Associate Professor, Civil and Environmental Engineering, University of Houston, Aug. 2001 - present.

Assistant Professor, Civil and Environmental Engineering, University of Houston, Sept. 1997 - Aug. 2001.

Adjunct Assistant Professor, Environmental Science and Engineering, Rice University, Sept. 1997 - Aug. 1999.

Executive Director, Energy and Environmental Systems Institute, Rice University, Houston, TX, April 1994 - Aug. 1997.

Faculty Fellow, Department of Environmental Science and Engineering, Rice University, Houston, TX, July 1994 - Aug. 1997.

Research Associate, Rice University, Houston, TX, May 1989 - March 1994.

Doctoral Graduate Student, Rice University, Houston, TX, Aug. 1986 - May 1989.

Senior Design Engineer, Edminster, Hinshaw, Russ &  Associates, Houston, TX, April 1985 - August 1986.
    Consultant, Houston, TX, November 1984 - March 1985.

Masters Graduate Student, Rice University, Houston, TX, Aug. 1983 - Oct.1984.

Research Assistant, Oklahoma State U., Stillwater, OK, Spring and Summer 1983.

Trainee Engineer, Midmac Engineering Co., Houston, TX, Summer 1980.