Public water system record
Howell Mountain Mutual Water Company
Serves Angwin and Deer Park, Napa County, CA · 1,240 people served
Federal records show 3 health-based violations and 1 monitoring/reporting issue for Howell Mountain Mutual Water Company in the last ten years. The most serious issue in this window was a resolved Total Trihalomethanes (TTHMs) violation.
System profile
- Health-based violations, last 10 years
- 3
- Resolved
- 3
- Unresolved
- 0
- Any acute record
- No
- Monitoring issues, last 10 years
- 1
Key facts
- Howell Mountain Mutual Water Company draws water from 2 wells and 1 surface water intake (1 of them for emergency, seasonal or other part-time use).
- Highest measured level in the last 10 years: Total Trihalomethanes (TTHMs), 0.0865 mg/L, federal limit 0.08 mg/L (1.1 times the limit), 2016.
- Most recent formal enforcement: compliance order (no penalty) by California, December 2022.
- Record on file since 1987, with 33 health-based violations before October 19, 2016.
- Lead pipe inventory: 0 lead and 0 unknown out of 396 service lines.
Check whether Howell Mountain Mutual Water Company serves your address
Health-based violations
Since October 2016Violation data reflects EPA records through March 2026. For the most current status, visit the EPA ECHO database.
| Contaminant | Rule family | Start date | Status | Acute |
|---|---|---|---|---|
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 82 µg/L, federal limit 80 µg/L (at or just above the limit)
|
220 | Jan 1, 2023 | Resolved | No |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.083 mg/L, federal limit 0.08 mg/L (at or just above the limit)
|
220 | Apr 1, 2021 | Resolved | No |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0865 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
220 | Oct 1, 2016 | Resolved | No |
Monitoring and reporting issues
Since October 2016Missed tests or reports, not contaminants found above a limit.
| Issue | Start date | Status |
|---|---|---|
|
Lead and Copper Rule
Monitoring and reporting
|
Oct 1, 2020 | Resolved |
Full record since 1987
EPA's records for Howell Mountain Mutual Water Company go back to 1987. Before October 19, 2016 they list 33 health-based violations (33 resolved) and 11 monitoring or reporting violations.
| Violations that began in | Health-based | Monitoring and reporting |
|---|---|---|
| 1980s | 0 | 1 |
| 1990s | 2 | 4 |
| 2000s | 16 | 5 |
| 2010 to October 18, 2016 | 15 | 1 |
| 2020s | 2 | 1 |
Most recent health-based violation before October 19, 2016: Total Trihalomethanes (TTHMs), began October 2016, Resolved.
Show all 33 health-based violations before October 19, 2016
| Contaminant | Start date | Status |
|---|---|---|
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0865 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
Oct 1, 2016 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 81.75 µg/L, federal limit 80 µg/L (at or just above the limit)
|
Jul 1, 2016 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.086 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
Jul 1, 2013 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.089 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
Apr 1, 2013 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0616 mg/L, federal limit 0.06 mg/L (at or just above the limit)
|
Apr 1, 2011 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0693 mg/L, federal limit 0.06 mg/L (1.2 times the limit)
|
Jan 1, 2011 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0907 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
Jan 1, 2011 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0731 mg/L, federal limit 0.06 mg/L (1.2 times the limit)
|
Oct 1, 2010 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0994 mg/L, federal limit 0.08 mg/L (1.2 times the limit)
|
Oct 1, 2010 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0755 mg/L, federal limit 0.06 mg/L (1.3 times the limit)
|
Jul 1, 2010 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1044 mg/L, federal limit 0.08 mg/L (1.3 times the limit)
|
Jul 1, 2010 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.065 mg/L, federal limit 0.06 mg/L (1.1 times the limit)
|
Apr 1, 2010 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.099 mg/L, federal limit 0.08 mg/L (1.2 times the limit)
|
Apr 1, 2010 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0816 mg/L, federal limit 0.06 mg/L (1.4 times the limit)
|
Jan 1, 2010 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.107 mg/L, federal limit 0.08 mg/L (1.3 times the limit)
|
