Mesh generation

Hi everyone,
I am building a 3D model of a rectangular area of dimensions 2200m x 2500 m. I have a 0.8m thick wall inside the model that i created using supermesh lines. Every time I try to generate the mesh I get an error message. I am using the gridbuilder option. Does anyone have an idea how to create an appropriate mesh, where I have large elements on the sides and very fine elements in my wall.
PS: I need to have the nodes at the edge of the wall (for modeling purposes).
Thank you

From the simulation point of view I suggest to choose a smooth gradation between highly refined areas within and around the wall to coarser areas slightly away from the wall. Under certain conditions, the GridBuilder may fail, especially if line features are present. A failure may be attributed on how GridBuilder internally treats lines within the supermesh to generate the FE-mesh. More details on the GridBuilder algorithm is provided in the FEFLOW Help.

I find this to be educational approximately linear in it.

You can also define the wall using super mesh (SM) elements instead of lines.  Ahalo of SM elements that grow in width with distance from the wall to facilitate control mesh density.

Pete