AG 1997 09 15 - Laserfiche WebLink

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Proposed Radio Tower Page 2 Cabarrus County Sheriff's Dept. The borings were drilled with a 4-1/4" hollow-stem auger. At selected intervals, a standard 2" o.d. split-spoon sampler was driven into the soil at the bottom of the bore hole with a 140-lb hammer falling 30". The sampler was first seated 6" with the hammer to penetrate any soil loosened by the auger, and then driven an additional 12". The soil was typically sampled at the ground surface, 3.5 to 5 fi, 6 to 7.5 fi, 8.5 to 10 fi, and at 5 ft increments of borehole depth thereafter. The number of blows required to drive the sampler the final 12" was recorded and is termed the soil's "penetration resistance". The penetration resistance is used as an index to the consistency of cohesive soils and the relative density of granular (noncohesive) soils. The soil consistency, along with Atterburg limits testing, or relative density is used to evaluate the soil's strength and foundation supporting capability. Representative portions of the soil from the sampler were placed in sealed sample containers and transported to my laboratory. Bag samples were obtained from the cuttings of each of the two borings located along the retaining wails as well as the borings on the cut side of the proposed building. Soil penetration testing and sampling were performed in general accordance with ASTM D 1586. The test boring records are attached which show the soil descriptions and penetration resistance. Summary of Subsurface Conditions Area Geolot, v The site proposed for the radio tower is located in the Charlotte Belt of the Piedmont Physiographic Province. The primary rock type in the vicinity of the site is granite which is part of the Salisbury Plutonic Suite. Granite typically fractures into blocks which weather into somewhat spheriodal boulders. The resistance to weathering of any type of rock mass varies throughout. Therefore, boulders which are more resistant to weathering can be encountered in borings and interpreted as "rock." When a boring terminates high, as did B-3, we offset the rig and drill a new hole to the termination level and resume the testing, if we can. If we continue to encounter refusal at that general depth, we can interpret the results as indicating that we have encountered a rock ledge, or perhaps even crossed a fault. Otherwise, the results may indicate a boulder of unknown size at depth. Boring B-1 was drilled at the stake for the west leg of the proposed tower. Medium dense white, tan, and black speckled brown very silty fine to medium sand was encountered in the upper two feet. Stiff white, tan, and black speckled brown fine sandy clayey silt was encountered to five feet. Very firm white, tan, and black speckled brown very silty fine to medium sand was encountered from 6 ft to 7.5 ft, becoming less silty to 10 ft. Hard white, tan, and black speckled brown silty File: 97-026R,$am