Dr. Mark Reeves, a Senior Scientist at INTERA from 1978 to 2000, passed away Thursday, March 11, 2010 in Katy, Texas at the age of 72 years. Mark played a key role in INTERA's corporate history. He was an expert mathematical modeler with over 30 years of experience in the ground-water area. From a background of theoretical physics and scientific programming, he moved into the field of environmental modeling in the late 1960s. He focused on waste-management problems in partially saturated, saturated, and multi-phased flow systems, and has written several well-known computer models in these areas. He led and participated in numerous projects with activities relating to high- and low-level nuclear-waste disposal, Class-I hazardous waste disposal, in situ mining, and other subjects. Sites considered include the DOE Oak Ridge Reservation in eastern Tennessee, the WIPP Site in southeastern New Mexico, the Yucca Mountain Site near Las Vegas, Nevada, and approximately one-third of all Class-I hazardous waste-injection plants in the United States. During his career, Mark developed software for mathematical modeling of ground-water systems for the safe burial of nuclear waste. While working at the Computer Sciences Division of Oak Ridge National Laboratory, he jointly with fellow scientists developed the FEMWATER and FEMWASTE, two well-known models which consider contamination problems in partially saturated, near-surface media. At INTERA, Mark led the development of SWIFT-II, a well-known model which considers contamination problems in fully saturated, fractured, and non-isothermal geologic media. Through his participation on the INTERA WIPP Project for Sandia National Laboratories, he joined a fellow scientist Dr. Banda Ramarao, in extending the adjoint-sensitivity code GRASP-II to include automatic calibration of flow fields. These codes served as the foundation for INTERA's waste management services—services that the company has now been providing for over 30 years. Mark was a mentor to many of INTERA's current senior staff and was perhaps best known for his ability to numerically formulate and solve challenging technical problems oftentimes with first-of-its-kind numerical solutions. He authored and coauthored approximately 50 publications, papers and reports on mathematical modeling of ground water systems. Since retiring from INTERA, he taught computer programming and advanced mathematics at several schools in Houston Texas and donated his time to the Texas Prison System where he helped educate and prepare inmates to lead more productive lives. Mark will be greatly missed on both a professional and personal level, and will always be remembered as an integral contributor to INTERA's history and success.