4620 SEAHURST AVE 2020-05-20 - Laserfiche WebLink

March 7, 2011 Mr. Paul ThompsonlKolbear, Inc. L&A Job No. 11-001 • Page 4 Location Plan. The test pits were located with either a tape measure or by visual reference to existing topographic features in the field and on the,topographic survey map, and their locations should be considered only accurate to the measuring method used. A geotechnical engineer from our office was present during subsurface exploration, who examined the soil and geologic conditions encountered and completed logs of test pits. Soil samples obtained from each soil unit in the test pits were visually classified in general accordance with United Soil Classification System, a copy of which is presented on Plate 3. Detailed descriptions of soil layers encountered during site exploration are presented in test pit logs on Plates 4 through 8. The test pits generally encountered a light-gray,very-dense, fresh till deposit at about 1.7 to 5.6 feet below the existing ground surface. This fresh till deposit is overlain by a thin layer of topsoil, an occasional layer of loose fill (encountered only in Test Pit 3), and a layer of brown weathered soil of medium-dense silty fine sand about 1.7 to 2.5 feet thick. The exception to the above soil condition was in Test Pits 5 and 6, located at southeast corner of Lot 2 and the northwest corner of Lot 1, respectively, in which a light-gray advance outwash deposit of dense, gravelly, slightly silty, fine to coarse sand was found underlying the layer of fresh till soil. GROUNDWATER CONDITION Only Test Pits 8 and 9 encountered a speck of groundwater seepage at the surface of the underlying fresh till deposit. The fresh till deposit underlying the site at shallow depth is of extremely low permeability and would perch stormwater infiltrating into the more permeable surficial soils. The underlying advance outwash soil is of moderate permeability and would allow some water to seep into the ground. The test pits were excavated in the midst of winter LIU & ASSOCIATES, INC.