You really have to know a little bit about everything. The more areas you know, the better you chances of landing a job. Education generally includes a four-year degree program in Environmental Science perhaps with a minor in a science of your choice. More often you will find candidates with degrees in chemistry or geology who have taken additional courses or a two-year degree in environmental science. Some positions require engineering degrees.
All positions require good math skills.
The course of study should include classes that deal with ecology, environmental law, occupational safety, sampling procedures and math, particularly college algebra and statistis. It all adds up. When applying for a job as an Environmental Technician It is very important to understand the focus of the company that you are applying to. If that company does gorundwater monitoring, then your resume and cover letter should reflect some qualification and interest in that particular position. Often this can be gleaned right from the yellow pages.