The house I purchased about 1.5 years ago has a drain field that slopes away from the house. The former owner described the system as a "raised bed" system. The basic layout is shown below with the septic to the left and the D-box to the right with laterals exiting on 3 sides. I had it professionally inspected prior to purchase.

*
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O--o---
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The drain field has shown a few lasting mushy areas at one edge of the drain field (depicted by the * above). I believe this is partly due to the constant rains the past few months, but there was standing water in the laterals when I opened the distribution box. Again this was just days after heavy rains. But I would expect no standing water if every thing was in perfect operating order. The mushy area concerns me because it is on the slope. So I expect water is not percolating correctly and is coming to the surface. I should note that there is also a tree just a few feet above where the wetness is located (i.e. (D-box)---tree--wetness). I would put the tree about 2 feet from the lateral. So my concern is that this could be due to a tree root. There is also signs that water has come to the surface near a small round sandy spot. No smell that I've noticed. What is the best course of action for determining the source of the problem? Is this something that I should wait until it is warm and dry out and dig up the area to see or is it something that should be attended to immediately? I had the tank pumped last month just to be safe. The operator said the tank looked good and there was no back flow. Any suggestions?