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20151005084623.pdfr-bnGE& 1 4 C 0 K P 0 0 A T 1 0 Geotechnical & Earthquake Engineering Consultants April 27, 2014 File No. 13-063-100 Mr. Nicholas Echelbarger Salish Landing LLC PO BOX 1088 Edmonds, WA 98020 Re: Salish Pavilion — BLD2015-0294 150 Sunset Ave S Edmonds, WA Dear Mr. Echelbarger, This letter presents geotechnical recommendations for the design of the foundations for the Salish Pavilion located at 150 Sunset Avenue South in Edmonds (see Figure 1). The building site is located at the southwest corner of the intersection of James Street and Sunset Avenue South, as shown on Figure 2. The Pavilion Building will be constructed at the northeast corner of the Salish Crossing shopping center in an area that has been used for parking and drive lanes. SITE CONDITIONS The shopping center was reportedly built in 1966 and the buildings were supported on piles with lengths on the order of 10 to 23 feet. Soils underlying the site of the shopping center include highly compressible peat that has contributed to as much as 3 feet of differential settlement between 1966 and 1980 when 3 geotechnical borings were advanced at the site to provide recommendations for building improvements. The locations of these borings, B-1-80 thru B-3-80, are shown on Figure 2 along with our estimates of the depth to the top of the soil bearing stratum within which the piles were tipped. Additional borings were drilled at the site in 1991 in conjunction with other improvements at the shopping center. The locations of these borings are also shown on Figure 2 as Borings B-1-91 thru B-3-91 and logs of all borings are presented in Figures 3 thru 7. As indicated in Figure 2, the very dense sands and gravels of the bearing stratum dip down to the east. As such the bearing stratum may underlie the Pavilion Building at a depth of about 20 feet. The soils overlying the bearing stratum include surficial gravel 3213 Eastlake Avenue East Suite B Seattle, WA 98102-7127 T (206) 262-0370 F (206) 262-0374 Page 2 of 5 April 27, 2015 Salish Pavilion fill overlying soft compressible peat with interbedded layers of loose sand. Groundwater may be present at a depth of about 9 feet. SEISMIC DESIGN PARAMETERS The following provides seismic design parameters for the site that are in conformance with the 2012 International Building Code (IBC), which specifies a design earthquake having a 2% probability of occurrence in 50 years (return interval of 2,475 years), and the 2008 USGS seismic hazard maps: Design Spectral Spectral S Site Spectral Control Site Acceleration Acceleration Coefficients Response periods Class at 0.2 sec. (g) at 1.0 sec. (g) Parameters (sec.) Ss S, Fa Fv SDS SDI To Ts 10.59 D 1.27 0.50 1.0 1.5 70.85 0.50 0.12 Although the site is underlain by very soft compressible peat and potentially liquefiable soils, we believe that a Site Class D conservatively bounds the expected site response under seismic conditions. There are no known faults within 5 km from the site. The nearest inferred fault is a strand of the South Whidbey Island Fault that has been inferred from geophysical surveys in the Puget Sound but fault traces have not been mapped on the mainland. Consequently, special designs for fault displacement are not required. The potential for earthquake -induced soil liquefaction in the loose to medium dense sand layers within the compressible peat is considered to be moderate. Consequently, pile foundations are recommended for the new building to mitigate potential settlement of the underlying soils associated with static and dynamic loading. PIN PILE FOUNDATIONS We recommend that the new Pavilion Building shell and floor slabs as well as the floor slab of the associated outdoor terraces be supported on 4 inch diameter pipe piles driven to refusal into the dense to very dense sands underlying the site at a depth of about 20 feet to avoid excessing long term settlements of the peat and potential liquefaction of sand layers within the peat. However, since the parking areas adjacent to the building will not be mitigated to preclude liquefaction and future settlement, utilities within the parking lot may experience distress at or near their entry of the pile supported building, which may result in breaks of water service and sewer lines. Detailed design recommendations are presented below. 