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REVIEWED RESUB BLD2021-0088+Geotechnical_Addendum_Letter_2+5.21.2021_8.15.38_PM+2211575Irerracon December 6, 2019 CA Senior Living Holdings, LLC 130 E. Randolph St., Ste 2100 Chicago, IL 60601 Attn: Mr. Michael Duggan — Vice President of Development P: (312) 248-2091 E: mduggan@ca-ventures.com Re: Geotechnical Engineering Report — Addendum Letter No. 2 Edmonds Senior Living 21200 72nd Ave. W Edmonds, Washington Terracon Project No. 81185173 Dear Mr. Duggan: This letter serves as an addendum to the Geotechnical Engineering report dated December 20, 2018 and was developed in general accordance with the Supplement to Agreement for Services (Change Order No. 2) dated November 15, 2019 and your email authorization dated November 21, 2019. Presented in this letter are the following: a summary of the subsurface conditions observed from advancement of additional soil borings near the southwest and northwest portions of the site supplemental geotechnical engineering recommendations as it relates to the subsurface conditions observed. Updated surface elevations for boring logs B-1 through B-4 based on interpolation of the topographic site plan which became available after the geotechnical engineering report was published The conclusions and recommendations presented herein are based on the shoring and foundation plan sets dated August 29, 2019 and October 3, 2019, respectively. SUBSURFACE CONDITIONS A total of four (4) soil borings were performed to provide additional subsurface information for aid in final design of the shoring and foundation plans. The soil borings were advanced via hollow - stem auger using a track -mounted drill rig and smaller, hand -portable drilling equipment. During soil boring advancement, soils samples were obtained in regular 2 1/2 to 5-foot intervals via standard penetration testing (SPT) until dense to very dense native soils were contacted. The subsurface conditions observed were generally consistent with those presented in the geotechnical engineering report though the fill unit (Stratum 1) was thinner and less apparent where explored. The dense to very dense native soils (i.e. Stratum 3), capable of an allowable Terracon Consultants, Inc. 21905 64th Ave. W, Suite 100 Mountlake Terrace, WA 98043 P (425) 771 3304 F (425) 771 3549 www.terracon.com Geotechnical Engineering Report — Addendum Letter No. 2 Irerracon Edmonds Senior Living Edmonds, Washington December 6, 2019 Terracon Project No. 81185173 bearing pressure of a least 5,000 psf, were observed between 5'/z and 11 feet near the southwest region and 3 to 5 feet near the northwest region below existing ground surface. Approximate elevations of the stratum contacts are presented on the boring logs. The location of the contact will vary between explorations and will not be known until earthwork construction. A site plan presenting the locations of the soil borings and the boring logs are presented as an attachment at the end of this letter. FOUNDATION DESIGN AND CONSTRUCTION CONSIDERATIONS Based on our understanding of the foundation plan, the dense native soils are likely to be present at or near the planned footing elevations for the majority of the perimeter footings along the shoring walls. Based on a projection of the contact elevations of dense native soils from the boring locations to the shoring walls for the above stated plan sets, it appears some overexcavation will be necessary: East Wall: Approx. 