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Near and Far Field Dilution Analysis of Manteca Discharge October 2006 <br /> Introduction <br /> Near field and far field dilution analysis of the Manteca discharge has been completed in <br /> support of the Manteca Wastewater Control Facility EIR, using local and Delta-wide <br /> versions of the 2-D depth-averaged models RMA2 and RMA 11. <br /> Background <br /> The 2-D depth averaged model of the San Joaquin River that extends from Old River to <br /> Vernalis was calibrated to temperature during the Manteca thermal plan exception <br /> modeling (LWA, 2006). This model is used for the current study to perform near field <br /> dilution analysis. <br /> In the past, the far field modeling effort used a tidally averaged 1-D link-node <br /> hydrodynamic water quality model to predict the fate and transport of Manteca effluent <br /> throughout the Delta system. However the link-node model cannot evaluate inter tidal <br /> impacts associated with a timed discharge, a key requirement for the present <br /> investigation. As a result RMA has applied the 1-D/2-D finite element Delta model <br /> (RMA2/11), which has gained wide acceptance with the Department of Water Resources <br /> (DWR) and others, to the far field investigations. <br /> Numerical Models <br /> To simulate the hydrodynamic and water quality responses in shallow estuaries, RMA <br /> has developed two computer programs, RMA-2 (King, 1986) and RMA-11 (King, 1995). <br /> RMA-2 is a generalized free surface hydrodynamic model that is used to compute a <br /> continuous temporal and spatial description of fluid velocities and depth throughout an <br /> estuary system. RMA-11 is a generalized two-dimensional water quality model that <br /> computes a temporal and spatial description of conservative and non-conservative water <br /> quality parameters. RMA-11 is designed to simulate both inter-tidal and tidally averaged <br /> water quality conditions. RMA-11 uses the results from RMA-2 for its description of the <br /> flow field. <br /> RMA-2 solves a set of differential equations that represent hydrodynamic response of <br /> shallow water waves throughout the estuary. They are essentially a hydrodynamic <br /> quantification of Newton's second law (i.e., force =mass x acceleration) and include the <br /> effects of momentum transfer, wind,bottom friction, the Coriolis force, and turbulent <br /> diffusion. The complex effects of turbulent diffusion are approximated by turbulent <br /> diffusion analogy(i.e. eddy diffusion). <br /> RMA-11 solves a set of differential equations representing the conveyance of dissolved <br /> or suspended material by advection and turbulent mixing. These equations are derived <br /> from a statement of conservation of mass. Eddy diffusion is also used to approximate the <br /> complex process of time dependent transport by turbulent mixing. <br /> Near Field Dilution Analysis <br /> Near field dilution analysis simulations were performed to analyze the dilution of the <br /> effluent plume in the San Joaquin River in the local vicinity of the Manteca discharge <br /> 1 <br />