Stormdrain Retrofit Demonstration Project


Completed construction of improvements at Outfall P30, Interstate 95

Statewide – Rhode Island

Client: Rhode Island Department of Transportation

Under the Intermodal Surface Transportation Efficiency Act of 1991, the Rhode Island Department of Transportation was given monies for the “design and construction of a stormdrain retrofit on Route I-95 and other highway runoff programs to protect Narragansett Bay.”

In a cooperative effort with the University of Rhode Island, Crossman Engineering developed a stormdrain retrofit program. This aggressive project targeted the major interstate highway outfalls, which transport non-point source runoff directly into Rhode Island’s major rivers within the Narragansett Bay Watershed, specifically the Pawtuxet, Moshassuck, Woonasquatucket and Seekonk Rivers. The interstate highways within the subject watershed include portions of Route I-95 and Route I-295 and Route 6, Route 37, and Route 10.

The initial study included the identification, assessment and prioritization of 196 highway outfalls. In Phase III, Crossman Engineering finalized the outfall prioritization, evaluated various stormwater BMPs, conducted a cost/benefit analysis at each outfall and finalized the Design Study Report.

For Phase IV, Final Design and Implementation, CE performed the necessary survey, hydrologic/hydraulic analyses, wetland delineation water quality assessments and prepared the final Construction Plans, Specifications and Bid Documents.

Types of BMP’s designed included:

  • Filter Systems
  • Infiltration Systems
  • Vortech/Swirl Separators
  • Wet Ponds/Wetland Systems
  • Detention Systems
  • Anti-Microbial Filters