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HomeMy WebLinkAbout19.22-383SEPTEMBER 13, 2022 22-383 RESOLUTION (CARRIED 6-1 LOST _______ LAID OVER _______ WITHDRAWN _______) PURPOSE: PROVIDE DIRECTION TO STAFF RELATING TO THE WATER FILTRATION PLANT CLEARWELLS RECONSTRUCTION / REHABILITATION DESIGN PARAMETERS INITIATED BY: DEPARTMENT OF PUBLIC WORKS WHEREAS, The Water Filtration Plant stores treated drinking water in structures, called clearwells, prior to pumping it into the water distribution system; and WHEREAS, the current clearwell structures range in age from 60 to over 100 years old and Wisconsin Department of Natural Resources (WDNR) surveys have identified deficiencies within the current tank structures; and WHEREAS, City staff with the assistance of the City’s engineering consultant, Jacobs Engineering Group, Inc. (Jacobs) has conducted a physical inspection of the existing clearwells, conducted groundwater sampling and analyzed the various options for rehabilitation or reconstruction of the clearwell structures and have presented those options to the City Council at a workshop and within the memorandum accompanying this resolution; and WHEREAS, the three potential options identified for Council consideration for the reconstruction/rehabilitation of the water filtration plant clearwells are: 1. Reconstruct the clearwells with at-grade circular pre-stressed concrete tanks and construct intermediate and high-lift pump stations. 2. Reconstruct the clearwells with at-grade rectangular cast-in-place concrete tanks and construct intermediate and high-lift pump stations. 3. Rehabilitate the existing clearwells to make them watertight, add required additional treatment process (UV Treatment), and construct a new high-lift pump station. WHEREAS, it is necessary to provide direction to staff to allow staff to prepare designs for reconstruction/rehabilitation of the water filtration plant clearwells to allow the City to continue to provide high quality safe drinking water to City of Oshkosh water utility users. SEPTEMBER 13, 2022 22-382 RESOLUTION CONT’D NOW, THEREFORE, BE IT RESOLVED by the Common Council of the City of Oshkosh that the proper City officials are hereby directed to proceed with design for the reconstruction/rehabilitation of the water filtration plant clearwells as follows: 1. Reconstruct the clearwells with at-grade circular pre-stressed concrete tanks and construct intermediate and high-lift pump stations. 2. Reconstruct the clearwells with at-grade rectangular cast-in-place concrete tanks and construct intermediate and high-lift pump stations. 3. Rehabilitate the existing clearwells to make them watertight, add required additional treatment process (UV Treatment), and construct a new high-lift pump station. (Council must amend this Resolution to strike two of the above alternatives.) I:\Water Filtration\Clearwells\17-18 WFP Clearwells\Project_Information\Correspondence\Memo\17-18 CC Memo Direct Staff to Proceed with Final Design 09-08-2022 Rev B.docx Page 1 of 4 TO: Honorable Mayor and Members of the Common Council FROM: James Rabe, Director of Public Works DATE: September 8, 2022 RE: Provide Direction to Staff Relating to the Water Filtration Plant Clearwells Reconstruction/Rehabilitation Design Parameters BACKGROUND The Water Filtration Plant stores treated drinking water in structures, called clearwells, prior to pumping it into the water distribution system. These clearwells are buried, cast-in-place concrete structures that range in age from approximately 60 to over 100 years old. The Wisconsin Department of Natural Resources (WDNR) Sanitary Surveys of the City’s water system identified deficiencies with these structures and directed the City to replace the clearwells. The 2014 inspection of the clearwells indicated they were in fair condition. State of Wisconsin Administrative Code Section NR811 (NR811) prohibits storing treated drinking water below groundwater to prevent potential contamination of the treated drinking water should the tank leak. Public Informational Meetings (PIM) were held in 2017 and in 2021 to present the concept of aboveground storage tanks to replace existing underground tanks. Following the 2021 PIM, neighboring residents expressed concern about the appearance of the aboveground tanks, including concern over the visual impact of having the large structures along the shoreline of Lake Winnebago. City Staff with the assistance of the City’s engineering consultant, Jacobs Engineering Group, Inc. (Jacobs), have collected and responded to questions related to the replacement of the tanks and placed these on the City’s website. During this time, Jacobs kept the two (2) regulatory agencies, WDNR and the Public