Since most of the Loop 1604 corridor lies within the Edwards Aquifer Recharge Zone which is a critical resource for the San Antonio community, the EIS will show compliance with all applicable rules regarding development of the roadway and stormwater runoff.  As such, the effects of stormwater runoff will be evaluated and context sensitive design measures known as BMPs will be incorporated into the Build Alternatives to help mitigate potential impacts and preserve the water quality and ecosystem that surrounds the Loop 1604 corridor. 

The EPA describes stormwater runoff as having two main components directly related to development of a road:   

• Increased volume and rate of runoff from impervious surfaces (i.e., paved roads), and
• Concentration of pollutants or total suspended solids.

Together, these components can cause changes in hydrology (the movement and distribution of water) and water quality that result in problems, such as:

• Habitat modification and loss,
• Increased flooding,
• Decreased aquatic biological diversity, and
• Increased sedimentation and erosion. 

Physical aspects related to urban runoff, such as erosion, can also substantially affect a body of water's habitat.  For example, alterations in hydraulic characteristics of streams receiving runoff may include higher peak flow rates, increased frequency of runoff rates, increased occurrences of downstream flooding, and reduced base flow levels. 

BMP tools used in context sensitive design rely on a prevention approach to deal with stormwater runoff rather than dealing with water quality issues after they impact the ecosystem. Effective management of stormwater runoff offers many possible benefits, including:

• Protection of wetlands and aquatic ecosystems;
• Improved quality of receiving bodies of water;
• Conservation of water resources;
• Protection of public health; and
• Flood control.

Today, many states like Texas are facing potential issues related to stormwater runoff.  Traditional flood control measures and stormwater management approaches like channeling the water downstream using curb inlets, culverts, and other drainage structures typically alters the natural flow of runoff by rechanneling the runoff downstream to a point source at the base of the drainage area, while not taking into account pollutants or any means of infiltration.  Traditional BMPs for stormwater control have been effective in removing pollutants, but the natural hydrology can still be negatively affected.  This can have harmful effects on ecosystems, even when the water quality is not compromised.  To address these issues, the EPA recommends a more sensitive approach that integrates the control of stormwater peak flows along with the protection of natural channels to sustain the aquatic habitat.