Trenchless Mandate Makes Rhode Island Water Project Possible.
Completed in December, the 10-mile, $33.4 million East Bay Pipeline included the construction of two pumps stations, a 1,200-foot dredged crossing of the Warren River, open trench construction of 48,000 feet of 24- and 30-inch ductile iron mainline, and a critical 4,600-foot horizontally directionally drilled (HDD) crossing of the Providence River.
Pasquale DeLise, executive director and chief engineer of the Bristol County Water Authority (BCWA) that owns the East Bay Pipeline, said the original plan to link three communities in Bristol County, RI, to fresh water supplies in nearby Providence was first envisioned in 1962.
He noted that part of the project's problem stemmed from the fact that Bristol County is located on a peninsula that juts out into Narragansett Bay, between Providence and Newport, RI. "This, plus the Providence River crossing - that raised the ire of environmentalists - thwarted the water project's progress for years."
The communities of Bristol, Barrington and Warren - known as East Bay- that make up Bristol County are now allowed to receive a maximum of 7.5 million gpd of water from the City of Providence. Prior to the inception of the BCWA, the 57,000 residents of Bristol County had relied on four small reservoirs and two wells, operated by a private company, for their water needs.
Plagued by inadequate supply and poor water quality for decades, the communities banded together and formed a tri-community council to resolve their water dilemma. This resulted in a decision to purchase the private company and, following approval by the voters, establishment in 1984 of the BCWA, a public agency.
DeLise said in 1988 the engineering firm of Weston & Sampson, Peabody, MA, was hired to evaluate the water supply needs of East Bay, and recommend a solution. Their findings indicated that for the amount of water needed, the best and most economical option, was to construct a pipeline link tapping the Scituate Reservoir(1) via the water distribution system in the City of Providence.
"Still, the project did not go forward for very long," DeLise said. "It took from 1988 to 1994 to engineer the project to a point where it was ready to be permitted, and from 1994 to 1998 to complete its construction."
When engineering services were procured in 1988, Camp Dresser & McKee Inc., (CDM), Cambridge, MA, was selected as the prime engineer on the originally proposed project and was responsible for its detailed design and construction services.
Russel Ross, a vice president at CDM, said that although all the design work was completed the same year, issues of environmental concern delayed the permitting process necessary for construction. Particularly troubling for environmentalists was a conventional dredged crossing of the Providence River and sizing of the pipeline to provide for future demand on Aquidneck Island.
DeLise said completion of the controversial pipeline might never have been realized if Rhode Island legislators hadn't become involved and passed the Bristol County Water Supply Act in 1993.
Key features of the legislation not only established that the pipeline would be built, but also dictated that location of the Providence River crossing be moved north to the area of Fields Point in the City of Providence, and that the method of installation be accomplished by either horizontal directional drilling (HDD) or microtunneling, thus eliminating the need for any excavation of the riverbed.
Moreover, the pipe size was limited to 30 inches in diameter and Bristol County and the BCWA agreed to keep operational and upgrade its existing water system. The Act also granted state funding to cover approximately 50 percent of the pipeline cost on the project and 100 percent of the costs for rehabilitating the existing water system.
First Contract Awards
To expedite construction, CDM divided the project into nine separate contracts and established a bid schedule for those contracts not involved in the redesign necessitated by the Act.
Describing the work under the six respective contract awards, Ross said all six relied on the original project design produced in 1988. Work under the respective contracts included: a booster pumping station in Barrington, built by Hart Engineering Corp., Smithfield, RI; an emergency pumping station in East Providence built by Monroe Construction Inc., Warwick, RI; 31,000 feet of 30-inch ductile iron main line construction built by C.B. Utility Co. Inc., Bristol, RI; and the 1,200-foot Warren River crossing, conducted by Harbor Marine Inc. of Warren, that relied on the open trench work being accomplished by underwater blasting to remove rock.
Beta Engineering Inc., Lincoln, RI, was hired by CDM as a subcontractor for the remaining contracts to provide engineering, design and construction management necessary to complete the overall East Bay project. The contracts covered the 4,600-foot HDD river crossing, 1,700 feet of 24-and 30-inch steel transmission main and various fitting necessary to complete the final HDD tie-ins on either side of the river; extending the new 30-inch main northerly 8,400 feet (built under contracts managed by CDM) to the eastern shoreline of the river crossing area; erecting a 90-foot steel fabricated pipe bridge; and relining a 350-foot section of an existing 27-inch RCP sewer line impacting the HDD drill site. Other work included regulatory permitting, land acquisitions and numerous environmental considerations impacting sensitive coastal zones.
