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DEM, NBC Announce Temporary Closure of Phase I Combined Sewer Overflow Tunnel in Order to Complete Connection of the Woonasquatucket CSO Interceptor

Shellfish Closures to Revert to Pre-Phase I Criteria While the CSO Tunnel is Removed from Service

PROVIDENCE - As a part of construction related to Phase II of the Narragansett Bay Commission's (NBC) extremely successful federally-mandated Combined Sewer Overflow (CSO) Abatement Program, the NBC will temporarily cease operation of the Phase I CSO tunnel. This planned change in operation is necessary in order to complete the connection of the Phase II Woonasquatucket CSO Interceptor to the Phase I tunnel, thereby increasing the amount of combined sewage that will be diverted from the Woonasquatucket River and sent to the Field's Point Wastewater Treatment Facility for treatment. The Phase I tunnel will be off-line for approximately three to four weeks beginning on or about March 19. In order to complete necessary Phase II construction, the tunnel will remain at approximately 60 percent capacity until September 2014.

During the time period that the tunnel is removed from service, DEM will enact shellfish closures for the Upper Narragansett Bay Shellfish Management Area using the criteria that were in effect prior to construction of the tunnel: Area A (including the portion know as "Conimicut Triangle") will close for seven days after 0.5 inch of rainfall and Area B will close for seven days after 1.0 inch of rainfall.

During the time period when the tunnel is put back in service but with reduced capacity and the interim tunnel capacity is not exceeded, DEM will enact shellfish closures using current criteria: "Conimicut Triangle" will close for seven days at 0.5 inch of rainfall, the remainder of Conditional Area A will close after 0.8 inch of rainfall, and Conditional Area B will close after 1.5 inches of rainfall.

When the interim tunnel capacity is exceeded, DEM will enact a seven-day closure of the "Conimicut Triangle," Conditional Area A and Conditional Area B starting on the date that the overflow(s) occur, as reported to DEM by NBC. As conditions and resources allow, DEM will conduct post-storm monitoring and use this data, along with operational information from NBC, to determine whether these areas can be opened earlier. NBC and DEM will work together to conduct post-storm sampling. Weather patterns, staff availability and the effectiveness of NBC's combined sewage treatment will determine when the post-storm monitoring will be conducted.

Based on the last five years of data it is anticipated that that interim tunnel capacity will be exceeded approximately three to five times. The actual number of days these areas are open to shellfish harvesting will depend on the specific characteristics of actual weather patterns.

Construction of the Phase II CSO improvements are nearing completion, and per a consent agreement with DEM, construction must be completed by December 31, 2014. Phase II consists primarily of connecting additional CSOs to the tunnel for treatment at the Fields Point facility, separation of storm water, and a constructed wet vegetated treatment system.

Related links

Department or agency: Department of Environmental Management

Online: http://www.dem.ri.gov/

Release date: 03-12-2014

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