1209 MADRONA AVE 2016-11-17 - Laserfiche WebLink

Geotechnical Engineering Et�aluation Packer Praperty Retaining Va'alls and Steep Slape E�faluation Evereit, ��Jashin�ton NGA File No. 870113 March 1l, 2013 Page I3 In tlle case of the heiical anchors, the contraetor should detern�ine the torque vaiues required to achieve the desired eapacity. However, the anch�rs should advance a niinimum af 20 feet from the face af the wall and one anchor be tested to canfrm design capacities. One anchor should be perfonnance tested to 200 percent of the anehor design capacity. The pez-farmance tesi should consist of cyclic loading in increments of 25 percent of the design load, as outlined in tt�e Federal Highways Administration {FHA} report ?�,To. FHV,'A/RD-821047. Tl�e test location shauld be detennined in the field; based on soil conditions observed during anchor ztistallation. All ather taebacks should be proof-tested to at least 130 percent ef design capacity. Vi��II �3ackfill and Slope �mproveardents ��e reconlmend that after the pin piles and tiebacks a:e instalied, a 4-inch perforated PVC pipe be placed behind the base af the retaining ��a11 that is allowe�l ta #7ow throngh the face of tl�e retaining wall to aid in drainage through the wall. The pipe should be surrounded by a minimum af one foot of drain rock and the drain rock entirely wrapped in a heavy-duty filter fabrie prior to the placernent of tlie rock spall back:fill. The drain should be tightlined into the existing drain system or independently do��n to the base of the slope and adequately anchored t� the slope. After the drain is instafled, the loose soils fro�n behind the entire extent of the �rall should be removed and repiaced with 2- to 4-inch rock spalls. Extreme care should be used as to not disturb the tiebacks or draina�e during rock spall placement. The removed soils could be plaeed near the bottom af the slope as directed by NGA. Areas af exposed soils and substantial unstabie debris, including, if possible, the extent of the slope onto The neighbol-in� property; should be cleared of the unstable material, covered v��iih erosion contral matting, and then planted with deep-rooted plants. For tke steep area directly belaw the new wall (20 feet or so) and, if possible, t1�e partion of the slide and exposed areas an the neighbo�•'s property, we recommend that �he expased sflil be covered with heavy duty erosion cantrol matting such as Tez�sar C350 Turf Reinforcement Mat, or equivalent. The erosion control znatting should be staked to the surFace at a minimum of five feet on center using �- to 3-foot long metal stakes with a"T" welded to the end. After the matting is placed, we recotnmended that deep-rooted vegetation be planted an tiie slope and grass seed be placed ta re-establish vegetation growth. The vegetation should be maintained until established. VJe recommend a mixture of 25% each of the follo«�ing vegetation: Snowberry lVELSOM GEQTECf,'nllCAL .4SSOCIATES, 1flrC.