This may be of importance to you , maybe not. But the following link has a large 36GB PDF Archive of PDF handbooks of a wide array of engineering disciplines such as agricuture, civil, construction, petroleum and wastewater.
LINK TO ARCHIVE
I dont know how relevant they will be to everyone here but as some people are trying to create sustainable communities worldwide I thought that at the very least I could share this link with you so you could have a look
thanks