At one time, Wallace worked as a detective investigating crimes against children.
A spokesperson with the Contra Costa County district attorney's office says the booking charges include two counts of having sex with someone under 18 and one count of intimidation of a witness or victim.
"Every once in a while a police officer does something wrong and like the general public, when they make a mistake, they're held to the standards that the general public is and they're held accountable," Walnut Creek Police Chief Joel Bryden said.
Wallace, 45, bailed out of the county jail shortly after his arrest. The district attorney's office has yet to file formal charges in the case.