My biggest challenge is that the approval authorities are not set up to address complex alternatives.  For example, the City of Ottawa just installed 4  LID pilot projects, to test performance.  At one point, 85 people were required to provide input into how the design would be evaluated - maintenance, operations, infrastructure, planning, landscaping, etc.  They have an efficient method for evaluating proposals, and that means specialization.  LIDs require different specialties, but the approval authority doesn't yet know what those are, and doesn't want to fumble.  So, they are very cautious, and will watch the prototypes like a hawk, and eventually have a 'made in Ottawa' set of approaches that will be able to get approval.  Which means taking what everyone else is doing under advisement, but ultimately doing things for themselves.

I'm designing a clever LID-based SWM solution for a small community outside of the City, and it requires 3 people to sit down with me.  It will save 5 million dollars over the alternative that was chosen in the previous EA process.  We're currently working on ensuring that the Ministry of the Environment approval process will go smoothly before we reopen the EA and offer this as an alternative. 

innovation is the main factor facilitating implementation of green infrastructure. Unfortunately, due to a myriad of factors -regulatory, poverty, resistance to change, etc stand out as some of the factors hindering its universality as a panacea to our old age traditions of being stuck to what we have. I am hopeful, time shall render these barriers non-existent.

http://ec.europa.eu/environment/nature/ecosystems/docs/green_infrastructures/GI%20Final%20Report.pdf

http://ec.europa.eu/environment/nature/ecosystems/docs/green_infrastructure_broc.pdf