map generation issues

ok so i have a block map generator which goes infinitely how would i get it to limit the Z axis to 10 blocks only no more?

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 using System;
 using System.Threading;
 
 
 [AddComponentMenu("VoxelEngine/WorldGenerator")]
 public class WorldGenerator : MonoBehaviour {
     
     private Map map;
     private ColumnMap columnMap = new ColumnMap();
     private TerrainGenerator terrainGenerator;
     private TreeGenerator[] treeGenerator;
     private bool building = false;
     
     
     void Awake() {
         map = GetComponent<Map>();
         terrainGenerator = new TerrainGenerator(map);
         
         Block[] woodBlocks = map.GetBlockSet().GetBlocks("Wood");
         Block[] leavesBlocks = map.GetBlockSet().GetBlocks("Leaves");
         
         treeGenerator = new TreeGenerator[ Math.Max(woodBlocks.Length, leavesBlocks.Length) ];
         for(int i=0; i<treeGenerator.Length; i++) {
             Block wood = woodBlocks[ i%woodBlocks.Length ];
             Block leaves = leavesBlocks[ i%leavesBlocks.Length ];
             treeGenerator[i] = new TreeGenerator(map, wood, leaves);
         }
     }
     
     void Update() {
         if(!building) StartCoroutine( Building() );
     }
     
     private IEnumerator Building() {
         building = true;
         Vector3 pos = Camera.mainCamera.transform.position;
         Vector3i current = Chunk.ToChunkPosition( (int)pos.x, (int)pos.y, (int)pos.z );
         Vector3i? column = columnMap.GetClosestEmptyColumn(current.x, current.z, 7);
         
         if(column.HasValue) {
             int cx = column.Value.x;
             int cz = column.Value.z;
             columnMap.SetBuilt(cx, cz);
             
             yield return StartCoroutine( GenerateColumn(cx, cz) );
             yield return null;
             ChunkSunLightComputer.ComputeRays(map, cx, cz);
             ChunkSunLightComputer.Scatter(map, columnMap, cx, cz);
             terrainGenerator.GeneratePlants(cx, cz);
             
             yield return StartCoroutine( BuildColumn(cx, cz) );
         }
         building = false;
     }
     
     private IEnumerator GenerateColumn(int cx, int cz) {
         yield return StartCoroutine( terrainGenerator.Generate(cx, cz) );
         yield return null;
         
         if(treeGenerator.Length > 0) {
             int x = cx * Chunk.SIZE_X + Chunk.SIZE_X/2;
             int z = cz * Chunk.SIZE_Z + Chunk.SIZE_Z/2;
             int y = map.GetMaxY(x, z)+1;
             int index = UnityEngine.Random.Range( 0, treeGenerator.Length );
             treeGenerator[index].Generate(x, y, z);
         }
     }
     
     public IEnumerator BuildColumn(int cx, int cz) {
         List3D<Chunk> chunks = map.GetChunks();
         for(int cy=chunks.GetMinY(); cy<chunks.GetMaxY(); cy++) {
             Chunk chunk = map.GetChunk( new Vector3i(cx, cy, cz) );
             if(chunk != null) chunk.GetChunkRendererInstance().SetDirty();
             if(chunk != null) yield return null;
         }
     }
     
     
 }