08-7752 - Laserfiche WebLink

Browse Search

Subsidence Investigation Mathewl Aley Rental Property Claim No. 223968 BCI Project No. 03-15564 November 2007 Page 3 Garage . Paint-filled stair-step crack at lower comer of north window (photo 6) Timing of Damage According to Mr. Frymyer, the interior and exterior walls of the house had not been painted since he moved into the house in July 2007. During our inspection of the property, we observed several patched or paint- filled cracks in the interior and exterior walls. Based on this data and our site observations, a portion of the cracking distress developed prior to the most recent painting event. However, we could not determine the precise timing of the cracking relative to the inception data of the insurance policy (September 6, 2006). 2.3 Ground Penetrating Radar Survey A ground penetrating radar (GPR) survey of the Mathew/Aley rental property was completed in conjunction with the site inspection and damage assessment. The purpose of the GPR survey was to evaluate the lateral continuity of the soil layers across the site. Anomalous variations in the subsurface, if present, may be related to hidden geologic features of interest in our investigation. The GPR survey was completed by BCI and consisted of a grid of 28 transects scanned over exterior portions of the site, at the locations shown on Figure 3. A summary report on the GPR survey is included in Appendix B. Inspection of the GPR transect profiles indicates the depth of penetration of the radar signal ranged from 14 to 16 feet below grade for the transects completed utilizing the 500 MHz antenna, and from 20 to 23 feet below grade for the transects completed using the 250 MHz antenna. On most of the profiles, a series of weak to moderate intensity, continuous, subparallel, horizontal and sinuous reflection events was identified at estimated depths of 7 to 11 feet below the land surface. The reflective horizon may represent the upper surface a subsurface clayey soil unit (clayey sand to sandy clay). One possible subsurface anomaly was identified in the GPR survey (Feature 1), at the location shown on Figure 3. The anomaly is located in the west yard, and is adjacent to the ground collapse feature below the front porch of the house. The anomaly is characterized by a zone of shallow disorganized reflective patterns and associated deeper signal penetration, and is interpreted to represent a shallow zone of disturbed soils and discontinuity within the underlying subsurface soil layers. 2.4 Hand Auger Borings and Test Pit Excavations Four shallow hand auger borings, HA-1 to HA-4, were completed during the site inspection and damage assessment, at the locations shown on Figure 2. Boring HA-1 was located along the south edge of the entry slab, adjacent to the ground collapse feature, and was advanced to a depth of 7 feet below grade. Boring HA-2 was located along the south wall of the house and was advanced to a depth of 7 feet below grade. Boring HA-3 was located along the east wall of the house and was advanced to a depth of 7 feet below grade. Boring HA-4 was located along the north wall of the house and was advanced to a depth of 7 feet below grade. In general, the borings encountered a similar soil sequence consisting of variably colored fine-grained quartz sand extending from the ground surface to the termination depth of the borings. The water table was not encountered in the hand auger borings. Soil boring logs are included in Appendix C. Two shallow test pit excavations, TP-1 to TP-2, were completed, in order to examine the type and condition of the house and bathroom addition foundations. The test pit locations are shown on Figure 2. Test pit TP-1 was located at the southeast comer of the addition and was excavated to depth of 7 inches below grade. Test pit TP-2 was located along the east wall of the house, near the northeast comer and was excavated to a depth of 19 inches below grade. Based on measurements and observations made in the test pits, the house foundation consists of a stem wall supported on a continuous strip footing founded at a depth of 16 inches below existing grade. The