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Appendix B <br /> Groundwater Velocity Calculations (Shallow Zone) <br /> Apache Plastics <br /> 2050 East Fremont Street <br /> Stockton , California <br /> Assumptions : <br /> • The following calculations assume that there is no dispersion or diffusion and that <br /> groundwater is flowing in a steady state . <br /> • Groundwater elevation data used for the calculations was derived from the most <br /> recent full/complete event for site . <br /> • Hydraulic gradient used to calculate the groundwater velocity in the shallow zone <br /> was based on results from the most recent groundwater monitoring event <br /> performed the site (Figure 3) ; the greatest calculated gradient (0. 0005 foot per <br /> foot [ft/ft] was used to perform the calculations . <br /> • The screening intervals for shallow groundwater wells VEW-2 (screened 34. 5 to <br /> 54 feet below surface grade [bsg]) and MW-2 (52 to 66 feet bsg) were used to <br /> determine the cross sectional heights. To calculate the groundwater velocity in <br /> the shallow zone an average height of 16. 75 feet was used to determine the <br /> shallow groundwater velocity . <br /> • The width of the shallow zone plume (Figure 4) was used to determine the <br /> thickness of the aquifer in which groundwater flows . <br /> • The rate of flow, or hydraulic conductivity value , was determined by field <br /> lithologic observations . For the shallow zone , the hydraulic conductivity value for <br /> silt (0. 003 centimeters per second [cm/sec] or 1 gallon per day per square foot <br /> [gpd/ft2) was used to calculate the groundwater velocity in the shallow zone . <br /> • Darcy Velocity was calculated using the following formula : <br /> V= Q/A <br /> V: Darcy velocity <br /> Q : Rate of flow for used hydraulic conductivity <br /> A: Cross-Sectional Area <br />