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16-217 10000 Edmonds Way GT Rpt Add x.pdfPanGEOC O R P O R A T E D Geotechnical & Earthquake Engineering Consultants November 29, 2017 File No. 16-217 Mr. Anthony Jansen Westgate Village, LLC 4025 Delridge Way SW 4530 Seattle WA 98104 Re: Geotechnical Report Addendum Foundation Bearing Pressures and Shoring Westgate Village Edmonds, WA Dear Mr. Jansen, This letter provides an addendum to PanGEO's September 17, 2016, geotechnical report (PanGEO, 2016) for the Westgate Village development in Edmonds (see Figure 1) to confirm footing bearing pressures within the lower parking level of the building and to provide lateral earth pressures for the design of shoring elements near the southeast corner of the lower parking level. The following briefly discusses our findings and conclusions. SUBSURFACE CONDITIONS Our 2016 report was based on three borings (B-1 thru B-3) which were drilled at the locations shown on Figure 2. At the time of the report, all parking was located outside of the building (i.e. no below grade parking) and all borings were drilled to relatively shallow depths (i.e. 10 to 16 feet) to be commensurate with the expected shallow foundations of the building. However, with the building development being subsequently revised to include one level of below grade parking, we recommended drilling 3 additional borings that extended the below grade parking. The locations of the new borings (PG-1-17 thru PG-3-17) are shown in Figure 2 and the logs of all boring are presented in Appendix A. The logs of the recent borings indicate that the foundations for the underground parking will be bearing upon dense to very dense, advance glacial outwash deposits consisting of fine to coarse sand. None of the site explorations encountered groundwater. The deepest borings extended to a depth of about 26 feet below the ground surface. 3213Eastlake Avenue East Suite B Seattle, WA 98102-7127 Tel (206) 262-0370 Fax (206) 262-0374 Geotechnical Report Addendum Westgate Village November 28, 2017 REVISED BEARING PRESSURE Our geotechnical report dated September 16, 2015 recommended an allowable bearing pressure of 3 ksf for foundation design. However, with the below grade parking extending about 10 feet below the existing ground surface, the deeper footings within the garage will be founded on dense to very dense glacial outwash deposits and these footings may be designed for an allowable bearing pressure of 6 ksf. SHORING The below grade parking will intercept and be located close to an existing cantilever soldier pile wall at the southeast corner of the below grade parking. Because construction will remove soil in front of the wall, segments of the wall will need to be analyzed by the project structural engineer (Quantum Consulting Engineers) to confirm that the existing wall will not be overstressed during the excavation for the underground parking level of the Westgate Village development. Consequently, we recommend that segments of the north and west existing soldier piles be analyzed for the following conditions: West Wall - Piles 44 & 45 Active: 45 pcf Passive: 0 pcf above El 306 (assumes soil removed for construction of garage) 600 pcf below El 306 (applies to 2 piles diameters) North Wall - Piles 1, 2 & 3 Active: 30 pcf Passive: 0 pcf above El 306 (assumes soil removed for construction of garage) 600 pcf below El 306 (applies to 2 pile diameters) The loads provided above are reflective of short term construction conditions that assume no surcharge loading behind the walls. Furthermore, passive resistance is excluded above the base of the new footings