Elm Street Rockslide Repairs Montpelier City Council Meeting

Elm Street Rockslide Repairs Montpelier City Council Meeting February 22, 2006

Rockslides Happen

THE PROBLEM: Ø Toppling of steeply dipping rock strata Ø Sliding of toppled strata on lower slope

Historic Slide Area Ø Slide scarp (light gray) at right crest, debris at toe of slope. Ø Lower chevron toppled debris set in motion

Historic Slide Area

Slide Mechanisms Ø Flexural Toppling at Crest Ø Lower chevron toppled debris set in motion

Slide Mechanisms Ø Flexural Toppling at Crest Ø Lower chevron toppled debris set in motion

Proposed Repairs Ø Stabilize Flexural Toppling at Crest with Un-tensioned Rock Bolts called Rock Dowels; Ø Scale slide debris and chevron toppled debris on the lower slope that could provide a source of future slide debris; Ø Stabilize and repair Cliff Street slide scarp with a rock nail retaining wall; Ø Stabilize adjacent steep soil slopes with a Tecco® soil retention system; and Ø Reduce the potential for further toppling with spot rock dowels, scaling, tree removal, dental shotcrete.

Project Progress Ø Temporary Rockfall Protection Measures

Project Progress Ø Stabilization of Cliff Street Slide Scarp Ø Drainage Installation and Shotcrete Facing

Project Progress Ø Utilities Relocation Ø Shotcrete Application Ø Monitoring of Loose Rocks

Project Progress Ø Layout, Anchor installation and Setup of Rockfall Catch Fence

Project Progress Ø Rock Nail Installation

Project Progress Ø Water Main Relocated

Project Progress Ø A Large Boulder…. .

Project Progress Ø Highwall Scaling and preparation of foundation area for new retaining wall.

Project Progress Ø Cliff Street Reopened February 14 th.

Project Progress Ø First layer of shotcrete and rock nails installed, Ø Scaling progressing downslope

What’s Next? Ø Completion of the retaining wall Ø Rock Bolting of the Highwall Ø Drain hole drilling

What’s Next? Ø Stabilization of soil slope transitions - Tecco Ø Final Scaling Ø Installation of Concrete Barrier and paving on Cliff Street.

Acknowledgements Special Thanks to Montpelier and State Folks Ø Tom Mc. Ardle – DPW Ø Police Chief Doug Hoyt, Department and Fire Department Ø Mayor Mary Hooper & City Manager William Fraser Ø VTrans – Tom Eliassen, Chris Benda, Bill Mc. Manus Ø Vermont Geological Survey – Larry Becker and Jon Kim Ø Vermont Survey and Engineering Ø Dubois Construction