My septic tank is located in front of my home, the yard slopes from the front to back. The front yard has a lot of trees (pine)and needles and very little grass. When I get a heavy rain the crawlspace gets a septic smell. When I bought the house I had a foundation drain installed after I noticed rainwater running in the crawlspace and a foundation drain fixed that problem. Could this have created the odor problem. I bought the home in the summer and the problem came up this winter. I had the tank pumped when I moved in and the systems works fine. How can find and repair the source of this odor problem?