CSO Background

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CSO Background


The City of Newport has over 90 miles of sanitary sewer pipes, many of which have been in operation for over 100 years. Prior to the 1970's, many of these pipes were designed as combined sewers- collecting both sanitary sewage as well as storm water during wet weather events. Since the 1970's the City has constructed several projects to separate the storm water connections from the sanitary sewer to reduce the number of CSO Events.

In November 1997 the Rhode Island Department of Environmental Management (RIDEM) issued the final discharge permit to the City including time schedules associated with study work at the Washington Street and Wellington Avenue Combined Sewer Overflow (CSO) Facilities.

In November, 1999 the City entered into a consent agreement (RIA-292) with the RIDEM regarding a plan to address the City's CSO Control Program. As required by the consent agreement the City submitted three Technical Memorandums (TM) that would be used to develop a detailed scope of work to develop a CSO Control Program in compliance with RIDEM and USEPA CSO Policies.

Between 2000 and 2004 the RIDEM and City discussed the approach for the CSO Control Program. In July 2004 the RIDEM approved the Request for Proposals prepared by the City for engineering services associated with the development of the City's CSO Control Program. The CSO long term control plan will be developed as a phased approach.

After RIDEM approval, the City Council awarded the contract to EarthTech in November, 2004. The program would initially address the Wellington Avenue CSO Facility as it was prioritized due to the USEPA designation of King Park Beach as a Flagship Beach.

Phase 1 2004-2005

The Phase 1 Part 1 work consisted of the following tasks and the work was completed in October, 2005:

     Data Collection/Field Investigations
  • Flow Metering of service area to Wellington Ave CSO Facility
  • Identification and Prioritization of Catchment Areas 
  • Thames Street Interceptor Manhole Inspections
  • Identified Work for Phase 1 Part 2

The work completed in Phase 1 Part 1 was submitted was submitted for review and approval by the RIDEM to proceed with the work associated with Phase 1 Part 2. Approval was received and EarthTech was authorized to proceed in February, 2006 with the following tasks:

  • Thames Street Interceptor TV Inspection
  • Flow metering in Catchment Area 6
  • Hydraulic Model Evaluation
  • Windshield Surveys
  • The following field work in the prioritized Catchment Areas 1, 3, & 4
    • Flow Isolation/ Follow up CCTV
    • Manhole Inspections
    • House to House Surveys
    • Smoke Testing
    • Dye Testing
  • Report on Results and Recommendations due to RIDEM January 31, 2007

The Phase 1 Part 2 report, which contains recommendations for Phase 2 work was reviewed and approved by the RIDEM in May, 2007. The City authorized EarthTech to proceed with the Phase 2 work in August, 2007.

The Phase 1 Part 2 report also identified work that the City could proceed with prior to final approval of the report. A Phase 1 Part 3 contract was awarded to EarthTech in November 2006 and included the following tasks:

  • Design for disconnection of 28 catch basins and rehabilitation of 290 manholes
  • Smoke Testing for Area 6
  • House to House surveys -Area 6
  • Flow isolation -Area 6
  • Dye testing - Area 6

Subsequently, the City awarded construction contracts to disconnect the catchbasins in July 2007 and repair manholes in September 2008. The repair work has been successfully completed.

Phase 2 2007-2009

The City authorized AECOM (formerly EarthTech) to proceed with the tasks for Phase 2 in August 2007. Phase 2 uses the field work from Phase 1 to identify long term improvements to the sewer system in order to comply with the RIDEM and EPA CSO policies.

The primary goal is to eliminate overflows from the Wellington Avenue facility. The Phase 2 report with results and recommendations was submitted to RIDEM for review and approval on March 31, 2009.

The report recommended a CSO control plan for the Wellington Avenue facility including obtaining additional sewer separation in combination with storage.

In addition work was recommended in the Washington Street CSO facility service area similar to the work completed in Phase 1 for the Wellington Avenue service area. The report concluded that improvements within the Wellington Avenue service area alone can not achieve compliance at the Washington Street CSO facility.

