Mass Volume company?

Hi

I am applying for a job. I want to describe the role I have worked in as

"I have two years’ experience working as a graduate accountant in a mass volume(?) fuel business..."

The company I worked at manages more than dozen petrol stations of its own, and buy and deliver fuel with its own fleet. I want to find a word to describe the high transaction volume nature of the business, the kinda busy quality.

If anyone can help out that would be great!