4937 SEA BREEZE WAY 2017-01-13 - Laserfiche WebLink

� Geotechnical Engineering Evaluation Pepe Retaining Wall Everett, Washii�gton C� NGA File No. 916915 April 27, 2015 Page 12 tieback installation to ve�•ify that tiebacks do not encounter any existing structures or underground uti I ities. No-Load Zone: The anchor portion of all tiebacks must be located a sufficient distance behind the wall face to develop resistance within a stable soil m�ss. We recommend the anchorage be obtained behind an assumed no-load zone. The no-load zone is defined by a line extending horizontally from the base of the wall back towards the residcnce a distance of tive feet. The line sho�ild then extenci up from the base elevation at an angle from the horizontal of 60 degrees. We expect that some undocumented fill may Ehist beyond 2he no-load zone. We therefore recom��end that the unbonded portion of the anchors extend through any �Il soils that u�ay exist outside the no-load zone. We recommend that we monitor soil conditions d�rring anchor installation in order to evaluate adequate penetration into competent soils. Soil Design Values: Load carrying capacities should be determined based on 1,000 psf grout to soil adhesion in the bonded portion of the anchors. We recommend that we review anchor design and proposed installation methods. We should also observe anchor installation and testing. The anchors should be permanent double-corrosive protected anchors. Tieback Anchor Installation and Testing: The contractor should be responsible for using equipment suited for the site conditions due to litnited site infortnation, a test anchor may be considered to verify site conditions prior to finalizing plans. One anchor should be performance tested to 200 percent of the anchor design capacity. The performance test should consist of cyclic loading in increments of 25 percent of the design load, as outlined in the Federal Highways Administration (FHA) report Na FHWA/RD-82/047. The test location sllould be determined in the field, based on soil conditions observed during anchor installation. All other tiebacks sllould be proof-tested to at least 130 percent of design capacity. Drainage Improvements The finished ground surfac�e should be graded s�ich that runofi� is directed to an appropriate stormwater collection system. Water should not be allowed to collect in any areas behind the wall or on pavement areas. Final site grades should allow for draina�e away from the residence and wall. We suggest that the finished ground be sloped at a minim�nn gradient ol�three percent, fior a distance of at least 10 Feet away NELSON GEOTECHNICAL ASSOCIATES, INC.