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• •nnedy/Jenks Consultants 1 ' redistribution. At the Thoroughbred Farm property, a sprinkler irrigation system can be installed if necessary to achieve uniform and efficient water distribution. ' 6.2 Subsurface Water Movement To evaluate the vertical movement of the water used on the properties under irrigation with ' reclaimed water, a vadose zone water flow model was constructed. The model provides a tool for estimating movement of water through the vadose zone. For purposes of modeling, a high initial soil water content and a leaching fraction of approximately 5 inches per year was ' assumed to be conservative. In normal agricultural practice, the soil profile may not be at the higher water content assumed and leaching would occur only periodically. The assumed leaching results in a small percolation flux past the upper soil profile on the offsite reclamation property. This percolation flow is unsaturated and moves slowly through the approximately 80-foot vadose zone between the bottom of the soil root zone and the groundwater underlying the site. 6.2.1 Modeling Approach Vadose zone water flow modeling was accomplished using an EPA-recommended computer ' code, HYDRUS-1 D (Simunek, J., M. Th. Van Genuchten, and M. Sejna, 2001) and code for Simulating the One-Dimensional Movement of Heat,Water, and Multiple Solutes in Variably ' Saturated Porous Media (USDA ARS Salinity Laboratory, 2001). This model uses finite element numerical methods to solve heat, water, and solute transport equations given user-specified physical conditions including boundary conditions at the ground surface and at a lower boundary. This model was used with site-specific data to estimate water movement below the upper soil profile or"root zone". A primary input to the model is information concerning the subsurface stratigraphy, which was available from results of construction of a groundwater monitoring well on the western boundary of the Jepsen Webb Ranch property and related subsurface borings performed using log data from the CPT investigation conducted on the Jepsen Webb Ranch property discussed in Section 5. In addition, climatic and irrigation information are also used as model input. Soil characteristics ' used in the model were based on information from the soil survey for the reclamation area sites and subsurface borings at the Jepsen Webb Ranch property. The hydraulic load on the irrigation areas is based on distributing the reclaimed water on both the onsite and offsite irrigation areas as described in the water balance. 1 6.2.2 Model Development The conceptual model for vadose zone water flow is based on the following assumptions: • Results of investigations at the Jepsen Webb Ranch property provided characterization ' of the subsurface stratigraphy at this site. e One-dimensional, vertical water flow dominates water movement at the reclamation properties. ' Reclamation Report, Page 17 Musco Family Olive Company 4�+s-grcu'r�aT^nyob{1121^201rp,pn_ oo�be'A9-rercrLlr=clama6on TNmxorecla wo: repoh UziB 11 M.doc