Decks, Patios, Porches and Docks - 16' X 24' Deck Not Attached/Joist&Beam Size/Pile Distance

I am Building A 16' Wide X 20' Long Deck that is not Attached to anything. I plan to run the deck board (4/5 X 6 heart ceder)the long way 20'. Also 2" X 6" treated pine Joists, 3 - 2" X 8" Doublewide beams running long 20'.My Question is with 16" canalever over outside beams I have a Span of 6' 8" Between Outside and inside Beams, Is this two much? I Also need help on spacing of pile down the three beams, I know my frost line which is 8' here in Craven, Saskatchewan, Canada, I would like advise on size and spacing of these piles ?

just a suggestion---

use 2x10 joists and only two beams

This will give necessary span strength for 16 foot span if 16" cant on either end

Put blocking in the center of joists to increases rigidity

I only suggest this as 8 feet is a LONG way down and the less holes to dig the better

This will however require larger footings 12-16 inch or larger

HOpe this helps-----josh

How do you dig down 8 feet and flare the base of footings?

I will take your ideas to the bank.
As for the flare on the pile we don't
worry about it at 8' feet thats alot
of concrete at the best of times.