Jan 1, 2010 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.093 mg/L, federal limit 0.08 mg/L (1.2 times the limit)
|
Oct 1, 2009 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0706 mg/L, federal limit 0.06 mg/L (1.2 times the limit)
|
Oct 1, 2009 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0639 mg/L, federal limit 0.06 mg/L (1.1 times the limit)
|
Jul 1, 2009 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0897 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
Jul 1, 2009 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0639 mg/L, federal limit 0.06 mg/L (1.1 times the limit)
|
Apr 1, 2009 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0897 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
Apr 1, 2009 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.083 mg/L, federal limit 0.08 mg/L (at or just above the limit)
|
Jan 1, 2009 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0611 mg/L, federal limit 0.06 mg/L (at or just above the limit)
|
Oct 1, 2008 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0863 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
Oct 1, 2008 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0627 mg/L, federal limit 0.06 mg/L (at or just above the limit)
|
Jul 1, 2008 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0863 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
Jul 1, 2008 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0848 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
Apr 1, 2008 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.084 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
Oct 1, 2005 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0661 mg/L, federal limit 0.06 mg/L (1.1 times the limit)
|
Oct 1, 2005 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0661 mg/L, federal limit 0.06 mg/L (1.1 times the limit)
|
Jan 1, 2005 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0943 mg/L, federal limit 0.08 mg/L (1.2 times the limit)
|
Apr 1, 2004 | Resolved |
|
Surface Water Treatment Rule
Treatment technique failure
|
Jun 1, 1993 | Resolved |
|
Surface Water Treatment Rule
Treatment technique failure
|
May 1, 1993 | Resolved |
Enforcement actions
California regulators took 8 formal enforcement actions against Howell Mountain Mutual Water Company between 1993 and 2022. The most recent was a compliance order (no penalty) in December 2022.
| Date | By | Action | Violations covered |
|---|---|---|---|
| Dec 6, 2022 | California | Compliance order (no penalty) | 1 violation (1 health-based): Total Trihalomethanes (TTHMs) |
| Sep 20, 2021 | California | Compliance order (no penalty) | 1 violation (1 health-based): Total Trihalomethanes (TTHMs) |
| Feb 4, 2021 | California | Compliance order (no penalty) | 1 violation: Lead and Copper Rule |
| Nov 21, 2016 | California | Compliance order (no penalty) | 2 violations (2 health-based): Total Trihalomethanes (TTHMs) |
| May 13, 2016 | California | Compliance order (no penalty) | 1 violation: Nitrate |
| Jul 10, 2013 | California | Compliance order (no penalty) | 2 violations (2 health-based): Total Trihalomethanes (TTHMs) |
| Dec 23, 2009 | California | Compliance order (no penalty) | 27 violations (23 health-based): Total Trihalomethanes (TTHMs), Haloacetic Acids (HAA5) |
| Aug 25, 1993 | California | Compliance order (no penalty) | 4 violations (2 health-based): Surface Water Treatment Rule |
What the violations mean
Total Trihalomethanes (TTHMs)
3 incidentsDisinfection byproduct levels exceeded the federal limit
Long-term TTHM exposure may increase bladder cancer risk
Where the water comes from
Howell Mountain Mutual Water Company draws water from 2 wells and 1 surface water intake (1 of them for emergency, seasonal or other part-time use). 2 other public water systems have emergency connections to Howell Mountain Mutual Water Company.
Annual water quality report
Howell Mountain Mutual Water Company must give its customers an annual water quality report (Consumer Confidence Report) by July 1, with the levels its tests found in the previous year.
Where the state allows it, systems serving fewer than 10,000 people may publish the report in a local newspaper or news site instead of mailing it, and must provide a copy on request.
Find a posted report with EPA's Consumer Confidence Report search
Testing your own water
To test the water at your tap, or a private well this record does not cover, use a laboratory certified for drinking water by California.
Certified drinking water labs by state EPA guidance for private wells