Hidden Valley Water District
What EPA’s and Colorado’s records show in this utility’s water: nitrate, arsenic and other regulated chemicals; lead and copper; and violations since 2016, with the certification that handles each result.
- Serves
- 155 people
- Connections
- 63
- Water source
- Surface water bought from another system
- Based in
- Evergreen, CO
- County
- Jefferson
- Owner
- Private
The ZIP code it serves
The short answer
2 results are above the health goal. The worst: Arsenic, above the health goal. 4 health-based violations since 2016.
What handles itWhat was found
Lead and copper: EPA SDWIS monitoring periods ending 2018 to 2025.
Nitrate, total trihalomethanes (TTHM), haloacetic acids (HAA5) and uranium: Colorado’s own results, samples taken from Feb. 10, 2020 to Aug. 22, 2026, with EPA’s 2012 to 2019 file for earlier years.
Arsenic, fluoride and chromium (total): EPA’s compliance monitoring file, samples taken from March 7, 2012 to Dec. 10, 2018. Newer results are in the utility’s annual water quality report.
Above the health goal2
Arsenic
Comes from the source
3.0ppb
Highest yearly average, 2012 to 2018
Averaged by year, the highest was 3.0 ppb, in 2018: below EPA’s legal limit of 10 ppb, but above its health goal of zero. That was also the latest year on file.
What handles it
- NSF/ANSI 58 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
- NSF/ANSI 53 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
Lead
Comes from pipes, often your own
3.5ppb
90th percentile, 2025
In the latest period, 9 in 10 homes sampled were at or below 3.5 ppb, below EPA’s action level of 15 ppb. The action level drops to 10 ppb on Nov. 1, 2027. EPA’s health goal for lead is zero.
What handles it
- NSF/ANSI 53 look for “Lead Reduction”
- NSF/ANSI 58 look for “Lead Reduction”
Below EPA’s limits5
Nitrate
Comes from the source
8.3ppm
One sample
2020, one sample: 8.3 ppm
The highest sample, in 2020, was 8.3 ppm, below EPA’s legal limit of 10 ppm. That is the only year on file, and its one sample was 8.3 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 11.7 ppm, in 2018, and EPA recorded a violation in 2018.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
Total trihalomethanes (TTHM)
Forms or is added in treatment
57.6ppb
Highest yearly average, 2020 to 2026
2026, one sample: 41.1 ppb
Averaged by year, the highest was 57.6 ppb, in 2021, below EPA’s legal limit of 80 ppb. In 2026, the latest year on file, its one sample was 41.1 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 18.9 ppb, in 2015.
What handles it
- NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
- NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
Haloacetic acids (HAA5)
Forms or is added in treatment
35.5ppb
Highest yearly average, 2020 to 2026
2026, one sample: 7.8 ppb
Averaged by year, the highest was 35.5 ppb, in 2023, below EPA’s legal limit of 60 ppb. In 2026, the latest year on file, its one sample was 7.8 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 4.8 ppb, in 2018.
What handles it
No certification claim covers this compound yet.
Fluoride
Forms or is added in treatment
0.19ppm
Highest yearly average, 2012 to 2018
2018, one sample: 0.15 ppm
Averaged by year, the highest was 0.19 ppm, in 2012, below EPA’s legal limit of 4.0 ppm. In 2018, the latest year on file, its one sample was 0.15 ppm.
What handles it
- NSF/ANSI 58 look for “Fluoride Reduction”
- NSF/ANSI 53 look for “Fluoride”
Chromium (total)
Comes from the source
3.0ppb
Highest yearly average, 2012 to 2018
2018, one sample: 3.0 ppb
Averaged by year, the highest was 3.0 ppb, in 2012, below EPA’s legal limit of 100 ppb. In 2018, the latest year on file, its one sample was 3.0 ppb.
What handles it
- NSF/ANSI 58 look for “Chromium (Hexavalent) Reduction”
- NSF/ANSI 53 look for “Chromium Reduction”
One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Uranium
What handles it
A certification covers specific claims, not a whole standard. Look for these claims on the certifier’s listing, not the box. Wording varies a little: NSF writes “Lead Reduction,” WQA just “Lead.”
