Pros
Field and office work balance. Field work is usually cancelled when weather is bad- you are not forced to be outside. Lots of different projects to work on means that you get a lot of experience, which is good if you are getting started in environmental science.
Cons
Doesn't help the community as much as they like to advertise. It is a business focused on profit, so if you are looking for a job that makes you feel like you are making a difference in people's lives or really helping the environment, this is probably not the job for you. Disclaimer: this might not be the case for all Tetra Tech offices/locations. The Chantilly, VA office works a lot with the DC government, so they are focused on collecting data to show government officials what work needs done. Very little is accomplished in terms of actual change that benefits the community. There is also a huge lack of diversity, which is especially shocking because DC and the surrounding area is a very diverse place.