CC WORKSESSION PACKET 06082021 - Laserfiche WebLink

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TOWER NUMBER ONE CITY OF ST. ANTHONY, MINNESOTA Copyright 2020 by KLM Engineering, Inc. Page 4 delamination primarily on the roof and bowl. Failures of this type will continue to occur due to age and normal deterioration exposing the underlying coatings to UV deterioration. Failures also include isolated pinhole corrosion, and typical coating damage on wear areas like handrails and ladders. The exterior should be recoated in three (3) years to maximize the life expectancy of the structure. See photos in Appendix A. It is more cost effective to remove the exterior and the interior coating at the same time. 3.0|RECOMMENDATIONS The photographs referred to in this section are in Appendix A. All drawings are found in Appendix B. The surface preparation requirements for all repairs as well as the requirements for welding are described in Appendix C. Based on an evaluation of the inspection data, the recommendations are: 3.1|Interior Wet Structural The following structural repairs are not required to be performed at this time and can be delayed until interior coating repairs are required. 3.1.1 Seal weld the following joints. Seal welding these joints will prevent rust streaking and corrosion in areas inaccessible to paint. In most cases the welding is to bring the interior area in compliance with AWWA D100-11. See photos 2 through 10. a. The overlap seam between the roof plates and the upper torus plates, b. The overlap joint between the dollar plate and the roof plates, c. The six (6) roof plate lap joints, d. Both sides of the intermittently welded upper shell course stiffener plate, e. The inside joint between the wet access manway and the dollar plate. 3.1.2 Add two (2) roof rafters, 1/2-inch by 8-inch bars, by 38-feet long spaced at 5-foot centers symmetrical around the finial vent to support a containment system when recoating the exterior of the tank. See photos 2 through 5. 3.1.3 Grind off all weld spatter and erection scab marks below the HWL. This will comply with AWWA D100-11. See photos 11 through 16. This work will require approximately 60 man-hours. 3.1.4 Replace the gasket on the 12 by 18-oval manway in the bottom of the wet riser. See photo 45. 3.1.5 Install a Grid-Bee GS-9 Submersible Mixer in the tower to provide mixing capabilities that reduce the likelihood and magnitude of ice formation in cold weather and prevent stratification in warm weather, improving water quality and reducing the necessity of chemical additives such as chlorine. Include the installation of all electrical components and control panel for proper operation through SCADA systems. Refer to KLM Drawing 61. 3.2|Interior Wet Coating 3.2.1 The interior wet coating is in good to fair condition with approximately ten (10) percent coating failures above and below the High-Water Line (HWL). Failures above the HWL consist of corrosion along unwelded roof plate weld seams and rust nodules at random locations. Failures below the HWL consist of rust nodules on weld seams, intermittently welded shell stiffener ring and random locations. See photos 2 through 20