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Indian River County File No. 06-5699 4.4 Construction Considerations -6- Roadway construction should be performed in accordance with the appropriate sections of the current edition of the Florida Department of Transportation (FDOT) Standard Specifications for Road and Bridge Construction. In accordance with these specifications, the removal of any organic materials (A-8 soils) including topsoil as encountered, and any plastic (A-2-6 and A-2-7) and high plastic soil should be accomplished in accordance with FDOT Standard Index 500 unless otherwise indicated on the plans. Backfill should generally consist of select material (A-3 and A-24) compacted in accordance with Section 120-9 of the Standard Specifications. In-place density tests should be performed on the fill soils to verify the specified degree of compaction. The minimum density test frequency should be in accordance with the FDOT Materials, Sampling, Testing, and Reporting Guide. Fill Placement and Side Slopes for Embankment Construction are presented in the FDOT Standard Index 505. As mentioned above, A-24 type soils and hardpan -type soils will likely be encountered along much of the alignment within the upper 6 feet (referenced from existing ground surface). The A-24 type soils can be used for roadway construction using strict moisture control (in-place moisture near optimum moisture content as determined by the Proctor test). Special compaction equipment (i.e., sheepsfoot-type rollers, etc.) and allowing time for the material to dry sufficiently may also be needed to use these soils in construction. If A-24 soils excavated from below the groundwater table are to be used for embankment fill, we recommend stockpiling the excavated clayey/silty soils as high as possible so as to increase the rate of drainage. Prior to their use, the -soils should be spread out and disced to further reduce moisture levels. Nevertheless, soil with high percentage of fines will be slow in draining and may present problems during compaction efforts. We note that the weakly -cemented, hardpan -type soils can be problematic for several reasons. Hardpan can be difficult to excavate, often requiring special equipment; especially in confined excavations such as utility trenches. Excavated hardpan -type soils are often cobble to boulder -size chunks of cemented soils which are not easily broken down for re -use as structural fill. In addition, when pulverized into fragments that can be compacted to an adequately dense matrix, the in-place soil often fails the relative compaction test because during laboratory preparation, the soil is pulverized into smaller particles, resulting in a denser laboratory matrix than that which can be achieved in the field. Alternative acceptance criteria may need to be used for hardpan -type soils used as fill. This criteria would need to be developed on a site specific basis after observing the contractor's earthwork methodology and the nature and condition of the compacted hardpan -type soils. Should any water -filled canals or ditches be reclaimed (or filled) for roadway construction, we recommend conducting further explorations relative to the soils beneath and within the canals, including additional soil borings and canal bottom probes. We also recommend that the designer add notes to the plans relative to potential difficulty in dewatering, using strict moisture control and any special compaction equipment for A-2-4 soils, maintaining positive site drainage, excavation of hardpan -type soils and wrapping pipe joints.