Solution — Trenchless crossings
HDD River Crossing Survey for River and Canal Bores
Bank levels, river-bed profile, soil logs and buried services on both banks, brought together so the bore path can be designed with confidence.
Quick AnswerAn HDD river crossing survey gives the drilling designer four things. They are bank and approach levels, the bed profile, soil conditions along the bore and the buried services at the entry and exit pits. We do all four with our own DGPS, echo-sounder boat, drilling rigs and GPR, and deliver them on a single profile drawing. For the land-side method, read: HDD route survey.
What does an HDD river crossing survey need to cover?
It has to describe the ground from the entry pit on one bank to the exit pit on the other: surface, water, bed and the soil beneath. A wrong bed level or soil log can bring the bore up short, into gravel it cannot steer through, or lose drilling fluid into the river.
The survey layers are fixed by physics, not paperwork:
| Layer | Method | Why the designer needs it |
|---|---|---|
| Survey control | DGPS static control on both banks | Both sides on one coordinate and height system |
| Bank topography | Total station and DGPS, levels across the approaches | Entry and exit angles, rig and pipe-string space |
| Bed profile | Single-beam echo sounder with DGPS on a boat | Minimum cover below the deepest point |
| Soil profile | Boreholes with SPT on each bank, as access permits | Steering, reaming and fluid design |
| Buried services | GPR and locator at pits and along approaches | Safe pit positions and pull-back route |
Why is the river bed profile so important?
Because the bore must stay well below the lowest bed level the river may reach, not only the level on the survey day. Rivers scour during floods and deposit again as water falls. Designers work from the surveyed bed, add the expected scour and then a safety margin; without a proper profile all three numbers are guesses.
Our single-beam echo-sounder boat records depth while a DGPS rover on board logs position, so every sounding has a coordinate and reduced level. Parallel lines either side of the main crossing line allow for bore drift and an uneven bed. On a narrow canal with little water, a level and staff along the bed during closure can replace the boat.
How are canals different from rivers?
Canals are shorter and more predictable, but they bring lining, embankments and fixed closure periods. A lined canal has a concrete or brick bed the bore must stay well clear of, and its embankment service roads carry their own cables. The annual maintenance closure is the best window for survey and drilling.
- Embankment top, inner slope and bed levels at each cross-section.
- Lining thickness, weep holes and drains where visible.
- A cable scan of bank service roads before pits are fixed.
- Department conditions, such as minimum depth below bed, shown on the drawing once you share them.
What about the services on each bank?
Entry and exit pits sit near roads, and roads near rivers carry water mains, cables and telecom ducts. The exit side may also need a long, straight strip for the pull-back string. Utility locating covers the pit areas, approach and string route with a locator and with ground penetrating radar, which reads buried pipes from the echoes of short radio pulses. Everything found is marked on the ground. Before your team opens a pit, follow our call before you dig in India guide to alert known service owners.
How scan results from both geophysical methods appear on plan and section is set out in read more on GPR survey deliverables. For the bank topography and plot boundaries where land is being acquired for pits, see how long land survey services take.
Which soil information matters for drilling?
Grain size, density and the presence of gravel or cobbles, recorded with depth. Fine sands and silts below rivers suit HDD if the fluid is managed; loose gravel and boulder layers are the classic cause of failed crossings. Our two rotary rigs drill boreholes with SPT at intervals, and samples are classified in an NABL-accredited laboratory. Boreholes sit on the banks; a mid-river hole needs a barge and is planned separately for long crossings.
Where do crossing surveys go wrong?
Most problems trace back to one of four shortcuts, and each one is cheap to avoid at survey stage.
- Two coordinate systems: Banks surveyed on different days from different reference points do not join, and the rig finds the error. A common DGPS control network on both banks solves it.
- One sounding line only: A single centre line misses a deeper channel a few metres away; parallel lines cost little boat time.
- Borrowed soil data: Logs from a bridge a kilometre away are tempting, but river deposits change quickly, so a borehole at the crossing is worth far more.
- Pits fixed before scanning: A pit pegged for rig access can hide a cable or water main. Scanning first lets the pit move a few metres, clear of existing utility lines, while it is still a peg.
Flood marks on bridge piers and embankments are photographed and levelled too, because they show how far the bed can move.
Keep the pull-back side in mind: a long pipeline string must be laid out straight before pulling, and that strip needs the same check for underground utilities as the pits.
What does the crossing survey cost?
Each layer is priced from our standard rates and combined in one written quote.
- Hydrographic survey day (boat, crew, echo sounder, DGPS): ₹60,000 per day; any mobilisation/travel cost, if applicable, shown in the written quote.
- Bank and approach topography as a route strip: ₹15,000 per km.
- Geotechnical boreholes: ₹1,500 per metre drilled including SPT, minimum ₹1,00,000 per site; laboratory tests per schedule.
- GPR scanning at pits and approaches: ₹24 per metre (₹32 for L-section), minimum order ₹50,000 in Delhi NCR and ₹1,00,000 elsewhere.
- DGPS control points: ₹3,000 per point.
GST is extra on all items. Most single crossings need one boat day, one or two topography days and two boreholes. Bank work in NCR begins the same day or within 1 working day. At rivers elsewhere, a team member living near the crossing begins at once, or within 1 working day at most.
How long until the drawing is ready?
Within three working days of the last field day, with soil classification following the laboratory results. The deliverable is one combined profile sheet showing ground, water, bed, soil logs and utility data, plus plan sheets, an Excel coordinate list and a KMZ. For a record of the finished pipe, see the FAQs below.
To plan dates around a canal closure or the dry season, start a survey enquiry with the crossing location, pipe size and any department conditions you already have.
Frequently asked questions
When is the best season for a river crossing survey?
The lean season after the monsoon recedes, when flow is low and the boat can work safely. Canal surveys fit best into the annual closure.
Can you survey a crossing that is only a seasonal stream?
Yes, if the bed is dry we level it directly with total station and DGPS, which is faster than a boat survey.
Do you record the pipe after drilling?
Yes, from the drilling log and a survey of both pits. See how long an as built survey takes for record drawings.
How many boreholes does a crossing need?
At least one on each bank for most crossings. Longer or more variable crossings may need extra holes, which the geotechnical engineer decides.
Will you get the department permission for us?
No, permissions stay with the project owner. We prepare the survey drawings and utility records the department typically asks to see.
What datum is used for levels?
Heights are reduced to the project datum or tied to a known benchmark, so bank levels and bed levels are on one system.
Get a written quote for your crossing
Services for HDD crossings
Written by Saniya Parveen · Technically reviewed by Rahul Rai · Updated 8 November 2026