08-8021 - Laserfiche WebLink

Browse Search

Subsidence Investigation Pittman Residence - Zephyrhills, Florida son Project Number: 3017839 5.0 LIMITATIONS 5.1 Ground Penetrating Radar According to ASTM D6429, GPR is the preferred method for investigating "voids and sinkholes". This is because the method provides high-resolution data with a minimum of interferences. GPR has been used in similar investigations to help identify shallow subsurface conditions that are frequently associated with karst features. In many cases, a GPR investigation has resulted in the identification and mapping of the boundaries of karst features and has helped characterize their size and geometry. However, this method is limited to the ability of the GPR unit to collect interpretable data at the project site. There is a possibility that karst features may exist at the project site and not be detected by the GPR technique due to small size, subsurface soil conditions, or the occurrence of such karst features below the depth of penetration of the GPR signal. Note that many GPR anomalies are not sinkhole or karst features. The presence of an anomaly should not be construed to reflect sinkhole activity simply because of its existence. 5.2 Standard Penetration Test and Hand Auger Borings The determination of soil type and conditions was only done from the ground surface to the maximum depth of the borings. Any changes in subsurface conditions that occur between or below the borings would not have been detected or reflected in this report. The maximum depth of hand auger borings is 10 feet bls unless otherwise noted. Soil classifications are based upon identifiable textural changes, color changes, changes in composition, or changes in resistance to penetration at the intervals from which such samples were collected. Abrupt changes in soil type, as reflected in boring logs and/or cross sections, may actually represent gradual transitions. Depth to the water table is based upon observations made while advancing hand augers and SPT borings. This depth is an estimate and does not reflect the annual or extreme variations that occur in this area due to fluctuations in rainfall, pumpage, and rates of evapotranspiration. Low permeability soils or sediments may not allow water to freely enter the borehole and, therefore, the water table may not be evident or it may only represent a transient condition. The depths are estimated from the immediate land surface, which is not surveyed or tied to a known reference elevation. 5.3 Site Figures The measurements used for the preparation of the figures in this report were made with a fiberglass measuring tape or measuring wheel. Such measurements are usually accurate to within ::1:5 percent. Right angles were estimated from existing exterior walls at the house; such angles are usually accurate to within 5 degrees. Figures in this report were not prepared by a licensed land surveyor and should not be interpreted as such. 5-1