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5.0 <br />5.1 <br />5.2 <br />DETERMINATION OF TIME TO GROUNDWATER <br />TIME TO GROUNDWATER METHODOLOGY <br />For this Terminal, ERM uses a desktop groundwater modeling technique <br />commonly used in the industry to determine the Time to Groundwater. <br />First, ERM obtained the recharge rate for the terminal using U.S. <br />Geological Survey (USGS) data, and used that information to calculate <br />transmissivity. Transmissivity is directly proportional to permeability <br />and thickness or depth to groundwater. ERM used Geographic <br />Information System (GIS) and Watershed Modeling System (using USGS <br />data, stream morphology, and hydrology) in combination with existing <br />site information to complete the transmissivity calculation and resultant <br />determination of vertical time to groundwater. <br />TIME TO GROUNDWATER RESULTS <br />The vertical Time to Groundwater is calculated to be less than one (<1) <br />day. This calculation is based on information provided below. Multiple <br />iterations of the calculation were performed based on differences in depth <br />to groundwater and multiple hydraulic conductivity values; however, <br />every scenario resulted in a time to groundwater of less than one day. The <br />following information is used to complete this determination: <br />ERM <br />• Calculation - <br />Depth <br />to GW <br />(ft) <br />k <br />k units <br />k (cm/s) <br />Time to GW (days) <br />4 <br />26 ft/day <br />9.17E-03 <br /><1 da (0.15) <br />4 <br />19 ft/day <br />6.70E-03 <br /><1 da (0.21) <br />4 <br />97 ft/day <br />3.42E-02 <br /><1 da (0.04) <br />Z <br />t = — <br />k <br />where: <br />5-1 <br />110870\CHEVRON\SPCC -JULY 2010 <br />