in case additional excavation is needed to facilitate construction of the garage walls. If the analyses of the existing walls indicate potential instability or overstress, we suggest designing remedial measures consisting of tiebacks to provide lateral restraint to the existing soldier piles. The remedial restraint could include conventional drill and grout in place tiebacks or helical anchors. Drilled and grouted tiebacks could readily provide tension capacities on the order of 100 kips and drilled helical anchors could provide lateral restrain on the order of 50 kips with a factor of safety of 2. All tieback restraint would require at least 1 load test to verify the tieback or anchor capacity. Additionally, a portion of the excavation located west of the north soldier pile wall will require excavation shoring. We believe that a cantilever soldier pile wall in this area would provide 16-217 10000 Edmonds Way GT Rpt Add.doc Page 2 PanGEO, Inc. Geotechnical Report Addendum Westgate Village November 28, 2017 adequate support to the adjacent hillside. The soldier piles in this area should be designed for the following: Active: 38 pcf Passive: 600 pcf @ 2 pile diameters below El. 306 We appreciate the opportunity to be of service. If you have questions or need additional information, please contact our office. Sincerely, W. Paul Grant, P.E. Principal Geotechnical Engineer Enclosures: Figure 1 — Vicinity Map Figure 2 — Site and Exploration Plan Appendix A — Boring Logs 16-217 10000 Edmonds Way GT Rpt Add.doc Page 3 PanGEO, Inc. Geotechnical Report Addendum Westgate Village November 28, 2017 REFERENCES PanGEO, 2016, Geotechnical Report, Westgate Village, 10000 Edmonds Way, Edmonds, Washington: Report to Westgate Village, September 17. 16-217 10000 Edmonds Way GT Rpt Add.doc Page 4 PanGEO, Inc. 16-217 Figure 1-L.grf 9/17/16 (09:56) SHE rIT7 r w Base Map Snohomish County SnoScape Map I z a 9 .._r' 220TH-ST SW J a. _ LLl � �O R �o Project Site s, 0 228TH ST SW 138TH STSkV SR 104 moo' 0� = r W 1 y U& 17V t MOe 179 --2261MaLSW w t� JJ r a 228TH ST SW (:itv of \Icnlntlakc r m m m w i 1236THSTSW > MI. 178 DRAWN BY: bHL CHECKED BY: WFU DATE: UU.14.10 z:\rroject\zu1b rrojecis\ib—zi/ luuuu LCIrnoncis way, Ldmoncis\Lamoncis Westgate Survey wim door rian.ciwg XX -2 B-2 G-1-1 30 0 30 60 ajb 1.0 V 4r N�W scale in feet E-1 E 42 Scale: 1" = 60' G-1 ...564ding 4, 0 LOT C 4LA20030307 PARCE V Notes: 1. Base map provided by Henbart, LLC, September, 2016. Elevations are based on the NAVD88 datum. 2. Boring logs for PanGEO borings B-1 to B-3 and PG-1 -17 to PG-3-17 are located in Appendix A. Locations for these borings are approximate and based on the relative locations of known site features. Legend: Proposed Development B-1/PG-1-17 PanGEO Borings PnC� 10000 Edmonds Way I N C 0 R P 0 R A T E 0 Edmonds, Washington SITE AND EXPLORATION PLAN FIGURE NO. 16-217 2 APPENDIX A BORING LOGS RELATIVE DENSITY / CONSISTENCY SAND /GRAVEL SILT / CLAY SPT Approx. Relative SPT Approx. Undrained Shear DensityN-values : Density (%) Consistency N-values Strength (psf) Very Loose <4 <15 Very Soft <2 <250 Loose 4 to 10 15 - 35 : Soft 2 to 4 250 - 500 Med. Dense 10 to 30 35 - 65 Med. Stiff 4 to 8 500 -1000 Dense 30 to 50 65 - 85 : Stiff 8 to 15 1000 - 2000 Very Dense >50 85 -100 Very Stiff 15 to 30 2000 - 4000 : Hard >30 >4000 UNIFIED SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP DESCRIPTIONS •�' GW: Well -graded GRAVEL Gravel GRAVEL (<5%fines) .....:...................................................... 