1994 - Geotechnical Services Report

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AET #94-1805 - Page 6 That load is in addition to the pile capacity needed to support the structure. Including drag load, we anticipate you may want to consider piles having a working capacity of 30 tons (20 tons building load and 10 tons drag load) per pile. We estimate pile lengths of about 40' to 45' below existing grade to attain a 30-ton capacity. We recommend the pile be driven with a hammer having a manufacturer's rated energy in the range of 15,000 to 25,000 foot-pounds. The pile lengths estimated above are based on static determinations from the boring log. We recommend the capacity be determined in the field with a driving formula such as the Engineering News Record formula. Our estimated pile lengths are based on attaining a factor of safety of about 2 against pile failure. It is also our judgment total and differential settlement of the recommended pile foundation should be less than 1/2". We recommend an experienced structural engineer be retained for design of the grade beam system. Construction Considerations Due to the compressible nature of the existing fill and swamp deposits, consolidation of the swamp deposits and subsequent settlement of lawn areas, driveways, sidewalks and other structures which are supported about the swamp deposits will occur. Utilities which are supported in or above the swamp deposits will also settle. Therefore, the design should include either supporting the utilities structurally or performing soil correction for support of the utilities. Another consideration when organic materials are present is the generation of methane gas. If these gases are trapped beneath an impervious surface layer, they will seek other paths to reach the atmosphere. If there are leaks into the structure, this gas can migrate into the building. Methane is heavier than air and is explosive. Therefore, sealing of the subsurface exterior and all service inlets through underground portions of the structure are important. You should also