Agenda - Council - 09/14/2021 - Laserfiche WebLink

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4.9 Utilities We anticipate that new utilities will be installed as part of this project. We further anticipate that new utilities will bear at depths ranging from about 7 to 10 feet below the ground surface. At these depths, we anticipate that the pipes will bear on native alluvial soils or compacted engineered fill. We recommend removing all vegetation, topsoil and any other unsuitable soil from beneath the utilities prior to placement. We recommend bedding material be thoroughly compacted around the pipes. We recommend trench backfill above the pipes be compacted to a minimum of 95 percent beneath slabs and pavements, the exception being within 3 feet of the proposed pavement subgrade, where 100 percent of standard Proctor density is required. In landscaped areas, we recommend a minimum compaction of 90 percent. Groundwater was encountered in the soil borings at depths of about 71/2 to 19 1/2 feet below the ground surface. Groundwater could be encountered during utility construction and dewatering could be required. See section 4.4 for dewatering considerations. 4.10 Bituminous Pavement Recommendations General The City may have standard plates that dictate pavement design. We recommend that the bituminous pavements be designed and constructed in accordance with the City standard plates. The following paragraphs provide general pavement recommendations in the absence of City standard plates. We were not provided any information regarding traffic volumes, such as Average Annual Daily Traffic (AADT) or vehicle distribution. We anticipate the streets will be used predominantly by automobiles, light trucks, school busses, garbage trucks and delivery vans (FEDEX, UPS etc.). Based on the anticipated number of homes in the development and assumed traffic types we estimate the roadways will be subjected to Equivalent Single Axle Loads (ESAL's) ranging from about 50,000 to 75,000 over a 20-year design life. This does not account for any future growth. Subgrade Preparation We recommend removing all vegetation, topsoil, and any soft or otherwise unsuitable soils from below the pavement and oversize areas. Prior to placing the aggregate base (Class 5) we recommend compacting the subgrade and/or performing compaction tests and/or Dynamic Cone Penetrometer (DCP) tests to identify soft, weak, loose, or unstable areas that may require additional subcuts. Backfill to attain pavement subgrade elevation can consist of any mineral soil provided it is free of organic material or other deleterious materials. Granular fill classified as SP or SP-SM should be placed within 65 percent to 105 percent of its optimum moisture content as determined by the standard Proctor. Remaining fill soils should be placed within 3 percentage points above and 1 percentage point below its optimum moisture content as determined by the standard Proctor. All fill should be placed in thin lifts and be compacted to a minimum of 95 percent of its standard Proctor maximum dry density with a large self-propelled vibratory compactor operating in vibratory mode. The upper 3 feet of fill and backfill should be compacted to a minimum of 100 percent of its standard Proctor maximum dry density. 11