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y r <br /> August 18, 2014 <br /> Gibson Bluff <br /> L&A Job No. 14-056 <br /> Page 21 <br /> in millimeters of soil particles of 10%, 60%, and 90%, respectively, passing by weight, <br /> and fins is the fraction of the fines passing the No. 200 sieve by weight. The values of <br /> Dlo , D6o, D9o, and ffines are shown or obtained from test results on Plates A-1 and A-2, and <br /> the determination of Ksat for the three soil samples are shown in the table below. <br /> ESTIMATED INITIAL INFILTRATION RATES, Ksat <br /> Sample Test D10 D6o D90 ffines a Ksat Ksat <br /> No. Boring No. Size Size Size cm/sec in/hour <br /> 1 1 0.1654 0.750 11.5 0.054 0.0312 44.6 <br /> 2 2 0.1150 0.790 17.0 0.073 0.0194 27.7 <br /> 3 3 0.1171 0.425 1.25 0.063 0.0325 46.5 <br /> a loglo(Ksat) = -1.57 + 1.90(D10) + 0.015(D60) - 0.013(D90)—2.08(ffines) <br /> Recommended Design Infiltration Rate <br /> We recommend the design infiltration rate for infiltration trenches or galleries to be used <br /> for onsite stormwater disposal for the subject project be determined by taking the lowest <br /> value from the table above and apply a factor safety of 6 to it. Therefore, our <br /> recommended design infiltration rate in the advance outwash sand deposits would be 4.5 <br /> iph (inches per hour). <br /> INFILTRATION TRENCHES/GALLERIES <br /> General <br /> It is our opinion that based on the soil conditions encountered by the test borings and the <br /> results of particle size distribution tests on the soil samples, the targeted Esperance sand <br /> LIU & ASSOCIATES, INC. <br />