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5. Wastewater Treatment Plant Updates 'ci�0�jlji� Incorporated 1892 Telephone (406) 758-7700 Douglas Rauthe FAX (406) 758-7758 Mayor Post Office Box 1997 Zip 59903-1997 Bruce Williams City Manager City Council Members: TO: Mayor Rauthe and All City Council Members Gary W. Nystul Ward FROM: Bruce Williams Cliff Collins DATE: November 8, 1995 Ward I Barbara Moses RE.: Repairs to Gravity Thickener Wardll Dale Haarr Attached to this cover note is a memo from John Wilson dated Wardll November 2, 1995. John's memo briefly explains the type of Jim Atkinson problem we are experiencing with our Gravity Thickener. This Ward III old information will be updated for you Monday night concerning what we have learned since November 5, 1995. Lauren Granmo Ward III Pamela B. Kennedy Ward IV M. Duane Larson Ward IV Telephone (406) 758-7700 FAX (406) 758-7758 Post Office Box 1997 Zip 59903-1997 Incorporated 1892 Memorandum Date: November 2, 1995 To: Bruce Williams, City Manager From: John Wilson, Assistant City EngineeP__L'_0 Re: WWTP - Emergency Repairs to Gravity Thickener This memo is a request for authorization to proceed with the design and implementation of emergency repairs to the wastewater treatment plant's fermenter thickener. Although the design for repairs will involve more research, the cost of options currently under consideration is estimated at $70,000 to $80,000. Obviously, we have not budgeted this amount. We will also look into the cost of replacing the facility. Our problem is the premature failure of a corrosion resistant coating for the roof beams, roof panels, side walls and bottom of this 85 foot diameter concrete tank. Emergency repairs are necrssary to prevent further deterioration of critical structural members. As part of the new plant construction, the existing gravity thickener was refitted and incorporated into the fermenter system. The fermenter enhances the production of volatile fatty acids and is essential to the phosphorus removal process. Because of strong odors, the exiting tank was refitted with a low concrete roof. The odor causing gas, hydrogen sulfide, also reacts with moisture in the air to produce sulfuric acid. Concrete is particularly vulnerable to the corrosive effects of sulfuric acid, so the design provided for a protective bituminous coal tar coating. Unfortunately this material has not performed well and has peeled away from about 25% of the concrete above the water line. The coating is also starting to fail below the water line. The thickener is currently off line and we are using alum, at a cost of around $1000 per week, to maintain phosphorus removal. Our preference is to put the tank back in service, knowing that we can return to make extensive repairs as soon as design work and scheduling will allow. Our general plan is to sand blast the interior and recoat the surfaces with another material. The options for "coatings" include a gunnite (spray -on) type grout, a fiberglass liner, or other materials, similar to a tar coating, which could be brushed or sprayed on. We have contacted Stanley Engineering, who was the process engineer for our plant. They tell us that the plant in Penticton, B.C. is having similar problems in their fermenter. Douglas Rauthe Mayor Bruce Williams City Manager City Council Members: Gary W. Nystul Ward I Cliff Collins Ward I Barbara Moses Ward II Dale Haarr Ward 11 Jim Atkinson Ward III Lauren Granmo Ward III Pamela B. Kennedy Ward IV M. Duane Larson Ward IV Telephone (406) 758-7700 FAX (406) 758-7758 Post Office Box 1997 Zip 59903-1997 Incorporated 1892 Memorandum Date: November 9, 1995 To: Bruce Williams, City Manager From: John Wilson, Assistant City Engineer--60 Re: WWTP - Gravity Thickener Repairs This memo is a request for authorization to solicit contractor's proposals for the installation of inspection ports and recoating of the gravity thickener. Our updated estimate for the project is $50,000. Over the past week we have evaluated the corrosive environment of the gravity thickener and researched various methods of corrosion protection. Based on that analysis, we have chosen to sandblast the remaining tar coating from the walls and roof of the tank and apply a new glass flake epoxy coating. This material will be applied with an airless sprayer, much like house paint. But given the confined working environment and special techniques associated Arith epoxy materials, the cost is estimated to be considerably higher that the average paint job. Three or four local contractors will be asked to submit proposals by November 27, when I will be back in the office. We intend to order materials and proceed with repairs by mid -December. The contractor's proposals will include the installation of a series of inspection ports. These will provide much needed access for future maintenance and inspection. The proposals will also provide for sandblasting and preparation; scaffolding, heating and ventilation as required; equipment and labor to apply the new coating; and cleanup. We will order and provide the inspection ports and epoxy coating materials. We have reasonably firm costs on sandblasting and materials, but it's hard to predict how contractors will respond to the requirements of working with special materials in a confined space. Douglas Rauthe Mayor Bruce Williams City Manager City Council Members: Gary W. Nystul Ward I Cliff Collins Ward 1 Barbara Moses Ward II Dale Haarr Ward II Jim Atkinson Ward III Lauren Granmo Ward III Pamela B. Kennedy Ward IV M. Duane Larson Ward IV