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City Council Regular Meeting Minutes <br /> May 12, 1998 <br /> Page 10 • <br /> 1 Marks asked for an explanation of the cathodic protection. <br /> 2 Richard Potz, Project Manager, RCM, explained that this protection was an induced <br /> 3 positive/negative ionic exchange. This protection works well in warmer climates but not as well <br /> 4 in Minnesota. The best means of stopping corrosion in this climate is with a coating system. <br /> 5 Cavanaugh questioned the life of a water tank and if the loose metal would be sandblasted. <br /> 6 Mr. Potz stated the average life of a water tower is 50 years. There are water towers around the <br /> 7 country which were built in the late 1800s and early 1900s. He stated that the St. Anthony water <br /> 8 tank could last 75-100 years. He confirmed that the loose metal would be sandblasted off. <br /> 9 Cavanaugh asked if a metal sonic screening had been performed. He also noted that the report <br /> 10 stated there was mold on the underside which should be removed to extend the life of the <br /> 11 overcoat. <br /> 12 Mr. Potz stated a pressure wash is performed to remove the mold and dirt. This will help the <br /> 13 overcoat to adhere to the surface. He stated a metal sonic screening had not been performed on <br /> 14 the tank. <br /> 15 Cavanaugh suggested that if the overcoat did not adhere, it could pull off paint that contained • <br /> 16 lead. He asked Mr. Potz if he had any experience with communities who performed the metal <br /> 17 sonic screening. <br /> 18 Mr. Potz stated he did not. He noted that Braun has a separate division which performs non- <br /> 19 destructive testing. He stated RCM could check the thickness of the metal on the tank. <br /> 20 Cavanaugh asked how long the water tank could last before another stripping. <br /> 21 Mr. Potz stated the recoat should last 12-15 years. <br /> 22 Cavanaugh stated the City is investing a lot of money on the premise that this is a 60 year tank. <br /> 23 He felt it was important to obtain the structural information before moving forward on this <br /> 24 project. - <br /> 25 Mr. Potz stated the difficulty in testing the metal is determining where to test and how many tests <br /> 26 to make. It is comparable to soil boring. <br /> 27 Faust asked if other Cities have done this testing. He also asked if any water towers had fallen <br /> 28 down. <br /> • <br />