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Indian River County File No. 06-5699 -4- 4.0 CONCLUSIONS AND RECOMMENDATIONS 4.1 General Soil Stratigraphy for Roadway The results of the field exploration and laboratory testing programs are presented on the Soil Boring Profiles sheet, Figure 5. The stratification of the soil boring profiles represents our interpretation of the field boring logs and the results of the laboratory examination of the recovered samples. The stratification lines represent the approximate boundary between soil types. The actual transitions may be more gradual than implied. The results of our borings indicate the following general soil types: Dark brown to dark gray slightly silty fine sand to silty fine sand with -- -- organics (topsoil) 2 Light brown to very dark brown fine sand to fine sand with silt A-3 I S Dark brown to very dark brown weakly -cemented fine sand to fine 3 sand with silt [hardpan -type] A-3 S 4 Light gray to dark brown fine sand with clay A-2-4 S 5 Light brown to very dark gray clayey fine sand A-2-6 P Soils encountered in the borings performed along the proposed alignment of 20' Avenue SW typically included suitable sandy soils with variable amounts of clayey and 'silty fine sands (AASHTO Classifications A-3 and A-2-4, Soil Strata Nos. 2 through 4) overlying plastic clayey fine sand soils (A-2-6, Soil Stratum No. 5). Soil Strata Nos. 2 through 4 (A-3 and A-24) may be considered as select materials based on FDOT criteria (Index 505). The use of these soils relative to embankment construction should be in accordance with FDOT Standard Index 505. We note that, while Soil Stratum No. 4 (A-24) is considered as select material based on FDOT criteria, it is our opinion that this soil type can be problematic for roadway construction. The clay content is sufficient that this stratum will retain moisture resulting in compaction difficulties. Recommendations relative to the use of clayey soils are presented below in Section 4.4. Organic material or "topsoil" was encountered at the surface along the majority of the project site to depths of about 6 to 12 inches. The topsoil should be stripped from the proposed alignment and not be used for roadway construction or utility backfill. The removal of topsoil and any other organic soils as encountered (i.e., muck) should be accomplished in accordance with FDOT Standard Index 500, unless otherwise noted on the plans. Qescripttoh Dark brown to dark gray slightly silty fine sand to silty fine sand with -- -- organics (topsoil) 2 Light brown to very dark brown fine sand to fine sand with silt A-3 I S Dark brown to very dark brown weakly -cemented fine sand to fine 3 sand with silt [hardpan -type] A-3 S 4 Light gray to dark brown fine sand with clay A-2-4 S 5 Light brown to very dark gray clayey fine sand A-2-6 P Soils encountered in the borings performed along the proposed alignment of 20' Avenue SW typically included suitable sandy soils with variable amounts of clayey and 'silty fine sands (AASHTO Classifications A-3 and A-2-4, Soil Strata Nos. 2 through 4) overlying plastic clayey fine sand soils (A-2-6, Soil Stratum No. 5). Soil Strata Nos. 2 through 4 (A-3 and A-24) may be considered as select materials based on FDOT criteria (Index 505). The use of these soils relative to embankment construction should be in accordance with FDOT Standard Index 505. We note that, while Soil Stratum No. 4 (A-24) is considered as select material based on FDOT criteria, it is our opinion that this soil type can be problematic for roadway construction. The clay content is sufficient that this stratum will retain moisture resulting in compaction difficulties. Recommendations relative to the use of clayey soils are presented below in Section 4.4. Organic material or "topsoil" was encountered at the surface along the majority of the project site to depths of about 6 to 12 inches. The topsoil should be stripped from the proposed alignment and not be used for roadway construction or utility backfill. The removal of topsoil and any other organic soils as encountered (i.e., muck) should be accomplished in accordance with FDOT Standard Index 500, unless otherwise noted on the plans.