4 to 5 feet between E5 and E12 South Wall: Approx. 1 to 2 feet between S3 and S23 These depths should be used for planning purposes only. The actual depth of excavation will depend on conditions exposed in the field at the time of construction. We anticipate that overexcavation along the West and North shoring walls will not be necessary for perimeter footings to bear on dense native soils. Footings located at the interior of the building will need to be overexcavated to dense native soils, if necessary. We assume the contractor will perform the overexcavation using shallow, sloped excavation cuts of limited length that will be backfilled immediately to reduce potential impacts to the shoring walls. We recommend that a geotechnical engineer observe the footing subgrades at the time of construction to help identify the dense, native soil unit targeted for footing subgrade. Recommendations for backfilling overexcavated footing subgrades are presented in the geotechnical engineering report. The backfilling recommendations presented in Addendum Letter No. 1 are not applicable for foundations designed for an allowable bearing of 5,000 psf. Backfilling must use lean mix concrete or controlled density fill (CDF) to maintain an allowable bearing capacity of at least 5,000 psf beneath the footings. The recommendations provided herein are to be used with the recommendations provided in the geotechnical engineering report. Recommendations for subgrade preparation can be found in the section of the geotechnical engineering report. Responsive ■ Resourceful ■ Reliable 2 Geotechnical Engineering Report — Addendum Letter No. 2 Irerracon Edmonds Senior Living Edmonds, Washington December 6, 2019 Terracon Project No. 81185173 We appreciate the opportunity to be of service to you on this project. If you have any questions concerning :r service, pleas- r-nf.-f 1 is Sincerely, Terracon Zachary L. P.Ut-71 III, F . Project Engineer Attachments: Site Exploration Plan Soil borings logs B-1 to B-8 Senior Engineering Consultant Responsive ■ Resourceful ■ Reliable 3 Geotechnical Engineering Report — Addendum Letter No. 2 Edmonds Senior Living Edmonds, WA December 6, 2019 Terracon Project No. 81185173 Irerracon •1�2. I t S I Boring (Nov- 2019) DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS AERIAL PHOTOGRAPHY PROVIDED NOT INTENDED FOR CONSTRUCTION PURPOSES BY MICROSOFT BING MAPS 0 z U) U) 0 z 0 0 w co U) LU m >J 0 z 0 0 a 0 w O BORING LOG NO. B-1 Paqe 1 of 1 PROJECT: Edmonds Senior Living CLIENT: CA Senior Living Holdings, LLC Chicago, IL SITE: 21200 72nd Ave. W Edmonds, WA o LOCATION See Exploration Plan U) Zp w d w O v Latitude: 47.8067' Longitude:-122.3303' w a~ — F- F o U.1 o w Z z LL _ rr> � w p� w a a �w z w 0 Approximate Surface Elev.: 379.5 (Ft.) +/- 0 ¢ m Q LU LL rn O ULU � DEPTH ELEVATION Ft. O a- 0.6 ASPHALT, approx. 1.5 inches of asphalt over 2 inches base coarse 379+/- SANDY SILT (ML), trace gravel, fine to coarse grained, olive brown to dark brown, moist to wet, soft, trace organics (FILL) 5 12 6-1-5 S-1 N=6 7.5 372+/- SILTY SAND (SM), reddish brown to brown, moist, medium dense, (RECESSIONAL OUTWASH) rust staining in top of S-2, possibly evidence of seasonal groundwater 18 8N=316 N=31 S-2 10.5 369+/ 1*113.0 SANDY SILT ML , olive gray to gray, moist, very stiff, GLACIAL TILL ( 1 9 Y 9 Y rY ( ) 366.5+/- SILTY SAND (SM), trace gravel, gray, moist, very dense 15 16-16-24 trace gravel, dense, interbedded silt 18 N=40 S-3 2 18 6" 0/ -30-5 11 -30-5 S-4 14 28 