Geotechnical Engineering Report 12 10 2024 submission

Mavis Store #2296 December 10, 2024 ECS Project No. 44:2100 Page 11 5.0 SITE CONSTRUCTION RECOMMENDATIONS 5.1 SUBGRADE PREPARATION 5.1.1 Demolition Prior to general earthwork and construction, demolition and off-site disposal any remaining below-grade foundation elements from past site development within the construction footprint is required. Existing below-grade foundation elements must be removed to a depth of at least 3 feet below the proposed subgrade elevation for the new construction, and in their entirety where they conflict with planned foundations and slabs. Hoe-rams or specialized demolition equipment may be required to dislodge and remove such buried obstructions. Existing utilities should be removed from, and relocated around, new structures. Excavations associated with removal of these items extending below the level of proposed subgrade should be backfilled with Structural Fill as specified herein. Demolition debris must be disposed of off-site in accordance with local, State, and Federal regulations. 5.1.2 Stripping and Grubbing Subgrade preparation should consist of removing all vegetation, trees, stumps, roots, topsoil, existing fill, pavements, debris and any soft or unsuitable materials within the limits of planned construction. Based upon the observations within the completed explorations, removal of topsoil should be anticipated within some areas. Deeper topsoil or organic-rich soils may be present in wet, low-lying, poorly drained areas and densely wooded areas. ECS should be retained to document that topsoil and other unsuitable near- surface materials have been stripped prior to excavation to construct subgrade elevations, placement of Structural Fill, and construction of new earthworks and structures. 5.1.3 Proofrolling Prior to subgrade compaction, fill placement or other construction on subgrades, the subgrades should be evaluated by ECS. Unless otherwise recommended herein, the exposed subgrade should be thoroughly proofrolled with construction equipment having a minimum axle load of 10 tons (e.g., fully loaded tandem-axle, on-road dump truck) travelling at a maximum of 1.5 feet per second (approximately 1 mile per hour). Proofrolling should be

ipment having a minimum axle load of 10 tons (e.g., fully loaded tandem-axle, on-road dump truck) travelling at a maximum of 1.5 feet per second (approximately 1 mile per hour). Proofrolling should be traversed in two perpendicular directions with overlapping passes of the vehicle under the observation of ECS. This procedure is intended to assist in identifying any localized yielding materials. Where proofrolling identifies areas that are unstable or “pumping” subgrade or has experienced permanent deformation more than 1/2-inch, those areas should be remediated prior to the subsequent compaction and placement of engineered fill or other construction materials. Remediate by undercutting and replacing the unstable/unsuitable soils in these area with compacted Structural Fill as described herein. Test pits may be excavated to explore the shallow subsurface materials to help in determining the cause of potentially unstable materials and delineate the extent of undercutting needed. 5.1.4 Potential Undercuts Where observed or otherwise identified (e.g., proofrolling, subsurface exploration logs, dynamic cone penetrometer testing), unsuitable soils must be undercut and removed. It is important to have ECS observe, probe, and test subgrade conditions prior to placing foundation concrete to document the bearing soils are what was anticipated and the extent of undercutting necessary, if any. Undercuts should be backfilled with Structural Fill up to the original design subgrade elevation required. Open-graded gravel (e.g., AASHTO No. 57) should not be used to backfill foundation undercuts as this