rreynolds, the damage that is inflicted on the structure of the soil when excavating the leach field trenches or bed while the soil is saturated is tremendous. The saturated condition lubricates the soil particles and causes the soil on the bottom, and the side walls to become compacted, and smeared by the backhoe, and the soil becomes significantly less permeable, sometimes impermeable. The amount of compaction and smearing are a function of the type of soil present at the site, and the amount of water between the soil particles.
When the septic tank effluent is applied to the leach field constructed in saturated soil, it will just pond up and surface or it might back up into the septic tank, and ultimately into your home. I suggest that you follow the recommendation of the local professionals, and wait until things dry out a bit. JWA