rock fragment in S-4, possibly over -stated blow -count 21.5 358+/ Boring Terminated at 21.5 Feet Stratification lines are approximate. In -situ, the transition may be gradual. Hammer Type: Automatic (ETR = 88 % ) Samples obtained using a 2" O.D. split spoon sampler Boring log updated from Dec. 2018 Advancement Method: See Exploration and Testing Procedures for a Notes: Hollow Stem Auger description of field and laboratory procedures used and additional data (If any). See Supporting Information for a>planation of symbols and abbreviations. Abandonment Method: Boring backflled with bentonite Surface capped with concrete Elevations were interpolated from a topographic site nl­ WATER LEVEL OBSERVATIONS Boring 1 rerraco, Started: 12-05-2018 Boring Completed: 12-05-2018 Groundwater not encountered Drill Rig: D-50track Driller: Holocene i 21905 64th Ave W, Ste 100 Mountlake Terrace, WA Project No.: 81185173 J of 0 z W zz 0 0 w M r U) J J w 3 0 z 0 O U) 0 w 0 BORING LOG NO. B-2 Paqe 1 of 1 PROJECT: Edmonds Senior Living CLIENT: CA Senior Living Holdings, LLC Chicago, IL SITE: 21200 72nd Ave. W Edmonds, WA o LOCATION See Exploration Plan J ro Zp Lu d w O U Latitude: 47.8067' Longitude:-122.331' w a~ — F- F o U.1 o w Z z LL _ ce> � w p� w a �w z w 0 Approximate Surface Elev.: 379 (Ft.) +/- 0 ¢ m Q LU LL rn O U � DEPTH ELEVATION Ft. OLu a 0.6 ASPHALT, approx. 1.5 inches of asphalt over 2 inches of base coarse 378.5+/- DRILL OUT 5 1 15 20.0 359+/- 2 POORLY GRADED SAND WITH SILT (SP-SM), light brown to brown, 4-13-25 moist, dense, (GLACIAL TILL) 12 N-38 S 4 22.5 356.5+/- SILTY SAND (SM), reddish brown to olive gray, moist, very dense, silty sand with interbedded silt 25 25-30-36 rust staining in S-5, possibly evidence of seasonal groudwater 18 N=66 S-5 ..26.5 352.5+/- Boring Terminated at 26.5 Feet Stratification lines are appro)amate. In -situ, the transition may be gradual. Hammer Type: Automatic (ETR = 88 % ) Samples obtained using a 2" O.D. split spoon sampler Boring log updated from Dec. 2018 Advancement Method: See Exploration and Testing Procedures for a Notes: Hollow Stem Auger description of field and laboratory procedures used Boring passed through an abandoned borehole of an unknown and additional data (If any). nature. Drill out upper 20 feet due to evidence of borehole backfill. See Supporting Information for a>planation of symbols and abbreviations. Abandonment Method: Boring backflled with Auger Cuttings and/or Bentonite Surface capped with concrete Elevations were interpolated from a topographic site nl­ WATER LEVEL OBSERVATIONS Boring 1 rerraco, Started: 12-05-2018 Boring Completed: 12-05-2018 Groundwater not encountered Drill Rig: D-50track Driller: Holocene i 21905 64th Ave W, Ste 100 Mountlake Terrace, WA Project No.: 81185173 J 0 z W U) U) 0 z 0 0 w co ro m J w 3 0 z 0 0 it U) 0 0 BORING LOG NO. B-3 Page 1 of 1 PROJECT: Edmonds Senior Living CLIENT: CA Senior Living Holdings, LLC Chicago, IL SITE: 21200 72nd Ave. W Edmonds, WA (3 LOCATION See -)loration Plan J W a ^ Latitude: 47.8066° Longitude:-122.3307° _ W Oz W w F p o w z z r a Jro a 2 w z � Appropmate Surface Elev.: 377 (Ft.) +/_ p m Q w LL w ro 00 w DEPTH ELEVATION(Ft.)O rn a y. TOPSOIL 7 +- SAND WITH SILT (SP-SM), trace gravel, brown to grayish brown, moist, medium dense, some woody debris and cobbles (FILL) 3.5 373.5+/- SAND WITH SILT fSP-SMI, light brown to brown, moist, medium dense, (RECESSIONAL GLACIAL OUTWASH) 5 6 5-6-13 S-1 N=19 increasing silt content, transitions to silty sand 10.0 367+/- 1 SILTY SAND (SM), light brown to brown, moist, dense, (GLACIAL TILL) 15-18-13 16 N=31 S 2 15 15 10-15-15 S-3 16 13 N=30 rust staining in S-4, possibly evidence of seasonal groundwater 2 18 10-11-21 N=32 S-4 • 20.5 356.5+/- 2 1. 