riprap under a bridge

We have a couple of projects coming up where we will need to place RR4 and RR5 riprap underneath a couple of existing bridges. The erosion has exposed the bottom of the concrete bridge ends and the road district wants riprap placed. I would like suggestions/ideas from you folks on the best way to do this. We are talking approx. 120tons on one bridge and 160tons on another. If all goes well and isnt too costly there are some other road districts interested in doing this also. Thank you

How high is the bridge from the water? How steep are the banks? How deep is the water? Is there a weight restriction on either bridge? These are a few questions that come to mind when trying to come up with a solution.

There are a vast majority of variables here. More specific information would be helpful. Keep in mind you have to make a dollar or two. If you got the job and can make a profit all is well and good. If not let someone else do it.

I have a sneaking suspicion that r5 is not large enough to protect the banks. We normally have a minimum placement depth for R rock as well. Obviously the bigger the rock, the deeper the placement. PENNDOT is funny about that kind of stuff though.

Bridge #1: Approximately 8-10ft from bottom of bridge to water. Slopes under bridge from water to abutment are 3-1. No weight restriction. Water is 3ft at normal flow
Bridge #2: 10-11 ft from bottom of bridge to water. Slopes under bridge are 3-1 on one end and 2-1 on end where water current is hitting. No weight restriction. Water is 4-5ft at normal flow.
Both bridges are 26ft wide with concrete decks on steel piling with concrete abutments. Access is decent on one side of each bridge. Not great but decent. This is a township project without state involvement.
We have done a couple of smaller bridges in last year with RR4 using mini excavator and placing top by hand as bridges were less than 6ft and was no water as they went over surface drains that only flow when it rains. Just trying to come up with better way to handle 12”-18” size rock than by hand

Would something like this work

Now that is one slick little machine Looks like it would be great and do just what we want - as long as it could handle the riprap.

I’m sure there’s different designs and sizes. Operator will need a light touch.

I'd probably tackle that with an excavator equipped with a tilt rotator - that's how do it for ditches and catch basins. Works well.

I've hauled many tons of riprap for dock landings, water crossings and general shoreline protection. I've used a tracked dumper with a heavy conveyor belt bed liner to protect the bed. The Yanmar C60R will haul 5-6 tons in a pass, run through swamps and exceed 35 degree slopes quite easily. I've even dumped 1/2 loads while on a 30 degree side slope. If you have access from the sides of the creek, a tracked dumper might be a fast option.

I was hired to do a shoreline riprap job for a fairly large dirt contractor at their lake house. I was questioned as to how I was able to move so many triaxle loads so quickly with minimal time, by myself. Load it, get it to the slope, back up to the top of the slope at a slightly pitched angle, start dumping at the top of the slope and keep working your loads until you hit the toe of the slope. Repeat process after tamping and filling any voids with a mini-ex, repeat until done. I think it was 13 or 15 tri-axle loads of rock in 2 days if memory serves me right. 4 loads per tri-axle so about 50-60 cycles to complete the job.