How to spawn prefab only in allowed area?

Hello, I'm using this code to spawn a prefab at mouse position, but I only want it to be allowed to be spawned in the area next to the street object. How can I do this?

  if (place_power_plant_coal && Input.GetButtonDown("Fire1")) {
              Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
              RaycastHit hit;
              if (Physics.Raycast(ray, out hit)) {
                  Instantiate(__power_plant_coal, hit.point, Quaternion.identity);
              }
  }