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HomeMy WebLinkAboutBLD1994-00216 Geo Tech r r LANDAU • . ),, ASSOCIATES. ;, , . .; -„,..v INC. Environmental and Geotechnical Services July 1, 1994 Mr. Ray Welch Pope Resources 781 Walker Way Port Ludlow, WA 98365 RE: SUMMARY LE I1 ER GEOTECHNICAL CONSULTATION AND CONSTRUCTION OBSERVATION SERVICES INN AT PORT LUDLOW TOWNHOMES PORT LUDLOW, WASHINGTON Dear Mr. Welch: This letter presents a summary of our observations and conclusions regarding the installation of piles for support of five townhome buildings at the Inn at Port Ludlow development. Landau Associates received your verbal authorization to proceed with our services on June 7, 1994. Our services included: • Performing a dynamic analysis to calculate appropriate pile driving criteria, including minimum blow count and refusal criteria • Observing the installation of the piles and logging each pile installation with a field log that recorded blow count information, pile tip elevation, comments and observations regarding obstructions encountered, and deviation of piles from planned locations • Preparing this summary letter. A total of 345 creosote pressure-treated timber piles were driven during the period from June 1.5 through June 28, 1994, by the pile subcontractor, General Construction. Piles ranging from about 25 to 50 feet in length were delivered to the job site; most of the pile lengths were about 25 feet. After driving a 50-foot pile to satisfactory driving resistance, the contractor cut off the remainder for use as a second pile. All of the piles, with the exception of one pile driven at an incorrectly-staked pile location, and subsequently not used, achieved the minimum blow count and (typically) the embedment criteria Landau Associates recommended for this project. Landau Associates recommended a minimum of 25 blows per foot or 10 blows for the last 3 inches of driving 07101/94 D:11\TPOCSTROJECTs\ SC.16T11165.RYI WORLD TRADE CENTER•3600 PORT OFTACOMA ROAD•SUITE 501 •TACOMA.WA 98-14•(1-06i 916-1403•FAX('061 9'6-15 31 EDMONDS: i2061775-(1t707.F\\ 201ii„S-(i-lim/SPOK:ANE(50(1327 o)737•F-AS i51i9i 3'7-9h91 (provided there were at least 20 blows for the preceding foot of driving). In addition to the minimum blow count criteria, a minimum embedment of 3 feet into medium-dense to dense native soil was recommended. At some locations, the piles encountered dense to very dense native soil and the driving resistance increased well above the recommended minimum blow count, hence the recommended minimum embedment was not achieved. However, in these cases, the piles were considered adequate and suitable for their intended use because of the high driving resistance developed. In general, the piles were installed in a routine fashion at staked locations. Some of the piles encountered obstructions during driving. The effect of the obstructions ranged from causing the piles to gradually deflect off staked locations, to causing damage to the piles. At those locations where the piles deflected more than a 4-inch tolerance from plan locations, the general contractor, Walsh Construction, was informed so that Walsh Construction could inform the project structural engineer (Ed Johnson) and request direction regarding any necessary revisions to the grade beam reinforcement details. At those locations where the-piles were damaged and rendered unusable, the piles were either extracted and replaced at the plan location or supplemental piles were installed adjacent to the broken piles at the direction of the structural engineer. In addition to requesting direction from the structural engineer regarding piles that deviated from staked locations, we understand the contractor will also contact the structural engineer regarding piles whose heads were driven below cutoff elevation. These were piles that did not achieve the minimum driving resistance until the pile head was driven below planned cutoff elevation. Information on each pile is summarized in Table 1; the piles are designated by their locations relative to a building line grid system developed in the field by Walsh Construction and Landau Associates. A convention of alphabetic grid lines extending from left to right and numeric lines extending from top to bottom of the pile layout Foundation Plan was used for each building. These grid lines were imposed along the centerline of each grade beam. We have retained individual field pile driving logs in our files. Following is a summary of pile-driving activities at each building location and at the proposed "waterfall" location. 