1209 MADRONA AVE 2016-11-17 - Laserfiche WebLink

r Updated Geotechnieal Ptan Review NGA File No. 8710B l3 Retaining Wall June 30, 2014 Everett, Washington Page 2 For aur use, ��e have reviewed the project plans titled "Packer Residence — 1209 Madr•ona Avenue — Everett, WA," prepared by CG Engineering, Inc., dated June 20, 2014. PLAN REVIEW We have reviev��ed geotEchi�ical aspects of the provided plans and found the plans to be in general accordance with our geotechnical report. The updated plans show that a concrete retaining wall supported on 2-inch diameter pin pifes and tieback anchors is planneci to be constructed in the ravine in the area of tl�e landslide. �['he wall will be roughly 21 feet long and wi(I eatend across the ravine starting at the southerii end of the lowest existing retaiiii�l� wall. "The exposed wall I�eight will be roughly two to eight feet. Eleveu, 2-inch diameter piil piles will be installed two feet on-center at the base of the retainin� wall, along with being restrained by four grouted tieback anchors extending back into the slope. Based on our discussions with the structaral engineer, we ui�derstand that all lateral loads for the retaining wall are being transferred to the grouted tieback ancl�ors and passive resistance is not beinb utilized on the pin piles. [n our originai report, we provided desi�n and construction recommendations for the 3-inch square tubing piles. We know understand that the concrete retaining wall will be supported on 2-inch diameter pin piles. We understand that the 2-iiich diameter pin piles ai•e to be drivel� to the same criteria as provided for the 3-inch square tubing. The pin piles will be embedded a minimum of 1 � feet below finished ground surface. For 2-inch diameter pipe piles driven to refusal as discussed in our report, we recommend a desi�� axial cotnpression ca�acity of two tons for each pile. Wc �inderstand that this value was utilia..ed in the upclated retaining wa.li design. The plans show that the wall will be back�lled with 2- to 4-inch rock spalls constructed at a n�a:cimum inclination of 1.� Horizoi�tal to 1.0 Vertical (1.5H:1 V). A 4-inch diameter PVG drain will be installed at the bottom of tlle rock s�alls directly beliiuci the retaining 1Wa11. These design features are all in line with our ori�inal geotechnical report. The anchors are shown to have a minimum 12-foot bonded length. This is consistent with our original repoi�t and should be more than sufficient to resist the design loads shown for the anchors. We have also reviewed the soil parameters that were used in the design and found those to be consistent with the recommendations provided in our original report. NELSON GEOTECHNICAL ASSOCIATES, INC. ( C� I