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36 OCTOBER 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 10 opportunity for the development of equipm ent, p ar ti cul arly a st abl e g roun din g m at eri al . Th e c o st of anode replacement is a large factor in the maintenance costs. It is believed that annual power and maintenance costs can be reduced. • The anode retrofit program contin- ued for many years after this early investigation. Figure 1, courtesy of EBMUD, illustrates the decrease in corrosion leaks due to the implemen- tation of CP over the years. This curve illustrates over 30 years of CP opera- tion and its benefit in extending the service life of the Mokelumne trans- mission line. Des Moines Water Works Anode Retrofit Program In a study presented by Klopfer and Schramuk, 7 the Des Moines (Iowa) Water Works (DMWW) distribution system con- sists of 1,380 miles (2,220 km) of pipes, of which 521 miles (838 km) have already reached their life expectancy while ~620 miles (998 km) will reach their life expec- tancy by 2020. The oldest pipes (~32 miles [51 km]) of cast iron pipes) in the system were installed between 1800 and 1899. An anode retrofit program was put into place to reduce the increasing number of pipe failures (reaching ~240 main breaks in 20 years). The anode retrofit program started in 2004 and continued to 2011, protecting ~15.6 miles (25 km) of 6- to 16-in (406-mm) diameter water mains. The total cost of the program was estimated at a little over $1 million dollars. The cost associated with fixing the main breaks over 25 years for the pipes that did not have CP systems was estimated at ~$4 million, and it was determined that the cost for replacing the broken mains was over $10 million. Considering an estimated useful life of 25 years for an anode retrofit system, the anode retrofit program com- pared to pipe replacement would result in $44,255 annual savings; and the anode ret- rofit program compared to pipe repair would result in $99,752 annual savings. An analysis was performed to compare the number of breaks for pipes with CP and without CP (No-APR). Figure 2 illustrates this difference in the cumulative total of main breaks. An average reduction of 90% in water main breaks was estimated. Summary The CP techniques, successfully applied for existing water pipelines, are hot-spot protection and anode retrofit programs. Hot-spot protection is a simple procedure that can be done during the routine break repair procedures with minimum costs and labor. It is a good starting point when launching a CP program, especially in small water departments with limited resources. Hot-spot protection can stabilize the num- ber of breaks for aging structures until either replacement or a more comprehen- sive protection program can be applied. Retrofit can ideally be applied to all pipes including smaller (6- to 12-in [305-mm]) mains that are usually installed without CP due to the high engineering cost. Documen- tation and experience of previous breaks FIGURE 1 Thirty years of CP operation and its benefit in extending the service life of the Mokelumne transmission line. Courtesy of EBMUD—Mark Lewis. FIGURE 2 DMWW main break comparison—anode retrofit program (solid-line) vs. no-anode retrofit (dash-line) program. CATHODIC PROTECTION