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

SERS Public Safeh, 9.1-1 Communication Tower ( SI Report No 704-05224-1 December 26, 2000 Page 5 for structural design purposes we recommend a soil profile at the site of Sc when considering the average of the upper 100 feet of soil. A ratio not greater than 5 percent critical damping should be used. If site-dependent earthquake response spectra or other specific design parameters are deemed necessary by the project structural engineer, or are required by the local governmental agency who has jurisdiction over the project, the geotechnical engineer should be promptly informed for further _valuation. 5.0 Conclusions and Recommendations Based on the results of our field work, laboratory evaluation, and engineering analyses, it is our opinion that the site is likely suitable for the proposed communication tower development provided the recommendations in the following sections are incorporated into the design and construction of the project. However, we were not able to explore the subgrade conditions within the footprint of the proposed tower. Our visual observations of[tie surface indicate the potet tial for deleterious and/or loose fill on the site. We recommend that at least one additional soil boring (if the foundation will be a drilled pier)or backhoe test pit (if the foundation will be a structural mat) be performed once access is provided to the tower footprint 5.1 Site Preparation In general, we recommend that all structural improvement areas be drained of surface water, and stripped of topsoil, highly saturated or disturbed soil, loose fill soils, and any other deleterious materials encountered at the time of construction. Additional site preparation will depend upon the proposed site grades, weather conditions and lower features. Prior to placing any fill, all structural areas should be proofrolled under the observation of the geotechnical engineer w'.th a fully Innrlprl tandem axle dump truck or similar rubber tired vehicle. Soils that are observes to rut or deflect excessively under the moving load should be undercut and replaced with properly compacted structural fill. After subgrade preparation dnd observation by the geotechnical engineer have been completed, fill placement may begin. The first layer of fill should be placed in a relatively uniform horizontal list and be adequately keyed Into the stripped subgrade soils Fill materials should be a well graded granular material free of organic or other deleterious materials, have a maximum particle size less than 3 inches, and fines with a liquid limit less than 45 and plasticity index less than 20 The on-site soils are generally considered to be suitable for use as structural fill, although they may require moisture conditioning prior to placement.