Septic Systems
Building outside city limits usually means a septic permit
If you build or buy a home in rural Navarro County, you will likely need a permitted on-site sewage facility (septic system) before you can occupy the property.
In Texas, any property that cannot connect to a public sewer must have an on-site sewage facility. This is commonly called an OSSF or septic system. You need a permit before you can build, repair, or change one.
In areas where the local county or city has not set up its own permit program, the TCEQ regional office handles permits. TCEQ stands for Texas Commission on Environmental Quality.
Getting the permit involves three steps: a site check, a design plan, and an inspection. If you are buying rural land, check the permit status of any existing system before you close. An unpermitted or failing septic system can cost a lot to fix. Contact TCEQ or Navarro County to find out who issues OSSF permits at your specific location.
Source to confirm: TCEQ – Getting a Permit for an OSSF