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C1 CA 40 i ATTACHMENT C Work Plan for South County Reverse Osmosis Water Treatment Plant Well Maintenance Program for Well Numbers i, 2, 3, 4, 5, and 6 May 30, 2000 Background The South County Reverse Osmosis Water Treatment Plant (WTP) is a 8.57 million gallon per day (mgd) treatment facility in Indian River County, Florida. The plant is approximately 18 years old and uses reverse osmosis as its primary form of water treatment. Raw water is supplied to the plant by six wells constructed into the upper Floridan Aquifer. The depths of the wells reportedly ranges between 600 and 700 feet. Well nos. I through 3 were constructed with the plant and reportedly have well screens, Well nos. 4, 5, and 6 were drilled after the initial WTP construction. Each well has an individual flow meter. The WTP has recently required more frequent changing of the prefilters that protect the reverse osmosis membranes. The regular schedule for changing the prefilters is once every three months. Due to clogging of the filters by a whitish yellow bacterial slime, the performance of the prefilters has been degrading rapidly. This situation has deteriorated to the point where the filters are required to be changed as frequently as every four days. WTP staff has isolated each well during normal production operations to help identify which wells are contributing the most to prefilter degradation. The wells that appear to be contributing the most to the filter degradation are well nos. 2 and 3. Due to sand production problems, well no. 6 is run on a limited basis. Water siphons back into the well when it is not pumping indicating that the check valve is not operating properly. The well is outfitted with an air release valve that appeared to be pulling suction through it. No baseline well performance data exists. The only wells that have access ports for the purpose of performing a step drawdown test are well nos. 5 and 6. The engineering firm, Camp Dresser & McKee, Inc. (CDM), was asked to matte a preliminary evaluation of the wells by the County. That evaluation is the basis for this work plan. Staff has requested that each well be investigated since it has been some time since maintenance on the individual wells has been performed. Based on the preliminary evaluation, several areas were identified that require further evaluation. These areas include surface facilities (valves, piping, controls, etc.) and subsurface facilities (casing, screen, pump, etc.) The following work plan discusses the recommended activities to be performed to further evaluate the wells at the WTI'. M02