San Marcos WWTP
Highway 123 And Interstate Highway 35, San Marcos, TX 78666 · Hays County · Publicly Owned Treatment Works
- Average flow
- 7.76 MGD
- Design flow
- 9 MGD
- NPDES permit
- TX0047945
- Effective
- Permit expires
- January 2030
- Population served
- 52,088
- CWNS 2022
San Marcos WWTP is a publicly owned wastewater treatment works in San Marcos, Hays County, Texas treating an average of 7.76 million gallons per day against a permitted design capacity of 9 MGD, serving about 52,088 residents. It discharges under NPDES permit TX0047945 (effective), which expires in January 2030, with 88 recorded violations in the last three years. EPA has recorded 2 formal enforcement actions naming the plant, the latest in March 2025.
Treatment technology
4 treatment structures and unit processes identified at San Marcos WWTP.
Available with a free Klarifi account
See the full treatment train at San Marcos WWTP: structures, unit processes and planned upgrades, with exact unit counts.
Compliance snapshot (last 3 years)
- Total violations
- 88
- Effluent violations
- 88
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
EPA enforcement history
Federal civil enforcement cases, compliance inspections and informal actions recorded for San Marcos WWTP in EPA's ICIS system.
- Formal actions
- 2
- 1 since FY2020
- Compliance actions
- $25,000
- required by EPA orders
- EPA inspections
- 0
- none on record
Latest case · Mar 2025
City of San Marcos Administrative Order
Administrative order · CWA, NPDES Permit Violations · Final Order Issued · Compliance actions $20,000
EPA's description of the case:
“On March 3, 2025, EPA Region 6 issued an Administrative Order (AO) under its authority pursuant to Section 309 of the Clean Water Act to the San Marcos Wastewater Treatment Facility. The AO was…”
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Source: EPA ECHO, civil enforcement case 06-2025-1716.
Full case history with a free Klarifi account
Every action against San Marcos WWTP with dates, milestones, violation types and EPA's complete case summaries, plus inspections and informal actions.
Key contacts
19 verified contacts for San Marcos WWTP, with validated emails and direct phone numbers.
Unlock 19 verified contacts (16 more than shown)
Names, validated emails and direct phone numbers for decision-makers at San Marcos WWTP, plus the full compliance history and discharge data.
Nearby wastewater treatment plants in Texas
Kyle · 9 mi away
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City Of New Braunfels · 10 mi away
0.05 MGD
New Braunfels · 14 mi away
2.12 MGD
Buda · 16 mi away
0.98 MGD
Buda · 16 mi away
1.78 MGD
New Braunfels · 16 mi away
3.2 MGD
New Braunfels · 16 mi away
4.62 MGD
Seguin · 17 mi away
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San Marcos WWTP: frequently asked questions
Sources and methodology
Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.
Data refreshed October 26, 2026; facility record last updated April 7, 2025.
Wastewater terms: POTW · MGD · NPDES permit · Inflow and infiltration · Lift station · Sludge dewatering · all terms