Highly accurate motorway crossing with tight exit window
In June 2026, Brownline UK helped complete a challenging motorway crossing in Scotland. This project was characterized by challenging soil conditions and a very limited space on the exit side next to the motorway. Brownline UK provided the accurate steering services necessary for the project’s success.
Project background
This aim of this project was the installation of two parallel water mains. With the construction of a new water reservoir nearby, infrastructure was needed to deliver the water to a pumping station in Luncarty. This required 2.3 km / 7500 ft of pipe to be installed, which will carry the water by gravity from the reservoir to the pumping station. The last leg of this pipeline would cross the A9 motorway at Luncarty.
Contractor Gmac Utilities Ltd. carried out the trenchless works to cross the A9. They called in Brownline UK to survey the pilot drills using the Drillguide Gyro Steering Tool.
Very narrow exit site
The drills were set to arrive on a very narrow strip next to the motorway’s access road. This strip was only 12 m / 40 ft wide, which left only a small window for the punch-out. The highest accuracy was necessary to guide the pilot drills safely towards the exit point.
The Drillguide Gyro Steering Tool was uniquely suited for this motorway crossing since it provides the highest accuracy under all circumstances – such as when the surface above the drill is inaccessible.
Accuracy and additional verifications
With the Drillguide GST equipped behind the mud motor, operators were able to rely on the highest real-time accuracy to steer the pilot drills. This accuracy was needed as the soil consisted of gravel and fractured sandstone, which could alter the drill head’s orientation in unpredictable ways. By carefully monitoring the directional measurements and borehole pressure readings supplied by the Drillguide GST, any deviations or mud circulation issues could be identified and appropriate action could be taken. This resulted in a safe and efficient crossing.
GPS track was used at several locations before crossing the A9 to confirm the gyro measurements. This independent verification provided extra confidence and reduced risks when crossing the motorway. With accuracy assured, the exit curve was started at a depth of 8 m / 26 ft below the traffic lanes. The drills then successfully reached the reception pit that was excavated on the exit site.
Following the accurate pilot phase, the pipe pull was successful and the project has since been completed to the satisfaction of all involved parties.
