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<br />8 <br /> <br />R-Value The underlying subgrade soils were composed of sandy lean clay corresponding to <br />the ASTM classification of CL. Soils meeting the ASTM Classification CL typically have R- <br />Values ranging from 6 to 18. It is our opinion that an R-value of 10 can be used for pavement <br />design. <br /> <br />Pavement Section Based on an estimated R-value of 10 and a maximum of 50,000 ESAL’s we <br />recommend pavement section consisting of a minimum of 3 ½ inches of bituminous (2 inches <br />of wear course and 2 inches of base course) underlain by a minimum of 9 inches of aggregate <br />base. <br /> <br />4.5 Materials <br /> <br />We recommend aggregate base meeting MN/DOT Specification 3138 for Class 5 aggregate <br />base. We recommend the aggregate base be compacted to 100 percent of its maximum <br />standard Proctor dry density or to meet MN/DOT Dynamic Cone Penetration testing <br />specifications. <br /> <br />We recommend that the bituminous wear and base courses meet the requirements of <br />MN/DOT Specification 2360. We suggest using mix type SPNWB330C for the Non-Wear <br />course(s) and mix type SPWEB340C for the Wear course. We recommend the bituminous <br />pavements be compacted to at least 93% of the maximum theoretical density for mix type <br />SPNWB330C and 92% of the maximum theoretical density for mix type SPWEB340C. <br /> <br />The improvements will include concrete curb and gutter repair. We recommend specifying <br />concrete that has a minimum 28-day compressive strength of 4,500 psi. We recommend <br />specifying 5 to 8 percent entrained air for exposed concrete to provide resistance to freeze- <br />thaw deterioration. We recommend slump, air content and compressive strength tests of <br />Portland cement concrete. <br /> <br />4.6 Stormwater Ponds/Infiltration Basins <br /> <br />The project will include constructing a storm water pond/infiltration basin on the project site. <br />We were not provided any information regarding site grades and or pond bottom elevations. <br />Soil borings SB-2 was completed within or near the proposed pond locations and encountered <br />sandy lean clay meeting the ASTM classification CL. It is our opinion that the infiltration <br />rate(s) presented in Table 2, which were obtained from “Minnesota Storm Water Manual”, can <br />be used for stormwater pond design. <br /> <br />Table 2. Infiltration Rates <br />In-situ soils Soil Description Hydrologic Soil <br />Group <br />Design Infiltration <br />Rate (in/hr.) <br />CL Sandy Lean Clay D 0.06 <br /> <br />It should be noted that soil infiltration rates can vary due to; soil moisture content, soil <br />compaction, the placement or introduction of fine-grained soils, topsoil or biofiltration media <br />and changes or variations in local groundwater levels. These variations may result in <br />additional construction costs and it is suggested that a contingency be provided for this <br />purpose. <br /> <br />214