Elm Street Rockslide Repairs

Montpelier City Council MeetingFebruary 22, 2006

Rockslides Happen

THE PROBLEM:

Toppling of steeply dipping rock strata Sliding of toppled strata on lower slope

Historic Slide Area

Slide scarp (light gray) at right crest, debris at toe of slope.

Lower chevron toppled debris set in motion

Historic Slide Area

Slide Mechanisms

Flexural Toppling at Crest

Lower chevron toppled debris set in motion

Slide Mechanisms

Flexural Toppling at Crest

Lower chevron toppled debris set in motion

Proposed Repairs

Stabilize Flexural Toppling at Crest with Un-tensioned Rock Bolts called Rock Dowels; Scale slide debris and chevron toppled debris on the lower slope that could provide a source of future slide

debris; Stabilize and repair Cliff Street slide scarp with a rock nail retaining wall; Stabilize adjacent steep soil slopes with a Tecco® soil retention system; and Reduce the potential for further toppling with spot rock dowels, scaling, tree removal, dental shotcrete.

Project Progress

Temporary Rockfall Protection Measures

Project Progress

Stabilization of Cliff Street Slide Scarp Drainage Installation and Shotcrete Facing

Project Progress

Utilities Relocation Shotcrete Application Monitoring of Loose Rocks

Project Progress

Layout, Anchor installation and Setup of Rockfall Catch Fence

Project Progress

Rock Nail Installation

Project Progress

Water Main Relocated

Project Progress

A Large Boulder…..

Project Progress

Highwall Scaling and preparation of foundation area for

new retaining wall.

Project Progress

Cliff Street Reopened February 14th.

Project Progress

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

What’s Next?

Completion of the retaining wall Rock Bolting of the Highwall

Drain hole drilling

What’s Next?

Stabilization of soil slope transitions - Tecco Final Scaling

Installation of Concrete Barrier and paving on Cliff Street.

Acknowledgements

Tom McArdle – DPW Police Chief Doug Hoyt, Department and Fire

Department Mayor Mary Hooper & City Manager William Fraser VTrans – Tom Eliassen, Chris Benda, Bill McManus Vermont Geological Survey – Larry Becker and Jon

Kim Vermont Survey and Engineering

Dubois Construction

Special Thanks to Montpelier and State Folks