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Mr. Timm Corner <br />Chief Environmental Coordinator <br />Clarification to RFI #090601 -A- CCV -R0015 <br />April 23 2009 <br />Sincerely, <br />JFL:jfl <br />amec <br />liquid. The PL represents the water content at which the soil can still be rolled, before crumbling. <br />The PI is the numerical difference between the LL and PL, and is an indication of the water <br />content range through which the soil behaves as a plastic material. An increase in the PI reflects <br />an increase in the moisture content range in which the material will behave as a plastic material. <br />From a construction standpoint, low PI materials (5 to 20) are generally easier to work with, as <br />they contain sufficient cohesion to promote bonding between the soil grains. High PI materials <br />( +30) can sometimes be difficult to work with as they contain a high amount of clayey materials, <br />which can be difficult to compact and may be prone to shrink/swell behavior. <br />The PI is sometimes correlated to swell potential, with swell potential increasing as the PI <br />increases. Based on Seed et al (1962), soils with PI values less than 15 are considered to have <br />low swelling potential. Therefore, increasing the PI from 5 to 15, will not increase the swell <br />potential for the soil. <br />Based on these reasons, it is AMEC's opinion that changes to the PI specifications on the FSB, Pipe <br />Bedding, and Granular Filter will not have any affect on the performance of the Phase 5 VLF. If you have <br />any questions or comments, please contact me at (303) 433 -0262. <br />AMEC Earth & Environmental, Inc. <br />John F. Lupo, Ph.D., P.E. <br />Principal Engineer <br />S: \PROJECTS \1125E CCV cqa \e - correspondence \clarification letter.doc <br />2 <br />