50% or more of the coarse GP Poorly -graded GRAVEL fraction retained on the #4 sieve. Use dual symbols leg. o p GM Silty GRAVEL GP -GM) for 5% to 12%fines. GRAVEL (>12% fines) ..................................................................... ................ • • • ................ GC : Clayey GRAVEL .............................................................. "' SW: Well -graded SAND Sand ; SAND <5 /o fines "" .;..'> 50% or more of the coarse SP : Poorly -graded raded SAND ............................. fraction passing the #4 sieve. Use dual symbols leg. SP-SM g ) . > ....:...................................................... SM : Silty SAND for 5%to12%fines. SAND (>1 2% fines) ...................................................................... ......................................................... SC : Clayey SAND ............................................................. : ML : SILT Liquid Limit < 50 .....:...................................................... CL : Lean CLAY ............................................................ == — Silt and Clay OL : Organic SILT or CLAY 50%or more passing #200 sieve :.................................. :...................................................... MH : Elastic SILT Liquid Limit > 50 CH , Fat CLAY .......................... ....................................... OH Organic SILT or CLAY ....... u HighlyOrganic Soils PT : PEAT Notes: 1. Soil exploration to s contain material descriptions based on visual observation and field tests using a system modified from the Uniform Soil Classification System (USCS). Where necessary laboratory tests have been conducted (as noted in the "Other Tests" column), unit descriptions may include a classification. Please refer to the discussions in the report text for a more complete description of the subsurface conditions. 2. The graphic symbols given above are not inclusive of all symbols that may appear on the borehole logs. Other symbols may be used where field observations indicated mixed soil constituents or dual constituent materials. DESCRIPTIONS OF SOIL STRUCTURES Layered: Units of material distinguished by color and/or Fissured: Breaks along defined planes composition from material units above and below Slickensided: Fracture planes that are polished or glossy Laminated: Layers of soil typically 0.05 to 1 mm thick, max. 1 cm Blocky: Angular soil lumps that resist breakdown Lens: Layer of soil that pinches out laterally Disrupted: Soil that is broken and mixed Interlayered: Alternating layers of differing soil material Scattered: Less than one per foot Pocket: Erratic, discontinuous deposit of limited extent Numerous: More than one per foot Homogeneous: Soil with uniform color and composition throughout BCN: Angle between bedding plane and a plane normal to core axis COMPONENT DEFINITIONS COMPONENT SIZE / SIEVE RANGE COMPONENT SIZE / SIEVE RANGE Boulder: : > 12 inches Sand Cobbles: 3 to 12 inches Coarse Sand: #4 to #10 sieve (4.5 to 2.0 mm) Gravel Medium Sand: #10 to #40 sieve (2.0 to 0.42 mm) Coarse Gravel: 3 to 3/4 inches Fine Sand: #40 to #200 sieve (0.42 to 0.074 mm) Fine Gravel: 3/4 inches to #4 sieve Silt 0.074 to 0.002 mm Clay <0.002 mm TEST SYMBOLS for In Situ and Laboratory Tests listed in "Other Tests" column. ATT Atterberg Limit Test Comp Compaction Tests Con Consolidation DID Dry Density DS Direct Shear %F Fines Content GS Grain Size Perm Permeability PP Pocket Penetrometer R R-value SG Specific Gravity TV Torvane TXC Triaxial Compression UCC Unconfined Compression Sample/In Situ test types and intervals 2-inch OD Split Spoon, SPT (140-lb. hammer, 30" drop) H3.25-inch OD Spilt Spoon (300-lb hammer, 30" drop) Non-standard penetration test (see boring log for details) Thin wall (Shelby) tube