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DRAFT To limit the risk of subgrade disturbance, all site stripping and excavation to finished grades should be completed using track-mounted hydraulic excavators equipped with smooth-edged buckets. The use of bulldozers equipped with smooth-edged blades may be appropriate in areas of gravel and cobbles subgrade. Following stripping or excavation to subgrade elevations, the exposed materials should be evaluated by a GRI representative, which may include proof rolling with a loaded dump truck or similar heavy equipment. Any areas of soft, loose, or otherwise unsuitable material disclosed by the evaluation should be overexcavated to firm material and backfilled with structural fill. In areas of gravel and cobble subgrade, the subgrade should be compacted after stripping or excavation following recommendations provided by a GRI representative based on observed conditions during construction, and as discussed in the following sections. 5.2.2 Wet-Weather Construction In our opinion, earthwork for the project can be completed most economically during the dry summer months, typically extending from mid-June to mid-October. It should be understood that the silty fill soils that mantle portions of the site and, to a lesser extent, potential zones of the underlying gravel and cobbles with higher silt content, are moisture sensitive and easily disturbed by construction activities when wet. Furthermore, groundwater is present at relatively shallow depths at the site and may approach the ground surface during the wet winter and spring months or following periods of prolonged or intense precipitation. Therefore, if construction occurs during wet-weather or wet-ground conditions, granular work pads and haul roads may be required to protect areas of silty subgrade soils and provide a firm working surface for construction activities. In our opinion, a 12- to 18-inch-thick layer of granular fill should be sufficient to reduce subgrade disturbance caused by lighter construction equipment and limited dump truck traffic. Haul roads and other high-density traffic areas will typically require a minimum-18- to 24-inch-thick layer of granular fill to reduce the risk of subgrade deterioration. Relatively clean, fragmental rock or gravel up to about 4 inches in size is commonly used for this purpose and can be capped with a layer of more finely graded crushed rock. The use of a geotextile fabric over the subgrade may reduce the risk of disturbance and maintenance needs during construction. Our experience indicates the gravel and cobbles at the site will generally provide a suitable all-weather working surface for construction activities, particularly when capped with a layer of compacted crushed rock. 5.2.3 Site Grading Preliminary grading plans for this project are still be developed; however, we anticipate minor site grading will be required to achieve desired grades. In our opinion, any permanent cut and fill slopes should be not steeper than 2H:1 V (Horizontal to Vertical) GRI #6497-A - 2.MO Indoor Football Practice Facility Page 8 August 26, 2021