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Subsidence Investigation Mathewl Aley Rental Property Claim No. 223968 BCI Project No. 03-15564 November 2007 Page 5 2.6 Floor Elevation Snrvey A floor elevation survey of the house interior was conducted in conjunction with the site inspection and damage assessment. The survey was completed using a digital water level to measure relative floor elevations at locations inside the house. The data were normalized relative to a base station datum of zero (0). The data were then plotted on a scaled map of the interior of the house and used to construct a floor elevation contour map, which is shown on Figure 4. During the floor elevation survey, three discrete floor slabs were identified, including the main interior portion of the house, the bathroom addition, and the garage. Data collected over the house interior indicate an overall elevation differential of 0.8 inch across the length and width of the floor slab. Allowable building standards and tolerances for interior floor slabs typically allow for maximum variation of'l'2-inch over a length of 10 feet. Most of the elevation data were within accepted construction tolerances. However, local elevation differentials up to 0.6 inch over 6 feet show slightly anomalous slopes in the floor in the kitchen, southeast bedroom and the utility room. The observed cracking distress in these areas was very minor, indicating the elevation anomalies are largely related to minor finishing and leveling defects associated with the original construction of the floor slab. However, the widespread cracking distress in the exterior walls may be indicative of some localized minor differential settlement along the outer edge of the floor slab. In the bathroom addition, the elevation date were within accepted construction tolerances. In the garage, an overall elevation differential of 1.9 inches was measured across the floor slab. Garage slabs are typically constructed with an outward slope to provide for drainage of stormwater. The pattern of elevation contours shows a northwesterly slope for the floor slab. When considered in conjunction with the reported water intrusion and patched cracks along the north wall, the sloping floor appears to be related, in-part, to some minor differential settlement of the floor slab. 2.7 Soil Survey Map Review Soils data from the Soil Survey of Pasco County, Florida (USDA-SCS, 1982) were reviewed as part of the subsidence investigation. The mapped soil unit in the vicinity of the Mathew/Aley rental property was identified as the Tavares-Urban land complex (map symbol 15). The SCS describes the Tavares soils as nearly level to gently sloping, moderately well drained soils consisting of sand to a depth of 80 inches or more. Typically, the surface layer is very dark gray sand approximately 3 inches thick. Below the surface layer, the sand is yellowish brown and light yellowish brown to a depth of 56 inches, very pale brown between depths of 56 and 76 inches, and white between 76 and 80 inches. In some places the soil has been radically altered. Some of the low areas have been filled or leveled during construction, and other areas have been cut, built up, or smoothed. Most areas of this map unit are artificially drained by sewer systems, surface ditches and canals. Tavares soils that are not drained have a water table at a depth of 40 to 60 inches for 6 to 10 months in most years. The USDA Soil Conservation Service classifications are based on an interpretation of aerial photographs and widely spaced hand auger borings. Borders between mapping units are approximate, and the transition between soil types may be very gradual. Areas of dissimilar soils can occur within a mapped unit. Therefore, the USDA soil units may not be accurate on the scale of a single property, and may not correspond to the hand auger and SPT boring results found in our investigation. However, the soil survey provides a good basis for an initial evaluation of shallow soil conditions in the area, and can provide an indication of changes that may have occurred due to land filling, excavation, and other activities at the site.