01The verdict: is Lower Base water safe?
Lower Base's drinking water has significant quality concerns based on EPA testing data. With a grade of B- (73.4/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 2 water systems serve approximately 3,101 residents using groundwater (wells).
20 unresolved violations on record
EPA records show open compliance items for this system. Most are administrative, but unresolved items are worth watching.
See what was cited ↓Lead is well under the limit
90th-percentile lead is 2.1 ppb — beneath the 15 ppb federal action level and under the 5 ppb watch threshold.
See the trend ↓8 violations in the last five years
Recent compliance history is the best predictor of future problems — the year-by-year record is below.
See the record ↓Lower Base's drinking water received a grade of B- (73.4 out of 100), indicating fair water quality. The city's 2 water systems serve approximately 3,101 residents using groundwater.
Lead levels were measured at 2.1 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 187 violations on record, including 5 health-based violations. 20 remain unresolved.
Lower Base ranks #2 out of 7 cities in Northern Mariana Islands for water quality, placing it above average in the state. Lower Base 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, Lower Base may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities. The system has seen 8 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
02What's in Lower Base's water
Every contaminant flagged in Lower Base, on one shared scale: distance to its own legal limit. The red line is the limit — anything past it is out of compliance, and the closer a bar gets, the less headroom the system has.
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. | 2.1 | 15 | ppb | Inorganic | Safe |
03Lower Base's ten-year track record
Each box is one year. A green check means no EPA violations; a numbered badge counts that year's violations — red if any were health-based, amber if they were monitoring or paperwork issues. The system has 187 violations on record, including 5 health-based violations. 20 remain unresolved.
6 of the last ten years were clean. The numbered years had EPA violations — red when any were health-based, amber when they were paperwork or missed-testing issues.
▲ Up 1.4 ppb since 2016. Latest reading: 2.1 ppb (2025) — 14% of the action level. Sampled at higher-risk homes (90th percentile).
04Where Lower Base's water comes from
Lower Base's drinking water is drawn from underground aquifers through wells.
Groundwater
Underground aquifers reached by wells — naturally filtered, but can carry minerals like arsenic and nitrate.
Local treatment
Groundwater generally needs less treatment — typically disinfection and, where needed, mineral removal.
2 systems
2 water systems (2 wholesalers), operated under private ownership.
3,101 people
Residents served across Lower Base's service area.
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 3,101 people through 2 water systems.
| System name | PWSID | Population | Source |
|---|---|---|---|
| Saipan Ice And Water | MP0000004 | 3,101 | Groundwater |
| The Water Company | MP0000063 | 310 | Purchased Groundwater |
05How Lower Base compares
Scores for nearby Northern Mariana Islands cities on one line, with the average marked.
dashed line = Northern Mariana Islands average (56/100)
Lower Base scores 73.4/100 — above the Northern Mariana Islands average of 56/100. It outscores 5 of 6 nearby cities.
40.2 / 100DSan Jose, MP
50 / 100BSinapalu, MP
78.2 / 100DChalan Lau Lau, MP
48.3 / 100CAs Matuis, MP
68.4 / 100DSan Antonio, MP
50.9 / 100
06What to do at home
Steps matched to what testing actually found in Lower Base's water — not generic advice.
A basic carbon filter still helps
Lower Base's water meets federal standards, but a simple carbon filter improves taste and adds a margin of safety against short-term issues.
Compare tested filters →Read your utility's annual report
Every utility must publish a yearly Consumer Confidence Report with its own testing results. It pairs well with the independent data on this page.
How to read a CCR →Watch for Lower Base alerts
We refresh EPA data monthly and surface new violations, advisories, and boil-water notices for your county on this page.
All water alerts →Frequently asked questions
Is Lower Base, MP tap water safe to drink?
Lower Base's water quality earned a grade of B- (73.4/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #2 out of 7 cities tested in Northern Mariana Islands.
What contaminants are in Lower Base's water?
Lead was measured at 2.1 ppb (90th percentile). 187 violations are on record.
How is Lower Base'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 Lower Base?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Lower Base's water come from?
Lower Base's water is sourced from Groundwater. The city has 2 water systems serving approximately 3,101 residents.
What health violations has Lower Base's water system had?
Lower Base has 5 health-based violations on record. The most recent violation was recorded in February 2023. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 20 violations remain unresolved.
Is Lower Base's groundwater at risk of contamination?
Lower Base 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 187 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 Lower Base's water compare to other cities?
Lower Base ranks #2 out of 7 cities in Northern Mariana Islands (better than 71% of state cities) and #9956 out of 15382 cities nationally (35th percentile). The grade of B- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.