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<br />11 <br /> <br />4.10 Utilities <br /> <br />We anticipate that new utilities will be installed as part of this project. We further anticipate <br />that new utilities will bear at depths ranging from about 7 to 10 feet below the ground surface. <br />At these depths, we anticipate that the pipes will bear on compacted sandy engineered fill or <br />sandy native alluvial soils, which in our opinion are suitable for pipe support. <br /> <br />We recommend removing all vegetation, topsoil and any other unsuitable soils, if <br />encountered, beneath utilities prior to placement. We recommend bedding material be <br />thoroughly compacted around the pipes. We recommend trench backfill above the pipes be <br />compacted to a minimum of 95 percent beneath slabs and pavements, the exception being <br />within 3 feet of the proposed pavement subgrade, where 100 percent of standard Proctor <br />density is required. In landscaped areas, we recommend a minimum compaction of 90 percent. <br /> <br />Groundwater was encountered in the soil borings at about 12 ½ feet, or deeper, below the <br />ground surface. We generally do not anticipate that groundwater will be encountered during <br />utility construction. See Section 4.4 for dewatering considerations. <br /> <br />4.11 Bituminous Pavements <br /> <br />General The Elk River may have standard plates that dictate pavement design and if so, we <br />recommend that the pavements be designed and constructed in accordance with the city <br />standard plates. The following paragraphs provide general pavement recommendations in <br />the absence of city standard plates. <br /> <br />Traffic We were not provided any information regarding traffic volumes, such as Average <br />Annual Daily Traffic (AADT) or vehicle distribution. We anticipate the streets will be used <br />predominantly by automobiles, light trucks, school busses, garbage trucks and delivery vans <br />(FEDEX, UPS etc.). Based on the plans provided we anticipate the development will include <br />at least 500 homes. Based on the assumed number of homes in the development and assumed <br />traffic types we estimate the roadways will be subjected to Equivalent Single Axle Loads <br />(ESAL’s) ranging from about 100,000 to 150,000 over a 20-year design life. This does not <br />account for any future growth. <br /> <br />Subgrade Preparation We recommend removing all vegetation, topsoil and any soft or <br />otherwise unsuitable materials from beneath the pavement subgrade. Prior to placing the <br />aggregate base, we recommend compacting and/or possibly test rolling the subgrade soils to <br />identify soft, weak, loose, or unstable areas that may require additional subcuts. <br /> <br />Backfill to attain pavement subgrade elevations can consist of any mineral soil provided it is <br />free of organic material or other deleterious materials. We recommend placing and <br />compacting fill and/or backfill as described in Section 4.3 except in paved areas where the <br />upper 3 feet of fill and backfill should be compacted to a minimum of 100 percent of its <br />standard Proctor maximum dry density. <br /> <br />R-Value R-Value testing was beyond the scope of this project. The near-surface soils <br />encountered in the soil borings consisted predominantly of poorly graded sand and poorly <br />graded sand with silt corresponding to the ASTM Classifications of SP and SP-SM. It is our <br />opinion an assumed R-Value of 50 can be used for pavement design.