Durable risers provide solution for sinking manholes
Problem: The City of Corning, N.Y., found that the manholes located on a two-mile stretch of roadway – which accounted for a bulk of the traffic coming into and through the city – provided the second biggest challenge (behind pavement deterioration) in maintaining city streets. Their issues were low spots in the road caused by low manholes. Corning’s storm and sanitary sewer systems averaged over 70 years in age. Over time, the mortar joints supporting the manhole frames and covers deteriorated, and the manhole covers settled into the roadway.
Solution: Previously finding it difficult to prioritize these repairs due to the cost and difficulty of alternative manhole adjustment techniques, they found their answer in Abart Industries - Top Hat Risers. Initially, the intention was to use the risers as short-term, temporary solutions that would also serve to remind them that certain manholes needed adjusting. However, they found that units installed on “high traffic” roadways held up with no issues for over three years, even with snowplows. They are reusable, durable rubber manhole risers that offer a cure for castings, and are an ideal solution for afterthought adjustments. Not only do they absorb impact from traffic, they protect the manhole structure and can be customized to fit virtually any manhole design.
Result: The risers provided a durable and versatile solution for a large problem, allowing Corning to provide smoother, safer roads. 315/730-2588; www.tophatrisers.com.
Paving contractor replaces 100 catch basin risers
Problem: Fthe resurfacing of the I-64/I-255 interchange near East St. Louis, Ill., paving contractors Keeley & Sons Inc. needed to install a total of 100 catch basin risers. The catch basins lined a barrier wall that separated access ramps from main lanes, which meant that crews working on the basins would be exposed to traffic. As part of the contract, lane closures had to be kept to a minimum. “We couldn’t close lanes at all during peak hours, from 6 to 9 a.m. westbound and 3 to 6 p.m. eastbound,” says project engineer Bob Germann.
Solution: Keeley & Sons decided to use catch basin risers from American Highway Products. The risers make raising catch basins and manholes to grade a relatively fast and reasonably priced process. The risers are custom-made for particular projects, and can be easily installed with hand tools, as the entire process takes just a few minutes per riser.
Result: Crews installed the risers after the binder course was laid, and before the final paving lift. Instead of a couple of weeks, all 100 catch basins were raised to grade in just two days. “I’m really glad we had the risers available,” says Germann. “Without them, we would have been forced to hammer out the existing frames and pour new concrete; it could have taken a couple weeks just on that part of the job.” 888/272-2397; www.ahp1.com.
City decides to rehab manholes instead of repair
Problem: One particular line of manholes in the City of Conroe, Texas, had to be continuously repaired after various spray liner options failed over a period of a few years. The city decided to find a permanent rehabilitation solution.
Solution: The city selected rehab manholes from Containment Solutions. The monolithic rehab manholes are made of noncorrosive fiberglass and install in a fraction of the normal time. The rehab manhole is simply inserted into whatever is left of the corroding existing concrete manhole and does not require confined-space entry or special ventilation equipment.
Result: The city not only repaired the manholes in a short amount of time, the new manholes were also warranted for 20 years. 877/274-8265; www.containmentsolutions.com.
Rubber manhole frame helps township eliminate inflow and infiltration
Problem: The aging infrastructure in the Township of North Glengarry (Ontario) was rocked after a 50-year rain event, causing floods and sewer backups. Inflow and infiltration through leaky manhole covers was a significant factor in the system overcapacity. The township needed to rehabilitate its manholes.
Solution: Hamilton Kent’s Lifespan System, a rubber manhole frame with a locking cover system, was piloted in eight locations. The first four units were installed in on-road locations. The others were designated for off-road use near a very active creek, which was decidedly critical for controlling I&I. The creek often overflows and the township didn’t want extraneous water adding to the city’s overcapacity problems. As a watertight system, Lifespan prevents sewer surcharge up to 3 psi and rainwater inflow up to 15 psi.
Result: The township has reported impressive results and no negative issues. By eliminating I&I at these access points alone, the residents will save money they would otherwise have spent on treating extraneous water at the plant and cleaning up after overflows. The installation team appreciated the ease with which the lightweight Lifespan System was installed. They have since ordered more units. 859/533-0849; www.hamiltonkent.com.
Precast manholes lead to significant savings for football stadium construction
Problem: Baylor University’s McLane Stadium is being built on a 93-acre site at the intersection of Interstate 35 and the Brazos River, the longest waterway in Texas. Along with its unique, tight location, the project required relocating sewer and electric transmission lines, along with water, sewer and drainage facilities to service the site.
