As part of our Open End Agreement, E02802, with Gannett Fleming (GF), Navarro & Wright Consulting Engineers, Inc. (N&W) utilized our in-house drilling capabilities to help PennDOT District 9-0 investigate this active slide area. The work was accelerated to avoid severe inclement weather predicted for the later part of the work week. The work was facilitated by PennDOT D9-0 forces who provided MPT services for the roadway borings.
The project included eight (8) original borings and two (2) supplemental borings. The supplemental borings were added at the request of the D9-0 Assistant District Geotechnical Engineer (ADGE) to provide increased insight into the cause of the active slide. We mobilized our truck-mounted rig to efficiently complete borings located within the roadway footprint at the crest of the slide and our track-mounted rig to perform the borings located within the slope of the slide. Mobilizing to the slope borings was more difficult because no access roads could be graded into the slope due to the risk of triggering a more damaging landslide.
Three hundred and six (306) feet of borings were drilled and grouted in just three (3) days. Our drill crew received high marks from the PennDOT’s ADGE for their quick fulfillment of the originally scoped borings and willingness to complete additional borings within a short timeframe. The soils encountered in the borings was mostly fill in the roadway borings and lean clay in the slope borings. An undisturbed Shelby tube sample was obtained with in the clay soils for future laboratory testing. The bedrock encountered was highly variable with much inter-bedding of the predominantly siltstone and sandstone. Thin layers of claystone were also noted in some of the borings which may represent a potential failure plane. One boring was not grouted to allow for more long-term groundwater measurements.