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Subsidence ln��stigation Quiros-Martinez Residence-Zephyrhills,Florida SDII Project Number•3023547 APPENDIX A EXPLANATION OF METHODS Ground Pen�etrating Radar Ground pene�trating radar (GPR) is a geophysical exploration tool that is used to detect shallow conditions in the soils adjacent to, and with appropriate conditions, underlying a structure. The method involves towing an antenna that generates a signal in the radar frequency range. This signal penetr�.tes the soil and, upon encountering changes in soi] conditions, a portion of the signal is reflected back to the antenna. By measuring the two-way travel time of this signal as it returns from .a reflector, the general configuration of soii horizons can be mapped. The depth of penetration and quality of the data depend on the subsurFace materials. GPR methods are used to detect unusual soil conditions (anomalies) in the shallow subsurface. These anom;�lies may reflect sinkhole conditions, underground utilities, changes in soil composition, water content, or orientation; and many other conditions. SDII tests these anomalies directly by standard penetration testing, cone penetrometer, or we place a boring between the anomaly and structure in order to determine if conditions represented by the anomaly extend to the structure. GPR methods are described in ASTM (American Society for Testing and Materials) Method D6432. Hand Auger Borings Hand auger borings are utilized to collect soils near the foundation of the structure and in areas where sampling of the soils in the shallow subsurface is prudent. The hand auger consists of bucket-type s,�npler and an extendable handle. The bucket sampler has sharpened tines designed to cut into th�,; soil. The soil passes through the tines and into a 3 inch cylindrical container from which the sai��ple is removed. Soil samples are collected in increments of 6 inches. Soil samples are placed in1��containers and labeled for classification in the Iaboratory. Hand auger b�orings are collected according to ASTM Method D1452. Test Pit Exc;7vations Test pits are excavated at the foundation of investigated structures. If additions have been added to the house, or if the investigator has reason to expect that the foundation vary around the structure, more test pits will be excavated. The investigator excavates to the bottom of the foundation, n��tes the manner of foundation and slab construction, and takes measurements where possible. There are no ��ublished standards for test pit excavation.