Drain Field Replacement in McLennan County, TX

In McLennan County, on-site sewage permits run through the Waco-McLennan County Public Health District rather than the county courthouse. Most new and replacement systems here are not gravel trenches: of the district's 462 authorizations to construct in 2025, 393 were surface-spray systems. The reason is underground. USDA soil surveys rate roughly four-fifths of the county as very limited for absorption fields, mostly because water moves slowly through blackland clays like Houston Black and Heiden.

Permits

Apply to the Waco-McLennan County Public Health District OSSF program, 401 Franklin Ave, Waco, (254) 299-2473. Fees effective Oct 1, 2026: $510 conventional, $710 aerobic, $285 minor repair, plus a $10 state fee. A minor repair covers things like expanding a tank or field or relocating a spray area.

Local conditions

Slow-permeability Vertisols (Houston Black is described by NRCS as very slowly permeable). Bedrock depth is a limitation on large areas. Shallow water tables are essentially absent, so the problem is clay, not groundwater.

What drives local prices

A spray or other designed system is the norm (85% of 2025 authorizations)
The aerobic permit tier ($710) vs conventional ($510)
Spray-area size set by the county's Ri value on TCEQ's isopleth map

Common jobs

Aerobic spray-field replacement on blackland clay
Spray-area relocation (minor repair permit $285)
Perc test and site evaluation for new home construction
Full drain field replacement after conventional field failure

Service area

Permits run through the Waco-McLennan County Public Health District, not the county courthouse.

Requests from Hewitt, Woodway and Robinson are routed to the same county provider.

Communities: Waco, Hewitt, Woodway, Robinson, Lorena, McGregor, China Spring, Mart, Moody, West, Bellmead, Lacy Lakeview, Crawford, Riesel

If it is an emergency

If sewage is surfacing, keep people and pets away. Texas requires emergency repairs to be reported within 72 hours. Contact the district at (254) 299-2473.

Questions about McLennan County

Is a minor repair permit enough to fix my drain field in McLennan County?

The district lists a $285 minor-repair permit for work such as tank or field expansion or moving a spray area. A full replacement is permitted at $510 (conventional) or $710 (aerobic) plus $10.

How big a spray field does a 3-bedroom McLennan County home need?

Using TCEQ's spray formula (Q ÷ Ri) with 240 gpd and an Ri of 0.064, about 3,750 sq ft. Confirm the Ri from the RG-472 isopleth map with the district.

Sources

Fees and rules change; confirm with the permitting office. Run the estimator for a cost range.