With a wide range of pipe materials to choose from, competition among pipe manufacturers is sometimes fierce, and performance claims and counterclaims can become confusing. On the other hand, such a wide selection of pipe offers civil engineers significant design options for potable water, wastewater, and stormwater projects to meet specific budget, performance, and installation requirements. The following project, product, and research reports – abridged for this article – highlight just some pipe applications and the design decisions behind them.
Airport stormwater drainage system
For the stormwater drainage system lines located around a new 10,113-foot-long runway at the Port Columbus International Airport, nearly five miles of ADS SaniTite HP polypropylene sewer pipe was used. Jon Pulcheon of George J. Igel & Co. Inc., the construction contractor responsible for the installation of the stormwater drainage system, explained that because the pipe, even the 60-inch-diameter sections, were lightweight, easily maneuverable, and resilient to the harsh environment of job sites, the crew was able to install the 18,000-plus feet of storm sewer pipe at maximum production rates.
"Shutting down an airport even for its own expansion simply cannot be done," stated Ryan Zenkewicz, HP market manager for Advanced Drainage Systems, Inc. (ADS), manufacturer of the SaniTite HP pipe. "Maximum efficiency is the goal of any project for any field. [The contractor] even timed one section, putting in 200 feet of 36-inch pipe in just 90 minutes."
Lightweight and easily maneuverable ADS SaniTite HP polypropylene pipe helped increase efficiency in installing a new stormwater drainage line at Port Columbus International Airport.
ADS SaniTite HP is approved by Ohio Department of Transportation and the City of Columbus for storm and sanitary use, providing an equal alternative to the RCP Class IV pipe. SaniTite HP 30-inch- to 60-inch-diameter pipe meets ASTM F2764. The 60-inch-diameter pipe has a triple-wall construction that provides a smooth interior and exterior wall design, supported by a corrugated structural core for improved stiffness and greater beam strength. With dual-gaskets and a banded reinforced bell, it exceeds the water tightness requirements of ASTM D3212. The pipe is available in 20-foot and 16.3-foot standard lengths from ADS to accommodate various trench box dimensions.
Information provided by Advanced Drainage Systems Inc.
Regional water management
Stuttgart, Ark., is about an hour east of Little Rock in an area rich in wetlands and known as the nation's duck hunting capital. The area also is known for its robust agriculture – especially rice farming. For most of the past century, however, agriculture has been depleting two large aquifers used to irrigate fields in the area. In fact, one of those aquifers could essentially be dry by 2015 and the other could follow suit in the foreseeable future.
To prevent that scenario, work has begun on the Grand Prairie Area Demonstration Project (GPADP), a $400 million water management plan for Arkansas, Lonoke, Monroe, and Prairie counties. GPADP will protect and preserve the Alluvial and Sparta aquifers while providing water for agriculture and preserving wetlands that attract millions of waterfowl each year.
The GPADP will utilize excess surface water and water from the White River to supplement a network of on-farm tail-water recovery systems. The first planned phase of the GPADP is a pumping station, which is currently under construction in the community of DeValls Bluff. The pumping station will draw water from the White River and transport it almost two miles to a 100-acre reservoir. Water from the reservoir will then be distributed to area farms by a series of canals.
Roughly 15,000 feet of piping, installed as twin lines, will run between the pumping station and the reservoir. American supplied Babcock Construction of Pheba, Miss., the initial 7,200 feet of 120-inch-diameter spiral-welded steel pipe for the first half of the needed piping material. Each pipe segment measures 54.5 feet long with one-half-inch-thick walls. The first phase of pipe installation is nearing completion.
Information provided by American
Water main replacement
Last year, the City of Olympia, Wash., was faced with finding the best replacement pipe material and installation method for a 50- to 60-year-old asbestos cement (AC) water main. The main had experienced three breaks over three years and had yet another break during the design phase of the replacement project.
