Increased water demands against the backdrop of challenges on water sources are necessitating pipe infrastructure projects to ensure the reliable delivery of water for the long term. A major consideration for every potable water project is choosing from among the variety of pipe materials on the market. With reclaimed water and desalination projects on the rise, pipe material choice also takes into account the water source.
Ductile iron pipe was the choice to meet increased water demands in Huntsville, AL. It is the fourth-largest city in the state and stands out as one of the fastest-growing major cities in Alabama over the past 15 years. Its municipal water system was the first established in the state in 1823 as the oldest system west of the Appalachians. The first cast iron pipe was laid in 1836.
Steady growth to the current population of more than 186,000 has necessitated a third surface water treatment plant to pave the way for the Huntsville Utilities Water Department to meet increased demand while providing its customers with reliable drinking water.
Huntsville Utilities provides drinking water to more than 90,000 customers from surface water and groundwater sources. The Southeast Water Treatment Plant began construction on a 266-acre site near Lake Guntersville in Marshall County, AL.
Initially, its treatment capacity will be 12 mgd, leading to 24 mgd within three years after filters are rerated in accordance with state criteria, and 96 mgd at total build-out. Once the Southeast Water Treatment Plant is complete, the utility’s system will include three surface water treatment plants and three groundwater plants and wells.
Brasfield & Gorrie operations manager Tony Stephens—who served as the lead construction project manager for the Huntsville installation—indicated that ductile iron pipe was the product of choice for the application. The American Cast Iron Pipe company was chosen to provide the materials and service required for a successful installation. The company is providing more than 20,000 feet of its 42-inch American Ductile Iron Pipe to transmit raw water from Lake Guntersville to the new treatment facility.
Approximately 40,000 feet of 48-inch pipe will carry finished water to the Huntsville Utilities distribution system. Additionally, American Flow Control is supplying 30 Series 2500 resilient wedge gate valves in sizes ranging from 6 to 16 inches and 14 American-Darling B-84-B fire hydrants. Stephens says that the pipe material chosen by the engineers was the most durable, long-lasting material for the application.
“American Ductile Iron Pipe is the most well-known process pipe material that we’re comfortable using,” he says. “It’s the most rugged, least problematic during installations. American is the premiere manufacturer and supplier. We use them exclusively because of the quality of their material and service.”
Project engineer Tetra Tech provided site selection, water quality testing, pilot studies, permitting, design, bidding services, and administration.
The entire project was designed in 3D, enabling the engineer to create more consistent contract documents with minimal errors and change orders.
Tetra Tech began working with Huntsville Utilities in 2005 to determine a suitable location for the new water treatment plant, notes Tetra Tech project manager Christian Dunaway.
Brasfield & Gorrie serves as the general contractor for the project. Garney Construction is the subcontractor, constructing the raw water intake structure and installing raw and finished water transmission lines.
The project stretches more than 10 miles from the new raw water intake structure on Lake Guntersville to the new water treatment plant and through three municipalities—Grant, New Hope, and Owens Crossroads—until it reaches Huntsville Utilities’ primary distribution system, says Stephens.
The work involved coordination among several government agencies, including the Tennessee Valley Authority, the US Army Corps of Engineers, the Alabama Department of Transportation, US Fish and Wildlife, and Alabama Department of Environmental Management.
A project in Bell County, TX
Maury D. Gaston, spokesman for American Cast Iron Pipe, says that in his travels throughout the country, he has spoken to numerous consulting engineers and water utility executives about the best available pipe material used in their project “and the common answer is it depends on what kind of service it may be, such as water and sewer.”
He says that many of those with whom he speaks favor ductile iron pipe for “its unique combination of toughness to handle challenging and demanding installation environments as well as its flexibility to resist excessive surge and water hammer, while at the same time, it has enough strength to withstand very high static pressures.”
Gaston says that ductile iron is “much more resistant to corrosion than the general public realizes, but if corrosion is a factor, it is easily and economically protected by the use of V-Bio enhanced polyethylene encasement.”
Many utilities are now adding an extra life extension component by calling for a zinc spray metallized coating on the pipe’s exterior, says Gaston.
“When you consider all of the various demands placed on a pressurized transmission or distribution water pipe, the attributes associated with ductile iron pipe best meet that total demanding package in the view of most consulting engineers and water utility executives,” asserts Gaston.