Service Commission of Wisconsin (PSC), updated on the status of the design. On February 4, 2022, the City and Jacobs met virtually with WDNR to discuss the clearwells replacement. During the meeting, the WDNR indicated they would be willing to consider an option which would allow the existing underground (below groundwater) clearwells to remain in service; however, the WDNR staff made it clear a physical inspection of the existing clearwells needed to be completed and that additional mitigation efforts would be necessary to ensure adequate treatment of water stored within the tanks if the integrity of the tanks had become compromised. WDNR also indicated that additional groundwater sampling and testing would need to be performed to determine what, if any, contaminants are present in the groundwater. I:\Water Filtration\Clearwells\17-18 WFP Clearwells\Project_Information\Correspondence\Memo\17-18 CC Memo Direct Staff to Proceed with Final Design 09-08-2022 Rev B.docx Page 2 of 4 At their March 8, 2022 meeting, the Common Council directed staff to execute a contract amendment with Jacobs for the purpose of conducting a physical inspection of the existing clearwells, conducting groundwater sampling, and providing analysis and recommendations in relation to the potential for extending the service life of the existing underground clearwell structures. Between the months of May and July 2022, staff worked with the consulting team consisting of Jacobs, Dixon Engineering, Inc. (Dixon), and AECOM to install new groundwater monitoring wells, obtain groundwater samples, conduct visual inspections of the clearwells, prepare inspection reports, and update potential rehabilitation strategies and cost estimates. Dixon performed the official inspection and completed all WDNR inspection forms. These inspection reports were submitted to WDNR. The visual inspections of the clearwells showed there are several deficiencies present, including failing wall lining, leaking cracks and wall penetrations, lack of baffle walls, corroding concrete, and corroding piping. The groundwater sampling showed the presence of fluoride, indicating the clearwells have been leaking treated water out of the tanks into the groundwater. The groundwater sampling also showed the presence of coliform and fecal coliform, which is not surprising given the proximity to Lake Winnebago and the significant presence of geese and seagulls along the waterfront. The presence of coliform and fecal coliform in the surrounding groundwater is of concern when there are cracks and penetrations present in the underground tanks. In order to assure that these contaminants cannot enter the treated drinking water supply, staff has adjusted operational processes to make certain that an outward water pressure is maintained in the tanks. On August 3, 2022, the City and Jacobs met virtually with WDNR to discuss the results of the clearwells’ inspections. During that meeting, the WDNR confirmed the only alternative that would result in full compliance with the requirements of NR 811 would be the complete reconstruction of the clearwells, raising them above the groundwater and the 100-year floodplain elevation. The WDNR also confirmed that if the City were to pursue a path of rehabilitation to restore the water-tightness of the clearwells, additional requirements would be imposed in order to protect the public health and safety. Those additional requirements would include practices such as: construction activities to restore the tanks to a watertight condition, more frequent visual inspections to ensure the continued water-tightness of the clearwells, removal of the earthen cover above the clearwells and installation of a membrane roof, and downstream treatment to ensure 4-log (99.99%) inactivation of potential viral contaminants. I:\Water Filtration\Clearwells\17-18 WFP Clearwells\Project_Information\Correspondence\Memo\17-18 CC Memo Direct Staff to Proceed with Final Design 09-08-2022 Rev B.docx Page 3 of 4 The results of the visual inspections, groundwater monitoring, and analysis performed was presented to the Common Council on August 23, 2022. The recording of the workshop can be found on Oshkosh Media’s YouTube channel (https://youtu.be/EGxRY1Bnoco). A pdf copy of the presentation from the workshop can be found on the Water Utility page of the City’s website (https://www.ci.oshkosh.wi.us/PublicWorks/WaterUtility.aspx), under the “Water Filtration Plant Clearwell Replacement Project” Heading. The WDNR has provided the City with an extended compliance schedule to respond to the outstanding issues relating to the clearwells project. By October 31, 2022, the City must provide a status update following the Common Council meeting. By January 31, 2023, the City must provide a corrective action plan and timeline to address the non-complying clearwells and to address all remaining items listed in the Sanitary Survey as Significant Deficiencies. ANALYSIS Based on the information gathered during the additional investigation into the potential to extend the service life of the clearwells and WDNR guidance, there are three (3) options for consideration: 1. Reconstruct the clearwells with at-grade circular pre-stressed concrete tanks and construct intermediate and high-lift pump stations. 