Pros
Very good working culture (teamwork, friendliness, management is very open to support to pursue your interests, considering the size, goals, and vision of the company, there are many leadership opportunities to pursue)
Flat (as opposed to hierarchical)
A wide range of opportunities when it comes to pool of "Environmental Engineering" skill-set. Various offices, each being strong in a certain niche market.
Cons
If you're considering to join the firm, then you need to know the type of projects you're seeking to pursue. Like every other consulting, the business focus is on certain client and certain type of work. Before joining, interview a number of employees to learn more about the projects and opportunities to make sure they match your interest.