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F1 F1 January 27,2005 NOA Project Number: E04070B Page 6 • pH varied from 7.1 to 9.2,with an average of 8.3 (Plate 2). Values of 6.5 to 8.5 are considered to be acceptable pH levels for public drinking water systems'. The pH of F1 the pond exceeded 8.5 on 15 occasions during the monitoring petiod. .Because all of these high values were noted when no water was flowing into or out of the pond,it seems likely that they result from a natural algal bloom on stagnant water. NOA has F! observed similar results at other local facilities with relatively stagnant ponds. j Freeboard ranged from 24.0 to 28.8 feet (Plate 7). The freeboard was recorded as 36.0 feet for the first three weeks of monitoring;but these values were due to.a transcription error. At no time during 2004 did freeboard approach the two foot minimum described in the WDRs (Discharge Specification B11). Measured increases in freeboard during periods of good data were on an order of magnitude that suggests evaporation may be responsible for the majority of water loss. • No odors were noted this year at the storage pond. Storage pond data is presented at the end of this document as Table 3. Discussion Data Trends The BOD of the influent into the pond and the storage pond water are compared in Plate 1. It appears that the influent BOD values are subject to significant variation,while the BOD of the pond water remains relatively stable. The data suggest that the existing water in the pond has a buffering effect on the BOD of the influent. Additionally, the influent water data collected does not include stormwater runoff,which is likely to have a diluting effect. The pH values of the influent into the pond and the storage pond water are compared in Plate 2. For the months in which influent was discharged to the pond, there is a strong correlation between the pH of the influent and that of the pond. Later,when influent is no longer discharged, the pH values of the pond fluctuate from week to week. The values are the highest in August and F, September and may be due to an algal bloom on the stagnant pond. NOA has noted a similar elevation of pH from algal growth at other local facilities. t J Residual chlorine and chloroform values in the storage pond are presented in Plate 5. It appears from this plate that a spike in residual chlorine concentrations in the pond is followed in one to two months by a spike in chloroform concentrations. This trend appears reasonable because chloroform FJis produced when free chlorine reacts with organic matter as a function of contact time. Fl� Fill7CFR Ch. 1,Part 143.3 National.Secondary Drinking Water Regulations,2000. lJ