Is Mountain Pass, CA Tap Water Safe to Drink?
Graded B+, with 3 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
83.9/100
waterverge.com Mountain Pass, CA — Water Quality Report
Mountain Pass's drinking water received a grade of B+ (83.9 out of 100), indicating good water quality. The city's 1 water system serves approximately 626 residents using groundwater.
Lead levels were measured at 0.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program.
The system has 7 violations on record, including 3 health-based violations. 3 remain unresolved.
What to know about Mountain Pass's water
Mountain Pass ranks #292 out of 694 cities in California for water quality, placing it mid-range in the state.
Mountain Pass relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
As a small community water system, Mountain Pass may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Mountain Pass, CA water safe to drink?
Mountain Pass's drinking water has significant quality concerns based on EPA testing data. With a grade of B+ (83.9/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 626 residents using groundwater (wells).
Recent water quality updates for Mountain Pass
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Mountain Pass's water quality assessment. Grade: B+ (83.9/100).
1 health-based. Contaminants: LEAD AND COPPER RULE REVISIONS.
Federal disaster declaration (FEMA DR-3592). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-3591). Flood event — may have impacted local water infrastructure.
Contaminants: Lead and Copper Rule.
Contaminants: Gross Alpha, Excl. Radon and U.
Key contaminant findings
Based on the most recent EPA sampling data for Mountain Pass's water supply.
Well within EPA limits.
Violation history
Mountain Pass's water system has 7 total violations on record, including 3 health-based violations. 3 remain unresolved. 2 violations were issued in the last 5 years.
Flood & environmental risk
San Bernardino County has experienced 10 federally declared disasters since 1980. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies.
Where does Mountain Pass's water come from?
Mountain Pass's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 626 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate.
What Mountain Pass residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Mountain Pass's water.
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Mountain Pass's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Drought conditions
D1 — moderate droughtSan Bernardino County is currently in D1 (moderate drought) per the U.S. Drought Monitor (week of May 5, 2026). Drought can elevate disinfection-byproduct (TTHM/HAA5) levels and taste/odor issues as utilities draw from lower reservoirs.
Source: U.S. Drought Monitor, updated weekly by NDMC, USDA, and NOAA.
Flood & disaster history
San Bernardino County has experienced 10 federally declared disasters since 1980. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 0.0 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Mountain Pass compares by contaminant
Explore where Mountain Pass ranks among all California cities for specific contaminants.
Water source & infrastructure
Where Mountain Pass's water comes from
Mountain Pass's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by private ownership and serves approximately 626 people through 1 water system.
Water systems serving Mountain Pass
| System Name | PWSID | Population | Source |
|---|---|---|---|
| MP MINE OPERATIONS LLC | CA3600172 | 626 | GW |
How Mountain Pass compares
Full California rankings →Mountain Pass's score of 83.9/100 is above the average of 57/100 among major California cities. It outscores 8 of 10 nearby cities.
Nearby cities
View California rankings →Learn more about your water
Guides and resources related to Mountain Pass's water quality findings.
Explore water quality across San Bernardino
Frequently asked questions
Is Mountain Pass, CA tap water safe to drink?
Mountain Pass's water quality earned a grade of B+ (83.9/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #292 out of 694 cities tested in California.
What contaminants are in Mountain Pass's water?
Lead was measured at 0.0 ppb (90th percentile). 7 violations are on record.
How is Mountain Pass's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Mountain Pass?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Mountain Pass's water come from?
Mountain Pass's water is sourced from Groundwater. The city has 1 water system serving approximately 626 residents.
What health violations has Mountain Pass's water system had?
Mountain Pass has 3 health-based violations on record. The most recent violation was recorded in October 2024. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 3 violations remain unresolved.
Is Mountain Pass's groundwater at risk of contamination?
Mountain Pass uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 7 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Mountain Pass's water compare to other cities?
Mountain Pass ranks #292 out of 694 cities in California (better than 58% of state cities) and #6207 out of 15744 cities nationally (61th percentile). The grade of B+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Mountain Pass's small water system affect quality?
Mountain Pass's system serves approximately 626 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has 7 violations on record.