Grab Rock core ® Vane Shear MONITORING WELL SZ Groundwater Level at time of drilling (ATD) 1 Static Groundwater Level Cement / Concrete Seal Bentonite grout / seal Silica sand backfill Slotted tip Slough Bottom of Boring MOISTURE CONTENT Dry Dusty, dry to the touch Moist Damp but no visible water Wet Visible free water PanGEO Terms and Symbols for 1 N C 0 R P 0 R A T E D Boring and Test Pit Logs Figure A-1 Phone: 206.262.0370 Project: Westgate Village Surface Elevation: 318.0ft Job Number: 16-217 Top of Casing Elev.: Location: 10000 Edmonds Way, Edmonds, WA Drilling Method: HSA Coordinates: Northing: , Easting: Sampling Method: SPT C 0 O Z Q E U) Q E C ; m �_ O p E >' MATERIAL DESCRIPTION N-Value A PL Moisture LL ®ROD Recovery El 0 50 100 0 • ' Medium dense to dense, brown, fine to coarse GRAVEL with silt and sand: dry, massive. (Fill). ......... ......... 2 Medium dense, brown gray, fine SAND with silt: moist, occasional gravel, homogeneous, non -plastic fines, indistinctly laminated. (Adv. Outwash). S-1 X15 9 4 8 Medium dense, interbedded, brown, fine to coarse SAND, fine SAND 20 and SILT: moist with wet layers, non -plastic fines with rapid dilatancy, laminated, trace gravel. (Adv. Outwash). 6 S-2 12 14 Medium dense, brown gray, fine SAND with silt: moist, occasional silt 8 S-3 X 14 18 interbed, non -plastic, some gravel, massive. Blow counts high due to gravel. (Adv. Outwash). 50/3 10 9 Dense to medium dense, brown gray, fine to medium SAND: moist, some non -plastic silt to with silt, occasional gravel, homogeneous, laminated. (Adv. Outwash). S-4 X 21 29 12 14 6 Becoming loose, occasional fine to carse SAND beds, some silt, 16 S 5 6 7 massive. Bottom of Boring. 18 Completion Depth: 16.5ft Remarks: No continuoous groundwater encountered during drilling. Thin wet soil lenses Date Borehole Started: 8/31/16 encountered. Date Borehole Completed: 8/31/16 Logged By: S. Evans Drilling Company: BoreTec, Inc PmGEO LOG OF TEST BORING B-1 I N C O R P G R A T E D Figure A-2 The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of Project: Westgate Village Surface Elevation: 316.0ft Job Number: 16-217 Top of Casing Elev.: Location: 10000 Edmonds Way, Edmonds, WA Drilling Method: HSA Coordinates: Northing: , Easting: Sampling Method: SPT N-Value A o Z ° m p PL Moisture LL Q (n L MATERIAL DESCRIPTION Q ®ROD Recovery El 67 U) 00 O 0 50 100 0 0 ' `t Sod and silty topsoil. Loose, yellow brown, very silty, fine SAND to sandy SILT: dry, slightly i. plastic fines, scattered gravel, homogeneous, massive. (Rec. Outwash). 2 4 S-1 1 4 4 Dense, brown and gray, interbedded, fine to coarse SAND with silt and 17 gravel, and SILT with gravel: moist, silt beds till -like, non -plastic fines, moderate weathering, fine bedded. (Adv. Outwash). S-2 15 'M 6 20 S-3 X 50/6 No recovery due to pushing cobble. Blow counts high due to cobble. 8 Dene, brown gray, gravelly SILT with fine sand: moist with wet layers, slightly plastic fines, till -like and massive. California sampler used to 10 enhance recovery. Blow counts high due to gravel. (Adv. Outwash). S-4 X 50/6 12 Dense to very dense, brown gray, fine to medium SAND with silt: moist with wet layers, slightly plastic fines, homogeneous, massive. (Adv. Outwash). 14 38 California sampler used to enhance recovery. Blow counts high due S-5 50/6 to gravel. Very moist. >? 16 Bottom of Boring. 