2. Reconstruct the clearwells with at-grade rectangular cast-in-place concrete tanks and construct intermediate and high-lift pump stations. 3. Rehabilitate the existing clearwells to make them watertight, add required additional treatment process (UV Treatment), and construct a new high-lift pump station. A comparison of the three (3) alternatives is in included in the table below. It is important to remember that with at-grade tanks, the City would be investing now in new storage tanks that are anticipated to last two to five times as long as the rehabilitated clearwells. Due to the age and condition of the existing clearwells, major investment is anticipated to be necessary in 20 to 30 years if a rehabilitation project is undertaken now. Comparative Criteria Alternative 1 Alternative 2 Alternative 3 Compliance with Wisconsin Administrative Code Section NR 811 Yes Yes No, hence need for additional treatment process Storage volume (gallons) 2,000,000 2,000,000 1,900,000 Estimated Service Life (years) 60-100 60-100 20-30 Estimated Construction Cost $12,699,000 $16,850,000 $20,911,000 Estimated 20-year Cost $16,110,300 $20,459,400 $26,854,900 I:\Water Filtration\Clearwells\17-18 WFP Clearwells\Project_Information\Correspondence\Memo\17-18 CC Memo Direct Staff to Proceed with Final Design 09-08-2022 Rev B.docx Page 4 of 4 All of these alternatives will require PSC “Authorization to Construct” approval. As part of the review process the PSC typically goes through, they will evaluate the alternatives available to the City, the cost of those alternatives, and the impact of those costs on the rate payers. Should the PSC determine that there is a feasible, less-costly option available than what the City has requested approval to construct, the PSC may determine that Water Utility Rate Payers dollars shall not be expended for the higher cost alternative. If that determination is made, the City would either have to find another means of funding the extra costs, or revise the project request to the lower cost alternative. FISCAL IMPACT The total estimated construction cost and the total cost of ownership over a 20-year analysis period for each of the alternative is listed in the table above. As noted in the above analysis, it is important to remember that the PSC may require any incremental amount above the lowest cost option be funded by sources other than Water Utility rates. In addition to the lowest construction cost, the at-grade round tanks also have the lowest overall long-term maintenance costs, with the at-grade rectangular tanks being more expensive and the rehabilitation alternative being the highest overall long-term maintenance cost. RECOMMENDATIONS There are various competing factors to consider in deciding which alternative to approve and implement. In the interest of doing what is right by the entirety of the City of Oshkosh Water Utility Rate Payers and providing the most affordable, high quality drinking water possible, staff recommends approval of Alternative 1: Reconstruct the clearwells with at-grade circular pre-stressed concrete tanks and construct intermediate and high-lift pump stations. This option has the lowest overall construction cost and, because pre-stressed concrete tanks use design and construction methods that mitigate concrete cracking and leaks, it has the lowest ongoing annual operation and maintenance costs. This option enhances public health protections and the City’s ability to provide affordable water service. Approved: Mark A. Rohloff City Manager JER/tlt 8/19/2022 1 Oshkosh Water Filtration Plant Clearwells Replacement Project August 23, 2022 ©Jacobs 20202 Project update – March through August 2022 Clearwells inspection and groundwater sampling results Collaboration with Wisconsin Department of Natural Resources (WDNR) Clearwells rehabilitation Clearwells alternatives comparison Compliance schedule Next steps AGENDA Clearwells Inspection Findings ©Jacobs 20203 May – June:Conduct physical inspections of empty Clearwells Install groundwater monitoring wells near Clearwells June – July: Prepare and submit to WDNR Clearwell inspection reports Develop Clearwells repair strategy Sample