Background Information

XYZ Homes is contemplating purchase of property on SC Lane in north east Cobb County, Georgia to develop streets and residential lots. We have received a copy of the preliminary concept plan for the proposed development. The development will consist of detached single-family residences.

The land is rolling ridges and swales typical of the Southern Piedmont Physiographic Province. Drainage is primarily to the west from higher elevations along SC Lane. The site is partially covered with mature trees and partially pastured. Four residences are present on four different parcels and several garages and sheds. A small pond is located at the southwest corner of the site.

The site grading scheme is currently being designed, and therefore, final grades are not fixed. However, based on typical requirements and the amount of relief which is present it appears mass excavation on the order of ten to fifteen feet is required. Depths of maximum fill are not known at this time, but are expected to be on the order of ten feet.

Site Exploratory Procedures and Findings

Eighteen auger borings were drilled using a CME-300 all terrain drill rig on September 8 and 11 . Sixteen of these borings extended to 20- or 25-foot termination depths. Two borings encountered refusal at depths of 21 and 22 feet. Cuttings from the borings were visually classified in the field by the driller. Locations of the borings shown on the attached plan were established by measuring distances from site landmarks.

Subsurface Findings

A surface veneer of topsoil/organic matter is present at the locations which were explored. Residual soils consisting of silty sand (SM) were present below the topsoil each location. The residual soils are the product of weathering in-place from parent crystalline metamorphic schist and gneiss. These materials are typically described as medium dense silty fine sands with frequent mica content.

Sixteen borings were drilled to termination depths of 20 or 25 feet. Borings B-7 and B-20 refused at depths of 21 and 22 feet respectively. Refusal could be caused by rock lenses or competent bed rock.

Groundwater was encountered in boring B-15 the time of drilling at a depth of 16 feet. Groundwater was not encountered in the remaining borings. Groundwater levels fluctuate seasonally and with climate changes and may be different in the future.

Evaluation and Recommendations

The following discussion and recommendations are based on the findings at the site and experience with similar project subsurface conditions.

General Site Assessment

The property is favorable for development from a geotechnical viewpoint. The residual soils are competent materials to provide shallow foundation support for typical single family structures. Similarly, these soils are suitable for pavement subgrade support provided the moisture content is within a practical range. The soils are readily used for construction of structural fill embankments to provide building and pavement support. Conventional soil excavation conditions are expected at most locations based on the test pit and boring results. Some difficult excavation should be expected at locations of partially weathered rock and refusal materials. Typically partially weathered rock can be loosened with large heavy excavating equipment. Refusal materials will frequently require blasting to be excavated. The following paragraphs contain specific recommendations pertaining to site development earthwork and foundation considerations.

Fill Construction

Subgrades to receive compacted structural fill should be stripped of topsoil and organic materials before placement of new fill material. These subgrades should be proofrolled with a loaded dump truck or other heavy equipment under observation of experienced soils technicians or engineers before placing fill. Areas that exhibit pumping or rutting should be excavated to firm virgin soil and replaced with compacted structural fill or stabilized in place. We recommend that no fill material be placed until subgrades have been observed and are considered suitable by your designated site personnel.

Material used as compacted structural fill for foundation and subgrade support should classify as a ML or a SM in accordance with ASTM D2487, with a plasticity index less than 20. Laboratory compaction tests should be performed on representative residual soils prior to beginning construction. Based on experience with similar soils the materials at the site are suitable for use as structural fill.

Compacted structural fill should be placed in lifts not exceeding eight inches in loose thickness and compacted to at least 95 percent of the maximum dry density determined by ASTM D698. Soil moisture should be maintained within 3 percent plus or minus of the optimum moisture content. We note moisture content in a few test pits was somewhat above optimum conditions and therefore some drying during placement may be required. Compacted structural fill should extend at least five feet beyond the limits of pavements or buildings; then be sloped as required to meet final grades. In pavement areas, we recommend that the top one-foot of the subgrade soil be compacted to 98 percent of the maximum dry density.

Fill construction should be observed by an experienced soil technician on a full-time basis to confirm that good construction practice is used. In- place density tests should be performed at a frequency of one test per 5000 square foot for each one foot lift of compacted fill. More frequent tests should be performed in confined areas such as trench backfills.

Slopes

The strength and stability of virgin materials which will comprise excavated slopes is controlled by planes of discontinuity which are relic joint structure from the parent rock. We have not performed an analysis of the stability of any proposed excavated slopes. Additional exploratory work, sampling, laboratory testing, and analysis will be required to assess the stability of excavated slopes. We will be glad to provide these additional services at your request.

The project will also require construction of fill embankments and fill slopes. We have not assessed the stability of constructed fill slopes for the project. However, good local practice has shown that fill slopes constructed at 2 horizontal to 1 vertical with clean soil compacted to a minimum of 95 percent of the maximum density determined by ASTM D698, are generally stable over the long term. Fill slopes should be benched into natural slopes with benches each 2-foot fill lift.

If the project grades require fill slopes greater than 20 feet in height, we recommend additional sampling, laboratory testing, and stability analysis be performed to estimate the factor of safety for the slope. We will be glad to provide this additional service at your request.

Foundations

Following the recommended site preparation procedures, the compacted fill soil and virgin residual soil subgrades should be suitable for shallow spread footing and slab-on-grade support using an allowable bearing pressure of 3000 pounds per square foot. Foundations should be inspected by experienced soil technicians or engineers prior to placing concrete to confirm that the expected bearing materials are present. Footings should be cleaned of loose and wet soil immediately before placing concrete. Settlement of residential foundations due to imposed loads is expected to be less than one inch for building code approved footings.

Limitations

The evaluation and recommendations contained in this report are based on the data obtained from the subsurface exploration and experience with similar projects. The test pit excavations and soil borings indicate subsurface conditions only at the specific locations and times, and only to the depths explored. They do not necessarily reflect variations that may exist between such locations. If subsurface conditions encountered during construction are different from those described herein, then the recommendations presented in this report must be re-evaluated.