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Geotechnical Report 2018 PMP Streets Arden Hills, Minnesota WSB Project No. 010111-000 Page 7 Based on traffic ADT of 500 vehicles, we calculated the roadway traffic to be equivalent to approximately 83,000 Estimated Single Axle Loads (ESAL’s) for flexible pavement design. Based on MnDOT’s Flex Pave Excel spreadsheet design utilizing granular equivalent charts, the granular equivalent of the pavement section should be between 16 and 17. We recommend the pavement section included in Table 3 below, which provides a granular equivalent of 17. Table 3: Recommended Flexible Pavement Section Section Thickness (inches) Bituminous Wear Course, MnDOT 2360 2 Bituminous Base Course, MnDOT 2360 2 MnDOT Class 5 Aggregate Base 8 As previously mentioned the use of a non-frost susceptible sand cushion will help reduce the effects of frost heave. In our opinion, a 30-inch thick non-frost susceptible pavement section typically provides adequate reduction in frost heave potential. This would include placement of about 20 inches of sand below the aggregate base to meet this recommendation. It should be noted that any sand cushion placed below the pavement section would provide positive benefits and reduced potential frost heave. Drainage of the sand cushion via drain tile will be necessary. Drain tile wrapped in a sock should be placed at the base of the sand cushion and tied into catch basins. We recommend the sand cushion contain less than ten percent (10%) passing the #200 sieve. Within several years after initial paving, some thermal shrinkage cracks will develop. W e recommend routine maintenance be performed to improve pavement performance and increase pavement life. Pavement should be sealed with a liquid bitumen sealer to retard water intrusion into the base course and subgrade. Localized patch failures may also develop where trucks or buses turn on the pavement. When these occur, they should be cut out and patch repaired. Periodic seal coating should also be applied, to preserve the longevity of the pavement. The pavement sections above provide options to meet the ESAL requirements. Other pavement design options would be acceptable as well as long as they meet the minimum requirements for bituminous thickness, aggregate base thickness, and can meet the ESAL requirements. 4.3 Utilities Invert elevations are anticipated to be within thirteen feet (13’) of existing grades and we anticipate the subgrade soils for the utilities will consist chiefly of lean clay, silty sand, clayey sand, and sands with silt. Underground utilities are expected to be installed by backhoes completing the excavations and pla cing fills. Soil compactors should be used to compact the fill in even lifts to the specified densities. Where organic clays or peat is present below the utility pipe, there is a risk of high total or differential settlement. We would recommend any of the following methods to reduce settlement below the utility pipe, 1. Remove the organic clays or peat to mineral soils. This would likely require excavation of 8 to 10 feet of organics / peat, and a 1.5:1 oversize below the pipe. 2. Install helical piers to support the utility pipe. We recommend contacting a helical pier contractor to obtain design and cost options. 3. Subcut the organics/peat a minimum of 3 - 4 feet and replacement with lightweight aggregate. The recommendations above would help to reduce settlement. Other options at this site may include using flexible jointed utility pipe, and installing geogrid below the pavement section to reduce the potential