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Geofogical Technics Inc. <br /> ' 2741 Riv ,Vau <br /> M.d&u,CalJomia 95351 <br /> (209)538-6424/$aX#538-5852 <br /> Work Plan — Supplemental Data <br /> George's Service <br /> ' 1600 Durham Ferry Road <br /> Tracy, California <br /> ' Project No. 425.2 <br /> October 13, 2000 <br /> t The following discussion provides answers to the information required in San Joaquin <br /> County, Public Health Services/Environmental Health Division's correspondence dated <br /> September 15, 2000. Our comments address their concerns as numbered in their letter. <br /> ' 1. Groundwater Velocity & Contaminant Transport calculations <br /> The equation we used for evaluating the velocity of groundwater is listed below and gives at <br /> best, the average velocity values. Combining Darcy's law and the velocity equation of <br /> hydraulics, canceling the area terms, and adding the porosity term derive this equation. <br /> ' v=Kdh/ndl <br /> v= groundwater velocity (length/time) <br /> K=hydraulic conductivity (length/time) <br /> dh/d1= hydraulic gradient(ft/ft) <br /> n=porosity (%) <br /> ' The values for these calculations are found in Tables 4 & 5 for groundwater gradient and <br /> Table 6 for soil geophysical parameters. The units that groundwater velocity was calculated <br /> for is the shallow aquifer from 10 to 20 feet below ground surface (bgs) and the intermediate <br /> depth aquifer from 30 to 50 feet bgs. <br />