In Versailles, France, an iron pipe installed in 1664 is still in service, says Gaston. The oldest iron pipe in the US dates to 1801. In North America, there are more than 566 water utility systems with documented continuous service of iron pipe of more than 100 years, says Gaston, adding that the group is called the “century club.” Of those, there are 25 water utility systems with documented continuous service of iron pipe of more than 150 years, according to the Ductile Iron Pipe Research Association.
A project in Bell County, TX
Water shortages are at the focus of the Carlsbad Desalination Project initiated by the San Diego County Water Authority (SDCWA), the first of 12 such plants due to be constructed in California. In “Fiberglass Pipe Helping Solve the World’s Drinking Water Shortage,” a paper that describes the project, Jeffrey LeBlanc, director of engineering for the Thompson Pipe Group and Matthew Sternisha, Kiewit Shea Desalination, outline the joint effort of tapping into the Pacific Ocean as a significant alternative water supply for desalination.
The project broke ground in December 2012, with pipe installation beginning on December 2013. It was completed on time in December of 2015, enabling the plant to deliver water to San Diego County businesses and residents.
Part of the project entailed the installation of nearly 2,100 linear feet of fiberglass pipe ranging in diameter from 24 to 72 inches to carry raw seawater and permeate product for the Carlsbad Desalination Plant. The plant and pipeline was taken on as an EPC design/build project by Kiewit Shea Desalination. The plant’s main process design of water pretreatment, reverse osmosis filtration, post-treatment and instrumentation and control systems was integrated by sub-contractor, IDE Americas.
A 42-inch AMERICAN Ductile Iron Pipe will carry raw water from Lake Guntersville to the new treatment facility.
The contractor outlined a construction schedule requiring a rapid-paced production of pipe and fittings to specification. Thompson Pipe Group was selected to supply the filament-wound fiberglass reinforced pipe (FRP) pipe materials through its Flowtite product.
The fast-paced construction schedule dictated that the contractor would confer with quality assurance and quality control representatives at the pipe manufacturing facility in Louisiana to ensure the highest quality product. Thompson Pipe Group worked with the contractor to optimize construction by adjusting the plans to eliminate potential challenges during construction, which was on a compressed schedule.
The collaboration reduced the up-front design and submittal phase, enabling pipe production to begin sooner while allowing for a more efficient installation process. The large-diameter fiberglass pipe installation included many methods and different joint types. The pipe manufacturer provided onsite field crews and technical support throughout the phases of the contract as a construction partner.
The pipe had to be buried at depths up to 18 feet and at some points 6 feet below groundwater level. One method, in addition to the traditional direct bury installation method, was installing 350 linear feet of 72-inch fiberglass pipe with a “jack and bore” application. The contractor and pipe manufacturer’s engineers designed a system to fit within the casing of the jacking tunnel.
The pipe sections were joined together within the tunnel using the pressure rated couplings to simplify the installation process and save time. Pre-cut fiberglass lamination kits shipped from the pipe manufacturer were used to conduct field butt wraps. In other project areas, the Flowtite fiberglass pressure-rated couplings enabled the contractor to eliminate many of the 72-inch field wraps and save time on the installation schedule.
Typical trench conditions for the underground pipe material included a crush stone pipe zone embedment material 6 inches under the pipe and 12 inches over the pipe. The fiberglass pipe includes a sand fortifier in the core of the wall construction of the pipe to provide pipe stiffness for buried pipe applications. There are two distinct layers of structural glass reinforcements found in the exterior and interior skin sections of the pipe wall. The FRP pipe was used in various sections throughout the facility, with each section having different requirements and corrosiveness levels placing severe demands on pipe, joints, and fittings.
HDPE pipe installed for a project in Bell County, TX.
For example, the seawater intake pipe carries highly corrosive exposed raw seawater with a salinity of approximately 4%. The FRP pipe materials utilized for the permeate water with chemical addition are exposed to various pH levels ranging from as low as 4.5 to as high as 11.7.
Because of the various conditions within the system, the resin manufacturer provided both polyester and vinyl ester resin to accommodate each pipe section’s requirements. To achieve physical requirements for the underground piping, two different pipe stiffness classes of 36 and 46 psi were utilized.
As a potable water application, the pipe requirements included compliance to the AWWA C950 and ASTM D3517 standards for fiberglass pressure pipe for use in water applications as well as NSF-61 certification for potable water application and be made with phthalate-free resins. The pipes needed to be strong enough to handle the soil load from burial depths of up to 32 feet of cover as well as AASHTO H20 traffic loading. Additionally, the pipe needed to be able to withstand the internal pressures of 118 psig, and handle negative pressure of 7.25 psi vacuum with the addition of 6 feet of groundwater pressure.
