This paper describes the results, and benefits, of a collaborative effort between computer scientists and applications researchers to construct an integrated modeling environment for environmental pollution modeling and control. The Geographical Environmental Modeling System (GEMS) was designed to enable a wide user community to gain access to advanced environmental modeling capabilities. Some of the system features include: distributed computing over high speed networks, geographically encoded object oriented data bases, extensible graphical user interfaces and interactive analysis capabilities. A unique feature of the project was the use of rapid prototyping to enhance the system definition by exposing applications researchers to the capabilities of modern software engineering.