Energy-Sector Civil Contractor — HV & Substation Works
Updated: Sep 4
Energy civils sit apart from ordinary earthworks. The trench depths, the bedding tolerances, the proximity to live plant, the sign-off chain back to the asset owner: all of it is tighter than a standard subdivision dig, and the consequences of getting it wrong are measured in outages rather than rework. We build the civil works that high-voltage networks and substations are stood up on, and we do it as a subcontractor to the principals who hold those programmes.
Draeinail is a civil and drainage contractor of about 25, based in Pukekohe and working across Franklin and the wider Auckland region, with a permanent crew in Queenstown as well. We've run roughly 20 years in the ground, and energy is one of four sectors we deliver into alongside infrastructure, drainage and subdivision. On the energy side we've subcontracted civils to Ventia and worked across Vector's programme, and we handled the civil scope on a Spark data centre upgrade in Takanini. That's the kind of work this page is about: cable trenching, duct banks, foundation and earthing civils, and the reinstatement that closes a job out clean.
If you run an energy programme, or you're a head contractor carrying an energy package and you need a civil crew who already understand the discipline, here's how we approach it and what we bring to site.
What HV and substation civil works actually involve
The civil scope on a high-voltage job is rarely the headline, but it carries most of the risk. Cables and joints live or die on the quality of the bedding and the consistency of the cover. Substation plant needs foundations that hold level and earthing that's installed exactly to the design, because nobody is lifting a transformer to fix a grid you laid wrong. So the civil package, done properly, is precise, documented work that the electrical and commissioning trades depend on.
Cable trenching and duct banks
HV cable runs need a stable trench, the right bedding sand, and cover and warning tape set to the network owner's standard. We profile the trench, lay and compact the bedding, install ducts or direct-buried cable to the design depth, and bring backfill up in controlled lifts so the compaction is even over the whole run. Where the route crosses a road or a service corridor, we set duct banks and draw pits and tie them into the existing network without surprises. Our excavators run from 5 to 35 tonnes, so we can match the machine to the trench instead of forcing an oversized digger down a tight reserve.
Substation foundations, earthing and plinths
Inside a zone or distribution substation the civil work is foundations, plinths, cable trenches, earthing pits and the bunding that keeps oil where it belongs. Earthing in particular is unforgiving: the conductor grid goes in at the depth and spacing the design calls for, gets photographed, and gets signed off before anything is covered. We build to that discipline. Transformer and RMU plinths come in dead level and at the right setting-out, because the gear that lands on them has no tolerance for a slab that's out.
Reinstatement and handover
A live network doesn't sit in a fenced compound, so most of our energy work ends in someone's road, footpath or berm. We reinstate to the road controlling authority's spec, get the as-builts and the compaction records in, and hand the corridor back the way the owner expects it. The job isn't finished when the cable's in; it's finished when the paperwork closes and the surface is right.
Plant and self-delivery
Energy programmes run to fixed outage windows, and a crew that has to hire in half its gear is a crew that's exposed to whoever else booked the yard that week. We own what we run, which is why we can hold a date. Our fleet covers most of what an HV or substation civil package needs without a single phone call to a hire desk.
11 excavators from 5 to 35 tonnes, so the machine fits the trench rather than the other way around
3 JCB telehandlers for materials handling, plinth work and lifting around constrained sites
Trucks, trailers and an articulated transporter rated to 25 tonnes for moving our own plant between sites
A hydro-vac for safe, non-destructive excavation around live cables and unknown services
Bypass and dewatering pumps to keep a trench workable in wet ground or a high water table
Trench and manhole shields so deep excavations stay safe and compliant
Our own traffic management, so road and reserve works don't stall waiting on a third party
Owning the transporter matters more than it sounds. When we mobilise to a site, we move our own machines on our own schedule. That tightens our control over start dates and it keeps mobilisation off your critical path.
