Although the pavement needed for SH 45SW represents 0.1 percent of the total area of the Barton Springs segment of the Edwards Aquifer Recharge Zone, the Mobility Authority plans to exceed water quality standards on this project to fully protect this segment.
SH 45SW will achieve a highway runoff total suspended solids (TSS) removal rate of at least 90 percent (10 percent higher than required by the Texas Commission on Environmental Quality) using a combination of structural and non-structural Best Management Practices (BMPs). TSS is a term used to describe the measurement of particles found in storm water that, if released in high concentrations, can impact aquatic life.
BMPs are techniques, measures, or structural controls used to manage the quantity and improve the quality of storm water runoff with the goal of reducing the contaminants collected by stormwater as it moves into streams and rivers. BMPs included in the design of SH 45SW are:
Permeable Friction Course (PFC)
PFC will be used throughout the SH 45SW project. PFC is a porous roadway surface used as an overlay on top of a conventional roadway surface. PFC comes with many benefits, including its ability to filter suspended solids and pollutants from stormwater. In addition, PFC has been shown to provide sound dampening benefits as well as reduced water spray which will improve visibility and safety.
Water quality ponds
Water quality ponds provide stormwater control by retaining and treating stormwater runoff. The ponds’ physical, biological and chemical processes work to remove pollutants, particulates, organic matter and metals before water is released into the environment.
In addition, grassy swales planned for inclusion on SH 45SW work to channel and treat stormwater runoff. Vegetation decreases the speed at which the runoff moves to enable absorption into the soil, which acts as a natural filter.
Linear sections of land called Vegetated Filter Strips will be installed along sections of the project to act as a buffer between the project and the protected areas around it. Strips work similarly to swales by slowing runoff and filtering it through plants, roots and soil.
Hazardous materials traps
Hazardous materials traps will be located at all stormwater discharge points (or outfalls) to creeks and waterways to prevent the accidental release of hazardous materials into a waterway.
Additional actions planned to protect against pollutants in runoff from the project will include:
- No herbicide use within the right-of-way
- Any equipment fuel or hazardous material storage, even if short-term, will be performed within a containment area to prevent the possibility of accidental discharge to groundwater
- Any equipment fueling will be performed at least 200 feet away from the nearest sensitive karst feature and water crossing
- Phased construction practices, where feasible, to limit the area and duration of construction disturbance
- During construction, an Environmental Compliance Manager will be on site to monitor construction activities and Best Management Practices