An 18-inch rock, weighing about 150 pounds tumbled down a hillside behind a home on Kula Kolea Place in Kalihi last night.  There were no injuries and no property was damaged.  The Department of Land and Natural Resources says the rock came from private land. Officials are assessing the situation today.  Last year, several large boulders rolled down the hill and struck three homes on Kula Kolea Place.