Sylva, NC – BLE performed a preliminary geotechnical exploration for the proposed Oaks Hall addition at Southwestern Community College in Sylva, North Carolina to evaluate subsurface and groundwater conditions and to provide preliminary foundation, slab, earthwork, and site‑grading recommendations. Our team advanced soil borings across the proposed addition area, logged subsurface conditions, and collected samples for laboratory testing.
Subsurface conditions consisted of a variable cover of fill (generally a few to several feet thick) over residual Blue Ridge soils—predominantly silty sand with gravel and occasional mica—grading into partially weathered rock and isolated rock lenses at greater depth. Auger refusal was encountered at one location and was interpreted as shallow rock. Groundwater was not observed during drilling but was expected to fluctuate seasonally and with nearby drainage features.
Based on the site conditions and the anticipated building loads, the team concluded that shallow spread footings were feasible provided column loads did not exceed about 200 kips and bearing soils were remediated where loose or unsuitable. Remediation methods included undercut-and‑replace with compacted engineered fill or crushed stone. If column loads exceeded the threshold, it was recommended that ground‑improvement using aggregate pier systems to control settlements and achieve the required bearing capacity. BLE also recommended maintaining a minimum setback from the adjacent slope and verifying foundation loads as design progressed.
BLE provided standard construction‑oriented recommendations to improve subgrade performance: remove deleterious materials, proofroll and undercut soft areas, place engineered fill in controlled lifts to specified compaction and moisture limits, protect subgrades during construction, and maintain positive drainage. Slabs were to be supported on a compacted aggregate base and considered for a vapor barrier where needed. We classified the site for seismic design as Site Class D. Additionally, our team recommended that BLE review the final foundation and earthwork plans and provide construction monitoring and quality control (proofrolling observations, density testing, and inspection of footing-bearing soils) to verify that the geotechnical recommendations were implemented.