Protecting Our Global Environment

Case Studies
Carman's River

As part of an 8.5 mile, 20-in. gas transmission project, Long Island Company (LILCO) faced the challenge of crossing an environmentally-sensitive area of Carman. s River in Yaphank, NY. The route of the main line followed a New York State Dept. of Transportation right-of-way on the south side of the Long Island Expressway between Holtsville and Yaphank areas in Long Island, NY. This new 20-in. main was needed to maintain adequate minimum pressures during forecasted peak load periods and to provide system reliability to LILCO. s transmission and distribution system located east of Holtsville.

At first, the route presented the normal pipeline obstructions created by existing underground facilities. All major road crossings had to be jacked and the pipeline could not be located in the roadway. Also there were work hour restrictions imposed by the permitting authorities to alleviate the traffic concerns. About 1,600 ft. from the eastern end of the project was the Carman. s River area. On both sides of the river is a . scenic wild and recreational. fresh water wetland area designated by the New York State Dept. of Environmental Conservation. Also, the river is classified as one of the few remaining native trout streams on Long Island.

Crossing this area posed a challenge in applying a special type of work methodology for the required crossing. After meeting with the Dept. of Environmental Conservation and evaluating the given parameters, it was decided that directional drilling offered the best option for this river crossing. However, the drill would have to be long enough to avoid the wetland boundaries. With directional drilling, no disruption to environmentally-sensitive areas and site restoration costs near the river would be eliminated.

Final length of the crossing was designed to be 1,630 feet. A 20-in. OD API 5LX52 carrier pipe with .375-in. wall thickness was chosen and coated with Shaw. s Pipe coating. Due to overall length and work area restrictions, stringing of the pipe was made with two consecutive lengths of welded pipe of 1,130 ft. and 500 ft. Difference in elevation between the entry and exit points was 20 ft. with the exit point of the drill being the higher. Carman. s River is located approximately 600 ft. east of the exit point of the drill and 1,000 ft west of the entry site. Accuracy of the drill was critical when a restriction was placed on the location of the gas main route. The main was required to be located 5 ft. to the south of the Long Island Expressway fence line. Since the industry accuracy for drilling is 1%, some concern surfaced that the drill would exit out of the allowable 16 ft. path to the north and enter the middle of a highway entrance ramp. This rap was located adjacent to the exit point of the drill. Bordering the southern limit of the 55 ft. right-of-way was a cemetery.

Carman. s River had been relocated about 20 years earlier and there were unknown factors on the type of conditions that might be encounter during drilling operations. Several questions were posed. What type of fill was used? Will gravel propagate the drilling fluid to rise to the surface? If a blowout occurred, would it contaminate the river and adjoining wetland areas? To provide answers, two core soil samples outside the wetland area were collected, one of the west side of the river (exit point of the drill) and one at 20 ft. from the river to the east side. The number of core samples and locations were restricted since they could provide an easy path for bentonite to find its way to the surface.

Both samples were taken 10 ft. away from the pipeline path. They showed the soil composition in the area to be primarily sand and gravel. The pipe route was designed with a 2,000 ft. bending radius and at a 25 ft. depth below the river bed to prevent slurry from finding its way to the surface.

Pipeline contractor for the project was Hendrickson Brothers, Inc., Valley Stream NY. Subcontractor for the directional drill was Environmental Crossings, Traverse City, Michigan. Initial drilling of the 8-in. pilot hole began with 8-in. drilling rods and an 8-in. cutting head. A jetting cutting method was used on the cutting head and initial drilling encountered heavy gravel in an area 100 feet from the entry site. Circulation was lost and the contractor had to retrieve the cutting head. Heavy mud was introduced until circulation was reestablished. Appropriate circulation is achieved when drilling fluids (bentonite slurry) return to the initial opening where they are collected in a slurry pit.

Entry angle to the ground was made at 12 degrees with a 2,000 foot radius configuration and exit angle of 12 degrees. Control wire (12 gauge) in the steering tool was fed through the drilling rods to provide survey data to the drilling operator. Two readings are provided from the control wire: (1) angle inclination (angle at which the steering tool is heading in the ground), and (2) azimuth of the cutting tool (direction in which the cutting bit is pointing).

