Help.. Insurance won't consider my car a total loss...?

My current insurance company is allstate. I have a 2005 TL with significant damages. The repair estimate came out to be $18,000. The value of the car is about $30,000. The front frame rails must be replaced and have to basically replace everything in the hood except the engine and trans. I don't feel safe driving around a car with those damages. I know repairs won't put it to original condition. Even the collision center recommends not to repair the car. Not only that, I am obligated to disclose this info when i decide to sell this car. I am also the not at fault driver of the accident. The other party has Mercury insurance. I want my insurance company to declare it a total loss. What can I do?