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o <br />Class B timber piles treated with creosote would be suitabr <br />for this site. Our estimated lengths for nominal 25-ton gross <br />capacity piles are 45 to 50 feet. <br />The piles should be driven to an actual gross load-bearing <br />capacity of at least 28 tons each, with a hammer having a rated <br />energy of at least 15,000 foot-pounds per blow. A pile-driving <br />formula may be used as a guide only, but a minimum embedment of <br />at least 20 feet into the underlying sand is required, notwithstand­ <br />ing the observed pile-driving bla^ counts. No pile on the projec <br />should be less than 42 feet long, measured from cut-off to pile <br />tip. <br />To allow for downdrag or negative skin friction effects on <br />the piles, caused by continuing settlement and consolidation of thi <br />peat and organic silt, it is recommended that the actual net worki ig <br />load on each pile should be limited to 16 tons. <br />The bottoms of the grade beams spanning the piles should be <br />at least 3h' below outside finished grade for frost protection <br />purposes. As an added precaution we recommend that at least 4” <br />of styrofoam insulating batts be placed below the bases’ of the gra <br />beams, to act as a cushion and additional preventative against <br />frost action. The house lowest floor slab should also be a <br />structural floor, supported on piles. <br />There is a definite tendency for the yard area to settle <br />away from buildings which are supported on piles, causing problems <br />at entry points into the structure, garage aprons, etc. Therefore <br />it would be advisable to place any required fill as early as <br />possible and to delay the actual house construction as much as <br />possible, in order to allow the situation to stabilize. <br />The use of driven piling is not mandatoiry for the detached <br />garage structure. This could be supported upon a heavily reinfor­ <br />ced, thickened edge concrete slab having internal stiffener ribs <br />in both directions. Some settlement of the garage would still be <br />likely to occur, but it should not restrict the utility of this <br />structure. <br />SUBTERRANEAN <br />ENGINEERING CORP. <br />MINNEAPOLIS. MINNESOTA