"We originally intended to use open trench for the project, since it's traditional and more of our local contractors would be able to bid on it," said Zheng Lu, project engineer for the City of Olympia. "However, the original AC main was underneath a high-traffic concrete panel road with asphalt paving, so in an open-trench installation we would not only have to replace the concrete afterwards, but also significantly restrict traffic during construction."
The municipality then looked into various trenchless installation methods, including cured-in-place pipe (CIPP) rehabilitation technology, static pipe bursting, and horizontal directional drilling (HDD). The CIPP method proved too expensive and would require the original water main to be shut down during the project. Pipe bursting was passed over because of the environmental sensitivities about AC pipe being split and propelled into surrounding soil. Directionally boring adjacent to the existing main, installing new pipe, and disconnecting and abandoning the old one was selected as the best way to get the job done.
For the replacement pipe, the City of Olympia specified CertainTeed Certa-Lok C-900/RJ restrained-joint PVC pipe. "Our maintenance crew already had the proper tools and fittings in stock for PVC and ductile iron pipe, but didn't have the fusion equipment or parts for HDPE pipe," Lu said.
Horizontal directional drilling allowed installation of 3,400 feet of 8-inch CertainTeed Certa-Lok C-900/RJ restrained-joint PVC pipe water main with minimal disturbance to roads, traffic, and businesses.
In reaching the 3,400-foot length of the 8-inch pipeline, contractor Wiseman Utilities Inc. made a series of bores ranging from 450 to 500 feet, based on the distance between intersections, where valves and hydrants would later be tied in. Pipe was pulled into bores behind a 16-inch back reamer, assembled in 20-foot lengths during the pullback process.
The contractor met its deadline, finishing in 45 work days, and the new water main easily passed pressure testing. After it was brought online, the old AC water main was plugged with controlled density fill and abandoned, per the regulations of the State of Washington Department of Ecology.
Information provided by CertainTeed Corporation
Underground stormwater detention
A first-of-its kind product application in North America debuted in northwestern Indiana when a stormwater detention system was needed for the City of Monticello. The city planned to replace a lift station at one of its wastewater treatment plants and add an underground storage system for combined sewer overflow (CSO). The existing treatment plant received large amounts of water during wet weather events from the discharge of the city's other combined sewers that lead to the Bryan lift station. In addition to the unnecessary treatment of millions of gallons of water, rain events surcharged the sanitary sewers leading to the plant and caused raw sewage backups throughout the city.
Wessler Engineering collaborated with Contech to identify the best approach to meet this site's challenges of limited space and a less-than-ideal subsurface, while still meeting all of the project needs and budget. Contech's DuroMaxx steel-reinforced polyethylene (SRPE) pipe was value engineered for the drainage and detention improvements because it provided the lightweight, structural advantages needed at a lower cost. The DuroMaxx CSO system was designed for 395,000 gallons of storage, but offered a smaller footprint than alternative systems.
A CSO underground detention system in Monticello, Ind., uses Contech's DuroMaxx steel-reinforced polyethylene pipe to provide 395,000 gallons of storage within a small footprint in poor subsurface conditions.
The ability to nest the 96-inch-, 84-inch-, and 72-inch-diameter pipes reduced the overall freight costs. The 80 ksi steel-reinforcing ribs with pressure-rated PE resin provide a strong and durable pipe. Since DuroMaxx has fewer joints to assemble onsite, installation is speedy. Use of electrofusion joints offers watertight protection, and the smooth inner pipe wall promotes hydraulic capacity.
"One thing we really like about the product is it is fast and easy to install, and doesn't need a large machine to lift the large-diameter pipe," said Greg Kuns, owner of F&K Construction.
Information provided by Contech Engineered Solutions
Water and sewer line replacement
The City of Rowlett, Texas, is in the process of completing construction on a $12.6 million utility improvement project called Merritt Road Paving Improvements. The project includes approximately 20,000 feet of water pipe and 9,200 feet of sewer pipe improvements. The city has experienced some rather significant corrosion failures during the last several years and elected to go with PVC pipe because it does not corrode. The project timing is such as to take advantage of now available higher pressure classes of large-diameter PVC pipe. Tri-Con Services is completing construction of the project for the city.