Solution: To accommodate the size and angles of connecting sewer pipes, and to address the requirement of a small construction footprint, the engineer designed five-sided precast reinforced concrete manhole structures manufactured by Hanson Pipe & Precast. The versatility of precast concrete allowed the contractor to connect the large-diameter sewer mains using only one structure at each point of intersection. Working with the design engineer, Walker Partners, Hanson provided preliminary designs of the special manholes, and estimated production times for building the structures. The fast turnaround times were a key factor in the selection of precast concrete for these unique structures.
Result: The manholes saved time and offered versatility and significant savings in installed cost over alternative materials. 704/752-4740; www.hansonpipeandprecast.com.
Monolithic rehabilitation stops I&I and provides full structural rehab
Problem: The City of Medford, Wis., made a commitment to reduce I&I in their collection system. They determined that reducing the clear water intrusions via both leaking and structurally failing manholes in their system would provide beneficial results long term. The city needed a nondisruptive, long-term, cost-effective method for their maintenance plan.
Solution: Infratech Infrastructure Technologies used Monoform to structurally rehabilitate failing manholes in the system. Workers cut and demo the street surface, remove the casting, demo the chimney section and place the forming system inside the existing manhole. The new structure is formed around the existing drops and flow is not disrupted. Concrete is poured between the existing structure and forming system, then allowed to cure. Forms are removed, the bench and invert are repaired, the casting is reset and the street surface is poured and finished. A complete monolithic pour provides a stand-alone product without detours, bypassing or disruption to adjacent utilities.
Result: The system produced brand new manholes designed to exceed H-20 traffic loading requirements and design life equal to installing new precast. It cost the city approximately half of what it would have spent to dig and replace the manholes. 763/428-6488; www.infratechonline.com.
Moisture-tolerant lining used to rehabilitate manholes
Problem: In September 2003, the City of Denham Springs, La., determined that they’d need to dig up and replace the city’s manholes, a job that was estimated to cost at least $20,000. Because of the high cost of the project, the city decided to look into rehabilitation options.
Solution: The city decided to rehabilitate their manholes using Enviroline 222 moisture-tolerant lining from International Paint – Devoe Coatings. It is a solvent free, two-component polycyclamine-cured lining system utilizing novolac epoxy technology to offer chemical resistance, adhesion to concrete, moisture tolerance, fast cure (rapid return to service in 8 hours at 77 degrees F), single-coat application, and abrasion and impact resistance.
Result: The city saved more than $18,000, and the job took only two weeks to complete. The manholes continue to operate flawlessly. 440/234-2900; www.international-pc.com.
City finds cost-effective manhole replacement system
Problem: Lexington, Ky., is the second largest city in Kentucky. With all of the activities in the area and the resultant traffic, the city realized it needed to make the streets as safe and smooth as possible. A few years ago, the sewer and street departments began to search for a better way to maintain sewer manholes. Manhole lid installations either deteriorated over time or went out of level due to street repaving. The conventional repair methods involving air hammers and saws were too labor intensive and cost prohibitive.
Solution: The search for a new repair method led the city to the Mr. Manhole system, which uses a powered cutter that operates on a backhoe or skid-steer loader. The cutter places a round cut outside the manhole perimeter and removes the manhole frame from the road with little manual labor. The system provides a quick and accurate way to rebuild the manhole frame and lid to the exact height and slope of the road. An added benefit of the system is its ability to stop groundwater penetration into the manhole chimney section.
Result: The Lexington maintenance department purchased the first system in 2008. The crews were trained and immediately set to work repairing the city’s manholes. The work went well and the response from the public was positive, so in 2011, the city purchased a second Mr. Manhole system. Jimmy Webb, superintendent of streets and roads for Lexington, estimates that 1,800 repairs have been completed to date. 419/229-3015; www.mrmanhole.com.
Epoxy resin used to rehabilitate 108 manholes
Problem: The public utility department of Baltimore, Md., was charged with rehabilitating 108 deteriorated brick and concrete manholes.
Solution:For this project, Spiniello Companies chose to use NeoPoxy International’s high-strength, corrosion-resistant NPR-5304 epoxy system. First, the manholes were pressure-washed at 2,500 to 3,500 psi. Although NPR-5304 is a totally hydrophobic product and can cure underwater, hot air was then blown on the surface for 15 to 30 minutes in order to get maximum adhesion. Following this preparation, NPR-5304 was sprayed onto the surface as a monolithic 250-300 mils in one pass without preliminary mortar repair. This direct-to-aggregate method gives the best results since aggregates are the most corrosion-resistant part of concrete, and act like additional anchors for the epoxy layer.
