AS SEEN IN ENR: Ringing Out the Old – HDPE Manhole Rings Look to Collar New Roads

March 18th, 2019

From Alaska to the Bahamas, Minnesota to Texas, municipalities are taking a deeper look at the durability and life-cycle costs associated with manhole collars. Too often these systems for topping off, reinforcing and adjusting road elevations are a secondary line item in a larger storm sewer installation project, lumped into the overall task of final adjustments.

Conventional practice is to use concrete or brick and mortar to form a collar—which is often the first component to deterioration from the constant pounding and vibration of vehicles and/or weather, especially freeze/thaw conditions. Led by some proactive agencies in Minnesota, public works engineers around the country are rethinking concrete collars. They are switching to fully recycled high-density polyethylene (HDPE) manhole adjusting rings that are more economical, lighter and durable.

the Ring

First manufactured in the 1990s, the LadTech HDPE manhole adjusting rings are made from 100% recycled plastic or high-density polyethylene (as defined by ASTM Standard D4976). The rings are designed to meet ASTM and AASHTO HS-25 specifications. The LadTech HDPE manhole adjusting ring was tested by American Engineering Testing, a third-party laboratory. The rings were loaded to 60,000 lbs and remained in serviceable condition. In fact, failure of the concrete catch basin and the manhole cover frame assembly halted further testing. Water penetration tests under ambient laboratory conditions were also conducted and showed no significant leakage.

Comparing the load/deflection performance of the ring stack exposed to asphaltic concrete with a similar unexposed ring stack, the deflection of the exposed ring stack was less than the unexposed stack (0.173 in. vs. 0.226 in.). In addition, HDPE materials will not corrode or deteriorate when exposed to the harsh hydrogen-sulfide environment found in most sewer systems.

Stacked Up

The HDPE collars were first installed on sanitary manholes in 1996 in Apple Valley, a community outside Minneapolis-St. Paul, Minn. Jim Fruechtl, former city engineering construction coordinator with Apple Valley Public Works Dept., recalls, “We had such a problem with manhole collars in our harsh conditions that we decided to give HDPE rings a try to see if laboratory testing translated to real-life conditions.”

The engineering department regularly checked the collars over the following winter and next few years. “There was no deterioration, cracking or breaking,” Fruechtl confirms.

He performed his own test, setting a steel plate on one of the HDPE rings and driving a loaded cement truck over it. He explains, “I wanted to see if I could crush it—but it passed with flying colors.” By 1998, Apple Valley specified HDPE collars exclusively. Fruechtl notes, “Initially contractors resisted because it was something new. But they learned to like them mostly because installation is much faster and safer.”

On average, it takes 1–2 hours to install a concrete manhole cover, and then the crew has to return later in the day to backfill to match grade. With the HDPE, installation is 20–30 minutes, and crews can immediately begin backfilling and tamping. The system is ready for asphalt overlay within 10.5 hours. Crews like working with the lightweight (6-lb) HDPE rings that don’t crack or break, and there’s no leftover material.

National Attention

To-date, the HDPE rings are now sole-sourced in more than 70 Minnesota cities as well as many cities in states that face freeze/thaw conditions and those with challenging soil conditions. In McAllen, Texas, HDPE rings are helping increase longevity of manhole covers in the region’s highly acidic soils since HDPE is highly resistant to stress cracking from exposure to chemicals and gases.

Just recently, the Washington Suburban Sanitary Commission (WSSC), among the largest water and wastewater utilities in the nation, approved HDPE collars for use by the maintenance division. In total, more than 4 million HDPE rings are in service nationwide with no signs of breakage or degradation.

Fruechtl confirms, “We installed LADTECH rings 20 years ago, and they look exactly the same today. These installs have eliminated inflow and virtually eliminated reconstruct.”

Plastic Manhole Adjustment Rings Improve the Quality of Sanitary and Storm Sewers

Water Engineering & Management
May 23rd, 2018

New plastic manhole adjustment rings are being installed in residential street projects in Minnesota.

Contractors and specifying engineers have never been able to specify the materials of concrete manhole adjustment rings used in sanitary and storm sewers. Different: construction companies use different mortar mixes. This results in unpredictable quality, compromising the entire sanitary or storm sewer installation. A new plastic adjustment ring made by LADTECH, Inc., Lino Lakes, Minnesota may help with this problem.

