webgl - Open world loading/unloading with asset bundle in unity

I have a very large environment which I have to load/unload in unity Webgl as I can't load them at once. So, I have divide the environment into 1000 x 1000m (1km) (each chunk is consist of three layer like objects layer, tree layer,floor layer) chunks and on my player I have attached this script for chunk loading/unloading, thanks to this guide.

    public class TileLoadingManager : MonoBehaviour
    {
        //[SerializeField]
        public string tileTag;


        //[SerializeField]
        public Vector3 tileSize;

        //[SerializeField]
        public int maxDistance;

        public GameObject[] tiles;

        // Use this for initialization

        void Start()
        {
            this.tiles = GameObject.FindGameObjectsWithTag(tileTag);
            DeactivateDistantTiles();
        }

        void DeactivateDistantTiles()
        {
            Vector3 playerPosition = this.gameObject.transform.position;


            foreach (GameObject tile in tiles)
            {
                Vector3 tilePosition = tile.gameObject.transform.position + (tileSize / 2f);

                float xDistance = Mathf.Abs(tilePosition.x - playerPosition.x);
                float zDistance = Mathf.Abs(tilePosition.z - playerPosition.z);

                if (xDistance + zDistance > maxDistance)
                {
                    tile.SetActive(false);

tile.GetComponent().AbLoadCall();

                }
                else
                {
                    tile.SetActive(true);
 tile.GetComponent().AbUnLoadCall();
                }
            }
        }


        void Update()
        {
            DeactivateDistantTiles();

        }
    }

Its loading/unloading my chunks but a problem is that, it is a costly method for load/unload as my object chunk (tile) count is around 4 (expected to grow). Additionally I am loading asset bundle from UnityWebReqest and destroying assets on-unload, so it very heavy task. So my question is that is this the right approach or I should need to adopt anything else?

EDIT: Bundle Loading Code Snippet:

public void AbLoadCall()
    {
        if (AbLoadCallCortoutineRef == null)
        {
            AbLoadCallCortoutineRef = StartCoroutine(AbLoadCallCoroutine());
        }
    }

    IEnumerator AbLoadCallCoroutine()
    {

        for (int i = 0; i < perRegionAssetBundleList.Length; i++)
        {
            yield return StartCoroutine(perRegionAssetBundleList[i].DownloadABCall());
        }

    }

Actual Loading Code:

    public IEnumerator DownloadABCall()
    {

        if (!abObjectInstantiated)
        {
            //Debug.Log(assetName + " , downloading assetbundle. . ");
            yield return StartCoroutine(DownloadAB(assetBundleURL));
        }
        else
        {
            //Debug.Log("Reactivintg");
            if (!abObjectInstantiated.activeInHierarchy)
            {

                //Debug.Log("Reactive done"+ this.assetName);
                abObjectInstantiated.SetActive(true);
            }

            if (floorL7MeshRenderer)
            {
                floorL7MeshRenderer.enabled = false;
            }

        }

        //else
        //{
        //    Debug.Log(this.name + " , Bundle object has alread available.");
        //}
    }

 IEnumerator DownloadAB(string bundleURL, string assetName = "")
    {
        Debug.Log(". . DownloadAB. . ,"+ this.name);
        isBundleLoading = true;


        www = UnityWebRequestAssetBundle.GetAssetBundle(bundleURL);
        //Debug.Log("web req about to send : " + assetName);

        yield return www.SendWebRequest();

        if (www.error != null)
        {
            Debug.LogError("assetBundleURL : " + assetBundleURL);
            Debug.LogError("www error : " + www.error);

            www.Dispose();
            www = null;
            yield break;
        }

        //Debug.Log("bundle loading , "+ assetName);

        // get bundle from downloadhandler
        AssetBundle bundle = ((DownloadHandlerAssetBundle)www.downloadHandler).assetBundle;


        GameObject bundlePrefab = null;

        bundlePrefab = (GameObject)bundle.LoadAsset(bundle.GetAllAssetNames()[0]);


        // if we got something out
        if (bundlePrefab != null)
        {

            abObjectInstantiated = (GameObject)Instantiate(bundlePrefab);

            abObjectInstantiated.transform.parent = envParent.transform;

            if (floorL7MeshRenderer)
            {
                floorL7MeshRenderer.enabled = false;
            }  

        }

        www.Dispose();

        www = null;

        Resources.UnloadUnusedAssets();
        bundle.Unload(false);
        bundle = null;

        isBundleLoading = false;
        //Debug.Log("bundle unloading completed ," + assetName);
    }