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Soil Suitability&Nitrate Loading Study Page 12 St.Patrick's Church, Escalon, CA [ Project No. 607.1 October 14, 2009 System Effluent Cone. NW r- Existin Res. 44m /L F Pro osed Cha el 80 m Proposed Church 80 m /L Proposed Rectory 44 m j o Proposed Schoo[ 60 m /L o7G Proposed Admin Bldg 60 m /L 0i-1 �-- Multi-Purpose Rm 60 m /L If Proposed Convent 44 m 1L a Meteoric Water ! � 1 Rainwater percolating through the soil is the primary leaching agent carrying nitrates to the groundwater. The estimate of the amount of deep percolation is based, in part of the long-term average annual precipitation and on the average evapo-transpiration rate (ET). The rate at which precipitation exceeds evapo- transpiration is the rate at which percolating meteoric water is available to leach nitrates to groundwater. According to the National Weather Service . (htt-P:Hcdo.ncdc.noaa.gov/), the mean annual rainfall at the Stockton Airport (the nearest reporting station) is 13.84 inches. The rate of evapo-transpiration is available from the website of the California Irrigation Management Information F System (CIMIS) (http:l/wwwcimis.water.ca.gav/cimisn. California has been divided into zones, and Escalon falls in Zone 12. The average annual evapo- transpiration rate for Zone 12 is 53.3 inches. In recognition of the fact that most of the precipitation falls during the winter months, while most of the evapo-transpiration occurs during the summer, the following table was prepared to provide a month-by-month breakdown. Month Mean Precip. Mean ET Percolation in.) in. in. i Jan. 2.71 1.24 1.47 Feb. 2.46 1.96 0.50 Mar. 2.28 3.41 - Apr. 0.96 5.10 May 0.50 6.82 Jun. 0.09 7.80 Jul, 0.05 8.06 - Au . 0.05 7.13 - Sep. 0.33 5.40 F Oct. 0.82 3.72 - Nov. 1.77 1.80 - Dec. 1.82 0.93 0.89 E 2.86 FL 2937 Veneman Ave.,#EB240 Geo-Phase EnvironmentalPhone: 2 - Inc. ( 09) 569 0293 Modesto, CA 95356 Fax: (209) 569-0295 F i