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City of Arden Hills Project B2502087 June 13, 2025 Page 10 C.1.d. Reuse of On-Site Soils Based on the completed laboratory testing program, the existing non-organic soils (both the naturally deposited soils and fill soils) on-site are generally considered suitable for reuse as engineered fill soil following moisture conditioning and compaction as outlined in this report. If encountered, organic fill soils are not considered suitable for reuse as engineered fill. Any materials to be used as engineered fill should be tested and approved by the engineer prior to placement. C.1.e. Groundwater Water was not encountered in any of the borings completed for this project. Groundwater may fluctuate in response to both seasonal and annual rainfall events. Surface runoff can collect in open excavation if left open during wet weather. If encountered, the water should be removed from excavations during construction and prior to placement of any utility structures. C.1.f. Construction Disturbance The existing soils encountered on-site, including clay-based soils, are highly susceptible to loss of strength when subjected to additional moisture or disturbance. The contractor should take precautions to limit the disturbance of these soils to the extent practical within the utility trench excavations. If disturbed, there is the potential that an additional subcut of these soils to depths of 2 to 3 feet may be necessary to re-establish a stable base for placement of engineered fill. In addition, a layer of stabilizing aggregate may be necessary to provide a stable working surface for construction. C.2. Site Grading and Subgrade Preparation We understand that as part of the 2026 pavement management project, there may be spot utility repairs in areas where FDR is to occur. The following sections under Section C.2 provide general site grading and subgrade preparation recommendations. C.2.a. Utility Subgrade Stabilization We anticipate the soils at typical invert elevations will be suitable for utility support. However, if construction encounters unfavorable conditions such as soft clay, organic soils or perched water at invert grades, the unsuitable soils may require some additional subcutting and replacement with sand or crushed rock to prepare a proper subgrade for pipe support. Project design and construction should not place utilities within the 1H:1V oversizing of foundations. Where soft/loose or organic soils are encountered below utility inverts, we recommend subcutting a minimum of 1-foot and replacing with crushed rock to help provide a stable working platform.