Frank Groffie, PG, CEG                  Geology consulting                      Clarity, communication, closure.                             Contact us ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
About   Fault investigation   Landslide investigation   Rock-slope analysis   Seismic hazard analysis   Site characterization   General geosupport	Landslide investigation  Landslides come in numerous types and sizes, from a few cubic yards to 0.2 cubic mile. Some are young and  obvious; some are quite ancient and hard to spot. Some are yet to occur: in the future. We’ve dealt with the  whole range. Issues include whether you should rebuild the ground, build a structural fix, avoid the landslide,  divert it, monitor it, or build catchment facilities to protect downslope improvements. These issues require  delicate evaluation. Mitigations sometimes involving high potential costs. Some examples of our work are  shown below.
	Debris flow prediction  ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯  This small valley lies northeast of San Francisco. The valley  floor has been proposed as the site of numerous residential  units, recreation, and open space. Landsliding and shallow  groundwater were among the issues we investigated.  Although there were no surface signs of debris-flow  deposits, Frank Groffie felt debris flows were another  important issue and initiated a program of analysis. Groffie1  analyzed 25 hillside channels and slopes where potential  debris flows might impact the future valley-floor develop-  ment. He used geologic evidence of ancient debris flows  seen in test pits, laboratory testing, geomorphology, and  published literature to discriminate between zones with and  without debris-flow potential. He recommended deflection  berms/walls and other minor development modifications at 3 locations where he predicted future debris flows.  The following December (2005), storms dropped 16.7 inches of rain at the  closest measurement station. That local 1-month rainfall amount was the  largest recorded since 1950, when local recordkeeping began. When the  skies cleared, Groffie visited the site and saw that his debris-flow predic-  tions were 100% accurate: At the exact 3 locations where debris flows  were predicted, minor debris flows occurred. And at all 22 locations (and  everywhere else) where he predicted they would not occur, none did.
	Large-scale landslide investigation  ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯  Landslide hazard evaluation can include documenting whether or not an existing landslide is present. At one  site we investigated, some geologists, published and otherwise, perceived large-scale landsliding on the site.  Others, including Groffie,1 did not. We based our conclusion (correct) on findings from deep drilled cores, test  pits, other techniques, and intense application of advanced geologic analysis. Investigation also included a  special technique called downhole logging, in which we geologists descend into a vertical drillhole about 110  feet below ground.  Landslide investigation can also include understanding the landslide deposits that are already, obviously pre-  sent, even when they initially flowed 35,000 years ago and may be hard for some to spot. We have used  trenches and aerial photos to carefully delineate the head margins and toe margins of such landslides. Trenches  have allowed us to directly expose their actual margins and locate them with accuracy. On one large site, drill  cores penetrated the landslide bases at depths of some 200 feet, and showed zones where a jumble of landslide  material flowed over an undisturbed buried ground surface complete with plant fragments and soil. Groffie also  directed instrumentation (inclinometers and piezometers) and age dating of landslide deposits.    2
	1. As employee of Berlogar Geotechnical Consultants, client legal relationship with that firm. Relevant technical documents on file      as public record with applicable public agencies.  2. Image on the right is of the 2005 La Conchita landslide, by U.S. Geological Survey, http://landslides.usgs.gov/.
Frank Groffie, PG, CEG, MSc, is Professional Geologist 4930 and Certified Engineering Geologist 1539, in good standing since initiation in 1989, with the State of California Board of Professional Engineers, Land Surveyors, and Geologists Web page last modified October 27, 2012.