A major marijuana growing operation has been put to a halt in Polk County.  Officials estimate that more than ten thousand live plants were seized Thursday and Friday.  Howard County Sheriff Butch Morris said the plants were discovered by a private citizen who reported the find to officers with the nearby Cossatot River State Park.  Law Enforcement Officers from the Polk and Howard County Sheriff's Departments, along with the Drug Enforcement Agency, State Park, Drug Task Force and the Grannis Police Department worked several hours to remove the plants.  Sheriff Morris said the plants were situated on less than two acres of Weyerhaeuser property located about a mile west of the Howard County line and approximately 2 1/2 miles north of U.S. Highway 278.  Authorities say several Hispanics were seen leaving the area when the plants were discovered, but no arrests have been made.  Sheriff Morris said the plants have been maintained by people living in a camp like structure that was built on the site.  Several gasoline powered generators were used to pump water from a nearby creek to irrigate the plants.  The growing operation is estimated to be worth several hundred thousand dollars.