I recently found myself in the familiar position of waiting on a septic system design before I could call a project feasible and today I dealt with a new wrinkle in the complex Sonoma County septic regulations. One of the hurdles you must vault on your way to approval is to be at least 100' away from the 10 year flood line. On this particular project there was an existing septic system. It turns out that the 10 year flood line has changed from what was considered the flood line several years ago. Not only can the regulations change but the facts about nature can too! A lot of times I'll counsel a client to have a topo survey done without including a lot line survey because the project may be safely away from setbacks and the premium for the lot line information can run well over ten grand. But if you are doing a topographic survey and you are near the russian river, you should consider including a (re)evaluation of the floodlines. The information is invaluable for a septic and system anytime and they are may have changed recently. It is worth the cost of this piece of knowledge to avoid a project-stopping conflict late in the game.