The project called for several thousand feet of 36-inch-diameter pipe and the city chose 36-inch DR18, pressure-rated, 235-psi PVC pipe manufactured by Diamond Plastics. The wall thickness for this pipe exceeds 2.0 inches and is a harbinger of many things to come for the PVC pressure pipe industry.
While Diamond Plastics has provided the industry's largest PVC pressure pipe at 48 inches since 2002, they are now in the process of adding 54- and 60-inch diameters as a result of the growing demand for corrosion-free sustainable products.
Information provided by Diamond Plastics Corporation
The City of Rowlett, Texas, is installing 36-inch-diameter Diamond pressure-rated, 235-psi PVC pipe as part of a utility improvement project.
Treatment plant raw water supply
The City of Norfolk, Va., needed to replace 92-year-old reinforced concrete pressure pipe that had reached the end of its useful life. The Cage Pipe Replacement Project Phase I, taking water from the reservoir in Suffolk to the 37th Street water treatment plant, was relatively straightforward as it runs parallel to an abandoned railroad. Those long stretches afforded Hanson Pressure Pipe the opportunity to introduce Norfolk to bar-wrapped concrete pressure pipe and the installation efficiencies it provides.
Hanson supplied more than 4,100 feet of 36-inch-diameter AWWA B303 bar-wrapped concrete pressure pipe in 32-foot lengths. B-303 pipe, available in diameters from 10 inches to 72 inches, is manufactured using welded steel cylinder with sized, welded steel joint rings attached. The pipe interior is lined with centrifugally applied mortar lining. A steel bar is helically wound tightly around the outside of the cylinder and securely welded to the steel joint rings. A coating of dense mortar is applied to the cylinder and bar wrap. The composite pipe reacts as a unit when resisting internal pressure and external loads.
Use of Hanson B303 bar-wrapped concrete pressure pipe in 32-foot lengths means fewer joints on Norfolk, Va.'s Cage Pipe Replacement Project.
Along with bar-wrapped pipe's durability, dependability, and ease of repair, its availability in laying lengths as long as 40 feet means fewer joints versus the pipe being replaced. The pipe also was installed at a somewhat greater depth – 4 feet – than the existing pipe. The existing soil, being relatively soft, required careful attention to the bedding.
Installation of the new pipe has progressed smoothly, according to the general contractor, with the B303 proving easy to work with and simple to install with no added accessories required for installation. Longer trench boxes are required to accommodate the 32-foot laying lengths. The B303 pipe weighs less, on a unit basis, than prestressed concrete cylinder pipe, which has resulted in cost savings for the installing contractor.
Information provided by Hanson Pressure Pipe Products
Emergency sewer line repair
On Thursday June 28, 2012, a sinkhole appeared on 92nd Street near Third Avenue in Brooklyn, N.Y. The block of 92nd Street between Third Avenue and Ridge Boulevard was closed to traffic as emergency crews from the city's Department of Environmental Protection inspected the sinkhole. Crews worked to stabilize the 70-foot-deep sinkhole and began planning a repair.
Hobas Pipe USA was contacted regarding the availability of pipes suitable for the repair. The next day, Hobas advised that 120-inch-diameter, 46-psi stiffness class pipe was available for immediate shipment. Within one day of receiving the purchase order, Hobas shipped the pipe to the jobsite. Although Hobas pipes are custom manufactured for specific projects, often existing inventory can be utilized for emergency projects.
Installation crews placed the pipe, finalized repairs, and returned the sewer to service. A study of the current infrastructure was conducted.
The fiberglass pipes will provide a long-term structural and corrosion-resistant repair to the sewer. Hobas fiberglass pipes ranging in diameter from 18 to 126 inches have been used across the country for sliplining for more than 25 years.
