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C7eala 4m,Twhato 1= Page 10 <br /> Site Conceptual Model Report <br /> Marci Property <br /> Project No 7012 <br /> August 23,2004 <br /> ' <br /> Seepagea Velocity <br /> _ v <br /> ' Seepage velocity (v) =permeability(K) x gradient(1) = Ki <br /> porosity (n) n <br /> ' K= 1X 10 cm/sec (typical literature value for silt/clay) =2 Sx 10-3 ft/day = 1 ft/year <br /> 1 =0 001 (average water table gradient for the site in"ft/ft") <br /> n=0 435 (porosity 43 5 % for MW-4 @ 65 feet) <br /> Substituting <br /> ' v = (1 ft/year)x (0 001 ft/ft) = 2 3x10-3 ft/year <br /> 0 435 <br /> ' Using the value of 2 3x 10-3 ft/year it can be theorized that the diesel contamination would <br /> take 17,391 years to travel the 40 feet from the UST location to the location of well MW-5 <br /> [17,391 x 2 3x10-3 ft/year= 40 feet]. Obviously the seepage velocity is an underestimate and <br /> ' preferential pathways of more hydraulically conductive layers exist for contaminant transport <br /> The diesel contain oration extends from the former UST location to wells MW-5 to the <br /> northwest and MW-6 to the southwest <br /> These calculations show that contaminant transport will occur but that predicting the time at <br /> which nearby receptors will be impacted is problematic The closest receptors are wells <br /> utilized for domestic drinking water source and they are threatened if the diesel plume <br /> migrates off site <br /> 3.0 POTENTIAL OFF-SITE SOURCES OF DIESEL CONTAAENATION <br /> ' GTI conducted a State & Federal Record Database Search for the parcel as available from <br /> Environmental Data Resources, Inc (EDR) The purpose of this task was to determine if an <br /> off site source of diesel contamination could be contributing to the groundwater plume ve 114 <br /> 4 <br /> ' parcels were identified in the immediate vicinity of the subject site with documented diesel <br /> releases- - - - -- ? <br /> ' ana(Z <br /> The following list of nearby properties was identified as suspected or potential sources of ey 4V <br /> diesel contamination from the EDR Report, which is attached in Appendix F The as l^-SS <br /> ' information reviewed includes the following details type of release, distance to site, Val <br /> regulatory status, etc give details and whether or not a factor <br /> Roadway Express, 3233 Loomis Rd, Stockton, CA 95205 Date of release July 14, <br /> t 1992, case has been closed on February 11, 1997 for LUST Chemical used—Diesel <br /> e National Freight Inc , 2850 Loomis Rd , Stockton, CA 95205 Unspecified oil- <br /> containing waste, HAZNET <br /> 1 <br />