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TABLE 3 <br /> PRECIPITATION AND Eto DATA FOR TRACY, CA <br /> Month Precipitation(in/mo) Eto Average Potential Deep <br /> (in/mo) Adj. Et Percolation(in/mo) <br /> January 2.93 1.24 0.74 2.19 <br /> February 2.21 1.96 1.18 1.03 <br /> March 2.38 3.41 2.05 0.33 <br /> April 1.51 5.10 3.06 <br /> May 0.71 6.82 4.09 -- <br /> June 2.09 7.80 4.68 -- <br /> July 0.28 8.06 4.84 -- <br /> August 1.05 7.13 4.28 -- <br /> September 0.84 5.40 3.24 -- <br /> October 1.06 3.72 2.23 -- <br /> November 2.10 1.80 1.08 1.02 <br /> December 2.38 0.93 0.56 1.82 <br /> TOTALS(in.) 13.18 57.0 ------ 6.39 <br /> The following is the Mass Balance Approach utilizing the referenced precipitation and Eto data: <br /> Available Rainfall= 13.2" (1.10 ft) <br /> Net Rainfall Recharge=6.4" (0.53 ft) <br /> Pervious areas: Grass area ball fields, decomposed granite areas, open areas= 12.6 ac <br /> Impervious areas: Buildings/concrete hardscape areas/asphalt paved areas=5.5 ac <br /> 1.10 ft x 325,851 gals/ac-ft=358,436 gals/ac x 5.5 ac= 1,971,399 gals runoff from impervious areas <br /> immediately flowing into subterranean stormwater chambers. (R1) <br /> 0.53 ft x 325,851 gals/ac-ft= 172,701 gals/ac x 12.6 ac=2,176,033 gals rainfall directly as recharge from <br /> pervious areas. (R2) <br /> R1 +R2=R= 1,971,399 gals+2,176,033 gals=4,147,432 gals= 12.73 ac-ft <br /> Page -6- <br /> Chesney Consulting <br />