Fiberglass pipes are manufactured with a uniform wall thickness and composition ensuring compliance with applicable standards, including, but not limited to, ASTM International D3262 and American Water Works Association C950.
Because of their inherent corrosion resistance they provide a long, maintenance-free service life; a 50-year or longer design life provides a a low life-cycle cost. Hydraulic characteristics are practically unchanged with time and leak-free joints mean zero infiltration/exfiltration. Smooth interior surfaces and oversize inside diameters permit greatest recovery of flow in rehabilitated pipelines.
Hobas delivered 120-inch-diameter, fiberglass pipe to the project site in Brooklyn (Verrazano-Narrows Bridge in background) within days of receiving the emergency order.
Information provided by Hobas Pipe USA and Fiberglass Tank and Pipe Institute
Use of CLSM backfill
Controlled low-strength material (CLSM) is being successfully used as a bedding material for vitrified clay pipe. It simplifies the installation of pipe, reduces labor and inspection costs, allows for early backfill, is easy to place, and provides a 2.8 Load Factor.
[Editor's note: According to the Portland Cement Association, CLSM is a self-compacted, cementitious material used primarily as a backfill in lieu of compacted backfill. It's also called flowable fill, controlled density fill, flowable mortar, plastic soil-cement, soil-cement slurry, K-Krete, and other names. CLSM is defined as a material that results in a compressive strength of 1,200 psi or less. Most current CLSM applications require unconfined compressive strengths of 200 psi or less to allow for future excavation of CLSM."]
No field installations using CLSM have resulted in flotation of clay pipe. However, buoyancy calculations done using the Archimedes' Principle (that a body wholly or partly immersed in a fluid is buoyed up with a force equal to the weight of the fluid displaced by the body) indicate that the pipe should have floated. Studies conducted by the National Clay Pipe Institute (NCPI) with its member companies on 8-inch, 18-inch, and 36-inch pipe have shown that the reason clay pipe doesn't float is that CLSM acts as a Bingham fluid. A Bingham fluid, also known as a Bingham plastic, is a viscoplastic material that resists movement at low values of shear stress in the fluid. Buoyancy forces generate shear stress in the CLSM. If the stress applied by the buoyant force does not exceed the shear yield stress of the CLSM, the pipe will not float.
For these reasons, it is important when using CLSM to use a high-density material such as vitrified clay pipe. Evidence from the field has shown that lighter-density pipe materials will float during installation and must be weighted down. It is also important that the CLSM needs to be prepared and placed correctly.
The Sioux City, Iowa, levee district didn't allow the use of granular bedding, so 36-inch vitrified clay pipe was bedded in CLSM.
Information provided by National Clay Pipe Institute
CSP design tools
Corrugated steel pipe (CSP) drainage structures have the design flexibility to be used in applications ranging from underground detention systems to stormwater conveyance systems to culverts and bridge replacement solutions. These customizable and economical solutions have been available to engineers for more than a century. To aid designers in the selection of the solutions for their project, the National Corrugated Steel Pipe Association (NCSPA) in partnership with the Steel Market Development Institute and the Short Span Steel Bridge Alliance have developed two new Web-based tools.
The first tool is eSPAN140, available at www.shortspansteelbridges.org, an interactive design module to assist bridge professionals in determining the optimum design of CSP, structural plate, and short-span steel bridges with spans as long as 140 feet. Based on basic user input, a customized solutions book is produced for that specific project. It is free of charge to users and provides significant time and cost efficiencies as a "one-stop shop" for all commercially available CSP shapes, profiles, and gauges as well as steel bridge fabrication and erection details.
