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July 21, 2014 <br />Two Single-Family residemces <br />L&A Job No. 14-065 <br />Page 22 <br />USDA TEXTURE TRIANGLE CLASSIFICATI�N OF SOIL SAMPLES <br />Sample Percentage Percentage Percentage <br />No. C1av Silt Sand/Gravel <br />1 3.7 8.8 87.5 <br />2 1.2 4.6 94.2 <br />USDA Texture <br />Triang;le Classification <br />Sand <br />Sand <br />The Stornlwater Mana�ement Manual for Western Washin�;ton 2005 Edition, published <br />by Washington State Department of Ecolo,gy, is used to determine estimated design <br />infiltration rates of the target soil layers from which soil samples were obta.ined. <br />�ccording to the table of Recommended Infiltration Rates Based an USDA Soil Textural <br />r, ,,� ,• ,,,-� , ,w� ,�3 �., � _�. t�� ���;�at��l S�nrt-t�ri� an�t l�t�g-t�z711 �nf.tltration <br />�,1�.���.�,�:����,�_ ,u�� ,_ - --, � � �_� .. <br />rates would be $ iph (inches per hour) and 2.0 iph, respectively, fc�rc "sa;�zd". ��Il�. l�ti�- <br />tenn rate is derived from the short-term rate with a correction factor of 4. The infiltration <br />rates thus determined for the soil samples are presented on the table below. <br />a ESTIMATED 7NFILTRATION RATES <br />Sample Test Pit Estiinated Infiltration Rate, Inch./Hour <br />No. No_ Short Term Correctio.n Factor Lon� Term <br />1 2 8,0 4 2.0 <br />2 3 g-� 4 <br />a Bas�:d on USDA Texture Triangle Classification <br />� <br />'I'he D�o siz�s of the soil samples determined from their p�r.rticle size distribution tests are <br />shown on Plate A-2. The Dlo size is ihe size of soil particles of 10% passing by weight. <br />According to the table of Alternative Recommended Infiltration Rates Based On ASTM <br />Gradation Testi� presented on Plate A-5, the Alternative Estimated Infiltratioil Rates of <br />LIU & ASS�CIATES, INC. <br />