Investigation – Wireless Communication Tower
Global Environmental Engineering Inc. (Global) performed a geotechnical engineering investigation to determine the general subsurface conditions at the site in order to provide foundation and related site preparation recommendation for the support of the communications tower. The field investigations for the project consisted of drilling four (4) borings, one (1) to 25-feet below ground surface and three (3) to 15 feet bgs. Borings were drilled with a rotary hollow stem auger.
Soil samples were obtained by Standard Penetration Tests (ASTM D-1568), which involved driving a 2-inch diameter split spoon sampler into the soil by dropping a 140-lbs hammer from a distance of 30-inches. The number of blows were recorded for each 6-inches of increment. The number of blows for the last 12-inches of penetration was recorded as the Standard Penetration Resistance.
Unconfined compressive strengths were estimated in the field using pocket penetrometers and ranged from 2.0 to 4.5-tons per square foot. During drilling, soils were logged using USCS standards and water levels were recorded when encountered.
Global’s geotechnical engineering investigation report concluded by saying the native soils would be suitable to support the proposed weight of the tower and recommended the use of spread footings at a depth of 4 feet below ground surface to support the tower. Global estimated the total settlement of the structure would be less than 1-inch based on the compressive strengths of soil and the weight of the tower.