Poor quality concrete rings have resulted in several problems. Many of the concrete rings arrive at the job site broken and unusable, adding to the overall adjustment ring cost. In addition, the rings often do not maintain a watertight seal. Groundwater seeps into the sewer, substantially increasing the wastewater treatment volumes. Rehabilitation projects are needed to replace cracked and leaking concrete rings.

Dave Hanson, the area supervisor for Bonestroo & Associates, a consulting and engineering firm located in Minnesota, is responsible for specifying construction materials for the city of Woodbury and Cottage Grove. He has been concerned about the lack of specifications when it came to concrete adjustment rings. “We were not able to obtain consistency in the installation of concrete rings-a problem I have been trying to solve for some time,” he said.

Because of his concerns Hanson was eager to try a new plastic adjustment ring made from high-density polyethylene (HDPE). These rings are manufactured to meet ASTM and ASSHTO specifications and are designed to exceed the wheel-loading requirements of ASSHTO HS25. They have been subjected to more than one million impact/load cycles and exhibit no physical deformation. In addition, the plastic rings will not corrode or deteriorate when exposed to the harsh hydrogen-sulfide environment found in most sewer systems. The rings are installed in accordance with specific instructions to ensure consistent quality, and performance.

Hanson has monitored the adjustment rings in two locations. He was concerned the rings might not hold up during the harsh Minnesota spring thaw. However, through visual inspection over a two-year time frame, he did not see any separation or movement. Because of the success of the evaluation, Hanson has specified the rings on 12 additional residential street projects.

Hanson originally was interested in the plastic rings to improve the quality of sanitary and storm sewer installations. However, he has noticed several additional advantages these rings offer over concrete rings. “Construction crews have told me the rings are much easier and quicker to install,” he said.

A LADTECH ring weighs about six pounds. A comparable concrete ring weighs 85 pounds. This makes the plastic rings safer to handle, reducing on-the-job injuries and eliminating the need for heavy equipment.

Though the initial ring price is slightly higher than its concrete counterpart, the following advantages lower the overall costs of the rings.

  • The cost to replace concrete rings that have broken during shipping and storage is eliminated.
  • The mortarless system allows for fast, non-temperature-critical assembly. Properly installed rings maintain a watertight seal. controlling the infiltration of groundwater and reducing wastewater treatment costs.
  • Rehabilitation projects to replace cracked and leaking concrete rings are eliminated.
  • Time and expenses associated with handing and storing heavy concrete rings are eliminated.

these patented manhole adjustment ring systems are made from 100 percent recycled HDPE plastic.


Finding the Missing Link

Tim Rossiter, CET
May 23rd, 2018

City’s sewer maintenance group finds a cost-effective, long-term solution to broken adjusting rings

Three years after installing IPEX LifeSaver Manhole Adjusting Rings on a busy city street, The City of Windsor, Ontario, in Canada, believes it has found the answer an effective solution to the expensive and labour-intensive replacement of broken adjusting rings. Since 1997, Windsor’s Sewer Maintenance Division has used Lifesaver Rings for the construction and reconstruction of almost 200 manholes.


The LifeSaver Ring is a new concept. It is a lightweight, 100% recycled polyethylene ring built to withstand the rigors of heavy traffic loading, freeze/thaw cycles and corrosive sewer gas.


Pete Matheson, Sewer Superintendent, explains. “Windsor has to deal with the highest volume of truck traffic on their streets of any municipality in Canada. Combine this loading with the high frequency of freeze/thaw cycles and the traditional adjusting rings and mortar simply cannot stand up. There is a manhole on a main road located in the wheel track of the truck lane that had to be rebuilt every three to four years using concrete adjusting rings. We installed LifeSaver Rings three years ago and there has been absolutely no deterioration of the rings to date. We purposely installed LifeSavers in this demanding location to determine if they would stand up to the severe loading.”


Pete also recognizes the reduction in potential liability due to the ease of installing LifeSaver Rings. “Using concrete adjusting rings and mortar, the traffic lane could be closed for as much as three days,” he says, “resulting in major inconvenience to the motorists and the potential for accidents due to the detour. We have found that we can install the rings much more quickly since they are lighter and don’t rely on mortar or shims to set the casting accurately to grade. The completed installation can be backfilled, paved immediately and reopened to traffic.”

