A chunk loading example from http://gamedev.stackexchange.com/questions/81235/how-to-load-stacking-chunks-on-the-fly

chunk loading example

private IEnumerator UpdateChunks(){
    for (int i = 1; i < VIEW_RANGE; i += ChunkWidth) {
        float vr = i;
        for (float x = transform.position.x - vr; x < transform.position.x + vr; x += ChunkWidth) {
            for (float z = transform.position.z - vr; z < transform.position.z + vr; z += ChunkWidth) {

                _pos.Set(x, 0, z); // no y, yet
                _pos.x = Mathf.Floor(_pos.x/ChunkWidth)*ChunkWidth;
                _pos.z = Mathf.Floor(_pos.z/ChunkWidth)*ChunkWidth;

                Chunk chunk = Chunk.FindChunk(_pos);

                // If Chunk is already created, continue
                if (chunk != null)
                    continue;

                // Create a new Chunk..
                chunk = (Chunk) Instantiate(ChunkFab, _pos, Quaternion.identity);
            }
        }
        // Skip to next frame
        yield return 0;
    }
}