St. Mary County, Louisiana
12 ZIP codes · Avg score 67/100 · Grade C · Updated 2026-06-04
Based on current EPA data, St. Mary County's 12 ZIP codes reflect fair but mixed water safety.
How St. Mary County Compares
How St. Mary County Compares
St. Mary County scores 4 points below the Louisiana state average (71/100) and 1 points below the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-04
ZIP Code Risk Map
Water Quality Map: St. Mary County, Louisiana
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 16.9 (asthma 10.7%, diabetes 17.6%)
Estimated additional annual cost per homeowner: $4,898, driven primarily by sea_level
Infrastructure: 0.345% avg pipe failure probability, 20% of ZIPs at high risk
50.2% of homes built before 1978 (lead paint era)
Violation History (2021–2025)
↑ Worsening trendEPA violation counts by year across St. Mary County water systems. Health-based shown in red, total in blue.
Peak year: 2025 with 29 violations. Past 5 years: 59 total (59 health-based). Health-based violations are rising versus the prior 2-year window — worth closer monitoring.
Source: EPA SDWIS historical violations. Data may lag 6–12 months for the most recent year.
County Health Indicators vs National Average
Black markers indicate national averages. Source: CDC PLACES, Census ACS.
Infrastructure Overview
Sources: Census ACS (housing age), EPA SDWIS (infrastructure risk model), state bridge inspection data.
Compound Risk Breakdown
Estimated additional annual cost per homeowner: $4,898
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
14,105 housing units in St. Mary County
Source: U.S. Census Bureau ACS B25034 (Year Structure Built).
Water Safety Affordability
How much it costs to fix water issues relative to home values in St. Mary County
Remediation costs are relatively manageable for most homeowners in St. Mary County, representing a small fraction of property value.
Remediation includes water filtration, lead abatement, radon mitigation, and flood protection where applicable. Source: Census ACS, EPA SDWIS.
Health Outcomes vs National Average
CDC PLACES data for St. Mary County residents
Black markers = national averages. Red = above national avg. Green = below. Source: CDC PLACES, Census ACS.
Water Systems with Most Violations
Top 5 systems in St. Mary County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | WATER & SEWER COMMISSION 4 OF ST MARY | 9,709 | 53 |
| 2 | St Mary Water & Sewer Commission #3 | 7,500 | 50 |
| 3 | Franklin Water Supply | 8,325 | 49 |
| 4 | St Mary Par Jt Water Sewer Commission 5 | 1,240 | 49 |
| 5 | Port of West St Mary | 400 | 49 |
18 total water systems serve St. Mary County.
All ZIP Codes in St. Mary County
12 ZIP codes tracked in St. Mary County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 70505 | Lafayette | 90 | A | 0 | — |
| 2 | 70381 | Morgan City | 87 | A | 4 (3 health) | — |
| 3 | 70522 | Centerville | 86 | A | 1 (1 health) | — |
| 4 | 70523 | Charenton | 79 | B | 4 (4 health) | $115K |
| 5 | 70342 | Berwick | 76 | B | 4 (3 health) | $191K |
| 6 | 70392 | Patterson | 69 | C | 5 (4 health) | $142K |
| 7 | 70340 | Amelia | 68 | C | 7 (3 health) | — |
| 8 | 70352 | Donner | 60 | C | 0 | — |
| 9 | 70538 | Franklin | 50 | D | 49 (30 health) | $109K |
| 10 | 70540 | Garden City | 50 | D | 0 | — |
| 11 | 70356 | Gibson | 47 | D | 0 | $118K |
| 12 | 70514 | Baldwin | 47 | D | 0 | $128K |
Recommended Buyer Guides for St. Mary County
Methodologically, the recommendation order reflects severity in the federal record: contaminants flagged in EPA detection records for this county outrank generic water concerns, FEMA-confirmed hazard ratings shift emergency-related categories upward, and CDC lead-exposure markers govern when lead-test kits and certified filters appear at the top of the list.
- Best Lead Paint Test Kits — 50.2% of homes built before 1978
- Best Under-Sink Reverse Osmosis Systems — Multi-contaminant removal at the kitchen tap
Deep Dive Reports
Detailed analysis for St. Mary County, Louisiana
Overview
St. Mary County in Louisiana covers 12 ZIP codes with an average Home Safety Score of C (67/100).
7 of 12 ZIP codes have recorded EPA violations. 48 health-based violations have been documented.
← Back to Louisiana water quality report
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Home values: U.S. Census Bureau ACS (median estimates by ZCTA)
Updated daily.