13-063-100 Salish Pavilion.docx PanGEO, Inc. Page 3 of 5 April 27, 2015 Salish Pavilion Pile Capacity - The number of piles required depends on the magnitude of the design load. An allowable axial compression capacity of 10 tons may be used for 4-inch diameter piles with an approximate factor of safety of 2.0. Penetration resistance required to achieve the capacities will be determined based on the hammer used to install the pile. Tensile capacity of pin piles should be ignored in design calculations. It is our experience that the driven pipe pile foundations should provide adequate support with total settlements on the order of/z-inch or less. Pin Pile Specifications - We recommend that the following specifications be included on the foundation plan: 1. 4-inch diameter piles should consist of galvanized Schedule-40, ASTM A-53 Grade "A" pipe. 2. 4-inch piles shall be driven to refusal with a minimum 850-lb hydraulic hammer. The driving criteria will be determined based on the actual hammer size selected by the contractor, and a static load test program (see discussion in Item 4). 3. To avoid piles "running" or driven to excessive depths into the bearing stratum, we recommend that all piles be driven with a closed end. 4. At least 3% (but no more than 5) of the 4-inch pin piles should be load tested. All load tests shall be performed in accordance with the procedure outlined in ASTM D1143. The maximum test load shall be 2 times the design load. The objective of the testing program is to verify the adequacy of the driving criteria, and the efficiency of the hammer used for the project 5. Piles shall be driven in nominal sections and connected with compression fitted sleeve couplers (see detail below — Courtesy of McDowell Pile King, Kent, WA). We discourage welding of pipe joints, particularly when galvanized pipe is used, as we have frequently observed welds broken during driving. POD 2" Po 6" N Now ;!R ool 6nqpaw 9:nwa¢;P on fl GA" Rw 9q�" 1 )X' to 2'wide X SProng ! ua aal Ring 0/4Pllowg ww;Ie9 rp W pope wu4evve D nven Swel Pqm Secdfan Beveled Q,Iiid po aid 11nsel'Blftl"Y 6. As required for this type of construction, the geotechnical engineer of record or his/her representative shall provide full time observation of pile installation and testing. 13-063-100 Salish Pavilion.docx PanGEO, Inc. Page 4 of 5 April 27, 2015 Salish Pavilion The quality of a pin pile foundation is dependent, in part, on the experience and professionalism of the installation company. We recommend that a contractor with experienced personnel be selected to install the piles. Lateral Forces - Lateral capacity of vertical pin piles should be ignored in design calculations. Some resistance to lateral loads may be accomplished by battering the piles to a slope no steeper than 3(H):12(V). Additionally, lateral forces may be resisted by passive pressures acting on the grade beams and pile caps. Passive resistance may be determined using an equivalent fluid weight of 500 pcf, assuming that the pile caps are backfilled with compacted City of Seattle Type 17 soil. Grade BeanvPile Cap Embedment - We recommend that the grade beams and pile caps located around the perimeter of the structure be embedded such that the bottom of the grade beam is at least 12 inches below the adjacent ground surface. Estimated Pile Length - The required pile length to develop the recommended pile capacity may vary depending on the actual subsurface and driving conditions encountered. For planning and cost estimating purposes, we estimate that an average pile length of about 30 feet will be needed. Obstructions - Obstructions may be encountered during pile driving. Where possible, the obstructions should be removed to facilitate the pile driving. If obstructions cannot be removed, the structural engineer of record should be notified to revise the pile layout to accommodate the adjustment. Geotechnical Observation — In accordance with the International Building Code, PanGEO will need to be present on a full time basis during driving of all piles and the load testing of selected piles to confirm the driving criteria used for the installations and also to confirm that all driven piles meet the requirements of the structural drawings. LIMITATIONS We prepared this report for Salish Landing LLC and the project design team. Recommendations contained in this report are based on a site reconnaissance, a review of pertinent