Safety, accreditation and the standard we hold
Energy clients audit their civil subcontractors hard, and rightly so. Working near live HV plant leaves no room for a crew that treats safety as paperwork. Our people are Site Safe trained, and our crews are competency-assessed against the Construction Safety Council Tier 1 framework. We carry confined space, first aid, traffic control and the driver endorsements the gear demands, and we run documented safe operating procedures backed by our own custom health and safety system rather than a borrowed template.
In practice that means we turn up with the SWMS already written for the task, the permits understood, and crews who know how to work to a network owner's rules around exclusion zones and live plant. We've delivered energy civils for Ventia and across Vector's programme; that work doesn't continue unless the safety record holds, and ours does.
On a high-voltage job the civil package is the quiet part that everything else stands on. Get the bedding, the cover and the earthing right, document it, and the electrical and commissioning trades inherit a clean site. Get it wrong and you're explaining an outage. We build for the first outcome.
Where we work, and the wider track record
Our home ground is South Auckland and the Franklin district, and we cover Pukekohe, Papakura, Takanini, Drury, Karaka, Paerata, Pokeno, Manukau and Wiri, out through Hobsonville, Whangaparaoa, Silverdale, Kumeu, Riverhead and the north-western growth corridor. We also hold a permanent crew in Queenstown, which means our energy and infrastructure capability isn't locked to one region.
Energy is one strand of a broader civil record. We've built public sewer on Penlink for Fulton Hogan, delivered Tauriko enabling works for Downer, and put in stormwater upgrades at Paerata Station and the Wiri EMU depot for TRS. We installed a detention tank on a Ryman site and delivered TDM subdivision works at Hobsonville. The point of listing them is simple: the crew that lays your cable trench is the same crew that's worked to the standards the country's larger contractors hold their subbies to.
How an energy job runs with us
We walk the route or the site with you, confirm the design intent, the network owner's standards and the outage windows you're working to
We price the civil scope against real plant and real crews, and we tell you what we can self-deliver versus what's genuinely a specialist sub
We mobilise our own machines on our own transporter, set traffic management, and start to the date we committed to
We trench, bed, duct and backfill to spec, build foundations and earthing to the design, and hold the inspection and sign-off points
We reinstate to the road controlling authority's standard and close out with as-builts, compaction records and the H&S documentation your audit needs
Do you work as a subcontractor to energy principals, or only direct?
Mostly as a subcontractor. We deliver civil packages for the principals who hold the energy programmes, and we've subcontracted civils to Ventia and worked across Vector's programme on that basis. If you're a head contractor carrying an energy package and you need a civil crew who already understand the discipline, that's exactly the arrangement we're set up for.
Can you handle work around live HV plant safely?
Yes. Our crews are competency-assessed to the Construction Safety Council Tier 1 framework and Site Safe trained, with confined space, traffic control and first aid certification. We run a custom H&S system with documented safe operating procedures, and we use a hydro-vac for non-destructive excavation around live cables and unknown services so we're not digging blind near energised plant.
What plant can you bring to a substation or cable job?
Eleven excavators from 5 to 35 tonnes, three JCB telehandlers, trucks and trailers, an articulated transporter rated to 25 tonnes, a hydro-vac, plus bypass and dewatering pumps and trench and manhole shields. We own it, so we don't wait on a hire desk and we can hold an outage date. We also bring our own traffic management for road and reserve works.
Which areas do you cover for energy civils?
South Auckland and Franklin are home, so Pukekohe, Papakura, Takanini, Drury, Karaka, Paerata, Pokeno, Manukau and Wiri, out through Hobsonville, Whangaparaoa, Silverdale, Kumeu and Riverhead. We also keep a permanent crew in Queenstown, so we can deliver in the South Island as well as across the Auckland region.
Do you handle reinstatement and as-builts, or just the dig?
The whole scope. We reinstate roads, footpaths and berms to the road controlling authority's standard, and we close out with as-builts, compaction records and the H&S documentation your client's audit will ask for. The job is finished when the paperwork is done and the surface is right, not when the cable's in the ground.
If you're carrying an HV, substation or energy civil package and you want a crew who already work to network-owner standards, talk to us. Request a quote or call Darryn Muir on 021 271 0035.