18 Completion Depth: 16.8ft Remarks: No continuous groundwater encountered during drilling. Thin wet soil lenses Date Borehole Started: 8/31/16 encountered. Date Borehole Completed: 8/31/16 Logged By: S. Evans Drilling Company: BoreTec, Inc PanGE&LOG OF TEST BORING B-2 I N C O R P O R A T E D Figure A-3 The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of Project: Westgate Village Surface Elevation: 316.0ft Job Number: 16-217 Top of Casing Elev.: Location: 10000 Edmonds Way, Edmonds, WA Drilling Method: HSA Coordinates: Northing: , Easting: Sampling Method: SPT N-Value A O Z p PL Moisture LL C Q Q ; E MATERIAL DESCRIPTION 0 E E C �_ >' El ROD Recovery El U) m O 0 50 100 0 Sod and topsoil. Loose, yellow brown, silty, fine SAND: dry, some medium to coarse sand, gravel, non -plastic, massive. (Rec. Outwash). 2 5 S-1X 6 4 5 Dense, multi -colored brown and gray, fine to coarse SAND with fine gravel: moist, trace to some silt, non -plastic, fine bedded. (Adv. Outwash). 14 S-2 X 18 6 24 Bottom of Boring. 8 10 ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... 12 ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... 14 16 ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... 18 ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... ......... Completion Depth: 6.5ft Remarks: No groundwater encountered during drilling. Boring drilled to confirm soil Date Borehole Started: 8/31/16 conditions in B-2, which were unclear due to poor sample recovery and likely cobble at Date Borehole Completed: 8/31/16 auger tip. Logged By: S. Evans Drilling Company: BoreTec, Inc PmGEO LOG OF TEST BORING B-2A I N C O R P G R A T E D Figure A-4 The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of Project: Westgate Village Job Number: 16-217 Location: 10000 Edmonds Way, Edmonds, WA Coordinates: Northing: , Easting: O Z (D a C cfl Q E 0 iZ E E E (I% 3 L cn U) C o m .� O n F 2 F 4 11 6 S-1 �X� 38 43 F 8 F 101 S-2 W 50/2 12 14 16 18 Surface Elevation: Top of Casing Elev.: Drilling Method: Sampling Method: MATERIAL DESCRIPTION 342.0ft HSA SPT Dense to very dense, brown gray, silty, fine SAND with gravel: moist, non -plastic fines, gravel sub -rounded and blocky, homogeneous, massive. (Till). Gravelly intervals at 6 feet, 7.5 feet and 9 feet. N-Value A PL Moisture LL The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of Project: Proposed Development Surface Elevation: 316.Oft Job Number: 16-217 Top of Casing Elev.: Location: 10000 Edmonds Way, Edmonds, WA Drilling Method: HSA Coordinates: Northing: , Easting: Sampling Method: SPT N-Value A O Z a > p PL Moisture LL C Q H Q (n E MATERIAL DESCRIPTION 0 E F U a) >1 ®ROD Recovery EJ U) m O 0 50 100 0 Asphalt, 4 inches. Dense, brown gray, gravelly, fine to medium SAND: moist, trace to some non -plastic silt, sub -rounded and blocky gravel, homogeneous, laminated with faint rusty laminae, slightly weathered. Occasional C)' sand interbeds. (Advanced Outwash). n .. 5 S 1 50/5 Blow count high due to coarse gravel or small cobble. '. 24 S-2 22 16:'.' e _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Dense, brown gray, fine to coarse SAND: moist, trace to some 10 non -plastic silt, homogeneous, laminated, occasional brown laminae. S-3 14 (Advanced Outwash). 22 13 S-4 X 19 22 15 S-5 111 15 -- — — — — — — — — — — — — — — — — — Dense, brown gray, fine to medium SAND: very moist, some 20 non -plastic silt to with silt, homogeneous, some gravel, laminated with 'IMF occasional rusty laminae. (Advanced Outwash)... ......... e Dense, brown gray, fine to coarse SAND: very moist, some non -plastic silt to with silt, homogeneous, laminated. (Advanced Outwash). 20 16 S-6 23 20 Dense, brown gray, gravelly, fine to medium SAND: very moist, some o.° .°. non -plastic silt, homogeneous, laminated with occasional coarse sand quartz grains. (Advanced Outwash). 25 12 `� S-7 22 33 Bottom of Boring. 