Laserfiche WebLink
F M Frattalone Excavating 8 Grading <br />April 7, 1987 <br />Page Two <br />Subsurface Conditions <br />Our soil borings were done both towards the northern end of the site, <br />in Block 1 and also towards the southern end in Block 2. To the north <br />you indicated existing grades are about 1' below final street grade. <br />In the south half, you indicated that existing grade was typically at <br />or slightly above (by 1') final street grade. <br />The logs of the borings are attached. Both borings indicate a thin <br />veneer of topsoil at the surface. At boring 1, the topsoil was found <br />to be organic or very black clay whereas at the other boring, the <br />topsoil was dark but not highly organic silty sand. In boring 1, the <br />topsoil layer was underlain by a 26' thick layer of fine alluvium in <br />turn underlain by glacial till and then again fine alluvium to the end <br />of the 46' deep boring. The fine alluvium varied from lean clays to <br />fat clays, and based on penetration values and laboratory tests run on <br />certain select thin wall samples, were found to be typically in a soft <br />condition. <br />In boring 2, the fine alluvium was found to be interbedded with coarse <br />alluvial sand layers to a depth of 15'. Between a depth of 15' and <br />21', the glacial till, clayey sand layer was encountered. The coarse <br />alluvium layers were found to be in a very loose to medium dense <br />condition and the fine alluvium layers to be of soft to medium <br />consistency. <br />Groundwater entered both of the borings and the times and levels <br />recorded are shown on the logs. These are similar levels to those <br />documented on the First Addition either by deep soil boring work or by <br />our manual boring and test pit observation work. Based on our previous <br />work and other knowledge of the area, it is our opinion that these <br />represent perched water conditions and that the true groundwater table <br />is well below these elevations. <br />Recommendations <br />Based on the boring information, we would suggest that soil improvement <br />for the streets include stripping of the organic clay or black clay <br />topsoil prior to establishing the minimum 2' thickness of granular base <br />material as specified. Based on the boring and our soil observation <br />work during excavation for the First Addition, we anticipate that this <br />surficial clay condition will exist only north of Allen Avenue. In <br />Page 85 <br />