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vs <br /> I _ �, ']4 f Y.. � h.. ,b�a'A- V""'S�, •SSY�Rf. e _ •� f rG912. <br /> 7:A- <br /> � ~ <br /> OROA�. -___1 r:onCr,I_ <br /> GeophysIcA' Consultants <br /> 1 <br /> y d <br /> April 28, 1987 <br /> SCS Engineers <br /> 6711 Sierra Court, Suite C <br /> oublin, CA 94568 <br /> Attention: Mr. Robert Livermore radar (GPR) survey that we <br /> round penetrating warehouse in <br /> This letter is in regards to a g was to investigate for <br /> recently Performed at the purposeGOf1thleasurveyBeas Company ties prior to <br /> Manteca, California. The purpose <br /> was conducted on April 36, <br /> possible abandonedlandergroundThdoffeldtsurveyn RobertlLivermore, SCS <br /> installing monitoring Geophysicist. <br /> 1987 by Kenneth Blom, Principal <br /> Engineers assisted with this work. <br /> Ground Penetrating Radar on _ <br /> } pro a continuous high resaltheshallow subsurface. <br /> GPR is a method that p of the 'radiated into the <br /> depicting variations in the ort duicai properties a traverse. The <br /> Electromagnetic Pulses of short durasiit isemoovedlalonglY <br /> ground from a transducer {antenna) <br /> e ability of a material to hold an electric <br /> radar signal is sensitive to differences in electrical cknto conductivity <br /> electrical permittivity (the properties occur. The reflected <br /> charge)- Portions of the radar sitheseappeflected ba <br /> from interfaces where a change in cross-sec <br /> can <br /> the same transducer and is transmitted through an <br /> energy is received by esameretarder. The resulting <br /> electrical cable to a graphical. stratification, the thickness ah as nd extent f <br /> provide information regarding <br /> Generally, relatively high electrical conductivities or <br /> fill structures. <br /> the location of buried high <br /> objects een mater. is can reduce <br /> other structur performance. <br /> low contrasts in the <br /> abiiityrandllimitlradar <br /> the penetration cap Inc. SIR-3 <br /> For this investig antenna. This antenna <br /> ation we used a Geophysical Survey System , provides <br /> impulse Radar System with a uen Megahertz frequency The typical <br /> ate depths of penetration <br /> relatively <br /> -is in the center of the rrequemcoYde�ange5 available and t�raveore p <br /> relatively high resolution at annotating distant- <br /> survey procedure was to hand tow the a electronicallyach <br /> Horizontal control was established by at'tern <br /> f parallel <br /> traverses in aurid patoints of <br /> at 2 foot intervals on the GPporapiles as determined.from. apmeasurtn <br /> l marks coverage consistedThe beginning and <br /> tape. The Survey <br /> 5 to 10 feet apart and 35 to 69 feet long. <br /> -- --- -- -- -each,traverse-_was marked in the field for later reference. <br /> _.... � ra'3 u,..g 1±:.CSS,:� . i:e��� _ ' �•� <br />