Missing, bounded or old measurements can produce a high score, including 100. Review coverage, dates and the current utility report before interpreting this indicator.

Surface water: sourced from rivers, lakes, or reservoirs

Health Information

What These Contaminants Mean for You

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Lead in Your Water

Lead is a toxic metal that can leach from aging pipes and plumbing fixtures.

Health Effects

Even low levels of lead exposure can cause developmental delays in children, kidney damage, and cardiovascular effects in adults. The EPA action level is 15 ppb, but health experts recommend no safe level of lead in drinking water.

Common Sources

Lead enters water primarily through corrosion of lead service lines, lead solder, and brass fixtures — especially in homes built before 1986.

What You Can Do

If lead is detected above 1 ppb, consider using a certified lead-removal filter (NSF/ANSI 53) for drinking and cooking water. Run cold water for 30 seconds before use if water has been sitting in pipes.

Common Questions

Frequently Asked Questions

The record-only indicator is B (84/100). It cannot determine whether your tap water is safe. Missing, bounded or old measurements can produce a high score. Check the coverage and sampling dates below and your utility's current notices.

ZIP code 80504 is served by 8 water systems using surface water sources, providing water to approximately 102,866 people. Surface water systems are more susceptible to contamination from agricultural runoff, industrial discharge, and weather events, but typically undergo more extensive treatment including filtration and disinfection.

The largest reported lead value or bound is 9.0 ppb, for the sampling period ending 12/31/1996. This is a system-level 90th-percentile record, not a measurement at your tap. Compare the sampling date and original utility report before interpreting it.

Yes — 1 PFAS compounds were detected in records associated with water serving Longmont, Colorado, and 1 result exceeded the numerical EPA MCL value used for comparison. UCMR5 occurrence results alone are not a regulatory compliance determination. PFAS rules and compliance timelines are evolving; verify current information with the utility and EPA.

Water systems serving Longmont, Colorado have received 4 violations in the last 5 years. Violations can range from paperwork issues (monitoring & reporting) to serious health-based violations where contaminant levels exceeded safe limits. Review the violation details above for specifics.

This public-record indicator cannot select household treatment. Confirm your supplier, current utility report and tap-testing results first; match any treatment to a certified contaminant-reduction claim and follow its maintenance instructions.

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