Before you build
McAllen Septic: Septic Site Evaluation in McAllen, TX
Every new septic system in Texas starts with a look at the soil where the drain field will go.
- McAllen, Edinburg, Mission and towns within 20 miles
- Licensed, insured local septic contractors
- Conventional and aerobic systems
- Written price before work starts
- Straight answers on TCEQ and county rules
McAllen Septic puts McAllen-area landowners in touch with the contractor who arranges the site evaluation for a new septic system. If you plan to build on a lot outside the sewer lines in Hidalgo County, this comes before any design or permit. The page covers what the evaluation involves under the Texas rule, who is allowed to perform it, how lot size changes the plan, and what the work typically costs.
A $600 to $800 soil evaluation is what matches the drain field to the ground under it, and a field built on a guess can end in a replacement that Fixr puts at $2,000 to $20,000.
What a Septic Site Evaluation Means in Texas
Texas does not rely on a bare perc test. Rule 285.30 in 30 TAC says every new system needs a site evaluation that examines the soil itself. The rule calls for a pair of soil borings or a pair of backhoe pits, one at each end of where the disposal area will go. Each is taken two feet deeper than the planned excavation, or until a restrictive layer stops it, and the evaluator also checks for groundwater. Those findings feed the system design. Many people still search for a perc test, and the contractor will know what you mean; the Texas paperwork simply calls it a soil evaluation.
Septic Site Evaluation Cost and What Changes It
$600 to $800
The Fixr range for a perc test, offered as a guide and not a quote. Bob Vila puts a perc test at $1,000 to $2,000, and the evaluation and design are billed apart from the county permit.
The Fixr perc test figure is the closest published match for this work, and the higher Bob Vila range shows how widely estimates vary. Neither is a Rio Grande Valley price, because no operator in the Valley posts one. Keep three costs apart when you compare quotes: the soil evaluation, the system design, and the permit fee charged by the permitting authority. Wholesale Septic Supply notes that in Texas the design itself comes from an engineer or a sanitarian with a licence, who then files it with the county. The county prints no current fee schedule for septic permits, and the office can give you the figure when you apply.
Who May Do a Septic Site Evaluation
Only a site evaluator licensed by TCEQ, or a professional engineer, may perform the evaluation, and a site evaluator has to hold an Installer II licence or a professional credential. That holds even when the owner plans to do everything else. Texas lets owners build their own system on a single-family lot they own, yet the soil work must still come from a licensed evaluator or engineer. Pits and borings mean digging, so phone Texas 811 two or more days ahead, as the Railroad Commission asks.
Lot Size Rules for a Septic Site Evaluation in Hidalgo County
State rule 285.4 sets a minimum of half an acre for a subdivision lot on public water using an individual septic system, and one acre where there is no public water. The county's subdivision rules, revised in 2025, put the same line on the plat: a septic lot needs a plat note of no less than 21,780 square feet with potable water, and a minimum width of 50 feet at half an acre or less, 65 feet above it. Where a lot is smaller than half an acre and has no sanitary sewer, the county Planning Department requires an OSSF design plan from a licensed engineer. Planning sits at 2818 S Business Hwy 281, (956) 318-2840.
Floodplain and Setback Checks Before the Septic Design
The county order adds a floodplain determination from the county Floodplain Administrator before any permit is issued. Inside any floodplain hazard area septic tanks are restricted, and a plat there has to show a flood-zone design: anchored tanks, backflow valves and a sealed cover. On the state setback table the drain field must stay 100 feet off a private well, absorption areas 75 feet off any stream, pond or lake, and the system 5 feet off the foundation and the property line. If you are buying land for a septic system near Hidalgo or anywhere else in the county, get the floodplain answer first.
Signs Your Lot Needs a Septic Site Evaluation First
- You bought land outside the city sewer and want to build
- You plan a second home on family land and need its own system
- The lot is under half an acre and no sewer line reaches it
- Rainwater stands on the lot long after a storm
- The tract may sit in a mapped floodplain
Start a Septic Site Evaluation in McAllen
Tell us where the lot is when you call, and we will pass you to a contractor who can arrange the soil work.
Call (956) 758-8136Frequently Asked Questions
Site Evaluation Questions From McAllen Homeowners
Is a perc test required for a septic system in Texas?
Texas requires a site evaluation under rule 285.30 rather than a bare perc test. A licensed site evaluator or engineer makes two soil borings or two backhoe pits where the drain field will go and checks for groundwater before the system is designed.
How much does a septic site evaluation cost?
The Fixr cost guide puts a perc test at $600 to $800, while Bob Vila puts it at $1,000 to $2,000. Neither is a Valley price. The design and the county permit are separate charges, so ask each quote what it includes.
Which signs mean a lot needs an engineered septic design?
In Hidalgo County, a lot smaller than half an acre without sanitary sewer needs an OSSF design plan from a licensed engineer. A tract in a floodplain hazard area also needs a special flood-zone design, with the tank anchored, backflow valves fitted and the cover sealed.
Can I do my own septic site evaluation?
No. Texas lets owners do their own install or repair at a single-family home they own, but the soil evaluation itself must be done by an evaluator holding a TCEQ licence or by a professional engineer. Paying someone else to build the system means hiring a licensed installer.
How long does a septic permit take after the evaluation?
Rule 285.3 gives the permitting authority 30 days to decide an application. Once granted, the authorization to construct lasts a year, and the installer owes the authority five working days' warning ahead of the construction inspection. Hidalgo County issues two permits: Installation, then Final Inspection.