Animals replanting over a septic leeching field

So I realize that my battle with chipmunks is a bit like peace in the Middle East and have come to terms (though I work hard to keep the snake population up).

With that said – I’ve noticed a ton of strawberry plants coming up this year over the leeching field of my septic system. I generally only plant wildflowers and such there since it is not advisable to harvest edibles growing over human refuse.

So here’s my question – assuming I move these strawberry plants to a more suitable location – how long are they considered “contaminated”?