groundwater and analyze for contaminants regulated under the Safe Drinking Water Act (SDWA) August:Review findings with WDNR Review project with Common Council 1 2 3 8/19/2022 2 Clearwells Inspection Findings ©Jacobs 20204 Clearwells are located on hardpan and appear structurally sound, in generally fair to good condition. There is evidence of concrete and metal corrosion. Chlorinated water contributes to corrosion. Concrete and Metal Corrosion Clearwells Inspection Findings ©Jacobs 20205 Previously installed shotcrete lining is in poor condition. Remaining shotcrete is damp in locations and potentially masking cracks. Complete removal of shotcrete is needed to expose, map, and measure unsealed concrete cracks. Deteriorated Shotcrete Lining Areas of Damp Shotcrete Clearwells Inspection Findings ©Jacobs 20206 Some concrete surfaces are spongey, a common effect after exposure to chlorinated water for many years. Removing the top ½-inch of interior surfaces by blast cleaning prior to applying new corrosion resistant lining is needed. Moisture or leaking around pipes at wall penetrations is evident and pipe wall sleeves require replacement. Damaged Concrete Surface Previously Repaired Leaky Wall Pipe 4 5 6 8/19/2022 3 Clearwells Inspection Findings ©Jacobs 20207 Active leaks were visible in the North and Center Clearwells. Following inspection, when the Clearwells were returned to service, Plant staff have maintained stored water surface elevations at least 1 foot above the groundwater table to mitigate groundwater infiltration. Flowing Roof Leak Flowing Wall Leak Groundwater Sampling Results ©Jacobs 20208 Two new, PFAS-free groundwater monitoring wells were installed, one east and one west of the Clearwells. Three rounds of samples were analyzed for over 170 SDWA regulated contaminants: microorganisms, disinfectants, organics and inorganic chemicals, radionuclides, PFAS compounds, and other water quality parameters. − 20 PFAS compounds analyzed: majority of results below detection limits; a few results too low to make certain quantitation. Most results were well below SDWA maximum contaminant levels (MCLs) or below the laboratory test detection limit. Some positive results for coliform, fecal coliform; some Standard Plate Count results > 500 colony forming units/milliliter. Collaboration with WDNR ©Jacobs 20209 IF THEN Buried cleawell is watertight Operation of non-compliant tank allowed with additional safeguards. Buried clearwell needs standard maintenance, like concrete crack repair, to restore watertight condition Standard maintenance work is not a project requiring WDNR review. Operation of repaired non-compliant tank allowed with additional safeguards. Buried clearwell needs major repairs including concrete crack repair to restore watertight condition, replacement of interior concrete lining to mitigate corrosion, and/or addition of sloped membrane roof. Major repair and improvement work is a project requiring WDNR review. At time of WDNR review, all tank deficiencies must be addressed to bring the tank into full compliance with current code. Two possible paths forward are available: 1. Complete major repairs to restore watertight condition and add a downstream treatment system to achieve 4-log (99.99%) virus inactivation. 2. Replace buried tanks with compliant (above groundwater and floodplain) tanks and a pump station to fill the tanks. “Buried clearwell” is a buried water storage tank located below groundwater table and below floodplain. Watertight buried clearwells do not comply with NR 811. 7 8 9 8/19/2022 4 Clearwells Alternatives ©Jacobs 202010 Repair and rehabilitate Clearwells, install new High Lift Pump Station and downstream UV disinfection. Construct new at-grade reservoirs, new Intermediate and High Lift Pump Station. − Circular pre-stressed concrete reservoirs. − Square and rectangular cast-in-place concrete reservoirs. Repair and Rehabilitate Clearwells ©Jacobs 202011 To rehabilitate and improve the Clearwells to meet several NR 811 requirements: Blast clean interior surfaces in preparation for crack repair in new shotcrete lining. Install replacement wall pipe penetrations for inlet and outlet piping. Install new Clearwells’ overflow pipes with retaining walls to permit free discharge along walls with earthen backfill. Repair and Rehabilitate Clearwells – Continued ©Jacobs 202012 To repair the Clearwells to restore watertight condition and rehabilitate structures to meet several NR 811 requirements: Repair concrete cracks with chemical grout injection. For significant leaks, utilize temporary leak drains to create dry conditions for all repairs. Blast clean interior surfaces and reline with shotcrete. Remove earthen cover from Clearwells’ roofs. Install new sloped membrane roofs with access hatches and security tank vents. Install interior baffle walls to prevent hydraulic short circuiting. 