RIDOT - Environmental Division - Office of Stormwater

Office of Stormwater Management (OSM)

The Office of Stormwater Management promotes stormwater management along RIDOT roadways to provide safe driving and protect the health of nearby waterbodies.  The OSM ensures that RIDOT projects and operations meet state and federal stormwater regulations.  Specific tasks & programs include stormwater design review, Stormwater Control Plan development for the Impaired Water Program, drainage system inspection and sampling for the Illicit Discharge Detection and Elimination (IDDE) Program, drainage system asset management, and Public Education and Outreach.

Consent Decree

RIDOT operates under a RIPDES Phase II MS4 PERMIT that regulates RIDOT stormwater discharge across all RIDOT roadways and facilities across the State. The RIDOT MS4 is an expansive system, with more than 25,000 catch basins and 3,800 outfalls that extend over 3,300 lane miles, approximately one-third of which are divided highways, the rest are rural and urban surface roads; about one-half of the system is within the MS4 Permit Area. RIDOT is authorized under a National Pollutant Discharge Elimination System (NPDES) general permit to discharge stormwater to waters of the United States through its MS4 permit. 

Stormwater Consent Decree

RIDOT is pledging more than $100 million over a 10-year period to ensure compliance with the Clean Water Act and a number of remedial measures under a consent decree with the Environmental Protection Agency. This initiative will reduce pollution from stormwater flowing into Narragansett Bay and hundreds of lakes, ponds and rivers throughout Rhode Island

Download Consent Decree

Clean Water Act

After an audit of the RIDOT MS4 program, RIDOT was found non-compliant with several permit requirements and entered into a Consent Decree with the EPA in 2015 to develop a state-funded program to ensure future compliance. As part of this Consent Decree, RIDOT developed the Impaired Waters Program, the IDDE program, and invested in the Asset Management of drainage.

eTool & Linear Manual


eTool was developed to optimize stormwater permit submission for all Rhode Island Department of Transportation (RIDOT) projects and to provide cross-reference data to Rhode Island Department of Environmental Management (RIDEM) and Coastal Resource Management Council (CRMC)

The RIDOT/EPA Consent Decree requires RIDOT to submit data based upon a different stormwater credit accounting system reliant on curves instead of simulated storm events. This Consent Decree reported data must be “mined” from hydrologic and hydraulic reports and various spreadsheets. eTool was designed to simplify the process, where project specific information can be entered and/or uploaded for stormwater management design and generate customized reports for submittal to RIDOT, EPA and RIDEM.

eTool website:  https://stormwaterapp-stg.dot.ri.gov/app/

eTool Support email: DOT.eTool@dot.ri.gov

Linear Stormwater Manual

Linear Manual was developed to outline a standardized process and tools to scope and design RIDOT projects. The content of the Linear Manual provides consistent guidance for complying with stormwater treatment requirements for State RIDEM & CRMC permitting and for the Consent Decree between RIDOT, the United State Department of Justice (DOJ) and the Environmental Protection Agency (EPA). 

Stormwater Control Plans

As part of RIDOT’s overall effort to comply with the requirements of the RIPDES MS4 General Permit and the Consent Decree, RIDOT has created a program to assess its stormwater discharges located within watersheds of listed impaired waters with stormwater related impairments (as defined by Rhode Island Section 303(d) List of impaired Waters), set reduction targets, implement structural controls, also known as stormwater treatment units (STUs), as well as implement enhanced non-structural controls to reduce its contribution to know water quality impairments.  For each waterbody segment impaired for stormwater related pollutants which receive RIDOT runoff, RIDOT has started developing Stormwater Control Plans (SCP).  The SCPs quantify RIDOT roadway’s stormwater related pollutant contributions and identify potential stormwater treatment controls and measures that can reduce those contributions.

To determine if a SCP has been developed within a project area, refer to the RIDOT Stormwater Program Web Map.

IDDE Program

The RIDOT Natural Resources Unit assists in determining permitting requirements for projects and oversees and reviews consultant prepared applications for content and accuracy. The Environmental Division acts as the main liaison with federal and state regulatory agencies such as the U.S. Army Corps of Engineers (USACE), the United States Coast Guard (USCG), the RI Department of Environmental Management (RIDEM), and the RI Coastal Resources Management Council (CRMC).

Permit Requirement

We must develop, implement and enforce a program to detect and eliminate illicit discharges or flows. The management program must include a storm sewer system map showing the location of all outfalls (the point where a waste stream discharges into a body of water) and the names of all waters that receive these discharges. The map also will show the location of catch basins, manholes and pipes within the system, physical interconnections with other regulated MS4s and private property connections. Our program plan must contain procedures to identify and target priority areas and locate and remove illicit discharges.

Illicit Discharge Detection Elimination (IDDE) Program: RIDOT continues to identify, map and describe all stormwater outfalls. During the outfall identification and location process, all outfalls are survey for dry-weather discharges to potentially identify illicit connections to our state system. We sample them for temperature, pH, conductivity, and bacterial contamination, as required by the general permit. Our investigation sometimes requires us to trace flows up the inlet pipe(s) to identify where it’s coming from using smoke or dye testing or video as needed. If an illicit connection is found, RIDOT will work with the responsible party and RIDEM to remove it.

The general permit requires that to the extend allowable under state law, RIDOT must prohibit and enforce unauthorized non-stormwater discharges into the state system. While RIDOT does not have the authority to establish such ordinances, the Department relies on RIDEM for enforcement.

Public Information & Outreach

RIDOT has implemented an ongoing public education program with a goal to provide information about the impacts of stormwater discharges to waterbodies while highlighting steps and/or activates that can reduce the pollutants in stormwater runoff to those waterbodies.

Green Infrastructure Sign Coordination