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F7Based ore and Hantzsche paper, they discuss three options to consider as potential methods e mounding phenomenon. The first is increasing the size of the disposal field. he average daily flow calculations found on Page 9, the disposal area is sufficient in modate the conservative projected flow volumes after completion of construction. The second method is elongating the shape of the area covered by the disposal field. As noted on the design plans, the mound system is elongated in a 2.6:1 length-to-width ratio. Thirdly, operating the field intermittently should decrease the mounding effect. As noted in this Report, effluent will be pumped by two alternating pumps that will pump small doses of approximately 85 gallons per dose. If it is determined at some point in the future that mounding effects are preventing proper effluent treatment and disposal,the area designated as the 100% replacement area may have to be activated. As noted on the plans,the 100%replacement area is composed of the existing mound system and additional reserve area to the east. E. SURFACE WATER INFORMATION Storm water management is proposed to be an on-site retention basin. There should be no impact to percolating effluent from the retention basin. Since the groundwater directional flow is north- northeast, percolating rainwater from this basin into the top aquifer mixing layer may create a dilution effect to the cross gradient percolating septic system effluent. Groundwater dilution effects can only be truly discerned with groundwater monitoring and modeling. According to a scientific paper authored by Shaw and Turyk(1994), reduction of nitrate concentrations in groundwater can occur primarily through dispersion, or by percolating rainwater recharge. Climatic ata: Rainfall versus Evapotranspiration NLS� It is generally and scientifically accepted that when precipitation exceeds evapotrans- �tion(Eto), deep percolation of surface rainwater may occur. Evapotranspiration refers to water evaporation that takes place both at the soil surface and transpiration by plants, and is defined as water loss from a large field of 4-to-7 inch tall, cool-season grass that is not water stressed. The following Table illustrates rainfall and evapotranspiration for the Tracy area. Precipitation data was obtained from the Soil Survey of San Joaquin County. The conservative "2 years in 10" data was used and not the "average rainfall"data. Evapotranspiration data was obtained from the California Irrigation Management Information System (CIMIS): 7 Chesney Consulting