An Optimized Approach For Managing Overhead Transmission Line Foundation Design and Construction Risk-Video

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The presentation evaluates three geotechnical investigation approaches for a 20-mile transmission line near Phoenix: an optimized, geology-based program with enhanced construction inspections; boring at every structure; and industry-standard sampling at selected structure types. The project included 161 drilled-shaft foundations and faced a 23-week construction schedule.<br /><br />The optimized approach used existing geotechnical reports, geological mapping, site reconnaissance, and strategically located borings to define four design zones and 22 soil profiles. During construction, qualified inspectors documented soil conditions, foundation geometry, reinforcement, and concrete placement, enabling rapid design adjustments when conditions differed from expectations.<br /><br />Post-construction comparisons showed the optimized method predicted minimum foundation capacity accurately at about 85% of locations, with field changes needed at only 2.5%. Its total installed cost was approximately $7.8 million—comparable to boring every structure—while the less intensive approach increased concrete quantities and could raise overall costs. The presenters emphasized that enhanced inspection provides reliable as-built information and can improve foundation performance without sacrificing schedule or quality.

Keywords

geotechnical investigation

transmission line foundations

optimized inspection

soil profiles

drilled-shaft foundations

construction schedule