On a west Texas site with 16 in of Class Ia soil over fractured rock, suitable OSSF systems include:

The choice of lined ET (Evapotranspiration) systems or mound systems is appropriate for the given conditions of 16 inches of Class Ia soil over fractured rock in west Texas.

Mound systems work effectively in areas where there is a shallow soil layer that may not provide adequate filtration or absorption for conventional septic systems. They are designed to create an artificial raised bed that provides a larger area for absorption. In regions with rocky substrates, using a mound can enhance the treatment of effluent by encouraging additional aerobic treatment before the wastewater infiltrates into the environment.

Lined ET systems are designed to minimize water loss while maximizing evaporation and transpiration. In arid regions like west Texas, this approach is beneficial since it effectively manages wastewater through natural processes. The use of a liner prevents percolation into the underlying fractured rock, thereby ensuring that contaminants do not reach groundwater, which is a critical consideration in areas with limited soil depth over rock.

Both approaches are suitable for the specified soil characteristics and environmental considerations, as they address the issues of limited soil depth, the presence of fractured rock, and the need to effectively manage wastewater in a sustainable manner.