“We have found that we can install the rings much more quickly since they are lighter and don’t rely on mortar or shims to set the casting accurately to grade.”

– Pete Matheson, Sewer Superintendent


Another big advantage of the LifeSaver Adjusting Ring system is that it is watertight when installed properly. The system incorporates a sealant between the manhole, individual rings and the casting to provide a waterproof installation.


Windsor’s Sewer Maintenance Supervisor, Charlie Armstrong, oversees the crews using the rings. Charlie comments, “The weight and durability of the LifeSaver Rings is a big advantage. When using concrete rings, heavy equipment is needed to handle the bundles and breakage is common. And we know that if we ever damaged a LifeSaver Ring, which is unlikely. it would be replaced by IPEX, no questions asked. The rings, using a combination of flat and sloped, provide a very accurate final grade for the casting. We don’t need shims or frost-susceptible mortar to adjust the casting.”


So if you’re frustrated with having to continually dig up relics from the past, use LifeSaver Manhole Adjusting Rings. You will soon realize the benefits that progressive municipalities like Windsor are enjoying.

Infiltration Elimination – A Minnesota Town Reduces Infiltration with Plastic Manhole Rings

Public Works Magazine
October 1st, 2007

There are about 20 million manholes in America, and all of them have essentially the same construction: a massive cone section rising up from the sewer.  Until the late 1920s, these cones were made of bricks.  In subsequent years, precast concrete arrived on the scene.  Above the cone section is a short section called the “chimney” which is capped by an iron frame and cover.

The Chimney is a tricky necessity.  Each one must be custom-built to the right height and slope for its location so the cover and frame are flush with the road surface.  And while each concrete chimney is unique, they all share one characteristic: they’re a headache.

“The rings break, so you get silt, rocks, and stormwater flowing into the sewer,” says Roger Glanzer, utilities supervisor for the Minneapolis suburb of Edina, which has a population of 47,000.  “that means you’re paying for treating water that doesn’t need to be treated.

Further, the chimney continues to deteriorate over time.  The deterioration, in turn, causes the roadway above to become prone to collapse, which leads to potholes around manholes.  The whole process leads to a lot of labor-intensive, expensive road repairs.

There are three main causes of manhole chimney deterioration:

  • Freeze-thaw cycle: this culprit is especially prevalent in the northern United States
  • Microbes: in sanitary sewers, they metabolize hydrogen sulfide gas, transforming into sulfuric acid. The acid gradually turns the mortar between the rings to dust.
  • Improper Construction: Building a concrete chimney requires skill, but the job all too often goes to a worker with little or no masonry construction experience.

In the late 1990s, Glanzer decided to use rings made of High-density polyethylene (HPDE), manufactured by Ladtech Inc. of Lino Lakes, Minn.  He’s happy to report he’s had good results.

“We put some of them in areas where we periodically go back and look at them to see if there’s any sign of infiltration or degradation,” says Glanzer.  “it’s been about eight years, and we’ve had no problems.  When sealed properly, they don’t allow infiltration.”

The rings are easier to handle because they’re virtually unbreakable and weigh a fraction of their 85-pund concrete counterparts.  In addition, the plastic rings can be installed more quickly because they interlock with each other and are self-aligning.  Workers seal the rings together with a butyl rubber compound.  Both HDPE and butyl rubber are highly resistant to acid.

“The only problem we’ve had was getting the engineering superintendent to change his specs,” says Glanzer.  “he didn’t think the plastic would hold up, but it does, and the crews like working with them.”

Glanzer has partnered with Ladtech’s distributor to train crews on the ins and outs of installing the rings.  Overall, they’ve found the process to be fairly straightforward.  Glanzer calculates that each installation (requiring a new cover and frame, and post-installation asphalt repair) costs about $700, which is paid for by sewer assessments.  It appears to be money well spent.

How To Build A Better Mousetrap Or Manhole Chimney

U.S. Water News
May 1st, 2007

With several decades experience in the precast concrete business, Dwight Wiedrich was very familiar with solving problems as they arose. So when a salesman pointed out some problems customers were having with the concrete rings used to build manhole chimneys, he took a swing – and hit a home run.

