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Kim9ey»>Horn <br />Page 21 <br />Figure 10: Treasure Coast Utilities Lead 90th Percentile Data <br />0.015 — — <br />— — — — — — — — - <br />0.014 <br />Stabilization Method <br />0.013 <br />1 <br />0.012 <br />Caustic, Corrosion Inhibitor <br />0.011 <br />2 <br />0.01 — <br />— — — — — — — — — — <br />0.009 <br />3 <br />0.008 <br />CO2, Caustic, Corrosion Inhibitor <br />0.007 <br />4 <br />0.006 <br />Caustic, Corrosion Inhibitor <br />0.005 <br />�. <br />0.004 <br />CO2, Caustic, Corrosion Inhibitor <br />TC Utility <br />. •.a. <br />.�, <br />0.003 <br />�i •r : <br />0.002 <br /># <br />0.001 <br />Caustic, Blending <br />0 <br />Jul -09 <br />Nov -10 Apr -12 Aug -13 <br />Corrosion Control <br />(CC) in place <br />Ally • <br />�...... 0-.-9 ... • <br />.� ........................... <br />Dec -14 May -16 Sep -17 Feb -19 Jun -20 Oct -21 <br />•••♦— TC Utility 3 - Lead --dp-- IRCU - Lead <br />, TC Utility 2 - Lead TC Utility 4 - Lead <br />••0••• TC Utility 6 - Lead ... 0... TC Utility 7 - Lead <br />-0- LCRR Increased Monitoring • a • • • CC System in Place <br />TC Utility 1 - Lead <br />TC Utility 5 - Lead <br />— — — Current AL <br />Utility <br />Treatment <br />Stabilization Method <br />TC Utility <br />1 <br />RO & NF <br />Caustic, Corrosion Inhibitor <br />TC Utility <br />2 <br />RO & B==end <br />Raw Water Blend, Caustic <br />TC Utility <br />3 <br />RO <br />CO2, Caustic, Corrosion Inhibitor <br />TC Utility <br />4 <br />NF & Bind <br />Caustic, Corrosion Inhibitor <br />TC Utility <br />5 <br />RO & NF <br />CO2, Caustic, Corrosion Inhibitor <br />TC Utility <br />6 <br />RO & Lime Softening <br />Caustic, Corrosion Inhibitor <br />TC Utility <br />7 <br />1 RO & Lone Softening <br />Caustic, Blending <br />As shown, IRCU's lead sample data is -elatively consistent with seven (7) analogous water system <br />purveyors in the treasure coast area and in compliance with the LCR. <br />COPPER SAMPLING DISCUSSION <br />Copper enters drinking water primarily from distribution and copper piping materials used in household <br />plumbing. The corrosion rate of copper is affected by pH, alkalinity, dissolved oxygen, chlorine residual and <br />possibly calcium (AWWARF 1985). Copper -containing protective corrosion scales formed in non - <br />phosphate -inhibited waters are pH sensitive (Reiber 1989). Experimental studies that investigated the <br />effects of generalized corrosion in service piping systems have shown that soft, acidic or low pH waters <br />develop high concentrations of copper during standing or stagnant conditions (Meyer 1981). The corrosion <br />potential of the water was found to be liess apparent in moderate- to high -alkalinity waters in which there <br />