7125 EVERGREEN WAY 2018-01-02 MF Import

Sent By: Zipper Zeman Associates, Inc.; JetSuite; May-12•99 18:06; Pa e 3/5 9 Rodlntd Toyau Clud Vehicle Lut J•237.(0 Everat[, Waehington t2 btay 1999 Page 2 tbe mimerical values �egarding mittimum vcrtical geogrid spacing and minimum geogrid len�ths ccquired for the various sect:oa4 of rockery es a fvnctioa of rockery heieht We have assumed a uaffic swcharge of 260 pounds per square foot (ps� in consideration of the eaticipate veiricle stoc�e above the rockeries. It is our rccommendation that Teasar SRI/[TX1400 Uniaxial Geogrid, or equivalent, be utiliud for the fill embanl�rnts which face rockeries tailer than 4 feet Tensar SS2/BX120� gsogrid, or equivaleat, is �ecommended for 4-foot high rockerics. Whcn placing t}u geogrid on the soil surfece, the front face of the yeogrid layer may be extended through the crwhed rock back5ll behind the fa.,-ictg rocks. We recommend tLat both the froat and bai;k ends of each geogtid leyer be secur�d ia tension prior to placcment end compaction of the structmal fill. muter;al above each geo�tid layec. This can be accomplished by staking the grids in place. 9uKace Water MnnaQement Pond Coueideradone We received from CG Engineerine a cross scctional detail illustcating the conGguradon of the surface water mena�ement pond pmposed for the uortheastern porfion af the site. The plaa depicts the pond and the edjscent rockery. We undcrstand that the pond will re desi�cd as a`�vet pond", wiih a normel water levcl of elevation 473 fect, aud a hi�h water level of elcvacion 473.4 feet Based upon our review, we offer the following recommendations: The pond is shown siwued relatively ciose ro the rockery. In conside:ation of the rccommended geogrid reinforcement of the fill embanl�ent in wluch the pond will be conshvcted, wc recommend that the pond be maved southward froni tl:e posirion shown such thxt the geogrid reinforcemcnt 2one is set back &om the pond surface a minimum 2-foat distance. We recommend that the fill material in the area which wili house the pond contain at leact 30 perccnt fina (that soil fraction pavsing che U.S. No. 200 sieve) in otder to limit watcr exfiltration. Should a lower permeability be desiizd, we su�gest that considerarion be given to tilling powdered bentonito clay into the upper I-foot of the iaterior pond surfuce, We suggest that 15 percent by weight beatonite be addcd to the soils, blendcd well at the soil's optimum moistuce contmt or slighdy above, attd compacted to the reeotntnend 90 percent densiry (AS1M:D-1557). Alumatively, an impesmeable synthetic liner, such as PVC or FIDPE, could be installed. • Surface drainage ai the base of the fill slope plenned for below, and north of, the rockery to provide a flowpath for nmoff or seepage. 'Ibe flowpath should direct all nuwff from thc siu, ead the apartmeats located near the north property boundary, to an appropriatc surface water discharge. Zjpoa Zeman ,Wociasa. Inc. 192]l36'AvsnueWu45uiteB3D1 Lyno�.w4Wa.bingim9lO76 (4251771•3701