A manhole chimney serves a crucial function by making sure the manhole cover is flush with the street. The chimney is a connecting link, usually about one foot high, between the massive concrete or brick cylinder at the bottom and the cast iron frame and cover at the top of a manhole. For decades, workers have built manhole chimneys the same way – by stacking numerous thin concrete rings on top of each other to bring the manhole up to the level of the pavement.

Problems with concrete ring chimneys are legion. The rings weigh about 85 pounds each, requiring a skid-steer loader to move and place them. However, because they are so thin and fragile, they tend to break when moved. Furthermore, it takes some skill to build the chimney. After it’s built, crews have to wait for the mortar to cure before back-filling the area around the chimney, frame and cover.

After construction, concrete chimneys fall prey to three unavoidable enemies: traffic loading, water and sulfuric acid. Traffic volume and weight have steadily increased over the years. The water finds its way inside the chimney either by flowing through the hole(s) in the cover or by infiltrating through the ground. The acid is a product of bacteria that metabolizes the hydrogen sulfide in sewage. Under the pressure of this triple attack, eventually the concrete and the mortar fail.

Wiedrich explains that “the chimney is the weakest part of the system. Under attack by water, sulfuric acid and vibration from traffic, the concrete turns into a fine powder. The powder gets between the rings and whatever adhesive was used to seal them up – so the adhesive releases its grip.”

Ultimately the manhole caves in, creating an instant road hazard. Considering that there are 20 million manholes in the U.S., and about 60 percent of them were built before 1960, this is a major problem. Looking for a better way Wiedrich knew there had to be a better way to build a manhole chimney. In 1995, Wiedrich received a patent for the man- hole chimney and founded Ladtech In. to market his invention. He serves as chief executive officer and Lana Wiedrich serves as president.

“I figured plastic was the way to go, so I began visiting manufacturers,” explains Wiedrich. “I asked for a type of plastic that would withstand high and low temperatures, constant loading by heavy trucks, and the attack of water and sulfuric acid. PVC wouldn’t work because it cracks at low temperatures. Rubber and composite materials were too expensive. And foamed plastics wouldn’t stand up to the load. Then one guy mentioned high-density polyethylene (HDPE). We [Ladtech] looked at its characteristics and it seemed to be a fit. That was in 1992.”

After crunching some numbers, Wiedrich concluded that HDPE chimney rings were feasible. He spent the next two years working through the design process.

“Ladtech’s computer expert gave us modeling information on impact and dead load, and we discovered that HDPE easily meets those requirements,” says Wiedrich. “A tougher question was: ‘How are we going to seal the rings together?’ The bottom ring has to bond to the concrete or brick manhole below; each ring has to bond to the next ring; and the top ring has to bond to the cover frame. Well, we tried every type of sealant we could find. We ended up with butyl rubber. It’s the only thing that sticks to everything. Then we went through 82 versions of the ring profile that didn’t quite do the trick. Version 83 was the one that worked!”

In 1995, Wiedrich received a patent for his invention called Ladtech Adjusting Rings.

Wiedrich says, “We suggest to agencies that they should always replace their chimneys when they open up manholes for any type of work. About 60 to 70 percent of sewer inflow enters either through the manhole casting or a broken chimney section. So that’s the best place to put your money – it’s the cheapest way to decrease inflow. We also point to our five-year warranty. Can they get that from the contractor who builds a concrete chimney? No! And yet people resist; they think it’s going to be cheaper and easier to use some kind of spray or hydraulic cement to seal up the existing concrete chimney. But those products won’t do any good if the concrete rings have deteriorated, and sooner or later they all do.”

Ladtech is enjoying fast growth, partly due to the influence of the federal government. The EPA has proposed a program called cMOM (Capacity Management Operation & Maintenance) as an addition to the Clean Water Act. If enacted, cMOM will require all sanitary sewer system operators to develop programs to monitor and control sewer system overflows. This will involve the rehabilitation of millions of failed manholes.

Wiedrich also owes his success to satisfied customers. More than 30 states and thousands of municipalities have officially approved Ladtech Adjusting Rings for use. Hundreds of thousands of the rings have been installed nationwide with zero failures reported to date. NOTE: Richard L. Kronick is a freelance writer.

