Water pipe from Well

> Some metal content...I need to possibly replace a 40+ year old
> galvanized pipe from well house to house about 20 feet away. =A0The
> pressure drop in the pipe while under flow has gradually been
> increasing over the last few years, due to restrictions from rust and
> mineral deposits. =A0The line is buried 36" to 48" deep, and I believe
> it is a straight run, (I did not put it in). Unfortunatly in the many
> years since it was buried, a hickory and a pine 12" to 15" diameter
> have grown up near the line. =A0I have a backhoe, but I'm sure digging
> it up would probably harm the tree roots, and I would rather not have
> to cut them down. =A0I'd like to replace the old galvanized line with a
> new line of galvanized steel or copper, but instead of 3/4" diam,
> something like 1 1/4" for minimal pressure drop to the house, (we do a
> lot of plant watering). =A0Thoughts on non invasive methods of replacing
> the line are needed! =A0Some ideas I had - maybe not good ones are the
> following:
>
> Pipe dream 1.) Take 2" pipe which I have on hand, and fit one end with
> a hollow cutter like a rota-broach. =A0This would then be pushed over
> the existing 3/4" pipe, while rotating it with a portable pipe
> threading head, which I could borrow. =A0I would also be feeding water
> in the open end of the pipe via a rotary coupling to help flush the
> "tool". =A0Hopefully the tool would follow the existing straight pipe
> run to the well house 20 feet away, and I could simply use the 2" pipe
> as a chase for the new 1 1/4" water line.
>
> Pipe dream 2.) Pull the old pipe with a hydraulic puller into the
> house's walk in basement, while using the well house end of the old
> pipe to pull in the new pipe. =A0Plastic line could be used, but I like
> the additional grounding of a metallic line, ( I have a 8' grounding
> rod at the main service entrance and at the shop sub panel), as I do a
> bit of TIG welding w/HF and I also think it helps with lightning
> protection to have as much grounding area as possible. =A0Pulling may
> not work if there is a union underground which is a distinct
> possibility.
>
> Pipe dream 3.) make a water lance from 1/2" steel pipe, =A0connect it to
> a hose from the water outlet in the well house and use it to washout a
> enough of a channel below the existing pipe to help free it up.
>
> Pipe dream 4.) Try and rod out the existing 3/4" 40 year old water
> line.
>
> Or lastly, call a company that does water jet or Hydraulic pipe
> installation under roadways, drives etc. =A0Not sure what the cost on
> this would be...I do have garage door access to the basement end of
> the pipe for a reasonably sized machine if needed, but would need to
> move some equipment out of the way.