The tasks in Phase 2 included the following:

  • Develop a calibrated hydraulic computer model of the collection system
  • Use the model to analyze existing and proposed conditions in the Wellington Ave facility service area
  • For proposed CSO control alternatives determine the impact of the control alternatives on the Washington St . CSO facility; Long Wharf pump station; and the Water Pollution Control Plant
  • Identify and recommend a long term plan for Wellington Ave. facility (i.e. sewer separation, storage and conveyance, etc.)
  • Design and prepare construction documents for the high priority sewer defects identified in Phase 1


EPA Intervention

In March, 2009 EPA notified the City of its intent to intervene in the consent agreement negotiations between the City and the RIDEM. In September 2009, EPA issued a draft consent agreement to the City stating that all CSO's be eliminated by 2015.  The City negotiated with revised compliance dates a Consent Decree with EPA, RIDEM and Environment Rhode Island which is effective as of October, 2011.  A Consent Decree modification was approved by all parties in December, 2015. 


CSO Control Program Implementation

In March 2010, the City contracted with CH2M Hill to serve as Program Manager to assist the City in negotiations with the EPA and the RIDEM with the development of a Corrective Action Plan for the City's CSO Control Program which will be part of a consent agreement executed between the City, EPA and RIDEM. CH2M Hill will assist the City with the coordination and implementation of the CSO Control Program.

2010 - 2012 Accomplishments

The consent agreement with the EPA was finalized in October 2011, the City has proceeded with a number of activities from the Corrective Action Plan.

The completed activities include:

  • 35 meters were installed in the sewer system and collected flow data over a one year period to assist in identifying sources of extraneous flow into the system.
  • Long Wharf Force Main emergency repair project completed.
  • Wellington Avenue sewer interceptor replacement completed.
  • Improvements to the Rail Road sewer interceptor located in the railroad right of way between Van Zandt Ave. and Bridge St.
  • Sanitary sewer repairs in the southern section of the City.
  • Catch Basin separation in Area 6 as identified by AECOM in Phase 1.
  • Improvements to the Thames Street sewer interceptor completed.
  • Enhanced and ongoing updating of the City's GIS wastewater collection system and storm drainage system mapping.
  • An optimization study of the City wastewater treatment facility located on Connell Hwy.
  • Expanded the hydraulic model to the entire sewer system.
  • Conduct investigations to identify public and private sources of extraneous flow. 
    entering the sewer system throughout the City's sewer collection system.
  • Complete an assessment of the current capacity of the sewer collection system.


System-wide Master Plan - 2012

In addition to the activities completed in compliance with the Consent Decree, the City developed a System Master Plan with estimates of the associated costs for the CSO Program which was submitted in November 2012 to EPA and RIDEM for their review and approval. The purpose of the System Master Plan is to utilize all of the data collected to date in accordance with the Consent Decree along with an evaluation of the effectiveness of projects that have been completed in order to develop a system-wide plan to reduce CSO events in the future. To ensure the program was executed in a manner acceptable to the community, the city established a CSO Stakeholder workgroup to provide input and feedback on the CSO program developed for the System Master Plan. In 2015, The City, RIDEM and EPA negotiated final modifications to the Consent Decree which gave final approval of the System Master Plan and set the schedule for its implementation.  

Current and Future Activities - as presented in the System Master Plan and Modified Consent Decree (October 2016)

  • Adjustments to Weirs within Thames St. Interceptor & America's Cup Ave. - Complete.
  • Additional Catch Basin separation Projects. - Some complete, some in progress.
  • Improvements to the Washington St. CSO Treatment Facility. - Complete.
  • Improvements to the Wellington Ave. CSO Treatment Facility. - In progress.
  • Improvements to the Ruggles Ave. Pump Station. - Construction commencing soon.
  • Upgrades to the Water Pollution Control Plant (WPCP). - In progress.
  • Sanitary Sewer System Improvements. - Ongoing.
  • Storm Drainage Improvements. - Ongoing.