Result: The project was completed successfully, and the manholes were back in service within an hour. Through this application of NPR-5304, the life span of the manholes was extended by approximately 50 years. 510/782-1290; www.neopoxy.us.
Flexible epoxy used to combat inflow and infiltaration
Problem: Inflow and infiltration entering the sewer system through manholes was causing severe collection system overflows during wet weather in the Village of New Lenox, Ill. Senior operator Keith McKeen needed a cost-effective and easy way to remove as much I&I as possible.
Solution: The Village started using Parsonpoxy FP from Parson Environmental Products, and applied it where the manhole frame meets the riser ring. Since Parsonpoxy FP is highly flexible, it can withstand the freezing and thawing environment.
Result: “Parsonpoxy FP is a cheaper cost per manhole than purchasing chimney seals, and can be easily and correctly applied by our summertime staff,” says McKeen. “It has also greatly reduced our I&I problem.” 800/356-9023; www.parsonenvironmental.com.
Base liners saves costs in manhole replacement project
Problem: In 1993 the Town of Oliver, British Columbia, connected a new housing development adjoining Tuc El Nuit Lake to its wastewater collection system. Individual septic systems were abandoned and replaced with new pipe side sewer connections. A new gravity-fed sewer line with 17 manholes was constructed between two lift stations. Intermittent flow created fertile conditions for hydrogen sulfide. The first sign of trouble was the sudden collapse of a sewer section near the wastewater treatment plant. The Tuc El Nuit Lake section was then examined, and inspectors discovered that the complete disintegration of the concrete manhole barrels was imminent.
Solution: It was also discovered that the concrete bases protected by the PREDL Systems North America MH base liners were in original condition. Steve Underwood, P.E. with TRUE Consulting, verified that the concrete bases survived without corroding. Complete structural integrity was preserved. They decided to replace the severely decomposed manhole barrels with new lined barrels and lids installed and supported by the original lined bases.
Result: The base liners embedded during the precast concrete manufacturing process completely protected the manhole base structure in the atypical conditions. The time, labor and material costs for the Town to repair this sewer line were dramatically less because the liners were originally specified. 604/415-9944; www.predlsystems.com.
Resin used to create core plug to stop sewer infiltration
Problem: A large volume of infiltration entered a sanitary sewer manhole in Brentwood, Tenn. The invert of the manhole had a visible 6-inch-diameter hole, likely created to release groundwater during the construction of the sewer. The hole’s plug had disintegrated, allowing groundwater and inflow from an adjacent creek to enter the system. The estimated leak volume was 250,000 to 300,000 gpd.
Solution: CK Masonry installed a bypass system to divert the sewer flow from the manhole in need of repair. They then injected Prime Flex 920 from Prime Resins through probes inserted into the creek bank to slow the flow of water from the creek and stabilize the soils voided by erosion around the manhole. A 1/2-inch injection hole was drilled into the invert of the manhole adjacent to the large hole allowing the infiltration. A Prime Resins Wall Stinger Nozzle was fitted to an 8-foot section of threaded iron pipe with a flow control valve to allow remote injection. The remote injection device was driven into the drilled hole in the invert. To reduce the inflow pressure the manhole outflow pipe was plugged and the manhole was flooded with water until equal with the adjacent creek. Prime Flex 920 was injected through the remote injection probe while a sand bag was held over the gaping hole in the invert. The manhole was drained and the sand bag was removed to reveal a perfect plug. CK Masonry then excavated some of the foam plug and installed a cementitious repair mortar to finalize the repair to the invert. The project was completed in one and a half days.
Result: Flow monitoring between Monday and Wednesday showed a reduction of base flow of 500,000 gpd. The repair was completed on Tuesday that week. That is an estimated savings of $1,400 per day in treatment cost alone. Additional savings for electricity for pumps were also achieved. 800/321-7212; www.primeresins.com.
Lining system provides concrete spalling corrosion protection
Problem: The city of Portland, Ore., noticed manhole concrete spalling from hydrogen sulfide corrosion, and cracking from natural ground movement. Over time, the damage progressed and repairs became necessary. The work had to be done during winter, with temperatures dipping as low as 40 degrees F. And because a section of road had to be closed for the repair, completing the job in a timely manner was paramount.
