I had put this topic up on a forum I used to use a few years back and thought that newbies would like the same info.
As of 2007 all New Build properties and re-build properties/renovations MUST have planning permission for septic tanks, cess pits. The rules originally stated that only septic tanks would now be allowed in BG, but on further investigation the EU commission will still allow for the construction of a cess pit/soak away, due to the heavy cost associated with septic tanks on the poorer community.
Even if you do not come under this category it is still worth making sure that your pit, (hoping that you use something and are not just letting it run into the nearest water way). Is on your skitza.
2 years ago it cost me 60 lev for the planning permission and took 3 months to get, mostly because the local planning man, just likes people to wait. I have yet to go back to have it put on my skitza as it has only just been completed. They gave me plans to follow if I wanted to use them, but not stipulated that I had too. I didn't have to pay for them either.
Normal rules of 3 meters from boundaries apply and if there is a water course nearby they will send an environmental officer out to check the area and possible impact if you opt for a soak away.. I didn't submit plans just filled in a quick form, then waited. I know that each area will probably have slightly different takes on this.
If your builder says it isn't needed.. DO NOT believe them, checks to new builds have been taking place in the coastal region and don't forget you would have included what you have on your census, so if it differs from the plans the have, (a lot of rural properties would have had nothing, or just a long drop or composting toilet) you are now on their radar..