When the city of Roanoke and its partners — Roanoke County and the city of Salem — bid to replace the Roanoke River interceptor two years ago, only three bids were received. The city tried again, this time receiving only two bids. However, what the pipeline industry viewed as an extremely difficult project to construct, Alex E. Paris Contracting Co. Inc. viewed as a challenge to be overcome.
Based in Atlasburg, PA, Alex E. Paris’s contract consisted of laying approximately 5,486 meters (18,000 ft.) of 167.6-centimeter (66 in.), prestressed concrete pipe and 1,828-meters (6,000 ft.) of 152.4-centimeter (60 in.) prestressed concrete pipe along a 8,229-meter (27,000 ft.) stretch to replace an old 121.9-centimeter (48 in.) line.
“The entire project follows the Roanoke River through the city area,” said Alex Paris, the company’s president. “Eighty percent of the project is located directly in the Roanoke River, on the edge of the Roanoke River or on the steep banks of the Roanoke River. The remaining 20 percent is in streets and city parks.”
The interceptor conveys wastewater flow by gravity along 14.4 kilometers (9 mi.) of the Roanoke River, from the Roanoke/Salem city limits to the Roanoke Water Pollution Control Plant in southeast Roanoke. The project, which began in December 1997, consists mostly of open-cut trenching for pipe/manhole installation. The project also had a 274.3-centimeter (108 in.) diameter by 109.7-lineal-meter (360 lineal ft.) tunnel. The tunnel was done by Farner Tunneling, Etowah, TN. The project should be finished in the spring of 2000, and will have an approximate value of $19.5 million.
“Early on, we made the decision to work on a continual basis, because of the complexity of the project and its closeness to the river,” said Paris. “The project worked seven days a week, and crews worked on a four-day rotation. The total number of people working on the project at any one point was between 40 and 50.”
The project only shut down for major holidays. At some points in the construction, the project was under way 24 hours a day.
There were many issues involved with constructing the line along the river that made it “a unique and difficult undertaking,” according to Paris. The biggest issue was a little “fishy.” The Roanoke River is home to two threatened species of fish and the Roanoke River Log Perch, an endangered species of fish. This meant that city planners, state regulatory agencies, citizens’ groups and the U.S. Fish and Wildlife Service were brought in on the effort.
None of the river work could be done between March 15 and July 1, the spawning season for the Roanoke River Log Perch. Plus, any silt from the trenching could be washed into the river and affect the log perch’s habitat. Stipulations in the contract concerning erosion and sedimentation controls, as well as maintaining adequate stream flows had to be addressed.
The next obstacle was an archeological one. During the permitting phase, the Virginia Department of Historical Resources discovered that the alignment ran through a prehistoric Indian habitat that had been occupied in the late Woodland Period (900-1600 A.D.). So, the interceptor was realigned to avoid sensitive areas.
An aggressive schedule and the threat of flooding also provided a challenge.
“Fortunately, during the project period thus far, the weather has cooperated,” Paris said.
Once provisions were made to overcome these obstacles, more complications surfaced.
“This has been the job from hell,” Paris said. “It’s got to be the toughest job in the country. I’ve never encountered conditions like this before.”
Issues arose due to a limited area to handle treating the water that must be discharged back into the river from the ditching and pumping operations. The minimum amount of water being pumped along the river on a typical day was three 10-centimeter (4 in.) pumps. The average per crew has been three, 10.1-centimeter (4 in.) pumps and two, 15.2-centimeter (6 in.) pumps.
“All this water must be run through some sort of treatment facility before it is discharged back into the river, which minimizes any sedimentation,” Paris explained.
The pumps that were used were mostly from New Jersey-based Godwin Pumps, and an assortment of ABS electrical pumps. Godwin hydraulic pumps and Gorman Rupp trash pumps also were among the numbers, which totaled 14 pumps at one time.
The ditches on the lower end of the project ranged, on average, 4.9 to 5.5 meters (16 to 18 ft.) deep. Those on the upper end averaged from 7.3 to 7.9 meters (24 to 26 ft.) deep. In some places, the sewer line depths reached 11.6 meters (38 ft.).
“Many unique ideas developed throughout the project to treat sediment from the water using some different shoring techniques than we would normally use,” Paris said.
These shoring techniques included a standard conventional shore box backed with plates, a “box-on-a-box” technique that consisted of a trench box inside of a trench box and telescoping as digging progressed, and a rolling strut system.
Much of the trenching equipment was supplied and serviced by American Shoring in New York.
The last, but not the least, difficulty on the project was the soils that the team encountered.
“The soils we encountered on this project were worse than anybody could have ever imagined,” Paris said. “They ranged from topsoil to river dirt, to sand, running sand and liquefied orange clay. The rock that we ran into was uneven and jagged and showed up throughout the trenching process. Over 24,000 cubic yards of rock were shot and excavated for the job.”
The excavation was primarily done with a Cat 375L excavator, a Komatsu 650 excavator and a Komatsu PC 1000 excavator. Rock was drilled with John Henry Drills mounted on Cat and Komatsu excavators along with a Gardner/Denver 3500. A host of Caterpillar 235s, 325 excavators and a Komatsu 400 excavator supported the main fleet. The Komatsus and Caterpillars used Hendrix quick couplers with Allied and Teledyne hammers. Each pipeline crew had John Deere and Cat rubber-tired loaders and Case rubber-tired backhoes. A Cat 988B with Balderson forks was used for unloading and stringing pipe throughout the project.
“The project has been a real experience for our company, it being the largest project we’ve done so far away from home. In today’s tough labor environment, [it] has been a real test of our fortitude,” Paris said.
Without the persistence of our good personnel, we would’ve never been able to complete this project, which many have viewed as practically impossible.”