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Response letter to Structuarl Review #2.pdfJuly 1, 201.4 Leif Bjodback Building Official, City ofEdmonds 1215th Avenue North Edmonds, WA 98026 Subject: Swedish Hospital Addition (Structural Review) -Wesponses Permit: 2014-0238 Refer to attached review letter, prepared by GeoEngineers, the Owner's geotechnical Should additional questions arise, please don't hesitate to contact me. Rachel Jenner, Project Manager Cc: Bryan Hall rylerxvwen Chuck Kolb Jnhnmeo:edvht xmyp,e,ker Andri,u^vins oanschnebe|e 223YALE AVENUE wvn,oSEATTLE vw,om^ r` 206 223 5555 nmooc1u000 WENGINEERS 8410 154th Avenue NE Redmond, Washington 98052 425.861.6000 July 1, 2014 Providence Health & Services 500 17th Avenue - Annex Building Seattle, Washington 98122 Attention: Bryan Hall Subject: Geotechnical Engineer of Record and Plan Review Swedish Edmonds Ambulatory Care Center Edmonds, Washington File No. 0822-008-00 [CIU MOR Irgi �- ZU0PI-:0110112 TZ�7T�7 This letter confirms our involvement with the Swedish Edmonds Ambulatory Care Center (ACC) project in Edmonds, Washington. Providence Health & Services has requested that GeoEngineers, Inc. (GeoEngineers) act as the Geotechnical Engineer of Record for this project. We have reviewed the Landau Associates report "Proposed Ambulatory Care Project, Swedish/Edmonds Hospital Complex, Edmonds, Washington" dated March 3, 2014. We have also reviewed the project plans and specifications dated July 10, 2014. We are in general agreement with the conclusions and recommendations provided in the Landau Associates report, except we are providing additional comments and recommendations for the project as follows: 1. On-site soils (except lacustrine deposits) may be used as structural fill during the dry season (June through September) to raise site grades and to backfill utility trenches across the site; except that on-site soils should not be used as structural fill below planned foundations. Lacustrine deposits should only be reused on site in landscape and other non-structural areas; otherwise they should be exported from the site. Imported gravel borrow should be used as structural fill during wet weather (typically October through May). 2. Prior to placing the non -woven geotextile over the subgrade for the Stormtech infiltration facility, the exposed subgrade should be evaluated by the geotechnical engineer. Existing fill and silty soils not meetingthe infiltration criteria must be removed from the subgrade. The contractor should limit routing Providence Health & Services July 1, 2014 Page 2 of equipment on the exposed subgrade in the infiltration facility prior to placing the geotextile and 12 -inch -thick layer of Gravel Backfill for Chambers. 3. The exposed subgrade in foundation excavations in existing fill should be recompacted to at least 95 percent of the maximum dry density per ASTM D 1557 prior to placing and compacting the crushed rock supporting foundations designed for a maximum allowable bearing pressure of 4,000 pounds per square foot (psf). I 4. Medium stiff to stiff lacustrine deposits consisting of silt and clayey silt were encountered in boring B-6-13 near grid B/5 down to about Elevation 353 feet. The bottom of the BF12.0 braced frame footings in this area along gridline XA and likely gridline A will be excavated into the lacustrine soils. We recommend that all remaining lacustrine deposits be removed from beneath the braced frame foundations down to native dense advance outwash. We estimate approximately 3 feet of lacustrine deposits exist below the planned braced frame footings in this area. The overexcavated areas should be backfilled with structural fill (crushed rock or gravel borrow) if designed using a maximum allowable bearing pressure of 4,000 psf, or can be backfilled with controlled density fill (CDF) or lean concrete if redesigned using a maximum allowable bearing pressure of 8,000 psf. 5. The building addition floor slabs may be designed to be supported on a 4 -inch -thick capillary break layer (with vapor retarder) placed over a prepared subgrade. In addition, after site demolition and clearing is completed in the building footprint, and prior to placing any new fill below the building footprint, the exposed subgrade areas should be proof -rolled and recompacted to at least 95 percent using a heavy vibratory roller compactor. Any soft or otherwise unsuitable soils observed during proof -rolling should be removed and replaced with structural fill. We are currently retained to provide the required geotechnical inspections during construction. We will provide additional recommendations if necessary during construction based on our observations. Z We understand the City of Edmonds provided the following review comment: 4) This Item remains to be addressed. WNW ffiggs. b. ms— in !NIN IN NOWN"• + _ • • design ! specifications. Provide - of x reviewthe and any corrections recommendations, If re! w..•.. ! .e or corrections identified, they are required to be incorporated into the revised, resubmitted drawings for review. GeoEngineers reviewed the project plans and specifications dated June 10, 2014. These documents were reviewed for conformance with the recommendations presented in the geotechnical report prepared by Landau Associates dated March 3, 2014. Based on our review of the plans, it is our opinion that the geotechnical aspects of these documents are consistent with the recommendations presented in the project geotechnical report. GE®ENGINEERS File No. 0822008-00 Providence Health & Services I July 1, 2014 Page 3 We trust this letter meets your current needs. Please contact us if you have and questions or comments. Sincerely,Y D. GeoEngineers, Inc. ��� dYr1S�l Timothy D. Bailey, PE v .� l/< 44203 Senior Geotechnical Engineer13°t�,+ Robert C. Metcalfe, PE, LEG Associate TDB:RCM:nid Disclaimer: Any electronic form, facsimile or hard copy of the original document (email, text, table, and/orfigure), If provided, and any attachments are only a copy of the original document. The original document is stored by GeoEngineers, Inc. and will serve as the official document of record. Copyright© 2014 by GeoEngineers, Inc. All rights reserved. E® NGINEERS File No. 0822-008-00