Case Studies - Winter 2018

Case Studies - Winter 2018

Grout reduces I&I in collections manhole

Sewer manhole leak fixed by grout injection

Problem: Colchester, Vermont’s wastewater system processes more than 100 million gallons of wastewater per year. When a significant groundwater leak was discovered at the joint between manhole pipe sections, IP&C Industrial Services was invited to evaluate the situation.

Solution: IP&C Industrial Services determined that the most cost-effective solution would be to apply a chemical grout injection system from AmTech Tank Lining & Repair. The crew drilled an injection path into the center of the crack. Flexible packing was wedged into the joint to slow the inflow. Fast-setting grout was pressure injected throughout the crack and voids created by groundwater outside the manhole pipe.

Result: Once the grout set, the leak and outside voids were completely sealed off. The Town of Colchester realized significant savings compared with curtain grouting or replacement of the manhole pipes. 

888-839-0373; www.amtechtanklining.com


City chooses centrifugally cast option to rehab manholes

Problem: The City of Hampton, Virginia, has a collections system that dates back to the early 1940s, and nearly 75 percent of the system is below the groundwater table. During a rain event of 1 inch or more, groundwater and rain-derived I&I greatly overtaxes the system’s capacity. In addition, inflow and infiltration contributes to the wear and erosion of pipes and manholes and increases pumping and treatment costs.

Solution: After careful consideration, Hampton selected the Permacast self-install solution from AP/M Permaform. The system centrifugally compacts high-strength fine-aggregate concrete on the prepared interior of a deteriorated manhole. The crew also re-establishes the bench and inverts and installs a plastic manhole insert to stop the inflow. The bidirectional spincaster is raised and lowered with a winch to achieve thorough coverage and complete compaction without having to trowel.

Result: Using the flow data and similar rain events to analyze the results, the efforts reduced inflow by 18 percent in their initial pilot program. The city subsequently implemented a full I&I reduction program, with a goal to rehabilitate 100 percent of the city’s 11,000 manholes. A three-person crew structurally now lines about 400 manholes each season between April and October. The crew averages between three and four manhole rehabs each day, depending on depth, condition, and access. 

800-662-6465; www.permaform.net


Access assemblies help a town prevent I&I issues and improve safety 

Problem: The Town of Cary, North Carolina, has dozens of streams and lakes located in its boundaries, and it is prone to occasional flooding. During major rain events, stormwater occasionally gets into the sanitary system, causing sewage backups that can overflow from manholes into nearby lakes. When sewage infiltrates creeks and lakes, fish and wildlife are endangered, and the town must deal with the resulting cleanup and potential fines. They needed to find a better solution. After trying elevated manhole covers, they discovered that the covers would pop off when stressed. A standard manhole cover weighs about 130 pounds and removing them while on a ladder 6 feet above ground was dangerous.

Solution: EJ provided the REVOLUTION Access Assembly, an elevated manhole cover that required no lifting. Once the bolts are removed, workers can easily rotate the lightweight cover away from the opening to access the manhole. It stays attached to the frame via a cast-in stainless steel rod. One worker can easily access the elevated manholes. It also seals tightly when closed, preventing I&I.

Result: “When the lid is seated correctly, the REVOLUTION works great for preventing any type of inflow, pretty much across the board, everywhere we’ve installed it,” says Robert Hirt, P.E., utility engineering supervisor for the Town of Cary. A backup along the Walnut Creek sewer outfall, following Hurricane Matthew in 2016, proved that point without a doubt.

800-626-4653; www.ejco.com


Grout reduces I&I in collections manhole

Problem: A municipality in Ocean County, New Jersey, had severe infiltration within its 8-foot-diameter manholes located close to a large streambed in an area with a high water table. The deteriorating manholes had reached a point of active and constant leaking through joints in the precast sections. A material was needed that would flow into the voids and cure rapidly, before the inflow could wash away the material.

Solution: Sauereisen F-370 Hydroactive Polyurethane Grout 22-ounce dual cartridge was the chosen solution. Hydrophobic chemical grouts are ideal for stopping water infiltration in concrete structures and the convenient cartridge package allows for repairs in confined spaces where pump injection is not practical. The grout can be injected directly into the wall of the structure, where it will expand nearly 20 times its original volume to fill the void. 

Result: Both the contractor and the municipality were very pleased with the ease of application and the results. 

