Timber wall not drying out...

Hey everyone - in search of advice. Below these sleepers is a decent amount of sand and gravel for drainage purposes, wrapped in a sort of geotec sheet to separate it from the soil below. The wall itself is retained with rock and hardfill.

Despite this, our newly(ish) built wall seems to be perpetually wet at the base. The total absence of direct sunlight during winter compounded by frequent rain probably accounts for part of it but we're concerned it will rot if we don't take action. We're thinking of piercing holes into the sheet somehow (it's way below the wall).

Any other suggestions on how to proceed? TIA

TL;DR: how do we keep this sucker dry at the bottom