SLIDE-PRONE COUNTY FINDS NO EASY SOLUTIONS

CONTRA COSTA COUNTY IN CALIFORNIA HAS ITS SHARE OF LANDSLIDES AND SLIPOUTS AND MAJOR BUDGETING FOR THEIR REPAIR OR PREVENTION PROGRAM. MOST OF THESE EARTH MOVEMENTS HAPPEN IN THE WESTERN EDGE OF THE COUNTY WHERE THE UNDERLYING WEAK SHALES AND SANDSTONES HAVE BEEN DEFORMED MORE THAN ONCE OBSCURING SIGNS OF ANCIENT MOVEMENTS. GEOLOGY NOT WITHSTANDING, NEW ROADS MUST BE BUILT AND OLD ROADS MUST BE WIDENED TO MEET THE NEEDS OF THE AREA'S INCREASING POPULATION. CORRECTIVE AND PREVENTIVE MEASURES ARE TAILORED TO EACH SITE AND INCLUDE A VARIETY OF OPTIONS INCLUDING HORIZONTAL DRAINS, DRAINAGE GALLERIES, FILTER BLANKETS, PERFORATED UNDERDRAIN SYSTEMS, REMOVAL OF UNSTABLE MATERIAL FOLLOWED BY CHEMICAL STABILIZATION OF THE SAME MATERIAL AND SUBSEQUENT PACING OF STABILIZED MATERIAL BACK IN THE SAME HOLE, AND WALLS OF VARIOUS TYPES AND SIZES. SIESMIC EXPLORATION IN THE AREA IS HELPFUL TO IDENTIFY FAULT ZONES AND OTHER HIDDEN CHANGES IN SOIL MASS. THE ESTIMATED COST OF PREVENTIVVE ACTION IS NOT LESS THAN $800,000 WITH NO GUARANTEE, FOR A SINGLE PROJECT.

  • Publication Date: 1972-5

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Filing Info

  • Accession Number: 00236375
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jul 17 1972 12:00AM