For More Information Ladtech Adjusting Rings, 651-415-1252, ladtech.com

Manhole Makeover – Engineering solutions for a successful renewal program

John Jurgens
May 1st, 2004

Manholes are the most visible point in identifying the condition of our underground infrastructure, and with the advent of effective pipe-repair technologies, manholes are receiving increased attention from municipalities. Leaks sealed out when pipes are lined are likely to travel to the next weakest part of the system – the manholes. And when any part fails, the whole system fails. Thankfully, manholes are the easiest segment to investigate and the most cost effective to repair.

When neglected, erosion from groundwater intrusion, corrosion from liquids and gases, and wear from dynamic traffic loads can lead to complete collapse of a manhole.

There are approximately 20 million manholes in the United States. Like pipelines, they come in a variety of sizes and materials, and more than half of them were installed before 1960. Often, one can determine the age of a system just by looking at the manhole lid. In older systems, the lids are often 18 inches in diameter

and have numerous vent holes. The manhole chamber below the lid of older systems generally is constructed of brick and mortar. Newer systems, on the other hand, have 24- or 36-inchdiameter

lids with only one or two pick holes and chambers constructed of precast concrete.

Old manholes in particular can suffer from serious problems. They are subject to erosion from groundwater intrusion, corrosion from liquids and gases, wear from dynamic traffic loads, and general deterioration from age. Any of these processes create structural fatigue or cause substantial inflow or infiltration. Out of sight, degradation is not easily monitored, but when neglected, complete collapse is likely.

Other influences that contribute to the structural decline of a manhole include soil movement and water table fluctuation (hydrostatic loading). Soil movement can be caused by naturally occurring events, such as earthquakes or freeze-thaw cycles, or it can be induced by nearby construction activities.

Once a rigid structure experiences movement, the foundation is set for deterioration to begin. A fracture in the wall of a manhole also can open up the possibility for erosion. More than half of the manholes installed in the United States never were pressure tested to ensure water/air tightness, and many have experienced ongoing infiltration. Over time, this constant intrusion takes a toll on a rigid structure. On a brick manhole, water movement will remove mortar between bricks, contributing to the loss of bricks and increasing the potential for failure of the structure.

Chemical attack is caused by effluent discharges and corrosive gases that eat away the channel and base of a manhole. These discharges have low pH levels, which cause concrete materials to deteriorate. Most public agencies have eliminated issues concerning chemical attack from contributor discharges. Nevertheless, microbiologically induced corrosion (MIC) is a process where aerobic bacteria metabolize hydrogen sulfide gas (H2S) and oxygen to produce sulfuric acid (H2SO4). Generally, MIC is most aggressive in manholes with a great deal of turbulence.

Selecting the proper repair method, however, is critical to a successful renewal program. Each type of problem demands an engineered solution. Regardless of the rehabilitation mechanism, adhering to the original substrata is crucial. Understanding the environment, the steps needed in preparing the surface, and the products being used also are important issues.

Manhole defects and repair methods

Being aware of various types of problems aids in the investigation of manholes in a system. Once manhole defects are identified, they can be classified into different types and then related to an effective repair method.

There are approximately 20 million manholes in the United States. More than half were installed before 1960.

Type I single defects can be repaired easily and usually inexpensively. Repairs generally range from $50 to $500 per manhole. These defects include frames and covers that leak because of poor fit, multiple vent holes, damaged adjusting rings, and shifted frames. They can be replaced or fitted with under-the-cover inflow protectors. Internal or external chimney seals are applied to correct damaged adjusting rings. Internal seals are available in mechanical or hand-applied versions made of a flexible membrane.

Individual leaks that have not resulted in structural erosion can be sealed with water plug or chemical grouts. Likewise, eroded benches and leaking channels can be patched and sealed. Additionally, damaged steps create a serious hazard and should be removed. In fact, most U.S. cities choose not to replace steps to reduce liability for unauthorized entry. Workers use safety harnesses and tripods for entry.

On a brick manhole, water movement can remove mortar, leading to the loss of bricks and eventual structural failure.

