WILLISTON (AP) - County parks and federal land in northwestern North Dakota are being used as garbage dumps, falling victim to vandals, trash, after-hours parties and all-terrain vehicles that tear through them, officials say.

The damage includes five Williams County recreational parks - Kota Ray, McGregor Dam, Blacktail Dam, Little Egypt and Spring Brook Dam, said Park Board Member Greg Zavalney.

Williams County officials discovered an expensive mess at McGregor Dam recently.

"Somebody shot up the bathrooms with a high-powered rifle," Zavalney said.

A pickup was driven up on the area's new dock and crushed, authorities said. Deputies estimated more than $2,000 in damage from the incidents, which likely occurred sometime between November and April.

"There is a lot of partying going on at all the parks. At Spring Brook Dam, someone burned half a picnic table for firewood," Zavalney said.

"Picnic tables cost $200 apiece. They are also using pieces of our shelters. Lumber costs a lot to replace," he said.

Jeff Keller, a federal park ranger and manager of the Williston office of the Army Corps of Engineers, said he sees the same problem on corps property around the Little Muddy River and Lake Sakakawea toward New Town.

"We see couches, furniture, appliances, dead cattle, dead horses, dead deer, yard debris and tree clippings," Keller said.

Zavalney said the County Park Board and the CrimeStoppers program have offered a $1,000 reward for the names of offenders.

The Park Board also has approved rules that will be posted, including a sunset closing time for guests, restrictions on camping stays without special permission, a ban on waste disposal except in proper containers, no hunting or shooting within park boundaries, and vehicle registration. Violators could be banned from the park or face "appropriate law enforcement action."

"These small parks are getting hit hard," Williams County Sheriff Scott Busching said.

Zavalney estimated repair and replacement costs total about $3,000 more than budgeted each year.

"We have money budgeted for maintenance and additional camp fees. Instead of park improvements, our money and time is going to vandalism cleanup," he said.

Officials also worry about fires, though Keller said closing off some of the sites has lessened that danger.

Busching said the "other 95 percent" of people who are not causing problems should help. "They have some responsibility in taking care of their parks, too," he said.