Loading...
HomeMy WebLinkAboutSite Preparation and Foundation - BLD Letters / Memos - 8/18/1977 TELEPHONE MAIN 4-3946 NEIL H. TWELKER & ASSOCIATES CONSULTING SOILS ENGINEERS Alaska Trade Buildins Mail To: P.O. Box 21328 Seattle,Washington 98111 August 18, 1977 KPFF Consulting Engineers Lloyd Building Seattle, Washington 98101 Attention: Mr. Dave Green Be : Site Preparation and Foundation Construction for Proposed Alder- brook Inn Dear Dave : On July 8, 1977 we examined the proposed site and borrow sources for your forthcoming Alderbrook Inn expansion program. We present herewith a report of our findings, conclusions and recommendations. Previous Investigations Our report of April 2, 1974 contains con- clusions and recommendations for foundation construction of a some- what different project on the same building site. From a brief sub- surface exploration performed at that time we concluded that the soil formation throughout the area of the proposed construction consists of moderately dense fairly clean gravelly sand and that excellent support conditions will be found for the proposed construction. Detailed conclusions and recommendations were submitted in the pre- vious report. A copy of which is attached hereto. Recent Examination The examination in July 1977 was made primarily to ascertain the suitability of material across the road from the project site [immediately east of the Alderbrook office structure; . Methods used in that examination consisted of reconnaissance of the roadcuts in the general area and shallow hand excavations. Conclusions and Recommendations From our examinations of proposed borrow souces we draw the following principal conclusions [which may be appended to our letter of April 2, 19741 ; 1. We anticipate that material encountered in the excavation east of the existing office structure will encounter dense, fine-grained materials. We believe the natural moisture con- tent of these materials will allow compaction to- produce structural KPFF Aucust 1a, 1977 Pace 2 Pills on which building elements can be placed, using bearing pressures of 4000 psi'. We point out however, that un;avorable weather during construction could interi'ere with compaction and make an alternative borrow source necessary. 2. In the event that material from the preFerrred borrow source cannot be employed as structural rill, a pit-run gravelly sand or excellent quality is available two miles from the project site. The gravel pit is also owned by ;.he Alderbrook management and is therefore available, if needed. 3. Structural fills of fine-grained material should be spread in uniform lifts not exceeding 6 inches loose thickness with each liFt thoroughly compacted by routing of loaded 'hauling equipment, repeated coverages of heavy crawler tractors, sheeps---Foot rollers, or heavy rubber tired rollers. The entire surface of the fill should be accessible at all times to the equipment used in construction of the fill . Compacted fill slopes to declivities steeper than 1 vertical to 2 horizontal should not be attempted. In the event that steeper fill slopes are desired [as in the vicinity of the peripheral concrete wall) the fill could be constructed beyond the intended slope and excavated back to the desired declivity [which for heights not exceeding 6 Feet, may be 1 vertical zo 1 horizontal) . 4. All backFill between rime grained fill and exterior peripheral walls should be made with the pit run sand or gravel from the upland source. Compaction by small vibratory equipment is recommended For the backfill zone. Sackfill should also be provided with a perforated foundation drain- 5. In the event the pit run sand or gravel must be used for the body of the structural fill , it should be placed in lifts not exceeding 9 inches loose thickness, with each li`'t compacted by repeated coverages or loaded hauling equipment, crawler tractors, heavy rubber tired rollers, or heavy vibratory rollers. B. The degree of compaction sought For structural Fills of either material is 95 percent oi' maximum density as determined by vibratory compaction test AASHO T-99. We request that we be noti=ied when excavation of zhe proposed borrow area is about to be undertaken in order that we may schedule a visit to the project site for the purpose OF conFirming usability of the prop osed,_,bor-r-aiu source. of WgS;'i-ram Very truly yours, NSIL H. T WcLKEH C r^,SSOCI ATES b Y Neil H. Twelker L NHT :a mt ^y10 ��„�'fi cc : Howard S. ` cam Attn : Ed Muskat Alderbrook Inn Attn : Wes Johnson Incl .