Challenge
GZA provides on-call stormwater services to the Rhode Island Department of Transportation (RIDOT) to assist in their compliance with a Consent Decree that details remedial measures required by the National Pollutant Discharge Elimination System (NPDES) stormwater regulations concerning discharge from Small Municipal Separate Storm Sewer Systems and industrial activity at eligible facilities operated by regulated small MS4 permits.
Solution
GZA’s services to-date have included:
- Illicit Discharge Detection and Elimination (IDDE) field assessments
- Engineering Design
- Stormwater Treatment Planning
- Technical Analysis
- Best Management Practice (BMP) selection and retrofit guidance
Select projects completed by GZA as part of this contract include:
- Completed a Stormwater Control Plan for the Pocasset River Watershed, which included evaluation of RIDOT roadways, stormwater treatment requirements and selection of stormwater BMP locations. GZA is currently evaluating feasibility for select BMPs.
- Completed closed-circuit television (CCTV) inspection of approximately five miles of stormwater conveyance system, including a high priority area where stormwater outfalls impact a popular beach. GZA’s work identified illicit discharges and areas which could be contributing to pollutant levels sags, etc.). Recommendations for stormwater pollutant reductions, including BMP modification and GIS/CAD mapping of inspected areas, were also included.
- Updated RIDOT’s online GIS mapping based on GZA’s field observations.
- Perform ongoing inspection and sampling of over 200 stormwater outfalls for potential illicit discharges.
- Complete system inspections and mapping to evaluate the accuracy of current mapping.
- Developed a state-wide management plan for street sweepings, catch basin cleanings, piping flushing and dredged sediments from stormwater BMPs. This work included meeting with regulators, RIDOT facility personnel, and visiting prospective sediment management sites. GZA developed a plan which included BMPs to be utilized during sediment removal and design of a central sediment processing/management area, including stormwater management. GZA developed construction plans and provided oversight during construction. The sediment management area is currently in operation.
Benefit
GZA’s ongoing engineering work under this long-held contract facilitates RIDOT’s compliance with stormwater compliance and completion of ongoing improvements to its facilities.
