Geotechnical exploration/review-2008

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AMERICAN ENGINEERING TESTING, INC. AET Project No. 22-00012 soils off-site, which could make this a cost effective alternative for improving the subgrade soils on this site. For this alternative, we recommend stripping the vegetative mat from the buildings. The underlying topsoil could remain in-place. We recommend placing fill to the planned subgrade elevation before the aggregate piers are installed. We anticipate that on-site lean clay (topsoil and non-organic clay) would be used to raise the grade in the pads. Some of the on-site soils could have relatively high water contents and could be difficult to compact. However, because the aggregate piers will be installed through the new fill, a high degree of compaction during placement is not necessary. We recommend that new fill placed within the aggregate pier improved zone be compacted to at least 90% of the maximum Standard Proctor dry density. We can review these compaction recommendations if the soil conditions are such that the desired compaction can not be achieved with reasonable effort. After new fill is placed to the desired floor slab subgrade elevation, the aggregate piers can be installed. The final depths and layout of the piers would be determined by the specialty contractor as a design-build contract. However, we anticipate that the aggregate piers would be spaced in lines along continuous bearing walls, in clusters under columns, and in a grid pattern under the floor slab. If the aggregate pier alternative is selected, we recommend that the following issues be considered prior to construction. • The specialty Contractor should prepare specifications for the aggregate pier foundation system. • One test pier should be installed by the Contractor's standard procedures and then load- tested to determine the modulus. The load testing setup and procedures should be selected by the Contractor and submitted to the project Geotechnical Engineer for review. The test Page 14 of 28