This is Volume I of a two volume set and the first of a series of interim reports which will be published under the Evaluation Framework Work Unit of the Evaluation of Environmental Investments Research Program. Volume I documents, from 10 case studies, an initial effort to identify the important planning issues presently being faced by Corps planners. This effort was conducted from March through November of 1994 by conducting a focus session with Washington level reviewers and by conducting a large number of interviews with Corps and non-Corps study team members. A comparative analysis identifies the important themes that emerged from this effort. Recommendations and future needs are also discussed in this Volume. (MM).