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Brookview Estates Reconstruction <br /> Ramsey, Minnesota <br />NTI Project No. 18.MSP06855.000 <br /> <br />The Contractor should be aware that the silty subgrade soils will be moisture-sensitive, and protecting <br />them from inclement weather will aid in maintaining stability. The stripping of the existing pavement <br />and aggregate base course should occur immediately prior to subgrade preparation and base aggregate <br />installation to minimize weather-induced instability. <br />Prior to installing the aggregate base, the existing subgrade should be scarified and re-compacted to a <br />depth of at least 12 inches. A proof roll test should then be performed to determine soft or unstable <br />subgrade areas. <br />The proof roll should be performed with a tandem axle dump truck loaded to gross capacity (at least 20 <br />tons). Acceptance criteria of the proof roll shall be limited to rut formation no more than one inch <br />depth (front or rear axles) and no pumping (rolling) observed during the visual inspection. Proof roll <br />tests should be observed by an experienced technician or geotechnical engineer prior to placement of <br />the aggregate base course to verify the subgrade will provide adequate pavement support. <br />If rutting or localized unstable subgrade areas are observed, those areas should be subcut, moisture- <br />conditioned, and re-compacted or removed to a stable depth. <br />If imported fill is required in paved areas, it should consist of debris-free, non-organic, mineral soil <br />similar in composition to the subgrade soils encountered in the surrounding areas. If sand is imported <br />into areas that are underlain by relatively impervious fine grained soils, the sand layer must be drained <br />with drain tile in order to prevent frost heave from water trapped within the imported sand layer <br />during freezing temperatures. Individual lifts of engineered fill should be tempered for moisture <br />content, placed, and compacted as <br />in Appendix B of this report. <br />For a 20-year design pavement life, Tables 4 presents our thickness recommendations for flexible <br />(bituminous) pavement. These recommendations were based upon the encountered subgrade <br />conditions, estimated R-value of 30 for the existing subgrade soils, the assumed AADT volumes, and the <br />City of Ramse typical pavement section for the respective project area. <br />1 <br />Table 4: Flexible Pavement Thickness Design <br />Interstate Area Residential Area <br /> <br />Calculated Required <br />2 3 <br />Pavement Section Pavement SectionPavement Section <br />Bituminous Wear Course (inches) <br />2 1.5 <br />Bituminous Base Course (inches) <br />2 2 <br />Class 5 or 7 Aggregate Base (inches) <br />4 4 <br />1.Assumed AADT volume of 600 and an average R-value of 30. <br />2.Assumed a minimum of 12 inches of engineered subgrade. <br />3.The subgrade appeared to be less firm at SB-2 and SB-7 (locations closest to the Rum River). <br />-2 and west of <br />SB-6. <br /> <br />Page 4 of 7 <br /> <br />