In a letter to EPA, AASHTO Executive Director John Horsley wrote that regulating stormwater quality as a point source is a difficult undertaking due to the variation of runoff water quality, the diversity of land uses, and the effectiveness of pollution controls. AASHTO is dedicated to working with EPA to develop cost-effective regulatory frameworks to strengthen its members' ability to reduce pollution from transportation infrastructure.

Horsley noted that state departments of transportation are unique as permit holders and asked that EPA refine the stormwater permit program based on this uniqueness to assist DOTs in increasing the effectiveness of their stormwater management programs.

"The states and the U.S. EPA have regulated the state transportation systems within the traditional municipal separate storm sewer system (MS4) general permit framework, although DOTs do not fit well within this model," Horsley wrote.

Unlike municipalities, DOTs do not have land-use ordinance or policing powers. Their infrastructure is passive and uniform, and is not designed for enforcing complex stormwater regulations. Their primary objective is safety, and enforcing stormwater regulations could put field workers at risk of injury.

AASHTO advocates that EPA develop a transportation-specific stormwater permit that provides states with the tools and framework to implement stormwater management programs for DOTs. The association is ready to work with the EPA on developing a regulatory system, Horsley stated in his letter.