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.
- 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.
- 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.
- 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.
- 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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