To provide a counterbalance to kid0339, the company culture at CH2M HILL varies depending on your location and your job function. I will speak about my own experience as a member of the engineering/scientific consulting staff. I've worked for the firm in several offices over my more than two decades with CH2M HILL.
Probably the principal thing you'll notice when you start working here is the focus on safety. It's a huge focus of management and it is drilled into every employee over and over. While some may cynically dismiss that as management just wanting to avoid costly claims (and I'm sure that's part of it), I am convinced these guys (and women) truly care about the well-being of our employees. It's too pervasive to fake.
You have to take a certification quiz annually on business conduct/ethics. The firm has been burned by unethical rogue employees in the past and is taking steps to reduce that risk.
As for dress and camaraderie, that varies substantially by location and by work group. Friday evening meetings at a local bar and lunches out together are certainly quite common where I work. Employees often participate in local city leagues as teams and do other activities (such as Habitat for Humanity).
Dress generally is business casual for office workers; field clothes for field staff. You'll occasionally see suit and tie, but that's the exception rather than the rule.