Three Montgomery County groups have hauled away 30 truck loads of brush and debris surrounding Turkey Branch Creek near where a 7-year-old was assaulted last month, but local residents were dismayed that a youngster had to be seriously injured before officials responded to a 14-year-old problem.

Steven Wilson Jr. was attacked along a secluded stretch of the creek on July 19 and suffered cuts around his left eye and on other parts of his face, according to police. A 10-year-old playmate has been charged in the incident.

Neighbors said at the time that the attack could have been avoided if the county had moved earlier on their requests to clear the debris from the area. They said the site had become a haven for teen-agers to hang out and take drugs, according to Nick Scholtz, who lives across the street from the site of the attack.

"It looks a thousand times better now," said Scholz. "I can actually see to the other side . . . . By opening it up, it becomes less of an attraction for teen-agers, less of a place to hang out, less of a danger for kids.

"I just wish this had been done before because maybe the opportunity for what happened to Stevie wouldn't have been there."

Yesterday, a bicycle, Big Wheel, red wagon and other children's toys cluttered the front porch of the Wilsons' one-story home.

"I heard about the clean up, I think it's a good idea," said Debra Wilson, Steven's mother.

"But I really don't want to talk to anyone right now," she added as she muffled a telephone receiver against her shoulder while answering the door. She said her son "is doing great."

Sandy Longcor, the Wilsons' regular babysitter, said Steven's eyesight seems to be fine. He visited her Rockville home two weeks ago and "appeared bright-eyed and bushy-tailed," she said.

Longcor said Children's Hospital did an excellent job treating Steven's wounds and scars, but she said "he'll probably need more surgery later. We're just glad to have him around."

Meanwhile, Steven's 10-year-old companion is being held in Noyes Juvenile Detention Center near Rockville. He has been charged with assault with intent to maim and filing a false report of a crime. The youth originally told police that two teen-agers attacked Steven.

About 50 persons, some wearing bright yellow hard hats and black or yellow T-shirts identifying their group, have spent the week working near the area where Steven was assaulted.

Crew members, ranging in age from 14 to 22, are part of three organizations: Go Teens, Montgomery County Conservation Corps and Maryland Conservation Corps. Two of the groups provide summer work to county students while the Montgomery County Conservation Corps also hires high school graduates for full-time work.

"When we first started, you couldn't walk through here or even look through here," said 19-year-old Doug Carranza, a member of Go Teens.

The recent graduate from Sherwood High turned down the sound of his Walkman, removed his work gloves and leaned on his rake.

"The neighbors really appreciate us being here because they can walk their dogs here and let their children play and still keep an eye on them," Carranza said.

Russell Hamill, assistant chief administrative officer for the county, said County Executive Charles W. Gilchrist asked him to study what could be done to improve the area after the assault.

Watching about 24 youths stuff garbage bags with twigs and branches while rakes scratched the ground in a dozen places, Hamill said, "These kids are working like beavers. It really looks great."