SEATTLE -- Members of the Green River Task Force plan a new excavation Wednesday in the hope of finding more victims of the Green River killer.

GREEN RIVER MURDERS CASE Complete Coverage Of The Case EXTENDED INTERVIEW: Judith Ridgway Shares Her Story Slideshow: Images From The Courtroom Slideshow: Ridgway At Crime Scenes Timeline: Key Moments In The Case Discuss: Your Thoughts On Plea Deal Photo Gallery: Ridgway, Victims, Police Investigation Video: Gruesome Details In Ridgway's Confession Survey: Support Plea Bargain? Court Documents On King County Website

Task Force members have spent months digging and sifting through dozens of sites, looking for human remains.

They were led to the sites by Gary Ridgway, who pled guilty last week to 48 Green River murders.

Detectives say Ridgway was very good at hiding bodies, making it difficult to find them.

"This is a man I surveilled in the 80's and followed on the highway and saw how well he knew that area. He was able to turn off and take a back road. We would lose him and he would reappear down the road. He knew all these areas like the back of his hand," said Detective Randy Mullinax of the Green River Task Force.

Task Force members are concentrating on four King County women still missing.

All are believed to have been murdered during Ridgway's killing spree in 1982 through 1984.