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Inflow to the pond consists primarily of diversions of water from the wastewater treatment plant. These diversions originate from two main sources in the Tracy area: Leprino Foods and Heinz USA. Diversions to the holding ponds may either be Industrial Raw Influent (mainly from Heinz USA, but possibly including small quantities of domestic sewage) that has not been treated, or Industrial Primary Effluent that has undergone primary treatment at the Wastewater Treatment Plant. Both of these diversions occur mainly during the can- ning season that extends from July through October each year, and are measured by the City with flowmeters and totalizers. Another potential source of water to the ponds is from pre- cipitation, which is expected to be a relatively minor source of water during the canning season. Outflow from the ponds may potentially occur in two ways: by evaporation from the surface of the ponds; and by infiltration through the base of the ponds. During the canning season, when temperatures are high and humidity is low, evaporation should be a relatively significant loss. Of course, the volume of water lost through infiltration is unknown and is the object of this study. The change in storage is the volume of water contained in the holding ponds at the end of the study minus the volume of water contained in the holding ponds at the beginning of the study. As might be expected, a large decrease in the volume of water stored in the ponds must be accounted for by either evaporation or infiltration. The relationship presented above may therefore be expanded as follows: I,., + P = Eo + Oinr., + (V2 - V,) where: I,„, = volume of water pumped into the ponds P = volume of precipitation onto the ponds Ea = volume of water evaporated Oiot;, = volume of water infiltrated through the base of the ponds V2 = volume of water in the ponds at the end of the measurement period V, = volume of water in the ponds at the beginning of the measurement period The relationship may be rearranged to solve for Oi„rl: Oir., = L, + P - Ea - (V2 - V1) ■ Thus, if each of the variables on the right side of the equation are measured, then the ” volume of water infiltrating through the base of the ponds may be calculated. I., will be measured using a flowmeter with a totalizer that will calculate the volume of water discharged through the pipe. The City will record the volume of water pumped through the pipe at the beginning and end of the measuring period. P and Eo may be estimated by obtaining data from the City's weather station. SAC/SAC36357/041.WP5 12 8/94