Type II defects are more serious and are identified as areas where some structural damage has occurred from unplugged leaks, resulting in voids or missing bricks and mortar joints; or where multiple Type I problems are evident. In these cases, a structural liner that reinforces and seals the damaged wall is warranted. Cementitious liners can be hand-sprayed, troweled, or centrifugally cast onto the prepared interior of old manholes to create a structural shell of sufficient strength to withstand groundwater pressure and dynamic traffic loads. The diameter and condition of the manhole determines the thickness of the hardened, cementitious shell.

Similar to SDR ratings for pipe, large-diameter manholes require correspondingly greater thickness for the same strength value. For example, manholes that are 72 inches in diameter require a liner to have a thickness of 1.5 inches to attain a strength value equal to that of a 0.5- inch-thick liner in a 48-inch-diameter manhole. Likewise, deep manholes are subjected to greater groundwater pressures, thereby requiring thicker liners in the lower portions of the structure. Structural reinforcement and sealing with a cementitious lining costs about $8 to $12 per square foot of coverage.

Type III defects relate to corrosion, the most common cause of deterioration in concrete sanitary sewer structures. Industry studies estimate that corrosion is the primary source of structural damage in three-fourths of all precast concrete manholes and lift stations installed during the last 30 years, with repair and replacement costs totaling billions of dollars.

The source of this corrosion can be chemical or bacteriological. When corrosion occurs in the areas contacted by the flow, chemicals are present in sufficient concentrations and temperatures to corrode the lower portions of the manholes. This type of corrosion is common in industrial sewers.

Leaks that have not resulted in structural erosion can be sealed with water plug or chemical grouts.

MIC, caused by acid-generating bacteria, is the most common corrosion in municipal sewerage. Thiobacillus bacteria thrive in the slime layer above the flows and secrete sulfuric acid. Wherever hydrogen sulfide gas is produced, these bacteria grow rapidly because the gas is their source of nourishment. Their rate of growth and the consequent damage is increased by high nutrient levels; long retainage times, which allow the sewerage to go septic; very warm temperatures; and turbulence, which releases the hydrogen sulfide gas. Understandably, MIC is most severe in coastal plains and warm climates with a great number of lift stations.

Cementitious liners can be centrifugally cast onto the prepared interior of an old manhole to create a structural shell sufficiently strong to withstand groundwater pressures and dynamic traffic loads.

The corrective action for this type of manhole and lift station damage is to place a protective barrier between the corrosive bacteria and the structural substrate. The most appropriate solution depends upon the severity of the deterioration, which is related to two sub-classes of Type III defects.

Type III-A defects are defined by corrosion that has done little damage or, on new structures, that has not yet begun. In such cases, a polymer coating may be applied to a properly prepared surface for protection. Thorough preparation and expert application is key to the success of this method. A high-pressure washing or sand blasting followed by an acid neutralizing rinse is best. The industry offers a variety of coating materials – such as epoxies, polyurethanes, polyureas (the reaction product of an isocyanate component and a resin blend component), and blended hybrid polymers – that can be brushed, roller-applied, spray applied, or centrifugally cast. The coating thickness (commonly 65 to 100 mils) must be sufficient to prevent vapor penetration, and it must be free of any holidays or pinholes that would permit bacteria to grow behind the coating. Prices for coatings used to remedy Type III-A defects are commonly $10 to $15 per square foot of coverage.

Type III-B defects are identified as structurally deficient walls caused by corrosion. The coating in this case must be applied at a thickness that will compensate for the structural value of the lost wall. This can be done by using a polymer coating of sufficient strength and applied at a thickness of 1/4 to 3/8 inch, or by using a composite or laminated liner that combines structural reinforcement and corrosion protection at similar combined thickness and strength values. Common solutions for the latter methods are cementitious liner/polymer composites and fiberglass/polymer composites (FGP). FGP liners may be hand-laid, or installed as a custom-fitted bag that is expanded and cured in place with steam. Costs for these methods range from $20 to $30 per square foot of coverage.

Separate and distinct alternatives to correct Type III-B defects are cementitious liners that retard or prevent production of acid-producing bacteria. Calcium aluminate cements generally retard the growth of bacteria by making surface conditions less favorable to their development. During the past six years, a U.S. environmental Protection Agency-registered, anti-bacterial additive has proven to prevent growth of the bacteria. In either case, the applied thickness is the same as for Type II repairs with correspondingly lower costs.

