HDD Contractor Faces Tough Rock Drilling Under the Illinois River

By Josh Ugrich October 5, 2026

The Alliance Three Rivers Interconnection project in Grundy County, Illinois, included four 20-in. steel horizontal directional drilled (HDD) crossings. Performing the HDD work was North Country Directional Drilling (NCDD) as a subcontractor to U.S. Pipeline.

While all four crossings encountered significant rock, the 2,204-ft Illinois River crossing presented the greatest challenge. This was because of its changing geology and elevation.

The work consisted of four crossings, all 20-in. steel:

Illinois River 2,204 ft (gyro)
I&M Canal 1,598 ft (wireline/gyro)
Railroad 1,415 ft (wireline)
Lock Road 1,270 ft (wireline)

All the crossings drilled in significant rock conditions, ranging up to 20,000 psi. This article focuses on the Illinois River crossing.

// ** Advertisement ** //

The Project

The Illinois River, consisted of a range of different soil formations and transitions throughout the bore hole. It also had an elevation change of roughly 35 ft from entry to exit. This impacted NCDD’s decision on how to ream the crossing. Soil formations at the surface were softer, consisting of clayey sands and silts down to roughly 25 ft of depth. There, the formations changed to be a claystone and mudstone formation of roughly 5,000 to 10,000 psi down to roughly 70 ft deep. It then changed into limestone where the psis ranged from 15,000 to 25,000 psi.

NCDD began its operations on the low side of the HDD. This was labeled as the “exit” side/pipe staging side of the HDD.

The NCDD crew ran all pilot operations with a 12-1/4-in. rock bit/motor combination from the low side. They punched out on the high side of the crossing. Then they rigged down the drill rig and staged the rig on the high side (entry) to resume pull reaming activities.

// ** Advertisement ** //

Because the diameter was smaller — 20 in. — and NCDD was using a 600,000-lb machine for its operations, the crew was able to begin the ream with a 30-in. rock reamer and continue the 30-in. pass through the entirety of the bore.