02-27-2002 Council Agenda - Laserfiche WebLink

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FEB 14 '02 05 :32PM BRAUN INTERTEC P.10/24 Drywall Supply, Inc. BBXX- 02 -010A January 29, 2002 Page 6 While light- weight structures such as metal storage buildings are more tolerant of differential movement, o.tticc /warehouse structures with light to moderately loaded lineal footings and coltunns are less forgiving to excessive total and differential settlement. In our opinion, supporting the buildings on typical spread footing foundations and supporting the slabs -on -grade would incur high risk — much higher than what would normally he acceptable. For this reason, deep soil corrections (soil corrections to at least remove the existing till and organic materials) or alternative foundation systems would be needed to provide a suitable building pad and foundation support. Based on the borings, it appears that excavation depths needed to remove the existing fill and organic soils would range between about I 1 to 23 feet. Given the depth of the excavations required and the presence of groundwater however, in our opinion, removing the unsuitable soils (an excavation /backfilI approach), although possible, would he difficult. Additionally, settlement of unexcavated lacustrine soils (soft days) would still occur under the weight of excavation backtill and additional fill needed to achieve design grade that would necessitate at least a construction delay period. Even if spread footing construction is abandoned in favor of alternate support options such as drilled piers, piles or GeopiersTM , settlement of the ground in general should be expected to occur over time in areas where new fill is added to existing site grades. Settlement or the existing fill and organic soils under their own weight will also occur throughout much of the site as the materials continue to consolidate over line. For this reason, sidewalks, curbs, concrete and bituminous pavements, and other at grade structures will be subject to differential movements. C.2.b. Affect of Groundwater on Construction. Groundwater was encountered at depths of about 9 feet. Excavations extending below the groundwater level to remove unsuitable soils will also need to be dewatered making the excavations more difficult. For this reason, alternative foundations types such as GeopiersM , drill piers or piles appear to be more applicable-for this site. C.3. Alternate Foundation Support Options With the present information, it appears that performing an excavation to remove the unsuitable soils and accommodate spread footing foundations will he impractical. Given the soil conditions, in our opinion, deep foundations such as drilled piers, piles or GeopiersTM should be considered. The following paragraphs briefly describe each foundation system.