The second tool is the NCSPA Service Life Calculator, which can be found at www.ncspa.org This calculator is the result of more than 50 years of research into the durability of the various coatings available for CSP, including galvanized, aluminized type 2, and polymer coating. Data from studies conducted during the last two years on existing installations of aluminized type 2 CSP and polymer-coated CSP have further verified industry recommendations. Within these two studies, more than 100 installations were inspected in 20 states across the country. The final research report on polymer-coated CSP is available on the NCSPA website; the full report on the Aluminized Type 2 study is expected to be published in early 2013.
Information provided by National Corrugated Steel Pipe Association
Study: Sealing cracks in concrete pipe
New York City Department of Environmental Protection (DEP) is conducting a year-long pilot study to evaluate a new method of sealing cracks in concrete water pipes that could eventually help stop leaks and maintain the Delaware Aqueduct – an 85-mile water tunnel that conveys approximately half of the drinking water from four upstate reservoirs to more than 8 million people in New York City, and 1 million people in Ulster, Orange, Putnam, and Westchester counties.
A Syracuse University lab test, funded in part by DEP, demonstrated that introducing lime and other chemicals into water flowing through concrete pipes can effectively seal hairline cracks and reduce leaks. In August 2012, DEP began a $4 million proof-of-concept experiment at the Rondout Reservoir that will simulate conditions in the Delaware Aqueduct and determine if this new leak-sealing technique can be applied on a larger scale.
Water from Rondout Reservoir is being pumped through three, 2,400-foot sections of 1.5-inch-diameter pipe. Scientists are testing different flow rates to determine if the lime and other chemicals introduced into the pipes will seal cracks under conditions similar to those inside the Delaware Aqueduct. A high flow setting simulates the velocity of water inside the aqueduct and will help determine if lime is deposited in cracks at that speed. A lower flow setting will help scientists learn if enough lime remains in the pipe to seal cracks after it travels for approximately 80 minutes – the time it takes water to travel from the reservoir to the leaking sections of aqueduct in Wawarsing. The experiment will also help researchers assess the extent to which lime deposits build on the walls of the pipe, which can reduce capacity in the aqueduct.
As water flows through the test pipes, modules spaced in 800-foot intervals simulate different-sized cracks and monitor changes in pressure that allow researchers to determine if those cracks are being filled. The experiment will also help calculate appropriate lime dosage and which chemical combinations are most effective at sealing cracks.
Information provided by New York City Department of Environmental Protection
Pipe made onsite
Mo Ehsani, Professor Emeritus of Civil Engineering at the University of Arizona, has designed a new, lightweight underground pipe consisting of a central layer of lightweight plastic honeycomb, similar to that used in the aerospace industry, sandwiched between layers of resin-saturated carbon fiber fabric. In combination, these materials are as strong, or stronger, than conventional steel and concrete pipes, he said. Ehsani's new pipe can be built onsite as a single section of virtually infinite length, hence the product name InfinitPipe.
"There are really two aspects to this invention," Ehsani said. "One is this new type of lightweight honeycomb pipe. Second is our ability to give clients an endless or infinite pipe, without a joint. That is a big, big breakthrough in the pipeline industry that has implications for natural gas, oil, water, and sewer pipes."
The secret of producing virtually endless pipe sections lies in the manufacturing methodology. Ehsani wraps the various layers of carbon fabric and honeycomb around a mandrel, a kind of tubular mold with a cross-sectional shape that matches the pipe's internal cross-section, which is typically, but not always, circular.
"We basically start with a tube and wrap the materials on the outside," Ehsani said. "A couple of layers of carbon fabric, then we put on the honeycomb and then a couple of layers of carbon or glass fiber on the outside. This becomes the pipe."
Carbon fiber, resin, and aerospace honeycomb are all very light materials that can be transported at a fraction of the cost of conventional prefabricated steel and concrete pipe, and Ehsani said he is looking for partners to develop an automated mobile unit to make the pipes onsite.
Information provided by University of Arizona Department of Civil Engineering
Concept drawing shows how a mobile pipe-laying truck could create a pipeline of virtually infinite length. Illustration: Reynard Perrin and Joerg Schmit