Res 1991-131 - Laserfiche WebLink

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costs, as well as the opportunity to stage facility construction as needed. 1. The San Marcos River is of excellent quality and reasonably constant floy. Minimum flow over the last 28 years of record was 46 cis (29.73 mgd) during the drought period of 1956. Average floy since 1956 has been 164 cis (105.9 mgd). Such a dependable source could provide for the initial volumes required for San Marcos to change to surface supply. Of course, the City would keep their wells to provide emergency water when needed. The excellent quality of the water would reduce the treatment process needs and ultimately the cost of a treatment plant. Only during periods of storm runoff does the quality deteriora te significantly. During these periods, the existing wells would be used to supplement water demands. As long as well water is available on a limited basis, plant cost can be reduced by less need for expensive backup systems, higher levels of treatment capability for short periods .of poor quality, and excessive storage facilities. 2. A preliminary plant design is proposed to provide treatment for an initial volume of 8 mgd and would be expandable to an ultimate capaci ty of 16 mgd. A schematic of the plant is shown on Figure 1. Initial cost of the facili ty would be reduced by not equipping the settling basins with sludge collection equipment. Again, the quali ty of the water is such that chemical treatment requirements should be minimal for the next five to ten years. Should quality deteriorate or when the City changes to another surface source requiring increased treatment efficiencies, sludge collectors could then be added. Treatment units proposed for the plant include the following: . Diversion conduit & riprap dam . Raw water pump station . Chemical feed . Rapid mix basin . Flocculator 8 Settling basins . Fil ters . Clearwell 8 Ground storage reservoir 6