J04 RB Geotech Report from 300 feet away.pdf

This is a Site Exploration and Geotechnical Engineering Report prepared by Twin Rivers Testing & Environmental, LLC for a proposed Tracker Mounted Array solar panel installation at the Indian Health Services (IHS) Hospital in Rosebud, South Dakota. The report documents subsurface conditions at the project site to support helical pile foundation design.

The exploration included two soil test borings drilled to 15 feet below ground surface on August 27, 2014. Subsurface materials identified include Sandy Lean Clay (CL), Clayey Sand (SC), and Poorly Graded Sand with Clay (SP-SC). Laboratory testing performed included natural water content, unconfined compression, No. 200 sieve wash, and Atterberg limits analyses. Key geotechnical recommendations include lateral bearing pressures of 180 PSF for Sandy Lean Clay and 250 PSF for Clayey Sand and Poorly Graded Sand; site preparation with removal of organic and unsuitable materials; structural fill placement in maximum 4-inch loose lifts compacted to 95 percent of standard Proctor maximum dry density; and compliance with OSHA excavation standards for temporary slopes and trenches. No groundwater was encountered during drilling. The 2003 International Building Code Site Class "D" is recommended for seismic design considerations. Comprehensive drainage measures and backfill compaction procedures are specified to prevent water infiltration and settlement issues. The report notes that boring logs should be provided to the helical pile contractor and that changes to project design or location require geotechnical re-evaluation before construction implementation.