Guidance Manua pdf
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- Jun-01 Aug-01 Oct-01 Dec-01 MIB, ng/L
- Jun-01 Aug-01 Oct-01 Dec-01 MIB, ng/L Squaw Peak Deer Valley
- November December % of samples >20 ng/L >10 ng/L
- April May June July August September October November
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20 40 60 80 Aug-99 Oct-99 Dec-99 Feb-00 Apr-00 Jun-00 Aug-00 Oct-00 Dec-00 Feb-01 Apr-01 Jun-01__Aug-01__Oct-01__Dec-01__MIB,_ng/L'>Jun-01 Aug-01 Oct-01 Dec-01 MIB, ng/L
Figure 2-1. MIB at the inlet to the Val Vista WTP.
MIB concentrations at the Squaw Peak WTP (Figure 2-2) were slightly higher than at Val Vista. As with Val Vista, MIB values > 20 ng/L occur primarily in late summer and rarely exceeded 30 ng/L.
Figure 2-2. MIB at the inlets of the Squaw Peak and Deer Valley WTPs.
9 The stretch of the Arizona Canal from the Squaw Peak WTP to the Deer Valley WTP was a major source of MIB. The Deer Valley WTP therefore had much higher concentrations of MIB than Squaw Peak. MIB concentrations at the inlet to the Deer Valley WTP generally remain above 20 ng/L from August through November, with sporadic episodes occurring before August.
The frequency of MIB values > 10 ng/L and > 20 ng/L during the three-year T&O study can be used as a rough guide for planning the annual T&O management program. Figures 2-3 through 2-5 show the percentage of samples with MIB > 10 ng/L and 20 ng/L during each month of the three-year T&O study. At the Val Vista WTP, MIB concentrations > 10 ng/L can be expected more than 50% of the time from July through November. MIB concentrations > 20 ng/L was common in September.
20 40 60 80 100 January February March April May June July August September October November December % of samples >20 ng/L >10 ng/L
Figure 2-3. Percentage of samples with MIB > 10 ng/L and > 20 ng/L at the Val Vista WTP. 0 20 40 60 80 100 January February March April May June July August September October November December % of samples >20 ng/L >10 ng/L
Figure 2-4. Percentage of samples with MIB > 10 ng/L and > 20 ng/L at the Squaw Peak WTP. 10
20 40 60 80 100 January February March April May June July August September October November December % of samples >20 ng/L >10 ng/L
Figure 2-5. Percentage of samples with MIB > 10 ng/L and > 20 ng/L at the Deer Valley WTP.
At the Squaw Peak WTP, MIB levels exceeded 20 ng/L more than 50% of the time in September and October. MIB levels were > 10 ng/L more than half the time from June through December, and in the month of March.
The situation is typically much worse at the Deer Valley WTP. For all months with observations, MIB levels routinely exceeded 10 ng/L, and MIB levels generally exceeded 20 ng/L from June through December.
In summary, the likelihood of encountering elevated MIB levels at Phoenix’s WTPs follows the order:
(highest) Deer Valley >> Squaw Peak >> Val Vista >> Union Hills (lowest) The occurrence of elevated MIB levels at each of the water treatment plants is summarized in Table 2-1.
Table 2-1. Number of months per year with MIB concentrations above threshold levels at Phoenix’s water treatment plants
Water Treatment Plant MIB > 10 MIB > 20 Union Hills 0 0 Val Vista 5 2 Squaw Peak 8 2 Deer Valley 10
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