Pros
Tetra Tech is an average company to work for. When there are projects to work on, it is an OK place to work and everyone is happy. However, at times, you struggle to stay billable, especially now that government is cutting funds on projects. Job security has not been great for the past 2-3 years. People are laid-back and there are a lot of people with diverse knowledge within the company. Hours are flexible and there is no dress code.
Cons
High overhead costs. Tetra Tech has hundreds, if not not thousand of offices, with 5-6 people working in it. It has also too many senior management and project managers who don't do anything. Quality of work is average, because most of the money is burned in the beginning of the project without actually producing anything valuable. Senior management has no vision on how to grow the company with its current resources. Tetra Tech buys a lot of smaller companies to grow and cook its financial books. If you don't have a project to work on, most likely they will not fire you, but they will tell you to take time off. Hence, you might still be a full-time employee, but not get paid. Needless to say, you are useful as long as you help them make money.