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Excavation Activities

LSST E-News : 
August 2015
Lower concrete platforms will support the summit facility building foundation. Image Credit: LSST Project Office

Excavation activities on site are nearing completion, but during excavation, substantial amounts of fractured rock and clay materials were discovered in the area where the support building facilities will be constructed. Removing the surface rock on the slope off the main peak revealed clay deposits that were not identified during the geotechnical surveys completed prior to construction. The general contractor, Besalco, has completed the removal of the fractured rock and clay, and following a detailed inspection by architectural and engineering firm Arcadis, a remedy of concrete fill has been identified and initiated to build up the necessary foundation.  The presence of bedrock lower into the hillside sufficient to support a remedy for the foundation of the summit facility support building has been confirmed and a design developed to replace the missing bedrock with concrete. The issue and remedy applies specifically to the lower sections of the summit facility building; the telescope pier and dome lower enclosure regions were previously confirmed to be located in competent bedrock. LSST, Arcadis, and Besalco worked together to define the solution. Besalco has completed the first phase of the remedy by creating concrete platforms from H10 concrete to use as the foundation support of the building columns. The second phase of the remedy is in progress using additional concrete to build up under the floor slabs and in toward the hillside. The solution will yield a technical performance consistent with the original design but has caused a 6 week delay in the construction. The delay was mitigated by early and preemptive permitting for a concrete batch plant that was not originally planned but is now the preferred and expeditious approach to creating the necessary concrete. Telescope and Site staff are working with their contractors to keep the delay within the existing schedule float so there is no impact on the Project's critical path.


LSST E-News Team

 

Suzanne Jacoby (Editor-in-Chief)
Robert McKercher (Staff Writer)
Mark Newhouse (Design & Production: Web)

Emily Acosta (Design & Production: PDF/Print)
Additional contributors as noted

 

LSST E-News is a free email publication of the Large Synoptic Survey Telescope Project. It is for informational purposes only, and the information is subject to change without notice. 
Copyright © 2015 LSST Project Office, Tucson, AZ

 

  

Financial support for LSST comes from the National Science Foundation (NSF) through Cooperative Agreement No. 1258333, the Department of Energy (DOE) Office of Science under Contract No. DE-AC02-76SF00515, and private funding raised by the LSST Corporation. The NSF-funded LSST Project Office for construction was established as an operating center under management of the Association of Universities for Research in Astronomy (AURA).  The DOE-funded effort to build the LSST camera is managed by the SLAC National Accelerator Laboratory (SLAC). 


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