Solution: Iron Horse Group, a Rhino Linings applicator, repaired the spalled concrete in half a day. Primer 101 was applied to the concrete next as a moisture barrier along with a light sand broadcast. Polyurethane Primer 161 was applied if the Primer 101 was beyond the 24-hour recoat window. A portable heater was used to cure the primers. The following day, Rhino Extreme was applied to the manhole’s walls, ceiling and benches at thicknesses ranging from 100 to 125 mils, depending on the expected hydrogen sulfide exposure. It will protect against corrosion, impact and abrasion damage. Because of its 450 percent elongation properties, it will also move with the earth instead of cracking. It cures quickly so return to service was fast despite the cold temperature and 50 percent inside humidity.
Result: The job was complete in less than two days. The damage was repaired, and a solution was installed to prevent further damage. 800/422-2603; www.rhinoliningsindustrial.com.
Lining system solves sewer overflow headaches
Problem: Groundwater infiltration into the sanitary sewer manholes in Waverly, Tenn., was causing sewer overflows. Two pump stations with 4-inch pumps were activated during each rain event, and surcharging caused manhole lids to float and a lift station regularly overflowed. Something needed to be done about the leaking manholes.
Solution: The 244 manholes selected for rehab were all below the water table. Approximately half of them were brick and half precast concrete. CTR Coatings, located in Powell, Tenn., remedied the situation by repairing and lining the manholes. Forty percent of the manholes were raised, replaced or reset, and root balls were removed from many of them. They were pressure washed and active leaks stopped with hydrophilic grout or hydraulic cement. A SpectraShield Lining System, a multilayer system comprised of a polyurea barrier coat, a surfacing layer of polyurethane foam, and a corrosion barrier of polyuria, was then applied to a minimum thickness of 500 mils. It dries in about 10 seconds, so the manholes were placed back into service immediately after the lining was installed.
Result: The pump stations have not kicked on since the manholes were lined. The lift station has not overflowed and the manhole lids no longer float from surcharging. Reduced flow means lower treatment costs, and the city no longer needs to worry about leaking or corrosion in their manholes. 904/419-4889; www.spectrashield.com.
Microsilica cement restores structural capability in corrugated metal culverts
Problem: Several deteriorated corrugated metal pipes were causing a dangerous and costly problem for a Port Malabar Florida community. Because the aging pipes and concrete crossing bridges provided both access to residents and a right-of-way to utility conduits, they wanted to use a no-dig, nondestructive rehabilitation method.
Solution: The Tramonett Company decided to use Reliner MSP cement from Standard Cement Materials to restore the pipe’s interior shell in accordance with Florida Department of Transportation specifications (Texas DOT and CALTRANS) for “Polymeric Concrete Repair Materials for Patching Spalls in Concrete Pavements and Joints in Box Culverts.” The contractor repaired the single-barrel 84-inch-diameter pipes by pneumatically applying a wet-mix microsilica cement to a 3-inch thickness using a hand-held nozzle and a separate spin-casting method using the Sun Rover III application machine.
Result: The cement provided an ideal solution. It is used to protect concrete, steel and fiberglass structures, and to repair chemical-damaged concrete in pipes, sewer manholes and lift stations, and to make vertical and overhead concrete surface repairs. The components are verified by the Environmental Protection Agency for wastewater use (and drinking water approved). 888/278-1337; www.standardcement.com.
Flex rib chimney seals reduce manhole inflow and infiltration
Problem: During the recent construction of a new subdivision near Louisville, Ky., the specifications stated that all manholes had to be vacuum tested after construction. Upon passing the vacuum test, an internal mechanical chimney seal had to be installed to prevent future inflow and infiltration into the system.
Solution: The project was awarded to Tru Test, and included more than 50 internal manhole seals. Dave Conrad of Tru Test has installed NPC Internal Flex Rib manhole chimney seals from Trelleborg Pipe Seals Milford for several years. The chimney seals were installed before the contractor had finished the final asphalt road surfacing. The solution consists of an EPDM seal with a rib design that allows vertical and lateral movement while still ensuring a watertight seal. The waveband technology creates an effective seal by concentrating the compressive force of the expansion band. The rubber is captured between the band and the concrete.
Result: After completion of the road grading, technicians went back to check the installation. The seal was already performing by holding back water that had leaked through the failed mastic and concrete grouting that the contractor had used to help pass the vacuum test. 800/626-2180; www.trelleborg.com/npc.