Septic Systems / OSSF
No city sewer? You may need a septic permit
Outside city limits in Starr County, you likely need an on-site sewage system — and that requires a permit in Texas.
Much of Starr County is rural and not served by a public sewer system. If your property has no sewer connection, you will need an on-site sewage facility (OSSF) — the official term for a septic system. In Texas, you need a permit to install, repair, or expand any OSSF.
The permitting authority is either the county or the TCEQ regional office. Before you buy land in an unincorporated area, find out whether the property has a working, permitted septic system. Older systems may not meet current standards. The TCEQ's OSSF page explains the rules and how to find your local permitting authority.
Source to confirm: TCEQ — On-Site Sewage Facilities (OSSF) for Homeowners