The April 1996 Rockland Landslide

General Summary

The April 16, 1996 landslide in Rockland, Maine, was a catastrophic event. Fortunately, there was no loss of life, but two homes were completely destroyed, and along with the total emergency operations, damage, and reparations, the cost had reached approximately $710,000 by the fall of 1996, and will most likely exceed that when all work is completed. Similar events have occurred before, both in Rockland and elsewhere in Maine, but not very often. A number of factors contributed to the slide including but not necessarily limited to a high, steep-sloped bluff, a thick section of poorly-drained clay, and a high water table.

The general geologic environment of the April 1996 landslide is present in places other than Rockland. Hence, at some time in the future, similar landslides will occur in Maine. Depending on the specific locality, the results could be as severe, more severe, or less severe than the April 1996 Rockland event. Exact prediction of these types of events is not possible.

Common sense and knowledge of general geologic conditions are useful in evaluating the general suitability of a construction site, but it is strongly advised that an engineering firm assess a "factor of safety" with respect to landslides for existing or planned individual sites in Maine.

Acknowledgments

The authors wish to express their thanks to the following individuals for their participation in the work of preparing this report: Robert Tucker and John Poisson of the Maine Geological Survey for their assistance with preparing the text and figures (all photography in the report is by John Poisson except where otherwise noted); Mike Foley and Craig Neil of the Maine Geological Survey provided seismic line data collection and reduction; Robert Estes of RGGI hand-augered borings and measured downhole vane shear strengths at the head of the landslide scarp. RGGI thanks Northeast Diamond Drilling for the test borings drilled at the site. Finally, the authors wish to thank the City of Rockland, in particular City Managers Cathy Sleeper and Richard Michaud and Wastewater Treatment Facility Plant Manager Steven MacDonald for supplying town data and information. We especially thank all private landowners for permitting access to their properties and talking with us during this unnerving episode.

Contents Introduction Description Other slides Factors Potential Action Summary References Appendix A Appendix B Appendix C Plate 1

Last updated on October 6, 2005