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Portola Geophysics <br /> 21 Santa Maria Avenue (415) 851-8751 <br /> Portola Valley, Ca. 94025 May 22 , 1987 <br /> 1017 <br /> Mr . LeonardoLeonardoAlvarez, <br /> EMCON Associates <br /> 1921 Ringwood Avenue <br /> San Jose , California 95131 <br /> SUBJECT : Seismic Refraction Survey , Harney Lane Sanitary Landfill <br /> Replacement Site <br /> San Joaquin County , California <br /> Dear Mr . Alvarez : <br /> With this letter report , we are presenting the results Of <br /> our seismic refraction survey of the Harney Lane Sanitary <br /> Landfill Replacement Site in San Joaquin County , California . <br /> Summary <br /> A total of six ( 6) individual seismic refraction lines <br /> with a combined spread length of 1800 lineal feet were recorded <br /> at a proposed landfill site in San Joaquin County , California . <br /> This work was performed in accordance with our Proposal for <br /> Geophysical Services dated April 28 , 1987 . The purpose of this <br /> survey was to evaluate the rippability and characteristics Of <br /> subsurface materials as well as the presence of groundwater <br /> beneath the project site . <br /> Interpreted Results <br /> Seismic refraction lines S- 1 through S-6 , with spread <br /> lengths of 300 feet each , were recorded in the locations <br /> indicated on Figure 1 . These locations (and line numbers ) <br /> correlate with the locations (and boring numbers ) Of exploratory <br /> borings performed by J . H. Kleinfelder and Associates in 1986 . <br /> Data and interpreted results are presented on Figures 2 through <br /> 4 . <br /> in general , the gently sloping to relatively flat alluvial <br /> plain comprising the project site is underlain by one ( 1 ) or two <br /> ( 2) velocity zones ( refractors ) to the depths surveyed . The zone <br /> closest—,I,Jw- the ground surface is characterized by low velocity <br /> ( 1250 -,-4,'5,60 ft/sec ) materials <br /> to depths from 0 to 7 feet , and <br /> t yp i Ca I y a few feet . The underlying zone is characterized <br /> by mi v"1*61ocity ( 2920 to 3850 ft /sec ) materials which extend <br /> from depths of 0 to 7 feet to greater than 96 feet . <br /> In the vicinity of line S-5 , three (3) velocity zones were <br /> encountered . Below a low velocity ( 1560 ft /sec) zone , low to <br /> For the purpos,e3 of this report , a seismic refraction line <br /> consists Of 12 geophon03 spaced at equal intervals of 25 feet <br /> along a straight line and monitored simultaneously while & sledge <br /> hammer was impacted off each end and/or at the center of each <br /> I i ne . <br />