Travis County sits right on top of the Balcones Escarpment, the geologic line that splits Central Texas in two. West of that line, thin Hill Country soil over limestone pushes most septic systems toward aerobic treatment. East of it, deeper Blackland Prairie clay supports a wider mix of conventional and aerobic setups. Add in Lake Travis and its cluster of lake communities, a fast-growing suburban ring, and pockets of rural land holding on against Austin’s expansion, and you get a county with about as much septic variety as anywhere in the state.
Urban core
Lake Travis communities
Hill Country estates
Suburban growth
Rural Travis County