10-2146 Approving Amendment 2 Water Supply Facilities Work Plan

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3.3.4 Performance of Existing Water System In general, the City treatment and storage systems are adequate to provide the level of service and meet FDEP and EPA requirements. However, there are three areas of deficiencies within the distribution system; TTHM MCL exceedance, frequent water main breaks, and fire protection. These conditions were stated in Amendment 1 but are re -stated below for ease of reference. 3.3.4.9 TTHM Exceedance Another area of concern are areas in the distribution system that exceed maximum total tri-halomethane (TTHM) contaminant limits. TTHMs are a byproduct of chlorine disinfection and the longer the water stays in the piping system, the greater the formation of TTHMs. Water treatment plant and distribution system sampling performed for the City's Initial Distribution System Evaluation (IDSE, 2008-2010) compliance and for the Potable Water Distribution Water Age Optimization (Reiss Engineering, 2009) indicate that areas of the City's water distribution system are not in compliance with maximum contaminant limits (MCLS) for EPA's Stage 2 Disinfection Byproduct (DBP) Rule (80 ug/L TTHM and 60 ug/L HAAS respectively). The City in 2008 increased chlorine disinfectant levels in .he system to counteract significant chlorine decay coefficients associated with older, encrusted pipes in its system: the City is first and foremost required to maintain positive disinfectant residuals in its distribution system to protect public health. The disinfectant level increase has exacerbated the Stage 2 DPB MCL compliance issue. Replacement of the older distribLtion piping will allow the City to reduce the chlorine disinfectant levels and he p comply with the Stage 2 DBP MCLs. Originally, the City installed automatic flushers in the long detention time areas to flush the high TTHM water from the system. The City has been actively removing the automatic flushers in an attempt to reduce water consumption within the City. However, the water quality problems are still present and are being addressed with manual flushing of the system. Figures 3-2 and 3-3 below summarize some of the MCL TTHM compliance issues in the City's water distribution system. Figures 3 attached (big map) provides a spatial estimation of the Stage 2 DBP MCL compliance issues based on using distribution system water age as a surrogate for TTHMs and HAA5s. As indicated in Figure 4, replacement of the proposed pipes will help reduce the Stage 2 MCL compliance issues in the City's water distribution system. M