CLEAN SOILS ENVIRONMENTAL, LTD. (CSE) was founded in 1989 by Denise M. Prosser. Ms. Prosser was then attending New Hampshire College to obtain her MBA. Her final project entailed researching new business horizons to develop a family business. The environmental consulting field was approximately 5 years old in 1989 with lots of growth potential. With this in mind, Ms. Prosser accepted the challenge and CSE was organized and incorporated. Ms. Prosser teamed up with Mr. William H. Mitchell, Jr., who had previous environmental engineering experience. Mr. Mitchell is now the president of CSE, with Ms. Prosser as the Business Manager and Chief Financial Officer.

In 1993, the Massachusetts Department of Environmental Protection (DEP) restructured their oil and hazardous waste cleanup program.  In an effort to reduce government oversight and speed up the remediation of contaminated sites, DEP partially privatized the cleanup program by developing the Licensed Site Professional (LSP) program.  The LSP program has streamlined the cleanup process by allowing Licensed Site Professionals (LSPs) to conduct assessments and oversee cleanups at contaminated sites while minimizing delays associated with DEP.   Mr. Mitchell was among the first in the country to obtain a full LSP designation from the Massachusetts Board of Hazardous Waste Site Cleanup Professionals.

Since 1993, CSE has successfully completed hundreds of projects and has serviced a large and diverse client base.