Emergency HDD Bore Restores Water Service
Most people in the Western hemisphere tend to take for granted that when we turn on the faucet, out comes clean and clear water. This is mainly because the utility infrastructure is often unseen, buried below the surface, and literally out of sight and out of mind.
Citizens of Custer County, Oklahoma, experienced in December 2022 what it is like not to have any water. The original installation of the water main dates to the late 1970s or early 1980s and used a Class 160 PVC pipe. During the middle of the night of Dec. 7, about 1,000 customers found themselves without water service as time and constant 140-psi pressure ultimately took their toll. It was imperative to get the line fixed as soon as possible.
Given the urgency of the repair, Custer Rural Water was insistent on the quickest repair possible. Custer Rural Water #3 contracted Igo Inc. as the water district considers them a continuing contractor and is expected to be a one-call, problem-solved solution. Igo Inc. chose horizontal directional drilling (HDD) as the method for installing an 8-in. HDPE replacement pipe and it was understood that there wasn’t any time allotted for re-drilling.
Although the planned bore was relatively short at a little over 300 ft, it involved crossing a dry creek bed with steep banks. A minimum of 7 ft of depth was required at the deepest point from entry, below the narrow creek bed, and immediately thereafter the bore needed to climb about 40 ft toward the exit.
To ensure that all the elevations and required depths were correct, Trevor Igo of Igo Inc. used a TeraTrak R1 to acquire the terrain elevations along the bore path and subsequently the bore plan.
The R1 is a smart measuring wheel that, in addition to measuring distance, also records elevations of the terrain. This allows for the real-time generation of continuous profile data for the terrain displayed via a complimentary app on a mobile device. By adding utilities and waypoints, a rod-by-rod plan can quickly be generated. A waypoint is a point that the bore must travel through, and in the case of the creek bed, a waypoint with a desired depth of 7 ft was entered.
The ground conditions consisted primarily of Sandrock and packed sand, which further underscored the benefits of a rod-by-rod plan. Although steering wasn’t expected to be difficult, knowing exactly which pitch and depth were required for each rod was going to make the pilot bore much easier to manage.
The plan called for a straight section at the outset at a little over -33 percent pitch down the entry side bank, then leveling off below the creek. The bore was then due to climb back up at a relatively steep ~42 percent pitch up the exit side bank.
The bore planning process took about 45 minutes which included clearing the path for the R1. The terrain mapping and planning of the bore only took about 15 minutes. After ascertaining that everything in the plan looked good, the pilot bore began. Igo used its Vermeer 24×40 S3 with a Falcon F5+ for guidance. Trevor Igo prefers the Falcon F5 because he logs every bore for his clients. Additionally, he finds the available annual fluid pressure readings incredibly important.
“Downhole fluid pressure provides great insight into how your bore is progressing in real-time. Learning what to watch for and understanding what those pressures are telling you lets you mitigate a problem before it becomes an issue.”
Annular fluid pressures were on average very low, 3 to 4 psi, which according to Trever Igo was because, “swabbing every rod, coupled with the right mud mixture, ensures a clean hole and good flow.”
Because of geology, Trevor Igo elected to use a Vermeer 5.5-in. Gauntlet drill bit. Steering turned out not to be problematic and he was able to follow the planned path quite well. For example, below the bottom of the creek where the plan called for a minimum of 7 ft, the recorded depth according to the LWD Log for that rod was 7 ft 1 in. In general, depth and pitch readings matched what had been called for, meaning the new pipe was installed where expected. More importantly, this significantly minimized the likelihood of pullbacks or redrilling – added work that would have meant even further delays in getting citizens’ water flowing again.
The pilot bore started at 8:30 a.m. and went smoothly. The 317-ft pilot bore was completed in a little under two hours with a maximum depth of a little over 22 ft being reached a few roods beyond the bottom of the creek. The hole was then pre-reamed with a 12-in. fluted. By 2 p.m., the new HDPE pipe was successfully installed. Trevor Igo credits his efficiency and success to having a plan which generally leads to a much easier installation, minimizing both torque and pulling loads. To further save time, the pipe had been pre-chlorinated and rinsed after fusing so it could go online immediately.
This was yet another case where HDD proved to be the most efficient means of installing a utility. From the time Igo got the call to water access being restored, only three days passed — an outcome as good as could be expected.
According to Trevor Igo, “Without the TeraTrak R1 and the easy-to-create bore plan, this bore would have been more difficult, and the repair would have taken much longer.”
Siggi Finnsson is senior product manager at Digital Control Inc.