Nitrate In Drinking Water In Colorado
What residents of Colorado need to know about nitrate in drinking water — including how it enters water, which utilities have documented violations, and what steps to take.
Source: EPA SDWIS, Colorado Department of Public Health and Environment (CDPHE), CDC · Last reviewed: 2025-01-01
Quick Answer
Is nitrate in drinking water a real concern in Colorado?
Yes — eastern Colorado's South Platte River basin has documented nitrate issues from feedlot operations and irrigated agriculture. The South Platte basin includes some of the highest nitrate concentrations documented in Colorado groundwater.
Is this mostly a public-water issue, a private-well issue, or both?
Primarily private well users in eastern Colorado's agricultural counties; some small public systems in the South Platte and Arkansas River valleys also draw from affected groundwater.
What is the main reason residents should care?
Colorado's eastern plains support large cattle feedlot operations, irrigated corn and wheat farming, and dairy operations. The South Platte River basin — from Fort Collins and Greeley south through Denver's eastern suburbs — has documented elevated nitrate in groundwater from feedlot waste, fertilizer runoff, and irrigation return flows.
Key Facts
| EPA Nitrate MCL | 10 mg/L as N |
| Weld County context | One of the largest cattle feedlot concentrations in the US — major nitrate source |
| South Platte basin | Documented elevated nitrate from feedlots, fertilizer, and irrigation return flows |
| Private well risk | Eastern Colorado agricultural county well users should test annually |
| State oversight | Colorado Department of Public Health and Environment (CDPHE) |
Why This Matters in Colorado
Colorado's Front Range agricultural corridor — particularly Weld County, which has one of the largest cattle feedlot populations of any county in the nation — generates significant nitrate loading from animal waste and fertilizer application. Weld County alone has millions of cattle in feedlots. Irrigation return flows and leaching from heavily fertilized corn and winter wheat fields contribute nitrate to the South Platte River basin's groundwater. CDPHE monitors public water systems in these areas; private well users on the eastern plains who rely on shallow groundwater are at elevated risk and should test annually. The Arkansas River basin in southeastern Colorado has similar agricultural nitrate concerns.
Critical — Infants Under 6 Months
Do not use tap water that exceeds 10 mg/L nitrate-nitrogen to prepare infant formula or feed infants under six months. Boiling will concentrate nitrate — do not boil. Use bottled water or a certified reverse osmosis system (NSF/ANSI 58) until the issue is resolved.
Colorado Utilities With Nitrate Violation Records
The utilities listed below have at least one nitrate violation on record in EPA's SDWIS database. Violations may be open or resolved — see individual utility pages for current status and risk level.
City of Greeley
Greeley · 132,310 served
Pueblo Board of Ww
Pueblo · 114,070 served
Town of Castle Rock
Colorado · 106,822 served
Ute Wcd
Colorado · 92,580 served
Parker Wsd
Colorado · 75,949 served
City of Englewood
Colorado · 57,332 served
City of Aspen
Colorado · 31,100 served
Arapahoe Cnty Wwwa
Colorado · 31,000 served
City of Lafayette
Colorado · 28,700 served
Town of Breckenridge
Colorado · 28,315 served
How Nitrate Gets Into Drinking Water
Agricultural fertilizer and manure runoff
Nitrogen-based fertilizers and animal waste applied to Colorado cropland can leach into groundwater or run off into surface water supplies. This is the dominant nitrate pathway in most agricultural regions.
Septic system effluent
Failing or poorly sited septic systems release nitrogen-rich wastewater near drinking water wells. Rural areas with high well density and aging septic infrastructure face elevated risk.
Concentrated animal feeding operations (CAFOs)
Large livestock facilities generate significant waste. Lagoon leaks and overapplication of manure to nearby fields can create localized nitrate hotspots in groundwater.
Natural geological deposits
In some regions, naturally occurring nitrogen compounds in soil and bedrock contribute background nitrate levels to groundwater independent of agricultural activity.
Who Should Pay Closest Attention
Private well users in Weld, Morgan, Adams, and eastern Colorado farming counties should test for nitrate annually. Households with infants in high-agricultural-intensity areas should use alternative water sources for formula preparation until nitrate testing confirms safe levels.
Households with infants under six months
Pregnant residents
Private well owners in agricultural areas
Households near livestock operations or CAFOs
Rural residents on shallow groundwater wells
Households with older or failing septic systems nearby
How to Check Your Situation in Colorado
- 1
Identify your water utility. Use the ZIP lookup below or browse the Colorado utility directory on this site.
- 2
Read your utility's page on this site to see its current risk level and any open nitrate violations.
- 3
Review your utility's most recent Consumer Confidence Report (CCR) — mailed annually or available on the utility's website. It must disclose any MCL exceedances.
- 4
If you are on a private well, arrange testing at a Colorado Department of Public Health and Environment (CDPHE)-certified lab. Your state health department maintains a list of certified labs. Annual testing is recommended in agricultural areas.
- 5
If you have an infant under six months, use bottled water or a certified RO system (NSF/ANSI 58) immediately as a precautionary measure — do not wait for test results if you are in a high-risk area.
- 6
If your utility issues a nitrate exceedance notice, follow their guidance and do not use tap water for infants until the issue is resolved.
Treatment Options
Carbon filters and boiling do not remove nitrate. Only the options below are effective.
NSF/ANSI Standard 58 — Reverse Osmosis
RO systems certified to NSF/ANSI 58 reduce nitrate by 85–95% at the point of use. Under-sink installation required. The most practical residential option for nitrate concerns.
Distillation
Distillation units effectively remove nitrate along with most other dissolved contaminants. Suitable for drinking and cooking water — not whole-house use.
Anion Exchange
Ion exchange systems designed for nitrate removal exchange nitrate ions for chloride on a resin bed. Effective as a point-of-entry system; requires periodic regeneration and monitoring.
Carbon filters do NOT remove nitrate
Standard pitcher filters, faucet filters, and under-sink carbon units — including those certified NSF/ANSI 42 or 53 — do not remove nitrate. Do not use these for nitrate reduction.
Frequently Asked Questions
Related Pages
Nitrate — National Overview
All U.S. utilities with nitrate records
Colorado State Overview
All utilities and water quality data
Lead in Drinking Water
A separate but common concern
Reverse Osmosis Guide
Removes 85–95% of nitrate
Well Water Guide
Private well testing and safety
All Contaminants
Complete reference library
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.