412-963-0303; www.sauereisen.com


Liner system helps Florida coastal city with I&I issues

Problem: Fernandina Beach, Florida, is situated on the shores of the Atlantic Ocean to the east and the Intracoastal Waterway to the west and receives an average annual rainfall of 51 inches. Consequently, the groundwater table is extremely high. Its principal sewer treatment plant is permitted for 2.5 mgd. The sanitary sewer system is older, with approximately 95 miles of gravity sewer, force mains and 1,461 manholes. The infiltration problem became so acute that plans were being evaluated for a treatment plant expansion expected to cost in excess of $20 million. 

Solution: Beginning in 2005, John Mandrick, Fernandina Beach utilities director, began a phased I&I reduction program using the SpectraShield Liner Systems for manhole rehabilitation and cured-in-place pipe. It is a multilayered lining system designed to stop infiltration and prevent corrosion.

Result: By 2014, flows had been reduced by 800,000 to 1 mgd. A major plant expansion was avoided, operating costs were reduced, energy savings were realized and groundwater was conserved. The Environmental Protection Agency estimated the reduction in flow reduced operating costs by more than $450,000 per year. The energy savings from the reduced flow volume is in excess of 200,000 kWh per year. Groundwater is now percolating into the local groundwater table and not the treatment plant. 

800-284-2030; www.spectrashield.com


Inside manhole drops replace failed outside drops

Problem: Many of the manholes in Saugus, Massachusetts, were originally installed with outside drops, which are difficult to access for inspection, cleaning and maintenance. As a result, the condition of most of these outside drops was unknown, and they could have been contributing to the city’s I&I issues.

Solution: National Water Main Cleaning, using design documents developed by CDM Smith, was contracted to fill in the outside drops and install new inside drops from RELINER/Duran. National Water Main Cleaning has established a procedure whereby the base of the outside drop is plugged with concrete prior to the drop being filled with pea stone or sand. A hydraulic cement cap is placed on top and worked to be smooth with the mainline pipe invert. The mainline pipe is then CIPP lined, followed by rehabilitation of the manhole. After the installation of a cementitious liner in the manhole, the inside drop system is installed. The system consists of a fiberglass drop bowl that is bolted to the manhole wall just beneath the high-level inflow pipe, and stainless steel pipe support brackets are used to attach the drop pipe to the wall. A flexible coupler is used to connect the drop pipe to the drop bowl, and a bend is installed at the pipe base in the manhole invert.

Result: The system was easy to install and allows the drop to be cleaned and inspected from above. 

800-508-6001; www.reliner.com


Rehabilitation of digester includes crack repairs

Problem: A digester located in Texas was showing severe deterioration, including deep cracks along the floor that were leaking water in areas throughout the unit. The number of cracks and leaks suggested that the water membrane underneath the slab may have aged and fatigued. 

Solution: Epoxytec recommended a combination of CPP Sprayliner and CPP Trowelable. Blended with reinforcing agents and various fibers, CPP Sprayliner creates a fiber-reinforced polymer lining when cured, offering high strength and flexural properties for partially or fully deteriorated structures. Surface preparation included abrasive blasting to achieve clean, sound, profiled concrete. The concrete was then sprayed with an initial coat of CPP Sprayliner to achieve an even finish throughout the substrate and to attempt to seal any hairline cracks and low-pressure leaks. Cracks were drilled to relieve water pressure. After allowing the initial coat to cure, drilling on some major leaking areas was conducted to alleviate pressure away from the cracks. Next, standard CPP was applied to these open cracks to finalize the repairs (now with no pressure). Once the majority of the cracks were sealed and repaired and the material was cured, the contractor grouted the relief drill holes and patched them with CPP Trowelable. The final step included spraying a coat of CPP Sprayliner to make all the surfaces uniform.

Result: All cracks were addressed, and CPP Sprayliner provided sealed protection that will prevent corrosion and future deterioration. This solution resulted in cost-savings and allowed a quick return to service without replacement or major reconstruction. 

877-463-7699; www.epoxytec.com


Rehabilitation of digester includes crack repairs

Problem: A digester located in Texas was showing severe deterioration, including deep cracks along the floor that were leaking water in areas throughout the unit. The number of cracks and leaks suggested that the water membrane underneath the slab may have aged and fatigued. 

Solution: Epoxytec recommended a combination of CPP Sprayliner and CPP Trowelable. Blended with reinforcing agents and various fibers, CPP Sprayliner creates a fiber-reinforced polymer lining when cured, offering high strength and flexural properties for partially or fully deteriorated structures. Surface preparation included abrasive blasting to achieve clean, sound, profiled concrete. The concrete was then sprayed with an initial coat of CPP Sprayliner to achieve an even finish throughout the substrate and to attempt to seal any hairline cracks and low-pressure leaks. Cracks were drilled to relieve water pressure. After allowing the initial coat to cure, drilling on some major leaking areas was conducted to alleviate pressure away from the cracks. Next, standard CPP was applied to these open cracks to finalize the repairs (now with no pressure). Once the majority of the cracks were sealed and repaired and the material was cured, the contractor grouted the relief drill holes and patched them with CPP Trowelable. The final step included spraying a coat of CPP Sprayliner to make all the surfaces uniform.