0 SANDY SILT (MIL), reddish brown to olive brown, moist, hard 356+/- SAND (SE!), trace silt, brown to reddish brown, moist, dense '..' rust staining in S-5, possibly evidence of seasonal groundwater 2 18 37 33- 25- N33- S-5 • 2s.s 351.s+/- SILTY SAND (SM), gray to dark gray, moist, very dense 26.5 350.5+/- Boring Terminated at 26.5 Feet Stratification lines are appropmate. In -situ, the transition may be gradual. Hammer Type: Automatic (ETR = 88%) Samples obtained using a 2" O.D. split spoon sampler Boring log updated from Dec. 2018 Advancement Method: See E)ploration and Testing Procedures for a Notes: Hollow Stem Auger description of field and laboratory procedures used Boring located in landscaped area. and additional data (If any). See Supporting Information for eplanation of symbols and abbreviations. Abandonment Method: Boring backfilled with bentonite upon completion. Elevations were interpolated from a topographic site WATER LEVEL OBSERVATIONS Boring Irerracon Started: 12-05-2018 Boring Completed: 12-05-2018 Groundwater not encountered Drill Rig: D-50track Driller: Holocene 21905 64th Ave W, Ste 100 Mountlake Terrace, WA Project No.: 81185173 J 0 z U) U) 0 z 0 0 w J W 0 z c� O it U) 0 0 BORING LOG NO. B-4 Paqe 1 of 1 PROJECT: Edmonds Senior Living CLIENT: CA Senior Living Holdings, LLC Chicago, IL SITE: 21200 72nd Ave. W Edmonds, WA o LOCATION See :nloration Plan J ro w EL O v Latitude: 47.8064' Longitude:-122.3304' wLU 0 a~ F- F o U.1 o w Z z LL _ ce> � w p� w a �w O z w 0 Approximate Surface Elev.: 376 (Ft.) +/- 0 ¢ m Q LU LL rn U � LU DEPTH ELEVATION Ft. O o- ASPHALT, approx. 1.5 inches asphalt over 2 inches base coarse + SILTY SAND WITH GRAVEL (SM), dark brown with olive brown mottling, o moist, loose, woody debris (FILL) o 12 S-1 • 5.5 370.5+/- 5 14 2-2-2 N=4 S-2 SILTY SAND (SM), grayish brown to brown, moist, medium dense, sand with silt interbeds (RECESSIONAL GLACIAL OUTWASH) 1 15 7-7-7 S 3 19 15 N=14 13.0 363+/- SAND WITH SILT (SP-SM), light brown to brown, moist, dense to very dense, silt interbeds (GLACIAL TILL) 15 16-27-28 decreasing silt content 17 N=55 S-4 9 6 18.0 358+/- SANDY SILT (ML), light brown, moist, hard rust staining observed in top of S-4, possible evidence of seasonal •20.5 groundwater 355.5+/- 20-- X 18 -20-26 9N=46 N=46 S-5 SAND WITH SILT SP-SM , trace silt, brown, wet, dense ( � becomes dark gray, very dense 25 17 18-30--30-36 S-6 25 89 25.5 350.5+/- SILT (MLI, trace sand, gray, moist, hard 26.5 349.5+/- Boring Terminated at 26.5 Feet Stratification lines are appro)amate. In -situ, the transition may be gradual. Hammer Type: Automatic (ETR = 88 % ) Samples obtained using a 2" O.D. split spoon sampler Boring log updated from Dec. 2018 Advancement Method: See E)ploration and Testing Procedures for a Notes: Hollow Stem Auger description of field and laboratory procedures used and additional data (If any). See Supporting Information for a>planation of symbols and abbreviations. Abandonment Method: Boring backflled with bentonite Surface capped with concrete Elevations were interpolated from a topographic site nl­ WATER LEVEL OBSERVATIONS Boring 1 rerraco, i Started: 12-05-2018 Boring Completed: 12-05-2018 While sampling Drill Rig: D-50track Driller: Holocene 21905 