- NSF/ANSI 53
Claims: Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction
For: Arsenic, Lead
Other certifiers’ wording: Arsenic (III) (50 ppb influent level)
- NSF/ANSI 58
Claims: Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction
For: Arsenic, Lead
Other certifiers’ wording: Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level)
At the tap, or for the whole house?
Lead and copper usually come from pipes and fixtures inside or near your home. A whole-house system sits where water enters, so it cannot catch what your own plumbing adds after it. For those, the filter that counts is the one at the tap. How whole-house systems compare.
Filters with those claims on a certifier’s listing
Disclosure: TapBuff earns a commission if you buy through some links on this page. It does not change which standard or filter we name. As an Amazon Associate, TapBuff earns from qualifying purchases. How TapBuff makes money
Countertop reverse osmosis
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 4, 2026
Certified for: Arsenic, Lead
Aquasana SmartFlow Reverse Osmosis (AQ-SFRO2)
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Arsenic, Lead
Brondell Capella RC250 Reverse Osmosis System
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Arsenic, Lead
Brita Tahoe Pitcher with Elite Filter (OB60, OB06)
Pitcher
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 13, 2026
- IAPMO listing:NSF/ANSI 53checked Oct. 13, 2026
Certified for: Lead
Violations since 2016
| Contaminant or rule | Type | Period | Measured | Status |
|---|---|---|---|---|
| Lead and Copper Rule Revisions | The required inventory of lead service lines was not completed or submitted on time.EPA: LSL Inventory | Oct. 17, 2024 | — | Resolved |
| Stage 1 Disinfectants and Disinfection Byproducts Rule | Treatment was not run by a certified operator as required.EPA: Treatment Technique No Certif. Operator | Dec. 1, 2023 | — | Resolved |
| Nitrate | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2018 to June 30, 2018 | 11.6 MG/L | Resolved |
| Combined Radium (-226 and -228) | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2016 to March 31, 2016 | 6.0 PCI/L | Resolved |
| Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 12 monitoring or reporting violations not shown. | ||||
What this report can’t tell you
Everything else. Nitrate, total trihalomethanes (TTHM), haloacetic acids (HAA5) and uranium results here are Colorado’s own from 2020 on, with EPA’s national file for 2012 to 2019. Arsenic, fluoride and chromium (total) come from EPA’s file alone, which ends in 2019. Hidden Valley Water District’s own annual report, which it must send you every year, has newer results for those and the contaminants this page does not show.
Your own plumbing. Lead results are the 90th percentile across homes the utility samples. Your home’s service line, solder and fixtures decide yours. A certified lab test is the only way to know.
What it means for your health. This page reports what the records show and EPA’s limits and goals; it is not medical advice. If you are worried about a health effect, talk to a doctor or your local health department.
Anything after the latest data. SDWIS data is from 2026 Q3; UCMR 5 didn’t sample this utility; Colorado’s results run from Feb. 10, 2020 to Aug. 22, 2026; EPA’s compliance samples are from March 7, 2012 to Dec. 10, 2018.
Testing your own tap
The 3 labs Colorado certifies closest to the area Hidden Valley Water District serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
GeoWater Services
Evergreen, CO · under a mile
Certified for bacteria
Hazen Research
Golden, CO · about 16 miles
Certified for nitrate, lead and copper, metals, minerals and other inorganics, radioactivity
Gilpin County Public Health Agency
Black Hawk, CO · about 16 miles
Certified for bacteria
Sources
- EPA UCMR 5 occurrence data, file of Oct. 15, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q3
- Colorado Department of Public Health and Environment, Water Quality Control Division, results from Jan. 3, 2020 to Oct. 6, 2026, read Oct. 17, 2026
- EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, file of Feb. 5, 2024
- Certified labs: CDPHE certified drinking water laboratories, read Oct. 16, 2026; distances from the Census 2020 ZIP code tabulation area gazetteer
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID CO0130045. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Read up on the 2 results above a lineWhat each one does to health, where it comes from, and the certification claim that addresses it.Start with Arsenic
- Get the utility’s own reportHidden Valley Water District must send you a water quality report every year. It covers contaminants this page does not show, and has newer results than EPA’s national file for the ones here that come from it.How to read it
- Test your own tap for leadYour service line, solder and fixtures decide the lead at your faucet, not the utility’s average.Lead in your water: what to do
- Compare certified filtersWhat the filters certified for these results cost over five years, cartridges included.Compare five-year costs