Saving When Repaving
How to cut manhole raising costs by 81% and extend new paving lifespan with adjustable manhole risers
In most cases, adjustable manhole risers are the safest, most efficient, and most cost-effective way to raise manholes to grade after streets are repaved with a lift of new asphalt. By analyzing all the costs of raising manholes, road maintenance supervisors and paving contractors can save significant money and time using adjustable risers, as compared to other methods.
Road repaving is a substantial portion of any municipality’s budget and—since asphalt is an oil refinery byproduct with no acceptable substitute—costs are rising dramatically as oil prices climb. To rein in repaving budgets, maintenance supervisors have to look elsewhere and some have managed to cut costs by taking a closer look at all the labor and costs associated with raising manholes to grade after new paving. Also, raising manholes effectively is an opportunity to improve public perception of street maintenance efforts.
Though seemingly a minor detail, cities can have tens of thousands of manholes and keeping them level and at grade is a difficult and important task even in mid-sized cities. South Bend, Indiana, for example has a population of 107,000 and raises 1,000 manholes annually (SolidWaste.com, 11/2000)
When manholes aren't raised to grade, surrounding paving is more likely to be damaged. In Kansas City (per A Look at the Effect of Manholes on Street Condition, a 12/2004, report prepared by Steve Rinne) there are 48,000 sewer manholes, 31,000 water valves, and a large, uncounted number of manholes placed by more than 20 private utility companies. 480 representative manholes were surveyed, and 30-percent were found to be substantially above or below grade.
The pavement around the
observed manholes was assessed. Around manholes at grade, only 11-percent of pavement was rated "bad"; however, around uneven manholes, 35-percent of pavement was rated bad. This is good evidence that uneven manholes contribute to pavement wear, which makes intuitive sense as well. In the
words of the report, "a sunken manhole is a pothole with a steel bottom," that retains water during freeze-and-thaw cycles. Raised manholes get excessive wear from ordinary traffic, snowplow blades, and other equipment. The National Asphalt Paving Association (NAPA) report, Thin Asphalt Overlay for Pavement Preservation, states plainly, "...smooth pavement lasts longer."
Road repaving is a substantial portion of any municipality’s budget and—since asphalt is an oil refinery byproduct with no acceptable substitute—costs are rising dramatically as oil prices climb. To rein in repaving budgets, maintenance supervisors have to look elsewhere and some have managed to cut costs by taking a closer look at all the labor and costs associated with raising manholes to grade after new paving. Also, raising manholes effectively is an opportunity to improve public perception of street maintenance efforts.
Though seemingly a minor detail, cities can have tens of thousands of manholes and keeping them level and at grade is a difficult and important task even in mid-sized cities. South Bend, Indiana, for example has a population of 107,000 and raises 1,000 manholes annually (SolidWaste.com, 11/2000)
Pavement quality around Kansas City manholes, per A Look at the Effect of Manholes on Street Condition, a 12/2004 report by Steve Rinne.
...smooth pavement lasts longer.
Assessing all costs of raising manholes to grade
It's difficult to accurately assess the costs of raising manholes because the issues involved are easy to overlook or minimize. Sometimes this is because the amount of work involved seems trivial compared to the overall task of repaving a section of road, and sometimes it’s because the costs of faulty manhole raising are deferred for months or years, or are speculative (such as liability for damaged vehicles) and hard to quantify. The following list of costs associated with manhole raising is compiled from interviews with more than 30 paving maintenance supervisors or paving contractors.
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Materials: Material costs are not the most significant factor in manhole raising expenses, mainly because it is pointless to consider material costs without also considering the labor of installation. Precast concrete risers, also known as ‘donuts’ or grade rings, are relatively inexpensive, for example, but are easily the most labor-intensive manhole raising solution.
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Labor: By analyzing time logs and maintenance reports, some road maintenance supervisors have been able to quantify the labor costs of raising manholes. In Shoreline, Washington (near Seattle) for example, the wastewater district maintenance manager analyzed three years of maintenance records and determined that raising manholes was costing about $500 per manhole for labor and materials. In this case, the district was covering the manhole at time of paving, then jackhammering new pavement at a later date, and digging out the manhole frame and raising with precast grade rings. In a similar scenario, the Southern California city of Ontario found that labor costs were $360 per manhole when using precast grade rings.
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Liability Claims: Where manhole rims with sharp edges are left proud of the roadway surface, or where manholes have not been raised and create distinct potholes, cities and contractors can be liable for resulting damage to cars. Common claims include broken rims and damaged tires. Similarly, manhole covers that bounce or rattle out of loose risers can lead to expensive claims.
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Pavement Damage: As shown in the Kansas City study cited above, uneven manholes are strongly associated with pavement damage. But even where the manhole is raised correctly, some methods require that existing pavement be chipped out around the new manhole . . .
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