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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Maintenance painting options are further discussed below: <br /> <br />Spot Repairs <br /> <br />Spot repairs, as the name suggests, involve surface preparation and coating <br />application only to the individual spots of corrosion or breakdown. The amount of <br />coating being removed is minimized, reducing the impact of hazardous materials <br />handling, contairunent, and worker protection due to the presence of lead, cadmium, or <br />chromium. Spot repairs also serve to repair the existing coating film only where it is <br />needed, repairing the corroded areas and stopping the propagation of the breakdown. <br />Coatings in essentially any condition may be spot repaired, but it is only pragmatic when <br />the level of breakdown is minor and somewhat isolated. A disadvantage of this approach <br />involves aesthetics. The repair spots are clearly visible. <br /> <br />A variation of this type of localized repair includes zone or area repairs. This <br />involves surface preparation and coating application over a larger area that exhibits more <br />concentrated levels of breakdown. For example, the exterior roof of a tank or just the <br />riser pipe is often zone painted. <br /> <br />Spot Repairs with Full Overcoat(s) <br /> <br />The addition of a full overcoat serves three primary purposes: the additional coat <br />provides additional barrier protection and helps to seal minor defects that are not apparent <br />when conducting spot repairs. It also offers an improved appearance when compared to <br />spot repairs. The addition of the overcoat also adds complexity and cost to the overall <br />project. The complexity changes because a contractor must now access all areas of the <br />structure to apply the full coat. The entire surface must also be thoroughly cleaned (i.e. <br />power washed) to remove chalk and surface debris. When top coating existing coatings, <br />it is usually recommended that a full prime coat be applied in addition to the full top coat. <br />Most coatings become brittle as they age and oxidize. The additional prime coat <br />promotes inter-coat adhesion of the new and existing materials. It should be noted that <br />overcoating has not been historically successful for any coating subjected to immersion <br />service. Therefore overcoating is not an option for tank interiors. <br /> <br />Complete Coating Removal and Replacement <br /> <br />Full removal and replacement is the final option for maintenance painting. It is <br />certainly the most costly option (especially when removing existing coatings that contain <br />toxic metals), but it offers the greatest opportunity for long-term protection. All of the <br />mill scale and weak paint are removed and a new system with a new design life is <br />applied. All lead paint is removed at the same time, eliminating hazardous metals from <br />future consideration, This method also provides the most pleasing appearance. <br /> <br />Any of these maintenance painting strategies may be used at any given time to <br />protect a structure. The main selection criteria is usually cost, but the long-term <br />maintenance strategy is also important. To consider spot repairs, the level of existing <br /> <br />Elevated Water Storage Tank <br />City of Arden Hills South Tank <br /> <br />32 <br />