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6-25-1998 8:02AH FROM PL1BL I C WORKS 333+671 O F_ <br /> 0 .1211 9O 21:12 51071:16, BLACK5TONE PACE" 03 <br /> ,A negative (cathodic) voltage of at least 0.$5 Volt as measured between the <br /> stntctum surface and a saturated coppericvpper sulfate reference clecoode <br /> coutactirrg the electrolyte. D+eterxnination of this voltage is to be wade with the <br /> protective current applied. Consideration should be given to voltage(IR)drop. <br /> WNC,LUSdQNa <br /> 1. Data for our testing are tabulated on the attached sleet_ Analysis of this data <br /> indicates that bUtl3 tanks at the Public Safety Building(kigure 1)do not meet the <br /> aforememioned criteria_ Twu of the four tunks at the Municipal Service Center <br /> (Figure 2)are receiving an efft-m-ye degree of comcnsion,prutectiou. <br /> 2. Anodes may be been consurwd and are no longer operativag effectively at the <br /> Public Safety Building for both tanks. The magnesium anodes warms installed, <br /> hc,wever,not connected to the tanks at either lomion tested. <br /> 3 The vent for the diesel tank at the Public Safety Building is shorted to building <br /> growd wbich may be contributing to the mwJA quatc levels Of cathodic protection. <br /> Alt other tanks at both slues:see non metallic(faberglasss)and pose no prrtblem. <br /> 5. No $t-,ay currents were detected during our investigation. <br /> REt'Y7MMENDA TIONS <br /> 1. Perfm n current regturement testing to determine the type of cathodic protection <br /> system required for complete conusion protection. Estirnated costs to perforin <br /> this additional testing arid preliminary design and engineering construction <br /> estimates is$$50.00. <br /> 2. Develop design details and specif"vk4Qm ful wostruction bidding fox installation <br /> of the CP System upgrades will follow preliminary desip acceptance bx the City- <br /> Cost estates for final design will be provided at that time- <br /> A3. n insulating cauplingAmiou slxvutd be installed on the vent for the dirsel tank,at <br /> the Public Sak Building to effectively malate the task.This should be done prior <br /> to any current mquiretncrtt testing and could be done by City pCr5otmel. <br /> 4. The annual iny�ectiotl of the cathodic pmtection systems should consist of <br /> stnKWM-to-soil potential measumements, current output of the anode beds, and a <br /> summary report to include field data acrd.recommendations as rcqui K4. <br /> 5_ While the Environmental Protection Agency (F-PA.) regWatitms mandate testing <br /> conducted on thu*0-yea intervals to determine the effectiveness of the i.nsrslled <br /> 2 <br /> okcistane <br /> Grvgp <br /> Ltd. <br /> t 325s3'aac.dot <br />