Sludge hauling costs

What kind of permits, fees, registration etc. is involved, if we decided to purchase our own dump truck to transport solids? We are now using a contractor for pickup and disposal at a nearby landfill. Which is more economical or less of a headache? Does anyone have a yearly cost figure to own and use your own dump truck? What size truck is the best? We generate approx. 15 ton per week.  Thanks!  nickstark@ymail.com