DeLise said, "HDD was the only practical solution to the 4,600-foot Providence River crossing. Unfortunately, when the feasibility and engineering phase of the project started trenchless technology was still in its infancy. That's why, when it became necessary to change the original design of the Providence River crossing, we made sure that Willbros Engineers Inc., (formerly Willbros-Butler), that had designed an earlier crossing on this same river got the bid.
Continuing, he said, "As a public agency it was possible to choose the engineer for the project, but not the contractor, which had to be competitively bid. It was decided that CDM would provide engineering services and that Beta Engineering - as a sub-contractor to CMD - would retain Willbros as a consultant for the design phase of the crossing. It was basically luck to have Houston-based Horizontal Drilling International (HDI) - the same company that had completed the earlier crossing - place the winning bid to construct the HDD portion on this job."
William Skerpan Jr., vice president of Beta Engineering, said the HDD portion of the work was indeed the most difficult and risky element of the entire project. Without a successful crossing, the East Bay connection to the Providence system, much of which was already completed, would not have been possible.
Skerpan noted that the earlier crossing completed by HDI for Algonquin involved a 3,200-foot pull-in of 18-inch diameter natural gas transmission line from Bold Point to the Narragansett generation station.
In part, it was the engineering expertise of Wilbros and the success HDI achieved on the Algonquin Gas project that helped sway Rhode Island legislators to allow the East Bay Pipeline to go forward and to rely on a trenchless solution to complete the Providence River crossing.
Work under HDI's contract on this project involved the 24-inch river crossing that extends 4,600 feet westerly from the East Providence shoreline across the Providence River to where it makes landfall in the City of Providence and 1,700 feet of 24-inch and 30-inch steel transmission main and various fittings necessary to complete final line tie-ins. It also included the erection of a 90-foot steel fabricated pipe bridge and relining of an existing 350-foot section of 27-inch RCP sewer line that was impacting the HDD drill site. In addition, the contract covered procurement of the 24-inch welded steel pipe for the project, interior and exterior coatings of the pipe with a fusion bonded epoxy and on-site pipeline assembly.
Both the land lay pipe work and site preparations required under HDI's contract was completed by Otis Eastern Services Inc., Wellsville, NY, and J.H. Lynch & Sons Inc., Cumberland, RI, working as subcontractors to Otis Eastern.
Skerpan said "Otis Eastern was also responsible for providing a 2-million gpd emergency by-pass pumping system on the East Providence side of the river to divert flow in the 27-inch sewer line that the HDD crossing would pass under once drilling operations got underway. As an extra precaution, Insituform Technologies, Inc., Chesterfield, MO, was contracted to reline the RCP sewer, owned by City of East Providence, prior to drilling start-up."
Continuing, Skerpan said, "Otis Eastern's crews were also active at the HDD exit location where a pipe staging area was set up for stringing crews to weld 40-foot sections of the 24-inch steel pipe in preparation for final pullback and tie-ins. While the planned exit target of the bore was located within a paved, relatively flat area, space was not sufficient to assemble the pipeline in a single string. Instead, the pipe was welded up in three sections."
The responsibilities of J.H. Lynch & Sons included the land lay portion of the ductile iron pipe work at the river approaches as well as assisting HDI with installing 25-foot high canvas tarps at selected locations around the perimeters of the construction area for site and noise control. Crews also poured concrete foundations where the HDD equipment spread was set up to contain water runoff and cleaning water. There was also a 40- by 100-foot concrete foundation poured to accommodate a drying area for solids.
In describing the 4,600-foot river crossing, HDI vice president Steven Meaders said, "Right from the beginning the project was tough. Crews were at a disadvantage because of the location of the equipment spreads on both sides of the river.
"The initial pilot bore was made from the fairway of Mobil's Silver Spring Golf Course in East Providence that is contiguous to the river. The exit location, north of Fields Point, is in an industrial and residential area that was constructed by the U.S. Army Corps of Engineers in the late 1920s. Soil investigations at the site indicated that as the drill transitioned out of the subterranean rock formation it would enter a 400-foot section of glacial till composed of an unconsolidated, heterogeneous mixture of clay, sand, gravel and boulders. The top 25 feet of soil, between the surface and glacial till, was of poor quality and prone to caveins. To make matters worse, the area had served as a landfill for a number of years, increasing the possibility of cave-ins or the drilling tool hitting discarded metal objects.
"We were also drilling through 27,000 psi limestone 90 percent of the time, which is about as hard as anything you can find in the U.S. This, combined with the length and diameter of the bore for a rock project, made it unusual, if not unique. While it's not the longest HDD rock bore ever attempted, it is among the largest in terms of diameter."
Meaders said to accommodate the directional bore, HDI mobilized two HD650 directional boring systems with 500,000 pounds of thrust and pullback to the job site.
