Last Updated 07/29/2026
Texas Stormwater Regulations
The state of Texas is in EPA region 6, and instead of statewide regulation operates regionally on MS4s. Volume control and post-construction requirements come from EPA/federally legislation and may vary based on additional municiple requirements.
“The Storm Water Management Program (SWMP) is a comprehensive program to manage the quality of discharges from the municipal separate storm sewer system (MS4). TxDOT does not utilize a single statewide SWMP but rather a district-specific SWMP that is based on a standardized plan.
The Texas Commission on Environmental Quality requires that the SWMP must contain a specified number of minimum control measures (MCM). In order to meet each required minimum control measure, TxDOT utilizes best management practices.”
Required Minimum Control Measures
“A Large or Phase I MS4 Permit is issued to an operator, such as a city or county, who owns or operates storm sewers or storm sewer systems that serve populations of 100,000 or more.
A Small or Phase II MS4 Permit is issued to an operator, such as a county, university or transportation authority, who owns or operates storm sewers or storm sewer systems that serve populations within urbanized areas.”
Excerpt from the Texas DOT Hydraulic Design Manual
Chapter 13 – Storm Water Management
Storm water is defined in the Construction General Permit (CGP) as “Rainfall runoff, snow melt runoff, and surface runoff and drainage.” For TxDOT purposes, storm water includes overland flow, and flow in ditches and storm drain systems.
Storm water management includes non-structural and structural measures such as the following:
- erosion control to minimize erosion and sediment transport
- storm water detention and retention systems to reduce peak runoff rates and improve water quality
- sedimentation and filtration systems remove debris, suspended solids, and insoluble pollutants
- vegetation buffers to reduce transport of pollutants.
Measures intended to mitigate storm water quantity and quality problems are termed “best management practices” (BMPs). These measures include detention and retention ponds which delay storm water flow and trap sediment, rock filter dams for the same reasons, silt fences to trap sediment, various filter materials in socks or tubes, and vegetation to retard flow and trap sediment.
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Frequently Asked Questions
Does Texas have one statewide stormwater program?
Not exactly. Texas is part of EPA Region 6, and rather than a single statewide program, the state regulates stormwater regionally through municipal separate storm sewer system (MS4) permits. Volume control and post construction requirements largely come from EPA and federal rules, and they can vary depending on additional requirements set by individual municipalities. This is why AQUALIS reviews each municipality’s own code in addition to state level requirements.
What is an MS4 permit, and are all MS4 permits the same?
No, they come in two sizes based on population served:
- Large or Phase I MS4 Permit: issued to an operator, such as a city or county, that owns or operates a storm sewer system serving a population of 100,000 or more
- Small or Phase II MS4 Permit: issued to an operator, such as a county, university, or transportation authority, that owns or operates a storm sewer system within an urbanized area
What is a Storm Water Management Program (SWMP)?
An SWMP is a comprehensive program for managing the quality of what gets discharged from an MS4. The Texas Commission on Environmental Quality requires that an SWMP include a set number of minimum control measures. Entities meet these measures by implementing best management practices (BMPs) suited to their system.
What counts as a best management practice (BMP) under Texas guidance?
Based on the state’s hydraulic design guidance, BMPs are the structural and non-structural measures used to manage stormwater quantity and quality. Common examples include:
- Detention and retention ponds, which slow storm water flow and trap sediment
- Rock filter dams, used for the same purpose
- Silt fences and filter materials (such as socks or tubes), which trap sediment
- Vegetation, which slows flow and helps trap sediment
The information on this page is provided for general informational purposes only and is not legal advice. Regulations change frequently — AQUALIS makes no warranty as to the accuracy or completeness of this content, and any reliance on it is at your own risk. Consult a qualified professional or your local regulatory authority to confirm requirements applicable to your specific property.
