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_— i LSI Adapt, Inc. <br /> Our recommcndcd valucs for thc cocfficicnt o1'horizontal subgradc rcaction (nh) and the <br /> vertical subgrade modulus (k�) for the soil layers encountcred at this site are presented in <br /> Tabic 4 bclow. Thesc values do not include a factor of' safety since thcy model the <br /> rclationship bctwcen contact pressure and displacement. Therefore, the swctural <br /> cnginccr or monopolc ivanufacturcr should scicet an appropriatc allowable displaccmcnt <br /> for dcsign, bascd on thc spcci`c rcquircmcnts of thc communication cquipmcnt mountcd <br /> on thc towcr. <br /> Table 4 <br /> Recommended Drilled Picr Horizontal Subgrade Reaction Values <br /> Depth Interval ne k,. <br /> (fcet) (pci) (Pcl) <br /> �-� 0 N/A <br /> 2-3 40 N/A <br /> 3-8 65 N/A <br /> Cac�cientofHorizontal kn=�n��) kh=k,!(1.SB) <br /> 3ubgrade Rcaction (pci) (Sand& SoR Clay) (Slift'Clay) <br /> Conshvction Considerations: Our cxploratian revcaled thc sitc soils to consist of up to about 3-fect of <br /> loose to medium dcnse, silt��sand with gravc (wcathcred glacial till) overlying dcnsc to vcry dcnsc, silty <br /> sand with gravcl (glacial till). It should be notcd that ovcrsizcd matcrial, such as cobblcs and bouldcrs <br /> ("glacial erratics") may bc cncountcrcd on a random basis within the glacially derivcd site soils. No <br /> groundwatcr sccpagc tvas encountcrcd witliln our site borings, at thc timc of cxploration. Howcver, <br /> dcwatcring may bc requircd, dcpcnding on the actual dcptl� and timc of ycar of drilled picr construction. <br /> The foundation-drilling contractor sUould be prcparcd to case thc c�cavation to prcvent caving and <br /> ravcling of ihc picr shaft sidcwall, if necessary duc to unanticipatcd soil or cxccssivc groundwatcr <br /> scepagc conditions. Should unaniicipated hcavy groundwater intlow be cncountcred during drilling, it <br /> may be necessary to pump the accumulated groundwater prior lo picr concrete placcmcnt. Altemativcly, <br /> thc use of'bcntonite slurry could bc utilizcd to stabilizc thc drillcd picr excavation. <br /> Drilled Pier Excavation Conditions: Thc clrilling contractor should bc prepared to cican out the bottom of <br /> thc pier cxcavation if loosc soil is oUserved or suspectcd, with or without the prescncc of slurry or <br /> groundwater. As a minimum, wc rccammcnd that thc drilling contractor havc a cicanout buckct on sitc to <br /> remove loose soils and/or mud from ihc bottom of the picr. If groundwatcr is prescnt and abundant <br /> within the pier holc, we rccommend that thc foundation concrctc bc tretnicd from thc bottom of the holc <br /> to displace the watcr and minimize thc risk of contaminating the conerctc mis. Thc Drillcd Shafi Manual <br /> publishcd by the Pcdcral Highway Administration rccommcnds that concrctc bc placcd by trcmic <br /> mcd�ods if morc than 3 inchcs of��atcr h:�s accmnulatcd in thc cxcavation. <br /> NeMel Go Tetra Tech June 25,2004 <br /> LSI Adapt Project No.WA04•17499-GEO Page 1� <br /> fj <br />