subsurface information, and our understanding of the project. The study was performed using a mutually agreed -upon scope of work. Variations in soil conditions may exist between the locations of the explorations and the actual conditions underlying the site. The nature and extent of soil variations may not be evident until construction occurs. If any soil conditions are encountered at the site that are significantly different from those described in this report, we should be notified immediately to review the applicability of our recommendations. Additionally, we should also be notified to review the applicability of our recommendations if there are any changes in the project scope. The scope of our work does not include services related to construction safety precautions. Our recommendations are not intended to direct the contractors' methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. Additionally, the scope of our work specifically excludes the 13-063-100 Salish Pavilion.doex PanGEO, Inc. Page 5 of 5 April 27, 2015 Salish Pavilion assessment of environmental characteristics, particularly those involving hazardous substances. We are not mold consultants nor are our recommendations to be interpreted as being preventative of mold development. A mold specialist should be consulted for all mold -related issues. This report has been prepared for planning and design purposes for specific application to the proposed project in accordance with the generally accepted standards of local practice at the time this report was written. No warranty, express or implied, is made. This report may be used only by the client and for the purposes stated, within a reasonable time from its issuance. Land use, site conditions (both off and on -site), or other factors including advances in our understanding of applied science, may change over time and could materially affect our findings. Therefore, this report should not be relied upon after 24 months from its issuance. PanGEO should be notified if the project is delayed by more than 24 months from the date of this report so that we may review the applicability of our conclusions considering the time lapse. It is the client's responsibility to see that all parties to this project, including the designer, contractor, subcontractors, etc., are made aware of this report in its entirety. The use of information contained in this report for bidding purposes should be done at the contractor's option and risk. Any party other than the client who wishes to use this report shall notify PanGEO of such intended use and for permission to copy this report. Based on the intended use of the report, PanGEO may require that additional work be performed and that an updated report be reissued. Noncompliance with any of these requirements will release PanGEO from any liability resulting from the use this report. Please call if there are any questions on this letter. Sincerely, W. Paul Grant, P.E. Principal Geotechnical Engineer Attachments: Figure 1 — Vicinity Map Figure 2 — Site Exploration Plan Figure 3 — Log of Test Boring B-1-80 Figure 4 - Log of Test Boring B-2-80 Figure 5 — Log of Test Boring B-8-80 Figure 6 — Log of Test Borings B-1-91 and B-2-91 Figure 7 — Log of Test Boring B-3-91 13-063-100 Salish Pavilion..docx PanGEO, Inc. Salish Pavilion VICINITY MAP PanGE& 150 Sunset Ave S M c o o p o stj% ,r a o Edmonds, Washington No. 13-063-100 1 Figure No.. 1 W „fJ e r t J ,r" �0 ••. -u✓1M .�.k A.N Stl" �'� JA a r, dU:A '" aru JadS Mw.. ,GdW a m^^ r-bnGEED Salish Pavilion 150 Sunset Ave S I OW C 0 It . 0 R A , 8 0 Edmonds, Washington SITE EXPLORATION PLAN STANDARD 5 10 15 20 25 35 SOIL DESCRIPTION 2" Asphalt Medium dense to loose, saturated, gray, slightly silty, medium to coarse sand (Fill?) Interbedded, very soft, brown peat and loose, saturated, gray, silty, fine to medium sand Dense to very dense, saturated, gray -brown, silty sand and gravel Boring complete at 31.5 feet June 25, 1930 LEGEND 2.0" C.D. eplit s2mp'er * _97arrple rot recovered U 3.0" O.D. undis'.--rbe4d ,a:r;1er i Piezc;rnater tip P E2-ipler pushed SZ 'Arzter level Atterberg Units: LiqWd limll IlVaral waler content Plzu;lc Limit I PENETRATION RESISTANCE A Blows per Not (140 lb. hammer, 30" drop) 10 20 30 40 5b P 7\_ 4 3 'yv :Water C ca I,- r t Edtionds Shopping Center LOG OF BORVIG JNO ' W-3355 B-1 -80 RITTEN110TJSE-Z)"1!jMA1Fig. 3., -1. W STANDARD < P•ENMATION RESISTANCE SOIL DESCRIPTION a z ,A glows per toot 0. (140 lb. hammer, 70" drop) a Surface Elevation: � u 10 20 30 40 Alt 2" Asphalt �^ Loose brown sand (Fill) Medium dense saturated re slightly...