Horizontal Drilling / Moling / etc. - recommendations, etc.?

[skwdenyer]

Hi all

I'm currently involved in restoring a house last lived-in many decades ago. The current sewage set-up involves a (private) pipe under the road joining two plots - house on one side, septic tank on the other. No, the septic tank can't be moved to the same side as the house...

The existing 4" clay pipe is no longer viable, for all manner of reasons. We need to get a new pipe / duct installed. The crossing is around 5m.

Yes, we *could* find a contractor with the right tickets and get the road closed to do an open trench. But this is proving surprisingly difficult (independent contractors with the right tickets are booked-up, larger firms are just overkill in terms of fixed costs).

Since I used to work on buried pipelines for Shell a very long time ago, I'm interested in alternatives. Can we mole / drill a new pipe in? We have a digger on-site, so creating pits is easy.

In terms of ground conditions (clay with cobble), this type of job is what we're looking at doing: https://www.youtube.com/watch?v=uygnX4q2mZk

Having rung around, it seems there just aren't many UK contractors with this sort of kit, whilst the specialist trenchless contractors don't seem to want to know about a project on this scale. Even the equipment hire companies don't seem very interested!

For reference, the property is on the south western edge of the Lake District.

So I'm looking around for options, and wonder if anyone here has experience in this area?

I'm at the stage of considering importing something like a Bullet Mole - https://bulletmole.com/?srsltid=AfmBOoqegorM_86gxA... - or a Borzit - http://www.borzit.com/ - in order to create a pilot hole.

I would then need to come up with a hole reamer of some kind. As an engineer by training, it seems logically better to put the really big loads into tension than compression. But I can already feel this project running out of control - I don't have a YouTube channel (yet...) to justify starting to develop my own towed drilling rig!

So does anyone have any suggestions or recommendations as to how I might try to get this resolved? Thanks!

[GliderRider]

Have you taken into consideration other utilities that may be in the path of what you need?

Assuming you have the necessary permissions and have done the surveys, then how about a trial to see if an electric earth auger will work horizontally?

One metre extensions for the shaft are available

If you hit stones then a swap to a diamond core drill using an adapter to fit the core drill to fit the auger may be necessary.

[normalbloke]

Can the existing pipework be relined(slip lining?) or a new pipe inserted or does it need to be in a new plan position completely? Thrust boring as you know, needs big pits and substantial machinery. I too used to work on high pressure fuel mains in the UK(Esso). I was involved when we pushed a new 10” fuel main in under a railway line, and also the M27 in a previous life! Good luck.

[Origin Unknown]

I can see why you’re trying to find other ways around opening up a trench, but if there’s a risk of other utilities in the road, using a mole is a non-starter. Maps of existing utilities are at best, guidance “there is a utility somewhere near by”, and rarely have any kind of accuracy. You’ll want a cat and genny to map out exactly where everything is on your planned route. And that’ll only work on a ferrous pipe if memory serves. Most services are PE, I think some had a wire in the plastic to aid CAT and genny use but I’m many many years out of this game and don’t recall. How will you find fibre? Imagine if you caught a gas service?

I think you need a competent contractor with the permissions and insurance and trench across the highway.

Also, a mole is surprisingly easy to “lose”. Ask me how I know.

[Cow Corner]

If, as I understand it correctly, you are considering moling under a public highway without correct permissions, skill, experience and insurance, that would be very risky - if you damage the highway or an existing mains service, any cost saving you might be hoping for could go up in a flash (literally…).

[skwdenyer]

GliderRider said:

Have you taken into consideration other utilities that may be in the path of what you need?

Assuming you have the necessary permissions and have done the surveys, then how about a trial to see if an electric earth auger will work horizontally?

One metre extensions for the shaft are available

If you hit stones then a swap to a diamond core drill using an adapter to fit the core drill to fit the auger may be necessary.

Thanks. The only street utility is mains water. Electricity and phones are all above ground, no mains sewerage. Permissions side of things is in-hand.

That earth auger is an option, but clearing the spoil is a problem - hence the Borzit has a water supply. But I agree the auger might be an option for enlarging the hole, if I also knock up a simple water feed to augment it. I’d need to figure out if that electric unit could run slowly enough (300rpm or so) at full power.

[skwdenyer]

Origin Unknown said:

I can see why you’re trying to find other ways around opening up a trench, but if there’s a risk of other utilities in the road, using a mole is a non-starter. Maps of existing utilities are at best, guidance “there is a utility somewhere near by”, and rarely have any kind of accuracy. You’ll want a cat and genny to map out exactly where everything is on your planned route. And that’ll only work on a ferrous pipe if memory serves. Most services are PE, I think some had a wire in the plastic to aid CAT and genny use but I’m many many years out of this game and don’t recall. How will you find fibre? Imagine if you caught a gas service?

I think you need a competent contractor with the permissions and insurance and trench across the highway.

Just to clarify this again, the only service under the roadway is water, the position of which is precisely known (because I'm in the process of connecting to it - there was no water supply for the house, either). There is no mains sewerage. All phone and fibre is above ground. There is no mains gas. This is a very rural location. We've already done a lot of research and surveying on this topic.

Origin Unknown said:

Also, a mole is surprisingly easy to “lose”. Ask me how I know.

Yes, that's a concern. Horizontal drilling would on balance be better than moling, especially if there's a chance of encountering boulders that might divert the path of something like a Grundomat.

Cow Corner said:

If, as I understand it correctly, you are considering moling under a public highway without correct permissions, skill, experience and insurance, that would be very risky - if you damage the highway or an existing mains service, any cost saving you might be hoping for could go up in a flash (literally…).