While drilling near the Long Island Expressway bridge abutment which crosses the river, an increase in magnetic interference was encountered. Environmental Crossings relied on the steering tool readings for penetrating this area. Pipe was located 45 ft. away from the nearest point of the bridge foundation. A Sharewell guidance system was used for tracking the steering tool. A Tru-Tracker grid system was placed at entry and exit locations for 300-ft. and 600-ft. respectively for secondary reading accuracy. During initial drilling operations the steering tool cutting head did not deviate more than 2-ft fro the proposed route. The cutting head exited a mere 2 ft to the south and 16 ft. to the west from a premarked exit location.

During final drilling stages for the pilot hole, two heavy gravel areas were encountered on both sides of the river. The drilling contractor had difficulty in building up the angle to make the cutting head turn upwards due to high gravel areas. this probably explains why the cutting head came out at a distance of 16-ft longer than intended.

Front reaming operations used an 18-in. reamer in a two-stage process. Front reaming allowed for most of the ground cuttings and drilling slurry to be recovered, handled, and re-processed at the lower entry location. A slurry re-claimer/recycler and new mixture tank were located at this location to avoid double handling of slurry at both entry and exit locations.

An 18-in. reamer was pulled back to the entry location and a 30-in. reamer was attached to its back. Forward reaming was re-started. During reaming, a higher viscosity mixture of bentonite was used to remove excess cuttings (sand and gravel) and to stabilize the bore hole. Due to ground conditions, it was necessary to direct reamers in the forward and reverse directions in certain areas to maintain and establish integrity of the hole.

Returned cuttings showed the presence of heavy gravel and loose sand. This caused the annular space in the hole to collapse at regular intervals and required more of this material to be retrieved from the hole. To assure integrity of the hole would be maintained, at 26-in. barrel reamer was pulled back in the hole for 633 ft. through the high gravel areas on the east and west side of the river. When condition of the hole was proved satisfactory, pullback operations began. A 20-in., 0.375-in. wall thickness, grade x-52 pipe was welded in two sections of 1,130 ft. and 500 ft. Pipe was pressure tested, jeeped, and all weld joints coated before it was placed on rollers for pullback.

The pipe end was attached to a swivel located behind the 26-in barrel reamer. This swivel was attached to a 20-in. cap with a welded eye. It was installed to prevent pipe from rotating. A barrel reamer was installed in front of the swivel and pipe to assure integrity of the hole, remove excess cuttings, and protect product pipe. Initially, 600 ft. of pipe was pulled in the hole. At this point, 20-in. pipe was 35 ft. below the river bed. A 10-ft. increase in depth was needed to remain clear of the gravel area. Pullback was halted to allow for a second 500 ft. section to be positioned on rollers and welded to the 1,130 ft. section.

This 20-in. weld, x-ray, and application of weld coating was completed in two hours. After welding, the driller moved pipe for 30 ft. in both directions to ensure that 600 ft. of pipe in the ground would continue to move freely. During pullback of the product pipe, maximum pulling force (thrust) was 80,000 ft.-lbs. This was reached at 300 ft. away from the gravel concentration on the east side of the river. Normal thrust in all other areas was at 50,000 ft. lbs. when pipe was being pulled.

Environmental Crossings. rig rated at 160,000 ft. lbs. was adequate for this work. Total pulling time for pullback of 1,630 ft. including setup of a second section of 500 ft. and a tie-in weld, was nine hours. With the soil conditions of gravel and sand, the solids control unit was a key factor in completing this crossing successfully by eliminating the need for removal and handling of the slurry. Drilling cuttings were passed through a three-stage separation process, reclaimed slurry was mixed with new slurry at the mixing tank, and then supplied to the drilling rig.

No problems were encountered with slurry blowouts and spills in sensitive surroundings in wetlands and Carman. s River. Slurry pits on both sides of the drill were contained to prevent overflows and properly managed throughout this project. The entire work area on both sides of the drill was enclosed and hay bales and silt curtains. The entire river crossing project was performed successfully with no detrimental impact to the area.

Underground/Trenchless Technologies " Environmental Crossings

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