•. l9ed grey, 5 silty medium to coarse sand (Fill?) Interbedded, very soft brown peat and loos 10 saturated, grey silty fine to medium sand P. 15 , Dense, saturated, grey -brown, 'silty sand 20 and gravel 25 Boring complete at 24:0 feet - --------- ----- W I,EG E. ND T 2.01, O.D. eylSt z; : rampler • Sample .1-A reccscred .2 9.0" O.D. &irpler ( Pit•torieter lip P 2"am;l:r puhhed `7 v4altr level Alterterg limas: Llgt4id lictlt "e ti Natural aster convent Plastc Urnit June 20', 19330 cd,nonds Slopping Center '.� OF BORING h0. R-2 -80 W- = 355 RITTEN'HOUSE-7ENIAN Rg. 4. "{)n.s ENGIN"EM3.1:;G ?.: D GEC tr w STANDARD m F- PENETRATION RESISTANCE w SOLE DESCRIPTION to A Mows per loot M O (140 lb. hammer, 30" drop) a Surface Elevation: 0 10 20 30 40 5" Asphalt Loose, saturated, mreo csalty sand grey, l d (Fill?) Interbedded very �..W4..�. .� 5 y brown peat, loose to medium dense, saturated grey, fine to medium sand —� :P Dense, saturated, grey -brown, silty sand — and gravel's - 25 Boring complete at 24.0 feet - °w - 35 .40 I.EEGF N D I 2.0" O.D, rsp`.it scLa t.arnp'er • Sp.rr•p,p nil rect'-verca 3.0"O.D. ur."_is:•,.rbed sa:-picr Piezorrseter tip P F.:n:;'c•r pus'led !Z water level A'.'e:t.:;,'i,...._. I .� - j}— L!gtsid llrnit PlaS:)c Limit June 25, 1980 r2 ": Walcr Canter.t I:d:,londs shopping center LOG OF ROi?::;G ;:0. B-3 -80 �Z 3 E cl.•..�PJxc AND c�c:. Boring 1 .-91 Elevation 15 Feet Sod Classification Sample Blows Depth System Symbol ,, Descriptlon Interval (feat) per Fooea) -- r asphalt 0.1-7.5 SM/GM Medium brown and gray,,, fine to coarse SAND with -" 2.5,,4.0 23' gravel and silt,„ and fine to coarse GRAVEL with sand and sift (medium dense, moist) OR 7.5-10.0 ME/Oil Dark brown to medium gray -brown SILT with 7.5-9.0 1 for 18• organics and reeds. and organic SILT (very soft, ' moist) 10.0.17.5 SP Gray, medium to coarse SAND with gravel 12.5-14.0 38 (medium dense to dense; wet) 17.5-19.6 GP Gray, fing to coarse GRAVEL with sand (dense to 17.5-19.0 52 very dense, wet) Boring completed to 19.0 ft on 7116/91. Groundwatir encountered at time of drilling at 9.0 ft. Boring 2 ® 1 Approximate Elevation 15 Feet SOU . J Clasadicatbn Sample Blows Depth System Interval per (feet). Symbol Description (feet) Foot(a) -- 2• asphalt 0.1-4.5 SWGM Medium brown to gray, silty fine to coarse SAND 2.5-4.0 12 with gravel and silty fine to coarse GRAVEL with sand (medium dense. moist to wet) (fill) 4.5-8.5 OUPT Dark brown to brown -black, organic SILT and 7.5-9.0 3 PEAT (very soft, moist) 8.5-14.0 MUOL Dark brown SILT with organics interlayered with 12.5-14.0 1 for 180 thin layers of gray, fine to coarse sand; sandier towards base, gradational contact (very soft, moist) 14.0-18.5 SP Gray, medium to coarse SAND with gravel and 17.5-19.0 21 trace silt (medium dense, wet) 18.5-22.5 SM Gray., silty, fine SAND with gravel (medium dense, 21.0-22.5 40 to dense, moist) (till)- Borin g completed to 22.5 4 on 7115/91. Groundwater enbountered at time of drilling at 14.0 ft. (a) Blows required to drive 2.04nch 00 split -barrel sample i foot with a hammer weight of 140' pounds and a stroke of 30 Inches. LANDAU ASSOCIATES, INC. Loq of Borings Boring 3 1 Approximate Elevation 15 Feet classification Samplir Blows Depth System " Interval per (feet) Symbol Descrption (feet) FootIa) .. 34.asphalt 0.2-4.5 SM/GM Medium brown to gray, sihy, fine to coarse SAND with gravel and silly fine to coarse GRAVEL with sand (loose; moist to wet) (flp) 4.5-9.5 MIJOL Medium 'brown and dark brown SILT with organics, 7.5-9.0 3 twigs and reads, and organic SILT (very soft to soft, moist) .9.5-22.0 SW/GW Dark gray, fine to coarse SAND with gravel and 12.5-14.0 87 sandy fine to coarse GRAVEL with trace sift (dense 17.5-19.0 50 for 5.5" to very dense, wet) 22.0-23.0 SP/SM Gray, medium to coarse SAND with gravel grading 22.5-23.5 50 for 5" to gray, (ins to medlUrn SAND with silt and gravel (very, dense; moist) (till) Test pit completed to 23.0 ft on 711Big 1. Groundwater encountered at time of drilling at 9.5 it, (a) Blows required to drive 2.0-Inch OD split -barrel sample 1 foot with a hammer weight of 140 pounds and a stroke of 30 inches. LANDAU ASSOCIATES, INC. Loy of Borings