Agreed. This isn't something to be considered lightly.

normalbloke said:

Can the existing pipework be relined(slip lining?) or a new pipe inserted or does it need to be in a new plan position completely? Thrust boring as you know, needs big pits and substantial machinery. I too used to work on high pressure fuel mains in the UK(Esso). I was involved when we pushed a new 10” fuel main in under a railway line, and also the M27 in a previous life! Good luck.

The current 4" clay drain carries sewage (or would do). It was laid as a "field drain" with un-socketed pipe sections held together with, frankly, luck. Over time, the sections have displaced relative to each other. There's also tree root impingement.

I've considered pulling a 63mm MDPE through the existing pipe (just about achievable) and using a collection tank and macerating lift pump on the house side to push sewage through the small-bore MDPE. That's doable, but doesn't solve all problems, such as rainwater.

Rainwater? Yes, when the 4" sewage pipe was laid (we don't know when, but 1930s seems about right at this stage), unbelievably they just chopped across an existing 4" clay pipe under the same road (at about mid-span), presumably believing it redundant (we've confirmed this with cameras down both pipes). That second 4" clay was the rainwater drain! So for the last however many decades, rainwater has run into this second 4" pipe, and then basically used the ground under the roadway as a soakaway... That has almost certainly accelerated the lateral displacement of the sewer pipe, and runs the risk of undermining the roadway entirely.

The only reason that's not been a total disaster for the road is because the house was abandoned in 1987, since which time the drains weren't maintained, became blocked, and rainwater just ran down the road from the house (also not something that can continue - there are no street drains on this road).

We've also discovered there was an abandoned well very close to the house (18" or so). Overflowing rainwater was using the well as a giant soakaway...

So whatever happens I need to run in a second 4" pipe (or a smaller pipe + tank + pump) to handle rainwater (the ground is impermeable clay, so no chance of a conventional soakaway and we're not allowed to use the old well as such, whereas I can discharge to a drainage field and, ultimately, a river on the other side).

In addition, a modern package treatment plant (to replace the septic tank) is going to need power, so I need to get a SWA cable under the road, too...

My starting point was to open a trench, remove the old 4" sewerage clay, dig further down, and insert a 10" duct, through which all services could be carried. I'm struggling to find a contractor for this at the moment.

So plan B became mole / drill to, say, 130mm, pull a new 110mm HDPE + power (SWA) through that opening, and then re-use the existing 4" clay sewerage pipe as a rainwater drain (potentially with lining). Which I'm also struggling to find a contractor for. For reference, the old clay pipes start at only around 400mm below the roadway, and run down at approximately 10 degrees (not a good fall for a sewage pipe, which should really be no more than 3 degrees to avoid problems with solids getting left, but fine for a rainwater drain).

And that's where I am right now.

My only other option is to install catch tanks on the house side for both rainwater and sewage. Then use lift pumps (with a macerator for sewage) to pump output through a 63mm MDPE pipe (sewage) and twin 25mm MDPE pipes (rainwater), all pulled through the existing 4" clay. This is achievable, and not stupidly costly. The only reason for trying to avoid it is that I then become reliant upon pumps (that will inevitably fail at the worst possible moment), or I have to use dual redundant pumps (which adds many £k to the cost).

The only silver lining in all of this is I've discovered I'm entitled to reclaim the SDLT paid on purchase due to the state of the building, so there's a chunk of cash coming back from HMRC to offset the increased costs of sorting this all out.

[Cow Corner]

Sounds like a very interesting project… fancy doing a build thread?

[skwdenyer]

Cow Corner said:

Sounds like a very interesting project… fancy doing a build thread?

Yup, that's on the roadmap. There have been a lot of false starts with this project, but a lot of it has been documented, and I do plan to write it up. My son also wants me to do a series on YouTube, but I'd have to learn to edit video first

Here's a taster of what I've been dealing with:



(there's a house underneath that...)

[Abtj]

You cannot legally dig under a road without permission from the appropriate authority.

There’s a reason you be has high costs in - contractors need to be experienced, permitted and insured

[ATG]

Abtj said:

You cannot legally dig under a road without permission from the appropriate authority.

There’s a reason you be has high costs in - contractors need to be experienced, permitted and insured

He has already said "the permissions side of things is in hand."

[Mr Magooagain]

A few years ago I managed to thread a new water main under a road to a campsite opposite. By luck we found an old unused rain pipe about 4 inches. It was blocked but we managed to get it clear and insert the new water main pipe through it.

What about a macerating brown pump your side of the road and trying to get the new smaller pipe through the old four inch clay pipe? Say 50mm.

[skwdenyer]

ATG said:

Abtj said:

You cannot legally dig under a road without permission from the appropriate authority.

There’s a reason you be has high costs in - contractors need to be experienced, permitted and insured

He has already said "the permissions side of things is in hand."

The high costs aren't to do with permissions per se. There are plenty of independent contractors with the right tickets and insurance; they're just insanely busy with work in our area. Contractors can pick and choose work at the moment, it seems, with plenty simply refusing to quote at all without even seeing the site or drawings.

As regards the licensing issue, that side of things is all in-hand with the relevant professionals and authorities.

As stated above, if I have to I'll go back to the tanks+pumps approach and not dig up / mole under the road.

[skwdenyer]

Mr Magooagain said:

A few years ago I managed to thread a new water main under a road to a campsite opposite. By luck we found an old unused rain pipe about 4 inches. It was blocked but we managed to get it clear and insert the new water main pipe through it.

What about a macerating brown pump your side of the road and trying to get the new smaller pipe through the old four inch clay pipe? Say 50mm.

Yup, that's one of the options. We'd need 63mm MDPE for the outlet. But we also need to carry rainwater and power. It is doable, just about, but it leaves us dependent upon pumps (that may fail) which is why I'd prefer to avoid it if I can.