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1' l, • , � PROJECT NO: 4220 91-1427 . DATE: September 11, 1991 PAGE: 2 SOIL OBSERVATIONS AND TESTING CONCLUSIONS (con't.�. In the eastern 10 to 12' of the building area addition, the exposed soils consisted of �reviously placed compacted fill, placed to provide structural support for the existing buildi�g. These�ll soils were judged to be in a well-compacted condition, as indicated by the results of soil compaction testing performed by our firm in 1976 during construction of the existing structure. The results of 43 compaction tests of fill placed to establish grade indicate the specified minim�im compaction level of 95%of the modified proctor density was obtained at the loc�tion and elevation of these tests. We recommend additional compaction testing be performed of back�ll pl�ced adjacent to below-grade foundation elements as well as surficial fill within floo"r slab areas above elevation 54'. PRO.TECT INFORMATION We understand the construction in progress will be a single-story addition to the west side of the existing structure. The addition will have overall dimensions of about 47.5' x 100' with an additional smaller area measuring 22' x 28' located at the southwest corner. The majority of the structure will be of slab on grade construction with finished floor at elevation 57'. A small portion of the building located in the south central portion of the addition will have a basement with finished floor at about elevation 48'. The building will be supported upon normal spread footings consisting of perimeter strip footings and isolated column pads on the building interior. Foundation elevation will range from about 47' along the south and southern portion vf the west building lines to about 51' on the north building line, and just below the floor slab on the building interior. The foundations have been designed based on an allowable bearing capacity of 2,000 psf. The results of a preliminary subsurface exploration (#4220 91-1043) conducted by our �rm were available for reference during our work. We refer you to this report for specific information regarding site soil conditions. In summary, the report indicated a typical soil profile consisting of � variable depths of fill and topsoil, underlain by clayey weathered till and till. The report indicated the weathered till and till underlying the surficial fill, topsoil and softer portions of the weathered till should be suitable for support of the construction in progress. OBSERVATION METHODS AND RESULTS During the period of August 19-23, 1991, we performed a series of intermittent site visits, wheh requested, during the excavation operations for the planned addition. During dur visits, severa� shallow hand auger borings were put down t� aid in dePicting l�cal suhsurface conditions. The exposed soils and those retrieved by our hand auger borings were classi�ed in general accordance with ASTM: D2488 and compared to those depicted by the preliminary test boring logs. Estima�es were made of the soil strength characteristics. AS A MUTUA�PROTECTION TO CLIENTS,THE PUBLIC AND OURSELVES,ALL TWIN CI7V TES7ING CORPOiiATIpN REPOR7S ARE SUBMITTED AS THE CONF�DENTIA�PROPERTY OF CIIENT3, Aub nU I I IOHI1Af1UW FOH t'UUUCAI ION OF Slnt EMENiS.CONGlU510WS UR E%IFiACtIUNS FROM OR FiEGAqUWG OUR REPORTS IS RESERVED PENDING OUR PRIOR WRITTEN APPROVAL.