Result: All cracks were addressed, and CPP Sprayliner provided sealed protection that will prevent corrosion and future deterioration. This solution resulted in cost-savings and allowed a quick return to service without replacement or major reconstruction. 

877-463-7699; www.epoxytec.com


Repairing a sewer while saving the trees

Problem: B. Braun, a large producer of medical products, operates a facility and wastewater treatment plant in a woodland park that is part of a delicate regional ecosystem with a dense forest with steep inclines. When a CCTV inspection showed that 1,000 feet of pipeline had been damaged by encroaching tree roots, they sought to rehabilitate the badly damaged wastewater system while preserving natural resources.

Solution: Tkm-Service GmbH oversaw the project and met with an expert from Trelleborg Pipe Seals to find the best solution to deal with the forest’s limited access and steep inclines. Trelleborg suggested the use of its DrainFlexLiner and POX HC120+ resin for hot water curing. The resin’s generous pot life allowed the crew over three hours to prepare the liner, carry it down the hill using large wheelbarrows and invert the liner into the manholes. Purpose-built water towers let the steep hill and gravity work to their advantage. The resin’s pot life helped maintain efficient workflow.

Result: After the liner cured, a leak test and CCTV inspection was performed. A liner sample was sent to a laboratory for further testing and the findings were positive: The cured liner was 100 percent watertight and the mechanical values exceeded normal requirements. The resin contains no VOCs or styrene, and not a single tree was felled. 

800-626-2180; www.trelleborg.com/pipe-seals


City gets proactive on manhole protection

Problem: The city of Fairmont, Minnesota’s wastewater collections system utilizes 75 miles of sewer lines with 30 lift stations. During routine inspection, one of the sanitary sewer force main manholes was identified as turbulent. The city decided to take the proactive measure of lining this 2-year-old precast manhole — which has a 6-foot diameter at the base and tapers to 4 feet by 13 feet deep — to protect the asset from any future corrosion and deterioration that would require costly measures to correct.

Solution: “We want to protect our assets. We have seen similar structures deteriorated. This force main sanitary sewer is only 2 years old, but we decided to be proactive and selected CLADLINER to seal and protect,” says Doug Rainforth, the city’s water and wastewater superintendent. The rehabilitation of this manhole was completed from start to finish in several hours. After the surface preparation, involving high-pressure waterblasting, a mortar pump was used to spray on CLADLINER. Once the product was firmly set, it was smoothed over with a chip brush, hand trowel and damp sponge.

Result: Rainforth says the decision to take a proactive approach to addressing the city’s sanitary sewer collections system will pay off for years to come. 

877-708-2523; www.cladliner.com


Liner system used to combat hydrogen sulfide damage

Problem: Albuquerque, New Mexico, has aging sewer infrastructure, a high percentage of which consists of concrete pipe that is more than 50 years old. Over the years, these pipes have suffered the effects of hydrogen sulfide, resulting in severe erosion causing sections of pipe to deteriorate completely.

Solution: TLC Plumbing explored a number of options and, in consultation with city engineers, decided that the best solution was to use Thermoform from Warrior Trenchless Solutions. The PVC-A fold-and-form pipe liner would allow them to get through areas where other materials would be too risky. Also, it is a seamless liner that provides a tight fit to the existing host pipe and would prevent any I&I. The material is highly chemical-resistant and is not affected by the presence of hydrogen sulfide. It is environmentally friendly and doesn’t contain any water-soluble chemicals that can leach into the surrounding ground. The installation process doesn’t rely on a chemical reaction. This meant the workforce and general public had no exposure to harmful vapors at any stage of the pipe rehabilitation process. The footprint required for the installation was minimal, and therefore disruption was minimized.

Result: TLC Plumbing initially evaluated Warrior Trenchless Solutions Thermoform with the city engineers and received their approval. TLC Plumbing has continued to install miles of this product for pipeline rehabilitation in Albuquerque and other surrounding municipalities without disruption to the existing asphalt, landscape, or environment. Pipeline integrity is being restored with a solution that will stand up to future assaults from hydrogen sulfide exposure. 

www.thermoformliner.com



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