The 4,600-foot crossing that required a 14 degree vertical bend in the first 1,200 feet of pipe and reached -170 feet below the floor of the Providence River kept drilling crews busy almost a full nine months.
For drilling in the hard limestone a 6 3/4-inch mud motor was used. For the remaining operations, HDI had three Continental Emsco mud pumps, each capable of pumping 500 gpm. Two were used and one was always on standby. The return fluid was processed through two HDI solids control units, each capable of handling 1,000 gpm. The fluid passed from the solids control units, through two centrifuges and back to a mix tank where it could be treated and again pumped down hole.
Meaders noted that formation differences and hardness in the subsurface rock encountered during the bore caused steering difficulties for crews.
"This had more to do with the ability to get the proper radius and alignment during the first 1,500 feet of the bore than actual penetration rates," he said. "The first 1,500 feet of the bore required a full 35 days, while the final 3,000 feet took only 20 days."
Once the pilot bore was completed, the second HD650 rig used on the job was set up at the exit of the pilot bore to assist with rock reaming operations.
"The two rig configuration selected was designed to allow the rig at the exit location to supply the pulling force and the rig at the East Providence location to provide the rotational torque and pumping," Meaders explained. "In this way the reaming could be conducted east to west, allowing all the mud and cuttings to return to the east where the recycling equipment was located."
Meaders said the drilling plan called for three reaming passes through the rock before opening the hole in the till and fill area, considered the most problematic from the very beginning. He estimates the distance between the till and fill, (at the edge of the rock), and the surface to be about 600 feet.
"We first opened the hole from 9 7/8 inches to 20 inches," Meaders explained. "The second pass enlarged the hole to 28 inches and the third and final pass enlarged it to 36 inches. All hole opening was accomplished with Lo Torque Hole Openers. Since we had identified the rock exit on the pilot hole, we knew the exact location of the interface and never attempted to enter the till area with hole openers until the hole was enlarged to 36 inches through the entire section of rock."
When difficulties were encountered opening the till section, the reaming direction was changed to the Providence side of the riven "Almost two weeks were lost in reaming the final 600 feet of hole because of the foreign objects encountered in the landfill area and, of course, the cobbles," said Meaders.
With the rock reaming complete, the rig on the Providence side of the river was removed to accommodate sidebooms to support the pipe during final line pullback. Although the pullback process is generally continuous, space was not sufficient to fabricate the pipe in a single string.
"Instead, the line was welded up in three sections, making it necessary for crews to pull-in two 1,600 -foot strings and a 1,200-foot string into the hole," Meaders said.
Down Hole Problems
As noted by Meaders, crews began experiencing downhole problems when the drilling assembly parted shortly after pullin operations commenced.
At the time the drilling assembly parted, the 24-inch pipe had only reached a few hundred feet into the rock formation. "Using the rig on the East Providence side of the river, all the drill pipe was pulled out of the hole so it could be inspected and to determine what caused the separation," said Meaders. "The inspection showed that the threaded connection on the swivel had failed.
To deal with the challenge, HDI personnel fabricated a fishing tool to snare the swivel. The fishing tool was pushed to the bottom of the hole and, on the first attempt, latched on to the swivel on the first attempt.
Meaders pointed out that crews were fortunate to make the down hole reconnection so quickly. Nevertheless, a decision was made to continue the pullback using the proprietary fishing tool.
Particularly pleased with the fishing tool's performance, which was strong enough to complete the pipe pull-in within two days, he said, "This saved us from having to withdraw the pipe and recondition the section within the till and fill area at the edge of the rock."
As quickly as the pipe surfaced at the entry point, the final line tie-ins were made to the existing Providence Water Supply Board's water distribution system in Providence.
DeLise said Bristol County began receiving water through the new pipeline on Dec. 18, 1998.
As to advise for other municipalities planning similar type projects, DeLise said there can surprises in undertaking a similar type project.
"Despite being successful in dealing with the many environmental issues and having Willbros Engineering conduct extensive subsurface exploration, we still didn't know the actual extent or hardness of the riverbed rock until the drilled crossing got under way. For us, this consequence proved costly. The hard rock conditions added an extra $6 million to the cost of the river crossing, which rose from $11 million to $17 million."
Nevertheless, DeLise is quick to point out that without this technology Bristol County would still be faced with inadequate supply and poor water quality. When weighing Bristol County's poor water supply and water quality against the $17 million cost of the crossing, he said, "HDD was the only option available and without it this project would have never been possible."
(1) The Scituate Reservoir is managed by the Providence Water Supply Board and provides water to many of the cities and towns in RI.
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|Date:||Mar 1, 1999|
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