10 11 12 8/19/2022 5 Repair and Rehabilitate Clearwells – Continued ©Jacobs 202013 Construct new High Lift Pump Station in Center Clearwell. − Abandon1985 High Lift Pump Station due to insufficient available space to complete improvements and need to install large diameter buried piping with containment. − Reuse 1985 High Lift Pump Station space for high lift pumping & distribution system hydraulic surge protection system. Add ultraviolet light (UV) disinfection downstream of Clearwells in new High Lift Pump Station. Repair and Rehabilitate Clearwells – Continued ©Jacobs 202014 ADVANTAGES Maintain similar visual impacts. Intermediate pumping not required. DISADVANTAGES Requires construction, operation, and maintenance of new treatment system to achieve 99.99% virus inactivation. Involves inherently lower-certainty repair methods to provided significantly shorter service life with anticipated major re- investment required in 20 to 30 years. Risk of groundwater inflow into Clearwells between inspections. Requires more frequent empty Clearwells inspections. Construct At-Grade Reservoirs ©Jacobs 202015 13 14 15 8/19/2022 6 Construct At-Grade Reservoirs – Continued ©Jacobs 202016 ADVANTAGES Drinking water protection from potential groundwater and flood water contamination. Complies with regulations and aligns with drinking water industry best practices. Involves conventional, lower-risk construction methods, with circular pre- stressed concrete lower risk than square cast-in-place concrete. Results in accessible facilities that are easier to maintain and repair when needed. DISADVANTAGES Highly visible structures impact lake views. Required construction, operation, and maintenance of new Intermediate Pump Station. Alternatives Estimated Construction Costs ©Jacobs 202017 ALTERNATIVES ESTIMATED CONSTRUCTION COST ClearwellsRehabilitation with High Lift Pump Station and UV Repaired storage tanks estimated service life: 20 – 30 years $20,911,000 At-Grade Rectangular Cast-in-Place Concrete Tanks with Intermediate and High Lift Pump Station New tanks estimated service life: 60 – 100 years $16,850,000 At-Grade Circular Prestressed Concrete Tanks with Intermediate and High Lift Pump Station New tanks estimated service life: 60 – 100 years $12,699.000 Alternatives Life Cycle Cost Comparison ©Jacobs 202018 At-Grade Circular Prestressed Concrete Tanks At-Grade Rectangular Cast in Place Concrete Tanks Extend Existing Clearwells Service Life Estimated Service Life, years 60 - 100 Estimated Service Life, years 60 - 100 Estimated Service Life, years 20 – 30* Tanks Tanks Repaired Clearwells Construction Cost $5,398,600 Construction Cost $9,548,300 Repairs Cost $11,139,000 Annual O&M Costs $11,000 Annual O&M Costs $31,200 Annual O&M Costs $63,500 20-Year Lifecycle Cost $5,588,600 20-Year Lifecycle Cost 10,088,300 20-Year Lifecycle Cost $12,122,900 High Lift Pump Station High Lift Pump Station High Lift Pump Station Construction Cost $4,746,100 Construction Cost $4,746,100 Construction Cost $4,746,100 Annual O&M Costs $148,700 Annual O&M Costs $148,700 Annual O&M Costs $148,700 20-Year Lifecycle Cost $7,277,100 20-Year Lifecycle Cost $7,277,100 20-Year Lifecycle Cost $7,277,100 Intermediate Pump Station Intermediate Pump Station UV Treatment Construction Cost $2,554,600 Construction Cost $2,554,600 Construction Cost $4,4850,000 Annual O&M Costs $41,100 Annual O&M Costs $34,200 Annual O&M Costs $143,000 20-Year Lifecycle Cost $3,254,600 20-Year Lifecycle Cost $3,144,600 20-Year Lifecycle Cost $6,915,000 20-Year Estimated Lifecycle Cost Storage and Pumping $16,110,300 20-Year Estimate Lifecycle Cost Storage and Pumping $20,459,400 20-Year Estimated Lifecycle Cost Storage, Pumping and UV $26,315,000 16 17 18 8/19/2022 7 WNDR Clearwells Compliance Schedule ©Jacobs 202019 By August 31, 2022 ✓Meet with WDNR to discuss inspection reports and Clearwell options By October 31, 2022 Provide WDNR status update following Common Council meeting(s) By January 31, 2023 Provide WDNR corrective action plan and timeline to address non- complying Clearwells NEXT STEPS ©Jacobs 202020 1. Move ahead ozone equipment replacement separate from Clearwells project Equipment reliability and obsolescence issues remaina concern Purchase ozone equipment 2022 Start ozone system replacement construction in 2023 2. Select Clearwells alternative, complete final design with community input on architectural finishes and site landscaping Inform permitting agencies of decision Apply for Safe Drinking Water Loan Program funding assistance Questions and Discussion 19 20 21