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HomeMy WebLinkAbout35. Future Agenda Items C:\Users\dianem\Desktop\2.22.22\35.docx Page 1 of 3 TO: Honorable Mayor and Members of the Common Council FROM: James Rabe, Director of Public Works DATE: February 17, 2022 RE: Clearwells Project – Update on Investigating Other Options The Wisconsin Department of Natural Resources (WDNR) first put the City of Oshkosh on notice that the current onsite treated water storage tanks (clearwells) did not comply with State of Wisconsin Administrative Code requirements as a part of the Sanitary Survey in 2007. Since that time, Public Works staff have spent significant time working with our engineering consultants to study options to bring our treated water storage into compliance with State regulations. Throughout the course of the studies, the team regularly communicated with State regulators (WDNR and the Public Service Commission of Wisconsin (PSC)). During a 2014 meeting with WDNR staff, it was made clear to the City that the WDNR would require the replacement of the clearwells in compliance with the State of Wisconsin Administrative Code requirements. For that reason, the City focused design efforts on clearwell replacement design concepts. During a web meeting on February 4, 2022, WDNR indicated they would be willing to entertain an option which would allow the existing underground (below groundwater) clearwells to remain in service. While that web meeting was not the place to discuss technical options, the WDNR staff made it clear that they would expect a physical inspection of the existing storage tanks to be completed and “additional mitigation efforts are necessary to ensure adequate treatment if the integrity of the tanks would become compromised and was undetected between inspections”. Based upon the results of that inspection, they would then entertain options from the City, with the expectation that there would be some other mitigation or treatment process in place to protect the drinking water in the event that groundwater was able to infiltrate into the tanks. This option would not be considered a reconstruction project, which would trigger the requirements for above ground tanks. C:\Users\dianem\Desktop\2.22.22\35.docx Page 2 of 3 If the Common Council desires staff to continue to explore this new option, we would work with our consultant design team to begin groundwater sampling and testing to determine what, if any, contaminants are present in the groundwater. After the ground thaws, the tanks could then be inspected in accordance with WDNR requirements. Based on the results of that inspection, we would then develop potential repair and mitigation options to discuss with WDNR technical staff. It is currently estimated that it would take approximately 6 – 8 months to complete the inspections and groundwater sampling, and to develop potential repair and mitigation strategies to present to WDNR and gain their approval. It is estimated that this additional work would cost approximately $140,000. Until groundwater monitoring can be started, and the physical inspection of the tanks is completed, we cannot reasonably estimate what the costs of pursuing this option would be. However, based upon the extensive experience of the Jacobs engineering team, they have prepared some potential estimates. A comparison of the costs is in the table below: Project Component At-Grade Circular At-Grade Square and Rectangular Extend Existing Clearwells Service Life Proposed tank size (gallons) Two 84’ Diameter tanks with 28’ wall height and 34’ to top of domed roof. (1,000,000 gal each) South, 92’ square. North, 84’ x 130’ rectangle. Both tanks have 17’ wall height and are 18’ to top of sloped roof. (850,000 and 1,150,000 gal, respectively) Existing North and South Clearwells would be maintained. The center clearwell would be demolished and the new pump station and treatment would be installed. Resulting capacity total is 1,900,000 gal. Inspection and groundwater sampling and analysis $140,000 Mitigation proposal to WDNR and design $190,000 Storage tanks cost $5,398,600 $9,548,300 Clearwells repairs $2,600,000 - $3,800,000 Pumping stations cost $7,301,700 $7,301,700 $4,746,100 New mitigation barrier and Pump Station redesign. Assumed UV disinfection $4,155,000 Subtotal $12,700,300 $16,850,000 $11,831,100 - $13,031,100 Ozone System $7,804,800 $7,804,800 $7,804,800 Emergency Generators $4,707,900 $4,707,900 $4,707,900 Demolition/site work $3,357,000 $3,357,000 $3,357,000 Auxiliary Improvements $1,210,600 $1,210,600 $1,210,600 TOTAL COST $29,780,600 $33,930,300 $28,911,400 – $30,111,400 C:\Users\dianem\Desktop\2.22.22\35.docx Page 3 of 3 We currently estimate that the best extension of life of these assets that we could achieve is 20 – 40 years. At such time, it is anticipated that reconstruction of the clearwells would be required. WDNR staff have made it very clear that, at such time as the clearwells are reconstructed, the requirements of the State of Wisconsin Administrative Code must be complied with. When asked if buried tanks with secondary containment would meet code, WDNR’s response was “The Department would not consider this to meet the intention of the code”. This means that eventually, the City will have to construct aboveground structures to maintain the storage above groundwater.