The desalination plant—located adjacent to the Encina Power Station in Carlsbad, CA—is connected to the discharge channel of the power station at two locations, with the intake pump station connected to the upstream portion of the discharge channel.
The project’s flow capacity is up to 108 mgd of raw seawater. About half of the seawater processed by the desalination facility would be converted to high-quality drinking water through the process of pretreatment, secondary pretreatment, reverse osmosis, post treatment, and product water storage and transmitted to Carlsbad and surrounding communities.
A finished repair. Approximately three hours
of downtime were saved by using HYMAX
couplings with only four bolts to tighten.
The remaining water with an elevated salt content is returned to the discharge channel where it is diluted with additional seawater before being discharged to the ocean to ensure the increased salinity will not impact nearby marine organisms.
Project specifications called for a minimum 30-year design and performance life. A 30-year water purchase agreement is in place between the San Diego County Water Authority and Poseidon Water for the plant’s entire output.
Other onsite improvements include an intake pump station and pipeline, concentrate return pipeline, sewer connection, electrical transmission lines, road improvements, and product water pump station and pipeline.
The Encina Power Station’s generators have been cooled by seawater sourced from the Agua Hedionda Lagoon, a man-made, shallow, coastal embayment owned by Cabrillo Power. The lagoon has been maintained by the power plant operators.
A concrete pedestrian tunnel on the north side of the new I-35 Bridge in Minneapolis, MN
The seawater-cooled power plant is expected to be decommissioned in the coming years with the desalination plant operators providing long-term maintenance and dredging of the lagoon.
There is a growing trend among municipalities nationwide for the use of reclaimed water to offset the increased demand on water systems. In Texas, the idea to do so emerged in 2009 for a project in which the Bell County Water Control & Improvement District needed to install pumps, pipes, and a control system to deliver 1 mgd to the City of Killeen Stonetree Golf Course about three miles from the wastewater treatment plant.
At the time, discussions centered on the cost benefits of the potential use of an abandoned 24-inch cast iron water line pipe and existing easement installed in the 1950s but had been abandoned for about 10 years.
The hope was that the abandoned water line would be sufficiently watertight, allowing use as a direct conduit for reclaimed water, says Ricky Garrett, general manager for the District.
The line continuously failed pressure tests, leading the team to examine other options. District personnel worked with a team from Brystar Contracting, which suggested sliplining the existing pipe with high-density polyethylene (HDPE) pipe for a long-term, durable, leak-free solution.
Concrete pipe used for stormwater over-flow
containment at O’Hare International Airport
The sliplining method lowered costs in contrast to doing a new installation by decreasing the construction time frame and allowing continued use of an existing right-of-way. Brystar worked with ISCO Industries to provide technical consulting on material selection and construction methods. ISCO also provided turnkey fusion services on the job, with 16-inch DIPS DR21 PE4710 purple stripe HDPE pipe fused together with McElroy fusion equipment, installing more than 10,000 feet of 16-inch pipe within about a three-week timeframe.
Garrett notes that it took many circumstances to come together for the sliplining to work well: an experienced contractor, sufficient working easement, about 10,000 feet of fairly straight transmission main with no fittings around which to maneuver, and accommodating weather. District officials anticipate they’ll be adding to the system in the near future.
In Racine, WI, a water main pit with three water mains going through it contained three aged isolation water valves needing replacement. The new valves were going to be installed outside of the water main pit, so new piping needed to be installed where the valves were previously located. The water supply needed to be shut off as the new piping was placed into the pit.
Racine’s construction department supervisor Mark Carr sought to minimize down time so that service could be restored to the 40,000 customers as quickly as possible, so he chose to use two Krausz USA 30-inch HYMAX VERSA couplings to connect each end of the ductile iron replacement pipe to cast iron on either side.
Once the water was shut down, Carr’s crew cut out the cast iron pipe and installed the new valve and ductile iron pipe with the HYMAX couplings on either end. The installation took about four hours. Carr had estimated that about three hours of downtime were saved by using HYMAX couplings, which only have four bolts to tighten. The HYMAX also is a one-piece coupling, making it simpler to install compared to other solutions containing as many as five pieces. With the fast and easy installation, Carr’s team not only saved time and money, but was also exposed to less risk on the job.Carr has had previous experience working with HYMAX couplings. “We are only able to serve customers as well as the products we use,” says Carr, adding that in his experience, the couplings offer strong performance and high reliability. “When you find a coupling that’s reliable, you stick with it.”