Type IV defects are indicated by severe structural damage that requires replacement. These problems are determined easily because field staff can recognize structures in this category. Excavation, removal, and resetting of a new structure is the most costly option because it requires bypassing flows, interrupting traffic, allowing for other buried utilities, and general social disruption. Depending upon the pipeline’s location, size, depth, and diameter, costs for replacement can range from $1,500 to $3,000 per vertical foot.

Two, less expensive options are no-dig and partial-dig solutions. No-dig methods use forms, which can be passed through existing openings and assembled entirely within the old manhole. An annulus space between the forms and the old wall is filled with standard, department of transportation-specification ready mixed concrete and vibrated into place creating a new, joint-free wall about 3 inches thick. In corrosive environments, a plastic liner with interlocking protrusions is fitted onto the form before placement of the concrete so that when the forms are removed, a fully plastic-lined concrete manhole remains in place.

In corrosive environments, a manhole can be replaced without digging by installing a plastic liner fitted to a form, and filling the annulus space between the form and the old wall with concrete.

Partial excavation is required to sleeve the old structure. For this option, the entire cone is removed and a smaller-diameter fiberglass or plastic pipe is sleeved inside. The annulus between the sleeve and the old wall also is filled with ready-mixed concrete and then a new cone is installed and the pavement is replaced. These options offer substantial savings, with costs ranging from $500 to $1,000 per vertical foot.

Inspection and testing

The most important part of manhole renewal is at the end of the project. When plastic linings, polymer coatings, or polymer composites are used, the project is not finished until the final repair product is tested thoroughly to verify installation integrity. The owner’s inspector can visually verify that the manhole is leak free and coated as specified. Spark testing or the use of a holiday detector verifies that the new polymer coating or plastic lining is free from pinholes and voids, and is uniform in thickness. The National Association of Corrosion Engineers’ publication, High Voltage Electrical Inspection of Pipeline Coating Prior to Installation” (NACE RP0274), is an excellent reference for inspectors.

Verification of bond is another important test that can be conducted on polymer coatings after the installed products have cured. The American Society for Testing and Materials’ document, Pull-off Strength of Coatings Using a Portable Adhesion Tester” (ASTM D-4541), describes the use of a portable adhesion-testing device to verify the bond of a polymer coating to a prepared substrate. Two testing options are used commonly: the bond may be tested to failure and a value recorded; or a predetermined bond strength is selected, and the polymer coating is tested up to that point.

The testing process gives data on two types of failure: when the polymer coating pulls away cleanly from the substrate and when the polymer coating pulls free with some of the substrate attached. In the latter case, the value recorded at failure represents the tensile strength of the substrate surface. The inspecting engineer must plan how to use these two types of data in the bond evaluation.

A drawback to this testing method is that it is destructive and requires repair of the test locations. However, it gives a good indication of how well the substrate surface was prepared and how well the polymer coating bonded to the substrate. In addition, deficiencies can be rectified before installation crews leave the jobsite.


Although many older manholes in the United States are in need of crucial renovations or even replacement, there is no need for newer systems to reach a critical state of disrepair. The technology and technical know-how is available to solve the myriad of deterioration issues that municipalities face. And acting now to preserve manhole quality and integrity certainly is more responsible from a financial point of view than waiting for the structural stability of a manhole to be compromised fully.

John Jurgens is principal of Trenchless Resources International based in Seattle. He specializes in manhole and trenchless pipeline rehabilitation. Jurgens can be reached at 425- 487-3325 or via e-mail at nodig@aol.com.

Lino Business Honored for Use of Recycled Materials

Quad Community Press
June 20th, 2000

Ladtech Incorporated, based in Lino Lakes, was recently honored by the Anoka County Board of Commissioners for its use of recycled materials to manufacture its product.

Ladtech produces manhole adjusting rings from 100 percent high density polyethylene recycled plastic, or “curb side waste,” said Lana Wiedrich, corporate secretary for Ladtech and wife of president Dwight Wiedrich. Last year Ladtech used three million pounds of curb side waste, like milk jugs, soap jugs and shampoo bottles, Wiedrich said. This year the company hopes to double that number. All commercial plastic has a number on it, Wiedrich said, and any plastic container with the number two on it is used for the manhole ring.  All manhole rings are concrete, Lana Wiedrich said, and “we developed the first recycled plastic one.” It takes 52 milk jugs to produce one two-inch ring. Dwight said. Ladtech has patents in the United States and Canada, a pending patent in Europe, and has distributors all over the country, Wiedrich said.

