Wet yard and septic systems in Texas: floods, runoff and soil
A standard Texas absorptive drain field needs two feet of suitable soil from the bottom of the trench to groundwater or a restrictive layer, and surface runoff must be kept off the disposal area. After a flood, do not use the system until floodwater has left every part of it. [1] [4]
Last checked · sources below · about this page
Not legal advice. Confirm soil, floodplain and permit rules for your lot with your local permitting authority before you build, buy or dig.
Why a wet yard is a septic problem
- Saturated soil cannot take wastewater
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Texas A&M AgriLife Extension notes that a soil absorption field saturated with rainwater cannot accept wastewater. Roof and paved runoff should be drained around the field, not onto it. [2]
- Keep rainwater systems away
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The U.S. EPA says to keep roof drains, sump pumps and other rainwater drainage systems away from the drain field, because excess water slows or stops treatment in the soil. [3]
State rules for drain fields and wet ground
Texas rules (30 TAC §285.33) require two feet of suitable soil between the bottom of a standard drain-field trench and groundwater or a restrictive layer.
- Two feet to groundwater or a restrictive layer
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For a standard absorptive drain field, Texas rules require two feet of suitable soil from the bottom of the excavation to either a restrictive horizon or to groundwater. The excavation must be in suitable soil as set out in the site-evaluation rules. Your local permitting authority can set a stricter rule. [1] [8]
- Surface runoff must be diverted
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The state drain-field rules say surface runoff impacting the disposal area is not permitted, and the planning materials must say how runoff will be diverted. Where rock sits above the trench bottom under allowed conditions, surface runoff over the disposal area must still be prevented. Your local permitting authority can set a stricter rule. [1] [8]
- When a standard field is not enough
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An evapotranspiration (ET) system may be used where soils are unsuitable for a standard subsurface absorption system because of texture, restrictive horizons or groundwater, and only where average annual evaporation exceeds rainfall. Other options (such as drip irrigation with secondary treatment, or surface application of disinfected effluent) have their own soil and separation rules. [1]
See also: The site usually decides
After a flood
- Wait for floodwater to leave
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AgriLife says not to use the system until floodwater has receded from every part of it, and to check for damaged lids or soil washed away. If tanks filled with floodwater, call a service provider. Do not pump the tanks empty while the ground is saturated: empty tanks can float out of wet ground and damage piping. [4]
Local flood and lot limits
- Counties can add limits
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TCEQ says local permitting programs can be more stringent than the state minimums. Montgomery County, for example, won't issue permits for septic systems in the regulatory floodway. Check the office that covers your address. [5] [6]
See also: Montgomery County
About this page
How wet ground affects a Texas septic system: the two-foot soil rule for drain fields, keeping roof and surface water off the field, what to do after a flood, and when the site needs a different disposal method.
- Content last changed
- Last verified
- Sources
- 8 sources, all primary, listed below
- Not covered
- Design of a replacement system for a specific lot; Edwards Aquifer special rules; Insurance coverage for flood damage
Contacts
Your local septic permitting authority
- What they handle
- Site evaluation, floodplain limits and permits. Find it by county with TCEQ's OARS lookup.
Sources
Each fact above cites one or more of these by number. Accessed is the date the source was last re-read.
- [1] 30 Tex. Admin. Code § 285.33, Criteria for Effluent Disposal Systems. Texas Administrative Code, via Cornell Legal Information Institute. Primary source.
Supports: Two feet of suitable soil; divert surface runoff; ET and other options when soil is unsuitable.
Accessed: . - [2] Onsite wastewater treatment systems: Septic tank/soil absorption field (L-5227). Texas A&M AgriLife Extension. Primary source.
Supports: Saturated fields cannot accept wastewater; drain roof runoff around the field.
Publisher's date: Fact sheet dated Sep 2008.
Accessed: . - [3] How to Care for Your Septic System. U.S. Environmental Protection Agency (EPA). Primary source.
Supports: Keep roof drains and sump discharge away from the drain field.
Publisher's date: Last updated .
Accessed: . - [4] Onsite wastewater treatment systems: Responding to power outages and floods (L-5475). Texas A&M AgriLife Extension. Primary source.
Supports: After-flood steps; do not pump empty tanks in saturated ground; inspect flooded equipment before power.
Publisher's date: Fact sheet dated Sep 2008.
Accessed: . - [5] Getting a Permit for an OSSF - Such as a Septic System. Texas Commission on Environmental Quality (TCEQ). Primary source.
Supports: Local programs can be stricter than state minimums.
Publisher's date: Page last modified .
Accessed: . - [6] How to obtain a permit to construct a septic system and obtain a notice of approval (with OSSF fee list). Montgomery County Environmental Health Services. Primary source.
Supports: Montgomery floodway ban.
Publisher's date: Handout revised .
Accessed: . - [7] OARS: Find a Local Contact (septic permitting authority by county). Texas Commission on Environmental Quality (TCEQ). Primary source.
Supports: Finding the local permitting authority.
Accessed: . - [8] 30 Tex. Admin. Code § 285.10, Delegation to Authorized Agents. Texas Administrative Code, via Cornell Legal Information Institute. Primary source.
Supports: Local permitting authorities may adopt standards more stringent than the state rules.
Accessed: .
Page history
- : Added that local permitting authorities can set stricter soil and runoff rules. Re-checked every source.
- : First version of this page.