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calculations is needed to more reasonably estimate the resultant nitrate-nitrogen percolation <br /> value. I recommend revising the analysis per the methodology outlined in Attachment 1. <br /> 2. Other Comments. Other comments that may or not be pertinent following recommended <br /> adjustment the methodology(Comment 1) are: <br /> a. Precipitation Data(Table 4). The values for monthly precipitation values for the Tracy <br /> area in Table 4(page 5)are labeled "2 years in 10"data from the Soil Survey of San <br /> Joaquin County. They are stated to be"conservative"(i.e., lower) as compared with <br /> average precipitation amounts; but they are actually significantly higher than average <br /> monthly precipitation amounts for Tracy. The total of the individual monthly amounts <br /> equals 19.54 inches,well above the annual average precipitation for Tracy(10 to 11 <br /> inches). The total given at the bottom of Table 4 is correctly copied from the source <br /> document(Soil Survey), but I believe it represents the"2 in 10 years"annual total,which <br /> is different from the total of the individual monthly values list. The average monthly <br /> precipitation values should be used in the nitrate loading analysis instead of the"2 in 10 <br /> years"values listed in Table 4. <br /> b. Annual Rainfall-Recharge Value. In Table 4 the estimated value for rainfall-recharge <br /> ("deep percolation") is given However, in the calculations that follow(middle of page 8), <br /> a value of 9.5 inches per year is inserted for R, without any rationale or reference. This <br /> should be resolved in responding to Continent#1 above. <br /> 3 <br />