GATEWAY VALLEY 90/10 PLAN

ENVIRONMENTAL IMPACT REPORT

ORINDA, CALIFORNIA

J. David Rogers, Ph.D., P.E., R.G., C.E.G.

This project involved a proposed 978 acre mixed use development including housing, commercial development, country club, and luxury hotel in the City of Orinda, California. J. David Rogers prepared the geology, soils, and seismicity sections of the Gateway Valley 90/10 Environmental Impact Report. Of considerable notice were the challenging geologic conditions of the site, including many landslides that would require environmentally sensitive mitigation prior to development of the site, and the extensive public interest involved with the planning process.

J. David Rogers' services included literature search of pertinent published geologic reports and maps of the area, peer review, detailed site mapping, geologic interpretation of stereo pair aerial photographs of the property, stereonet analysis, and engineering and geologic analysis of the provided field and laboratory data. The purpose of our studies was to provide geotechnical recommendations and documentation for the DEIR and FEIR, response to extensive DEIR comments, and public presentation/speaking at City meetings.

The landslide features mantling Gateway Valley tended to be large dormant bedock
landslides overlain by geologically-youthful surficial failures, as sketched here. This situation
is typical of the entire Lamorinda area, where the deeper-seated bedrock slides were
not typically recognized prior to the late 1980s. Such features were extensively
explored during the Gateway Valley investigations in the 1990s using large
diamater bucket auger borings. A new fault strand was also mapped
through the project area.