After years of disbelief at the resistance of engineers to implement "green" strategies, I can finally answer the question of why - FEAR. I came to this realization when I was examining some of my own reservations. Despite the fact that I am enthusiastic about sustainability and green design, and have a passion for finding a better way to engineer green, I still have a reservations about implementing green strategies on some projects. I believe that this is the underlying reason for all engineers, and from my own experience as a civil engineer I have come to understand this to be true for others that I come into contact with.
It's FEAR of the UNKNOWN and FEAR of FAILURE, that drives us to stick with the warm and fuzzy feelings of doing it the same way it has been done for years. The bottom line is that many green techniques, especially those that are civil engineering related, such as raingardens, bioswales, bioretention, etc are relatively untested. And the areas where they have been tested, Prince George's County Maryland, Portland, Seattle and so on don't always have conditions that translate well to other parts of the country. This lack of familiarity and basis for comparison makes it somewhat more risky to design and spec these green techniques. Without a really solid set of design guidelines, engineers are forced to do some of their own research, make their own judgments and think outside the box. And while I admit this can be unsettling at times, its one of the reasons that I got into engineering in the first place - to figure things out and find a better way. I have been feeling my way through it for a number of years and there have been plenty of times where my designs have not turned out quite like I expected. There have been a different reasons for that; the contractor didn't install it correctly, it wasn't maintained correctly, I made assumptions that were incorrect, etc. but I have learned from all of them, and I think that's the key. For the most part the "green" techniques available to engineers don't involve anything truly new, they are just different applications of the knowledge set that we already have. In my opinion, this is engineering in it's purest form - taking knowledge and fact and applying it in a practical way to solve a problem.
I can acknowledge that I sometimes feel some apprehension when implementing a design strategy that hasn't been successfully implemented in my area before, but we can't simply stick to the status quo because of that FEAR. It's time that we as engineers work to find a better way, rather than just going with the flow and designing like we have for the past 50 years. To do that we need to come together with our colleagues to vet innovative and practical designs and we need to support those within and outside our own professions to have the confidence and creativity that we need to solve the problems of our typical development process.