07/01/94 D:IWPDOCSIPROIECISNISC116700165.RPT 2 LANDAU ASSOCIATES,INC. -Building 100 Prior to pile installation, the contractor removed existing concrete and brick foundations around the former smokestack footing. Most of the building 100 area was excavated about 4 feet below adjacent site grade. The first 18 piles installed at this location were emplaced with the pile driving rig adjacent to.the excavation. The remaining 20 piles were driven with the pile driving rig in the excavation. A total of 38 piles were driven during the period from June 23 to June 27, 1994. This total includes one extra pile installed adjacent to'a pile that broke on June 23. That pile was replaced at the direction of the structural engineer with one to the east of the broken pile. About 3 piles were driven until their heads were below what we understood to be the cutoff elevation. Building 200 A total of 86 piles were driven at this location on June 15 and 16, 1994. Problems encountered included an obstruction at 3 feet depth at one pile location. The pile tip was broken by the obstruction. The pile was extracted, the pile tip trimmed, relocated 2 feet north of-the plan location by Ted Wilson, Superintendent for Walsh Construction, and successfully redriven. Two piles did not achieve satisfactory driving resistance during their initial installation; thosepiles were later redriven to-satisfactory driving resistance with a mandrel. The pile heads were at or just below cutoff elevation after driving. Building 300 A total of 82 piles were driven at this location during the period June 16 through June 20, 1994. One pile encountered an obstruction when the pile was embedded at 17 feet below ground surface and broke near the ground surface before satisfactory driving resistance was achieved. The broken pile was extracted and the obstruction was excavated, using a hydraulic excavator. The pile was replaced at the plan location with a new pile that was driven to satisfactory resistance and embedment. Two piles did not achieve satisfactory resistance during their initial installation; they were redriven to satisfactory resistance using a mandrel. The heads of these 2 piles appeared to be at or above cutoff elevation after driving. One pile achieved a final blow count of 10 blows per foot and was not redriven to the recommended minimum blow count of 25 blows per foot. From conversations with the project structural engineer, we understand a capacity of 15 tons is required for that pile. Our evaluation of the pile driving data indicates this pile will have sufficient capacity for its intended loading. 07/01/94 D:IWPDOCSIPROJECTSIMISC1167x01.55.KPr 3 LANDAU ASSOCIATES,INC. - Building 400 A total of 77 piles were installed on June 27 and 28, 1994. In addition to the 77 piles placed at the plan locations, one pile was driven to an embedment of 12 feet at an incorrectly- staked pile location. The pile rig unsuccessfully attempted to extract that pile, which was cut off at the ground surface and another pile installed at the proper location. Other problems included one pile that moved about 7 inches off of the staked location during driving and did not, at first, achieve satisfactory driving resistance. This pile was later redriven with a mandrel to satisfactory resistance, although the pile head was driven to approximately 3 feet below ground surface (about 11/2 feet below proposed cutoff elevation). Another pile deviated approximately 8 inches off of plan location, apparently from encountering an obstruction during driving. Another pile broke at the ground surface and 4 feet above ground surface at the very end of driving. The pile did not exhibit behavior that would indicate it was damaged below the break at the ground surface and, according to a representative of Walsh Construction, this pile could be successfully trimmed below the lower break and incorporated satisfactorily into the pile cap. The piles that deviated from plan location were identified to Walsh Construction, who inform the structural engineer so that appropriate revisions, if necessary, can be made to the pile caps. Building 500 A total of 57 piles were driven satisfactorily at the building 500 location between June 20 and 23, 1994. There were no apparent problems with any of these piles. Waterfall Piles Four piles were installed for proposed waterfall installations. Two piles were located outside of the north end of building 500, and 2 piles were located between the southwest corner of building 500 and the Inn at Port Ludlow Hotel, currently under construction. These four piles were installed without incident. In summary, it is our opinion that all piles were installed in general accordance with the project plans and specifications and our recommendations (except as noted above) and are suitable for support of the proposed structures. 07/01194 D:IWPDOCSWROJECrS1MISC116700165.RPT 4 LANDAU ASSOCIATES,INC. We trust this summary letter meets your needs. We have enjoyed serving you on this interesting project. If you have any questions, please contact us at (206) 926-2493. LANDAU ASSOCIATES, INC. By: d,-.. - d. J,--.......,.._ .",--, ',, , J. C . - William D. Evans, CPG - -/ �u ,I'l' 11 Project Manager ,91 1 : ' - ,l- x and L` %Oi\JALG` tep en J. oover, P.E. ' Project Engineer WDE/SJC/mlm No. 176001.65 attachment: Table 1 cc: Ed Johnson 07/01194 D:IWPDOCS1PROJECTSIMISC116700165.Rn 5 LANDAU ASSOCIATES,INC.