Wiedrich said Ladtech’s man- hole adjusting ring is more effective than the standard concrete man- hole rings because it’s long-lasting, environmentally friendly, cost-effective, will not corrode from sewer gasses, It’s lightweight, it’s a mortar-less system and prevents storm water infiltration. It will also save money for cities, counties, states and contractors.

“We’re just changing what’s been going on forever.” Wiedrich said.  “We’re trying to get people to understand that change is necessary”.

Dwight Wiedrich, who has worked in the concrete, pipe and manhole industry for 30 years, is not against concrete and thinks it’s an excellent product, but he said concrete is not meant to be two inches thick, be shaped like a doughnut and not be reinforced.

Wiedrich also said that concrete doesn’t come with a warrantee and concrete costs climb when the concrete rings are breaking. Ladtech’s ring comes with a 10-year replacement warrantee, Wiedrich said.

Ladtech has been in production for a little over two years and Wiedrich said the company has come a long ways in a short time. The adjusting ring complies with all the government standards for infrastructure, something the concrete rings have not always complied with, but Wiedrich said that’s because concrete has always been used.

“We’ve finally come up with something better;” Wiedrich said. “We’ll be forcing concrete to meet these standards.”

Wiedrich said recycled plastic is used because it’s durable material and will stand the test of time. The minimum amount of time the Ladtech plastic manhole ring is expected to last is 100 years, Wiedrich said. It also helps the environment by removing garbage from landfills and reusing it productively, Wiedrich said. The materials are supplied by Recycling Alternatives Incorporated (RAI) in Mound. RAI also forms the material into the Ladtech-designed ring mold.

The award presented by the Anoka County Board of Commissioners was presented in April and coincided with Earth Day, Wiedrich said. Wiedrich said the award was important for Ladtech because it shows the company is complying with new world standards toward recycling.

“It was an honor to be recognized so early in our company’s history.” Wiedrich said. “It lets us know we’re on the right track.”

Tim Bartlett is a staff writer for Press Publications and can be reached at (651) 407-1235.

Sewer Rings – Environmental & Health Issues

Solid Waste Management Coordinating Board
April 1st, 2000


The next time you drive over a manhole, you just might be driving over recycled plastic. One Minnesota company has developed a molded plastic manhole adjusting ring made of 100% recycled plastic that competes with non-recycled concrete rings. The rings are used to raise manhole covers up to street level after road surfacing. As many as 50 recycled milk jugs and detergent bottles are used to make a single 27-inch plastic sewer ring that can last up to three times as long as a concrete sewer ring.

Recycled plastic rings have been tested for impact resistance and compressive strength, as well as examined for their effects related to temperature changes. They were found to perform similarly as concrete.

In many ways, the recycled plastic rings outperform traditional concrete rings. The recycled plastic rings weigh just over five pounds, while conventional concrete rings weigh about 85 pounds. The plastic rings can be easily handled by one person without the need for heavy lifting equipment, reducing the time and cost needed to install the rings. In addition, the light-weight plastic rings lower the risk of employee injury associated with lifting heavy concrete rings.

Recycled plastic rings are a longer lasting alternative to concrete. since they are not prone to crack or break and do not corrode when exposed to salt. Maintenance schedules for city. county, and state road repairs vary widely; some overlay roads every three years while others may wait up to 15 years. No matter when maintenance is performed, more often than not, the concrete adjusting rings need replacing. Although the actual life cycle of the plastic rings has not been determined, the manufacturer provides a 5-year warranty. This is in addition to their normal “no charge” replacement for any rings found broken prior to installation.

Recognizing the advanced quality of this product. in 1996 the Minnesota Department of Transportation Mn/DOT) approved these plastic rings for statewide use. Refer to Appendix F for Mn/DOT’s technical memo or plastic adjusting rings.

VEHICLES AND ROAD MAINTENANCE Sewer Rings Environmental and Health Issues



Reprinted from: Environmentally Preferable Purchasing Guide

Published April, 2000 by Solid Waste Management Coordinating Board