Septic tanks will probably be holes in the ground--right next to their water well.
Looking at the concrete by enlarging photo...of boy does it look poor. https://www.usnews.com/dims4/USNEWS/8288114/2147483647/resiz... Not an engineer but having seen dozens of homes being built I doubt this can take a 7.0 earthquake.
The best way to improve the lives of Haitians is obviously to help them emigrate but they're quite, quite motivated to do that already.
America is politically incapable of a long term occupation, look at Iraq or Afghanistan. Real nation building would require running a country in a profoundly undemocratic way for at the very least a decade, more likely two or three. The US isn't even capable of winning a war of occupation given the political constraints it operates under. If they had the support of 60% of the population for a thirty year and 0.1% protested against it they wouldn't do it. Russia or China might, at a push Singapore, but a Western country? Give me a break.
And don't be a coward with your throwaway. dang may have bowed to pressure with the shut up or be banned to yummyfajitas Chris Stucchio but nothing will ever change if we're all cowards.
After all, it's not like it's the dirt that's causing their problems. We agree they need foreign rule, but instead of bringing them to foreign rule, we could bring foreign rule to them.
Rather than exporting the whole population, it seems like it'd be a lot easier to import a few tens of thousands of foreign bureaucrats, leaders, and functionaries to run the senior half of government. The U.S. could take over the country and turn it into a Puerto-Rico like protectorate.
This would be much faster and less disruptive to both the U.S. and Haiti.
Over the next twenty years the US culture wars are going to get worse and worse. While there is not currently a Democrat consensus on Open Borders there does seem to be one that enforcing immigration laws is immoral. Support for amnesty has gone up by a lot since Trump was elected and Open Borders is only going to become more mainstream. There is actually a plausible path to letting huge portions of the Haitian population immigrate to the USA. It only requires one administration to do something. There is none for anything that looks even remotely like colonialism, even with consent. That would be a twenty year project if you plan to do anything but help for four, eight years before the next President pulls out.
Paul Romer put a lot of time and effort into trying to get Charter Cities off the ground, one, anywhere. He failed. Exporting good governance by consent is not possible if you have to work with real polarised democracy because there's not going to be elite or popular consensus.
They want to build infrastructure, but since nobody owns the land they're squatting on, there's no way to raise money via land taxes. The technocrat answer to that would be individual septic tanks and solar panels, but because there's no land ownership and no law enforcement, you'd have to be nuts to invest any serious money in building a house, because a gang would just take it from you. Classic development trap.
Jonathan Katz talked about Corail/Cannan in The Big Truck That Went By, and he wasn't positive. https://www.amazon.com/dp/B009OZN6GM/ Published in 2013, but it doesn't sound like much has changed.
1: Port-au-Prince gets about twice as much rain as Seattle per year, and is routinely hit by hurricanes. If you don't manage the stormwater, it washes your house downhill. Sewage systems have also become important, since UN peacekeepers brought cholera with them after the earthquake.