A registered tow truck operator may receive compensation from a private property owner or agent for a private impound of an unauthorized vehicle that has an approximate fair market value equal only to the approximate value of the scrap in it. The private property owner or an agent must authorize the impound under RCW 46.55.080. The registered tow truck operator shall process the vehicle in accordance with this chapter and shall deduct any compensation received from the private property owner or agent from the amount of the lien on the vehicle in accordance with this chapter.