You probably dont need that much grout to prime with, I used 2 Yards of grout (1.5-1.6M3) to prime through over 2000 feet of 5 inch line. 

Pumped a hopper full of water ahead of the grout, then the 2 yards grout, and then the concrete. It went out about 500 feet across a bridge, then dropped 200ft or so straight down, then turned, went through a diversion valve, out past that, then up and over to the pour.

Primed out beautifully every time.

I like your idea of balls ahead and behind. I did a job with my father, and he used a ball ahead, and behind.. Was going down hill about 650 feet for train bridge piers. there was a camels hump at the bottom of the hill to slow the concrete down.

Good luck with your pour

im just curious how did the balls look when they came out after the prime, were they chewed up at all? 2000' is a long way to go and keep wet even with slick line.

on the 2000 feet push i didnt use any balls. Just water and grout pushing ahead

I'm very interested in seeing the pictures. To be honest I swear when I need to put over 150 feet. I can only imagine 2000+ feet. I would also be curious in terms of logistics. How many guys working on the pump,  how long to set up  etc. Also have you asked the guys at putz? They have seen quite a bit and I'm pretty sure they would have suggestions for you.

Good luck

I pumper 2400 ft on a down grade of about 5%. I used a Putz 14000 trailer pump.  I used a ball to slow down the flow to lubricate the pipe. I used a 9 cement sack mix with a small amont of sand. I got my ball back after prime out and washed it out. I did this numerous times as the pour lengths decreased by 50 ft per day. I never lost a ball and primed out everytime.

I've pumped some massive 2000-3000 ft laydowns with line pumps before. I used about a yard for prime and primed out 7 seconds in between each stroke of the cylinder. When i went to wash out, we took a rented air compresser and blew a pig out. They arent that bad unless a driver washes out in the hopper... then it gets real.

can't wait to be there

I have done 2000 ft plus pours with no problems , just make sure you leave all chemicals out of the mix, such as water reducers and plasticizers, I have had great success using newspaper in plastic bags in front of water then another in front of grout, good luck and hope to see the pics soon.

Here a little update of the project. Dipstick and me done already several poor’s, no problem whit priming but in the first concrete that come out of the line we have far too much air. We are busy whit fine tuning. One of the towers we hope to be on top in a few weeks and then starts another challenge. because one of the supers told me between the lines that the bridge deck will be made whit some amount of lite weight concrete