319 76TH PL SW 2016-01-01 MF Import

SERS Public Safe 9-1-1 Communication Tower 31 Report No. 704-05224-1 December 26, 2000 Page 10 open over night. Cast-in-place piers should fill the entire excavation. If casing is used, it should be withdrawn as the concrete is poured, while maintaining the casing bottom at a level below to top of the concrete. The geotechnical engineer or his representative should be present during pier drilling and pier concrete placement operations to monitor subsurface conditions and to observe the drilled pier excavation prior to concrete placement. If the concrete is allowed to free-fall, the chute should be positioned such that the falling concrete does not come in contact with the sidewall of the excavation or the steel reinforcing. Typically, the concrete should not be allowed to free-fall a distance greater than 8 feet. When free-fall distances would be greater than 8 feet, a tremie or concrete pump should be used to mitigate the potential for concrete component segregation. Once placed, the concrete should be properly vibrated for the full depth of the pier in accordance with ACI recommendations. The drilling contractor should be prepared with appropriate and adequate equipment with sufficient size and torque for drilling into the very dense silty sand with gravel stratum 5.4 Equipment Building Foundation Support Based on the results of our geotechnical investigation, it is our opinion tho' the proposed lightly loaded equipment building can be supported on a conventional shallow foundation designed for a maximum allowable soil bearing pressure of up to 4,000 psf, when founded on the undisturbed, very dense silly sand with gravel stratum, or on an engineered, g:anular structural fill placed overlying the very dense, native silty sand stratum. We understand the proposed equipment structure is lightly loaded and probably does not require a soil bearing capacity of 4,000 psf. However, we are not familiar with the soil conditions above the very dense silty sand stratum within the footprint of the proposed construction. Nor are we aware of the depth at which the very dense soil will be encountered. Once access is possible to the proposed site, as stated earlier, we recommend an additional subsurface investigation (either a soil boring or backhoe test pit) so that we can provide more appropriate, and possibly less conservative (i.e. requirement to bear on the very dense silty sand with gravel), soil hearing capacity recommendations. The allowable bearing pressure stated above includes a safety factor of 3 and is intended for dead loads and sustained live loads and can be increased by one-third for the 'total of all loads, including short-term wind or seismic loads. The continuous and isolated footings should be at least 18 and 24 inches in width, respectively and extend to a minimum depth of 18 inches beneath the lowest adjacent exterior grade to provide frost protection. The structure should be constructed at least 10 feet laterally from the lop of any slopes, whit., should be permanently graded no steeper than 2 horizontal 1 vertical.