64th Ave W, Ste 100 Mountlake Terrace, WA Project No.: 81185173 J tr O z w U) 0 z O 0 w co LU >J O z 6 O a U) O BORING LOG NO. B-5 Paqe 1 of 1 PROJECT: Edmonds Senior Living CLIENT: CA Senior Living Holdings, LLC Chicago, IL SITE: 21200 72nd Ave. W Edmonds, WA o LOCATION See :nloration Plan J ro w EL O v Latitude: 47.8064' Longitude:-122.3308' wLU 0 a~ F- F o U.1 o w Z z LL _ ce> � w p� w a �w z w Approximate Surface Elev.: 378 (Ft.) +/- 0 ¢ m Q LU LL rn O U � DEPTH ELEVATION Ft. OLU a TOPSOIL, brown to dark brown, moist, loose — ' 1.0 377+/- SILTY SAND (SM), trace gravel, yellowish brown to brown, moist, medium dense, (RECESSIONAL GLACIAL OUTWASH) 5 3 9-8-4 S-1 N=12 6 14-14-10 S 2 N=24 1 11 14-24-50 N_74 S 3 10.5 367.5+/- SILT ML yellowish brown to brown, moist, very stiff 11.0 �� Y rY 367+/- POORLY GRADED SAND WITH SILT (SP-SM), trace gravel, yellowish brown to grayish brown, moist, dense to very dense, (GLACIAL TILL) 15 11-17-26 S 4 N=43 15 14 16-19-18 S-5 N=37 16.5 361.5+/- Boring Terminated at 16.5 Feet Stratification lines are appro)amate. In -situ, the transition may be gradual. Hammer Type: Rope and Cathead Samples obtained using a 2" O.D. split spoon sampler Advancement Method: See E)ploration and Testing Procedures for a Notes: Hollow Stem Auger description of field and laboratory procedures used and additional data (If any). See Supporting Information for a>planation of symbols and abbreviations. Abandonment Method: Boring backflled with bentonite upon completion. Elevations were interpolated from a topographic site nl­ WATER LEVEL OBSERVATIONS Boring 1 rerraco, Started: 11-26-2019 Boring Completed: 11-26-2019 Groundwater not encountered Drill Rig: Acker Soil Mechanic Driller: Boretec i 21905 64th Ave W, Ste 100 Mountlake Terrace, WA Project No.: 81185173 J 0 z LU U) 0 z 0 0 w co LU m >J 0 Z 0 it U) 0 0 BORING LOG NO. B-6 Paqe 1 of 1 PROJECT: Edmonds Senior Living CLIENT: CA Senior Living Holdings, LLC Chicago, IL SITE: 21200 72nd Ave. W Edmonds, WA o LOCATION See ':nloration Plan J ro w EL O v Latitude: 47.8064' Longitude:-122.3311' wLU 0 a~ F- F o U.1 o w Z z LL _ ce> � w p� w a �w z w Approximate Surface Elev.: 378 (Ft.) +/- 0 ¢ m Q LU LL rn O U � DEPTH ELEVATION Ft. OLU a 0.5 TOPSOIL, brown to dark brown, moist 377.5+/- ' !: POORLY GRADED SAND WITH SILT AND GRAVEL (SP-SM), yellowish ° ro brown to brown, moist, medium dense, (RECESSIONAL GLACIAL OUTWASH) @S-1, wood debris. fine roots 4, 12 13-12-9 S-0 N=21 5 9 30-33-36 S-1 r115.5 372.5+/- POORLY GRADED SAND (SP), yellowish brown to light brown, moist, very dense, trace silt, trace gravel (GLACIAL TILL) N=69 1 15 27-32-36 S 2 N=68 15 15 35-30-42 S-3 N=72 ..:16.5 361.5+/- Boring Terminated at 16.5 Feet Stratification lines are appro)amate. In -situ, the transition may be gradual. Hammer Type: Rope and Cathead Samples obtained using a 2" O.D. split spoon sampler Advancement Method: See E)ploration and Testing Procedures for a Notes: Hollow Stem Auger description of field and laboratory procedures used and additional data (If any). See Supporting Information for a>planation of symbols and abbreviations. Abandonment Method: Boring backflled with bentonite upon completion. Elevations were interpolated from a topographic site nl­ WATER LEVEL OBSERVATIONS Boring 1 rerraco, Started: 11-26-2019 Boring Completed: 11-26-2019 Groundwater not encountered Drill Rig: RCT60 Driller: Boretec i 21905 64th Ave W, Ste 100 Mountlake Terrace, WA Project No.: 81185173 0 0 z U) 0 z O 0 w co U) LU m >J O z 0 0 J H Q O W BORING LOG NO. B-7 Paqe 1 of 1 PROJECT: Edmonds Senior Living CLIENT: CA Senior Living Holdings, LLC Chicago, IL SITE: 21200 72nd Ave. W Edmonds, WA o LOCATION See Exploration Plan J ro Zp w d w O v Latitude: 47.8066' Longitude:-122.3311' w a~ — F- F o U.1 o w Z z LL _ ce> � w p� w a �w z w Approximate Surface Elev.: 378 (Ft.) +/- 0 ¢ m Q LU LL Q rn O U � DEPTH ELEVATION Ft. OLU a 0.5 TOPSOIL, brown to dark brown, moist 377.5+/- POORLY GRADED SAND WITH SILT AND GRAVEL (SP-SM), yellowish ° ro brown to light brown, moist, (medium dense), (RECESSIONAL GLACIAL OUTWASH) '. 5.0 373+/- rJ ''•. POORLY GRADED SAND WITH SILT AND GRAVEL (SP-SM), yellowish ° rp brown to light brown, moist, dense, (GLACIAL TILL) 13 9-21-24 S 1 N=45 :;Ifs ••i ° 8.5 369.5+/- 16 1 N136 1 S 2 SILTY SAND (SM), trace gravel, yellowish brown to brown, moist, dense 1 15 10-19-30 S-3 N=49 15 10-20-19 S-4 N=39 14.0 364+/- Boring Terminated at 14 Feet Stratification lines are appro)amate. In -situ, the transition may be gradual. Hammer Type: Rope and Cathead Samples obtained using a 2" O.D. split spoon sampler Advancement Method: See Exploration and Testing Procedures for a Notes: Hollow Stem Auger description of field and laboratory procedures used and additional data (If any). See Supporting Information for a>planation of symbols and abbreviations. Abandonment Method: Boring backflled with bentonite upon completion. Elevations were interpolated from a topographic site nl­ WATER LEVEL OBSERVATIONS Boring 1 rerraco, Started: 11-26-2019 Boring Completed: 11-26-2019 Groundwater not encountered Drill Rig: RCT60 Driller: Boretec i 21905 64th Ave W, Ste 100 Mountlake Terrace, WA Project No.: 81185173 J 0 0 z LU U) U) 0 z 0 p w co U) LU m >J 0 z 0 O U) 0 0 BORING LOG NO. B-8 Page 1 of 1 PROJECT: Edmonds Senior Living CLIENT: CA Senior Living Holdings, LLC Chicago, IL SITE: 21200 72nd Ave. W Edmonds, WA (3 LOCATION See -)loration Plan J W ^ v Latitude: 47.8068' Longitude:-122.3311' W pz W Q }a ~ F F p W o w Z z LL F a F �> � a > p� J a ¢w z a O Appropmate Surface Elev.: 380 (Ft.) +/- o m Q w a s ro 00 w DEPTH ELEVATION(Ft.)O rn a ASPHALT + -TlzGGREGATE BASE COURSE + SILTY SAND WITH GRAVEL (SMI, grayish brown to dark brown, moist, (medium dense), (FILL) . • 3.0 377+/- 10-26-27 POORLY GRADED SAND WITH SILT (SP-SMJ, trace gravel, yellowish 12 N-53 S 0 brown to brown, moist, dense to very dense, (GLACIAL TILL) 5 yellowish brown to light brown 14 10-19-25 S 1 N=44 18 16-25-28 S 2 N=53 1 yellowish brown to grayish brown @S-4,increasing gravel content 15 12-19-19 S 3 N=38 18 12-21-25 S-4 N=46 15 18 8-17-27 S-5 N=44 16.5 363.5+/- Boring Terminated at 16.5 Feet Stratification lines are appro)dmate. In -situ, the transition may be gradual. Hammer Type: Rope and Cathead Samples obtained using a 2" O.D. split spoon sampler Advancement Method: See E)ploration and Testing Procedures for a Notes: Hollow Stem Auger description of field and laboratory procedures used @S-1, S 3, and S 4, rock fragments, blow count might be over and additional data (If any). stated See Supporting Information for eplanation of symbols and abbreviations. Abandonment Method: Boring backfilled with bentonite Surface capped with concrete Elevations were interpolated from a topographic site WATER LEVEL OBSERVATIONS Boring Irerracon Started: 11-26-2019 Boring Completed: 11-26-2019 Groundwater not encountered Drill Rig: RCT60 Driller: Boretec 21905 64th Ave W, Ste 100 Mountlake Terrace, WA Project No.: 81185173