3003 W CASINO RD BLDG 45-12 2016-10-20

777X Static Test Building I 3 ■ Sand. A layer of medium dense to very dense sand with silt to silty sand was encountered in all of the borings at the surface or underlying the asphalt with the exception of boring HC-8. This layer extended to depths between 8 and 32 feet bgs. This layer deepens to the west of the site and is thickest at the location of the stockpiles and extended to 32 feet below the exiting surface in the southwest corner of the site. Boring HC-9 had comparatively higher organic content within the sand, including a zone with peat from 10 to 14 feet bgs. ■ Silty Sand(Glacial Till). A layer of native glacial till was encountered below the asphalt road in borings HC-8 and beneath the sand in the remaining borings. This layer consists of very dense, silty sand with variable gravel content. The Standard Penetration Test(SPT) blow counts in this layer were consistently greater than 50 blows per foot(bpf). This layer has been delineated as the bearing layer at the site and elevation contours of this layer are included on Figure 2. Groundwater Conditions Due to the mud rotary drilling method used, groundwater conditions were not readily apparent during drilling. Boring HC-7 was left open overnight to allow the ground water level to stabilize within the borehole. The groundwater at this location was measured to be at a depth of 9.4 feet bgs,or approximately at elevation 557 feet. Based on this limited quantity of groundwater data,we recommend using a slightly higher groundwater level of 560 feet for design of retaining walls. Standing water was observed on site in the drainage ditch to the north of the site along 94th Street SW and at an approximate elevation of 565 feet in the stormwater pond on the southwest corner of the site at the time of drilling. Note that measured groundwater levels represent the times indicated. Fluctuations in groundwater levels may occur due to variations in rainfall,temperature,seasons, and other factors. It is important that the contractor provides contingencies for dealing with perched groundwater on this project. GEOTECHNICAL ENGINEERING CONCLUSIONS AND RECOMMENDATIONS This section presents our recommendations and conclusions for geotechnical aspects of design. Our recommendations are based on our current understanding of the project and the subsurface conditions interpreted from explorations at and near the site by Hart Crowser and others. If the nature or location of the facilities is different than we have assumed,we should be notified so we can review,change, and/or confirm our recommendations. Earthquake Engineering This section provides a brief overview of potential seismic hazards and our recommendations to develop the code-based seismic design parameters. ■s ALAI 19106-01 HAWOZOwsME May 29,2015