GTA provided geotechnical design and construction observation and testing for landslides associated with a 42-mile-long natural gas pipeline in Pennsylvania and West Virginia. The pipeline traversed very steep topography located in landslide-prone geology. The pipeline, which was designed and constructed by others, experienced many severe landslides. There were 20 slides occurring at 12 different locations. GTA was retained by the owner/operator to provide geotechnical consulting services for the landslides.
The initial phase of geotechnical services consisted of field visits, obtaining field information relating to the landslides and surface/subsurface drainage, evaluating the contributing factors of the landslides, and performing preliminary laboratory soils testing. GTA then further evaluated the subsurface conditions and drainage conditions using test pits. GTA developed landslide repair plans for each slide, which included plans, cross-sections, details and specifications. The repairs consisted of geogrid reinforced slopes, surface drainage systems, subsurface drainage systems, groundwater trench cutoff drains, and benching configurations. GTA also participated in pre-bid meetings, answered contractor questions, compiled construction quantities, and reviewed bids with the owner. Construction observation and testing consisted of evaluating excavation depths, drain placement, pipe and aggregate backfill for drains, and compaction of soil backfill.