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Minnetonka Custom Homes STS Project 99189 June 24, 2003 Page 2 Laboratory Testing Procedures The penetration test split-spoon samples were visually examined by a geotechnical engineer to estimate the distribution of grain sizes, plasticity, consistency, moisture condition, color, presence of lenses and seams, and apparent geologic origin. The engineer classified the soils according to type using the STS Classification System, which is closely based on the Unified Soil Classification System. A chart describing the STS Classification System is included in the Appendix. An explanation of typical laboratory procedures is presented in the Appendix. We also determined the natural moisture content, density and unconfined compressive strength of selected soil samples. Some of these data are shown on the boring logs, and some of the data are appended at the rear of this report. Exploration Results This property is on the north shore of Jennings Bay within the West Arm of Lake Minnetonka. The height of the slope surrounding the lake at this point is about 60 feet, from pavement level of County Road 19 to average water level in Lake Minnetonka. The major naturally occurring soil type is low plasticity clayey glacial till deposited by the Des Moines ice lobe of the Wisconsin glaciation. After this soil was formed, it became desiccated, and is now over-consolidated (that is, it has been subject to stresses in the past which are greater than the present overburden pressure). We found only minor amounts of surficial soils including fill and topsoil. The major soil type to a depth of at least 50 feet is sandy clay with traces of gravel and random thin sand lenses, some of which are water-bearing. Natural moisture contents of the sandy clay vary from about 32% to 14%, and tend to decrease with increasing depth. Standard penetration N-values are in the range of 16 to 41 blows per foot, representative of a stiff to hard consistency. Unconfined compressive strengths were found to be 3400 to 5600 pounds per square foot. Groundwater Conditions Boring 1 extended to a tip elevation of about 960.7 feet at 30 foot depth, and was dry. In boring 2, we observed groundwater at 25.6 foot depth while drilling corresponding to elevation 952.5 feet. We believe that the groundwater in boring 2 emanated from a sand seam within the clay till profile. The average long-term water elevation in Lake Minnetonka is 930 feet. The Lake Minnetonka water level is controlled within a relatively small range of fluctuation by the Grays Bay dam. Analysis and Recommendations The clay soil at this site is competent. The house can be supported on conventional footings bearing directly on the native sandy clay, or on compacted sandy clay fill. A conventional footing design may be used. We recommend that the footing stresses on the clay subsoil should not exceed 2,000 pounds per square foot. Continuous footings under bearing walls should be at least 22 inches wide for practical reasons, regardless of the theoretical bearing pressure on the subsoil. Footings in unheated areas such as under an entry canopy of under the overhead garage door should be based at least 5 feet below outside finished grade for frost protection. Similarly, footings supporting an attached, elevated deck should be based at least 5 feet below grade. We recommend that a perimeter drain system be installed around the outside of the house, in accordance with FHA Special Bulletin 87-1. The backfill around and over the drain pipe should be a free-draining granular material such as pea gravel or 1-1/2 inch crushed rock. We strongly recommend that the on-site clay soils not be used as wall backfill, except for the uppermost 12 to 18 inches. Clayey backfill against