"They told me it doesn't matter. If something happens five years from now, 20 years from now, they will do what it takes" to investigate tips, Cox said.
Cox also revealed West Valley City police have suspicions about his daughter's late brother-in-law, Michael Powell. Cox said police did not share specifics with him but said they could not account for Michael Powell's whereabouts when Susan Powell disappeared, and he moved away from family shortly thereafter. Michael Powell committed suicide in Minneapolis on Feb. 11 of this year.
"We thought Michael was avoiding the conflict and the situation by moving away, but it turns out he may have been preserving himself," Cox said.
The investigation has already presumably cost West Valley City hundreds of thousands and maybe millions of dollars, taking dozens of police officers to the deserts of Utah and Nevada, plus Powell's hometown of Puyallup, Wash., and now Oregon, searching for a body and executing search warrants.
The only person of interest in her disappearance, her husband, Josh Powell, died last year after killing his two sons and then himself. Suspicion has been cast on his father, Steve Powell, who is now serving a prison sentence on unrelated voyeurism and child pornography charges, although circumstantial evidence in the public record would indicate any involvement came after Susan vanished.
Steve Powell has denied any involvement in his daughter-in-law's disappearance.
The latest search started after Chuck Cox gave police a tip that her remains may be in a heavily wooded area of Scotts Mills. A handful of West Valley City detectives, as well as local law enforcement and volunteers, began searching the area with cadaver dogs Tuesday.
Cox said that an aunt and uncle of Josh Powell rented the property a single house on about 180 acres at the time of the woman's disappearance.
Anne Bremner, an attorney for the Cox family, said Michael Powell had said in a deposition that he had driven to Oregon and abandoned a vehicle there.
Bremner said she's still interested in seeing more work at the property, including the possibility of having volunteers go to the site to help search.
WVCPD also have searched the desert near Ely, Nev., and in Utah's Tooele, Juab and Millard counties for the woman's remains.
Susan Powell was last seen Dec. 6, 2009 at her West Valley City home. Josh Powell claimed he left about midnight and went camping in the West Desert with his sons, then ages 4 and 2.
Particularly since his grandsons died, Cox has offered mixed reviews of West Valley City police, sometimes praising and sometimes criticizing how they investigated the disappearance. Cox on Thursday said he still thinks his son-in-law should have been arrested, but West Valley City police have recently shared some information about the case that made him appreciate the work of detectives.
Cox said he expects West Valley City police to release more information soon.
"Not to say [West Valley City police are] perfect, or that I agree with everything they did, but they did a good job," Cox said.
The Associated Press contributed to this story.