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Case Study: 1400' Horizontal Directional Drill Project (Video Content)
Thursday, March 24, 2016
The scope was simple, auger under a road and push pipe through, drill 1,400' and pull back pipe, and finally open cut and tie it all together. But Not everyone can wake up, go to work and drill a big hole in the ground that goes in at one point and comes up precisely at another, some 1,400' away. In our pipeline and utility world it happens all the time. It is the best way to get pipelines under rivers, roads and rail roads. Midwestern Contractors has gotten good at it. Acting as the General Contractor we recently undertook a project to relocate a pipeline under and around a road construction project by using Horizontal Directional Drilling (HDD) and an Auger bore. The entire relocation was 1,700'. the working space was cramped, traffic had to be flowing on the adjacent arterial road. The drill string was laid out in a curved area with no straight line entry into the drill hole. These were just a few of the challenges our Project Manager and Superintendent faced on this job.
Pulling back pipe string
(R) Drill machine and stem set up. (L) Drilling pilot hole
Welding Pipe String (M. Purpura Photos)
Planning for this project started in the fall of 2014 with bid documents released in 2015 and work starting in the winter of 2016. This congested interchange is being transformed into a diverging diamond configuration. Numerous pipelines, sewer, water, power and tellecommunications lines are running along this corridor. There are also major water mains crossing the drill path, and a combination of residentilal and commercial ingress and egress across the drill path.
Setting up for the auger bore operation (Steve Olsen Photos)
The laydown area was occupied with work on a 90" water main and was cleared out just in time to recieve the 50 sticks of pipe and fittings required for the project. Our crews helped clear out the laydown yard and offloaded the pipe. Then the drill path, drill entry and drill exit points were prepped prior to bringing in the drill rig. Traffic control measures and signage were put into place. Mats were laid, and all utilities were pot holed, identified and labled with the depth to the utility. At the same time our drill string crews mobilized in we began stringing and cribbing pipe. Welding also started up and the 700' string sections began to take shape.
After the drill rig was brought the drillers began boring the pilot hole. In addition to Utility Damage Prevention Planning, Midwestern Contractors also follows an Inadvertent Release Plan in the event of frac outs during the drilling process. These two planning documents enable us to avoid utility damage and to respond quickly and professionally to any type of inadvertant release wherever and whenever they may occur.
Pulling back pipe string (J. Pfleeger Photos)
The pilot hole proceeded smoothly through gravelly clay material at a depth of over 40 feet. Welding production was ahead of schedule when the pilot bit emerged precisely on location. The reaming operation proved to be challenging due to areas of heavy clay clogging the reamer and slowing progress. During this slow down we shifted the welders over to the auger bore which picked up the pipe at a point of intersection and carried it under the arterial roadway. This string was welded, and coated in preparation for the bore.
With reaming on the 1,400' drill complete the pullback was scheduled and executed without interuption. The reaming operationwas somewhat tedious due to heavy clay and frequent clogging of the reamer. The two 700' strings were joined and the pull back continued. Construction traffic entering and leaving the site had to excercise extreme caution due to the volume of traffic and fequent lane closures and realignments carried out by the highway construction that was ongoing during our project.
- Drill length: 1,400'
- Drill depth: 60'
- Number of days for pilot hole: 7
- Number of days for reaming: 15
- Inches of weld: 2,000
- Pipe diameter 16"
- Maximum shoring depth: 23'
- Cubic yards of earth moved: 150
- Number of crane mats required: 100
- Soil type: compacted hard clay and gravelly clay
A small 200' section of open cut was made more difficult by the exit angle of the drill. This excavation required engineered shoring to allow the crews to work 23' below grade. Ground water infiltration was a problem. Pumps were running continuously as the drill pipe was cut back. Fittings were welded in place to reduce the angle of the pipe and to make the tie-in simpler. The entire 1,800 foot assembly was then hydrotested for continuity.
Reverse color view of welder's hand tools (L) (R), Welding 40' inside a 16" Pipe (C) (M. Purpura photos)
23' Deep engineered shoring inplace for open cut tie-in section, (Steve Olsen Photo)
Welding offset from drill pipe to auger bore (J. Pfleeger Photos)
After the drill a gauge plate was pushed through the pipe, no deformation occurred. When the offset was welded more pipe was lowered into the excavation in preparation for tie-in.
Lowering a section of tie-in pipe (L) Gauge Plate after pigging (C) Positioning Tie-in pipe 23' deep shoring (R)
Projects like this one are complex. They require dilligence on the part of all parties to carry out safely and to achieve high quality results. The work, once completed must last for decades and every detail of the job is important. We thank our crews, subcontractors, foremen, and our customer for working as a team to make projects like this one a success. Midwestern Contractors delivers pipeline construction and maintenance services throughout the Midwest including Michigan, Ohio, Indiana, Illinois, Pennsyvania, Wisconsin, Minnesota, Iowa, Nebraska, Kansas and Missouri.
After completing the tie ins the project continued with the removal of the deep shoring systems, sand padding the pipe, backfill with flowable fill material and restoration work. All the while traffic control was still in place and surface water was managed and routed to filter bags before discharge back to ground water. One other aspect of the project was the removal of the old pipe which was originally placed at a depth of cover of 50 inches. The sections that could not be removed were plated, grouted and abandoned in place. The following photos tell the story and show some of the steps required to complete a project like this one.
1. Plating pipe. 2. Crossing a gas line (Note: Well point dewatering in place). 3. Removing old pipe.
1. Flowable Fill in open cut section. 2. Water filtration. 3. Flowable fill in tie in area.
Final pipe removal and restoration will take place in August of 2016. Much of the old pipe was sheared into transportable lengths as it was removed. There is a lot of work on the front and back ends of the actual drilling process. This particular project was complicated by the cramped working corridor, traffic, and surrounding construction activities associated with the highway expansion work.
Thanks to Ztylus.com for the 4 in 1 iPhonography lens kit, and to Steve Olsen and Jon Pfleeger for their photos submitted through Construction View. For information on Construction View contact [email protected]
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