30 Completion Depth: 26.5ft Remarks: No groundwater encountered during drilling. Date Borehole Started: 10/12/17 Date Borehole Completed: 10/12/17 Logged By: S. Evans Drilling Company: BoreTec, Inc PanGEe LOG OF TEST BORING PG-1-17 I N C O R P O R A T E D Figure A-6 The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of Project: Proposed Development Surface Elevation: 316.0ft Job Number: 16-217 Top of Casing Elev.: Location: 10000 Edmonds Way, Edmonds, WA Drilling Method: HSA Coordinates: Northing: , Easting: Sampling Method: SPT N-Value A o Z p PL Moisture ILL ) ~ E MATERIAL DESCRIPTION 0 E a� >1 ® ROD Recovery U m O 0 50 100 0 >- Concrete, 6 inches. Dense, brown gray, fine to coarse SAND with gravel and silt: moist, t , sub -rounded and blocky gravel, laminated, slightly weathered. Occasional sand interbeds. (Advanced Outwash). 5 16 S 1 30 29 ° ° ° tPe° 7 Z °° Very dense, silty, fine to medium SAND bed, non -plastic to slightly S-2 15 27 °° plastic fines, gravel beds and fine to coarse sand beds, 1 inch silty ° X°° clay interbed, laminated and fine bedded. 10> -- — — — — — -- ------ — — — — — Dense, brown gray, gravelly, fine to coarse SAND: moist, some S 3X31 28 48 non -plastic silt, gravel sub -rounded and blocky, laminated. (Advanced Outwash). 27 °°° — — — — — — — — — — — — — — — — — — — — — — — — — — — — — Very dense, brown gray, fine to medium SAND: moist to very moist, S-4 32 34 some non -plastic silt to with silt, homogeneous, laminated, occasional brown laminae. (Advanced Outwash). 15 16 Occasional fine gravel. S-5 25 30 20 17 Finer / coarser beds, occasional gravel. S-6 X 23 17 25 21 Fine to medium SAND with fine to coarse SAND interbeds. S-7 33 33 Bottom of Boring. 30 Completion Depth: 26.5ft Remarks: No groundwater encountered during drilling. Date Borehole Started: 10/12/17 Date Borehole Completed: 10/12/17 Logged By: S. Evans Drilling Company: BoreTec, Inc PmGE(D LOG OF TEST BORING PG-2-17 0 C 0 H P 0 R A T E D FigureA-7 The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 of 1 Project: Proposed Development Surface Elevation: 316.Oft Job Number: 16-217 Top of Casing Elev.: Location: 10000 Edmonds Way, Edmonds, WA Drilling Method: HSA Coordinates: Northing: , Easting: Sampling Method: SPT N-Value A O Z a > p PL Moisture LL C Q H Q (n E MATERIAL DESCRIPTION 0 E F U) a) >1 ROD Recovery ®EJ U) m O 0 50 100 0 ° e Asphalt, 2 inches. Dense to very dense, brown to brown gray, gravelly, fine to coarse ee� SAND: moist, some non -plastic silt, fine bedded and laminated, o e°e moderately weathered with shattered granitic gravel. (Advanced e�e Outwash). 0 e� 5 S-1 33 33 e°°°° e°°° Gravelly, fine to coarse SAND, some silt. 34 p� 'S°et,9 14 Interbedded, fine to medium SAND with silt, fine to coarse SAND with S 2 14 gravel, and silty, till -like beds with gravel. Drilling quiet at 8_5 feet._ Dense, brown gray and brown banded, fine to coarse SAND: moist, 10 10 some non -plastic silt to with silt, homogeneous, finer / coarser beds, S-3 16 laminated and fine bedded. (Advanced Outwash). 19 0/1 Dense, brown gray, fine to medium SAND: moist, some non -plastic silt S-4 119 1 to with silt, homogeneous, laminated. (Advanced Outwash). 23 15 12 Very moist, fine to medium SAND, laminated. S-5 19 16 20 11 Grading very dense. S 6 24 33 25 13 Dense, fine to medium SAND, laminated. S-7 25 23 Bottom of Boring. 30 L ......... ......... Completion Depth: 26.5ft Remarks: No groundwater encountered during drilling. Date Borehole Started: 10/12/17 Date Borehole Completed: 10/12/17 Logged By: S. Evans Drilling Company: BoreTec, Inc PanGEe LOG OF TEST BORING PG-3-17 I N C O R P O R A T E D Figure A-8 The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of