No Cover Left Unturned
Boro of Bergenfield, N.J., uses a systematic manhole inspection
and maintenance program to keep its sewers functioning efficiently
By Rosalie E. Leposky
Manholes in cities seem to
be everywhere, but most people notice them only when workers have to use them
and interrupt traffic, or when drivers complain because they make the pavement
uneven and cause wheel-balance problems.
city maintenance workers know that manholes are important facilities: the
entrances to a municipal sewer system. They serve best when inspected on a
regular schedule that anticipates problems and saves the community’s
time and resources.
After years of random inspection and maintenance, the Boro of Bergenfield, N.J., embarked in 2002 on a systematic program of inspection, repair and record-keeping for all of the 1,500 sanitary-sewer manholes in its system.
“Systematic inspection of manholes helps to avoid over-jetting of some pipes and erratic maintenance of others,” says John P. Pampaloni Jr., manager of sewer operations. “We saw the need for a whole-community manhole maintenance system on a regular basis when we found some of our areas were over-jetted and others were never done. Now we schedule regular inspections throughout the whole boro. About once every five years, we try to inspect manholes in each boro street.”
Clay, iron, asbestos
Bergenfield is a century-old, three-square-mile commuter community of single-family homes and apartment complexes with a population of 26,400. “The Department of Public Works is responsible for the city’s 297,000 feet of sanitary sewers,” says John. “The system has no lift stations; it relies entirely on gravity to collect sewage, which then is pumped to a wastewater treatment plant seven miles away in Little Ferry.
“Our sewer pipes originally were clay, ductile iron, and asbestos. Today, most of our old pipes are clay, and the remaining iron pipes are not a problem. Most of our asbestos pipes have been removed, except for four or five streets that need to be removed. We know where they are. We monitor them carefully for breaks and cracks.”
Bergenfield’s pipes vary from six to 24 inches. Between manholes, the average distance is 250 feet to 275 feet. “When we inspect the manholes as part of normal maintenance, we use confined-space entry procedures,” John says. “Between manholes, we use video inspection cameras to assess the condition of the pipes.”
addition to the regular biennial inspection sequence, above-ground
inspections, video inspections, and jetting are performed on a spot basis
Above-ground visual inspection is the simplest, John says. It involves looking at the manhole cover and looking down into the hole. “We have identified hot locations with a high number of stoppages and excessive infiltration,” he says. “They need to be monitored weekly while we decide how to solve the problems. Solutions may vary from a simple repair to completely digging up and replacing the system.”
When a line must be replaced, the boro hires an independent contractor. In this part of the country, pipe bursting isn’t done, and pipe lining is a new concept that John is studying. “We typically use visual inspections and video inspection to get the best replacement and repair descriptive information,” says John.
When video inspection discloses that pipes need cleaning due to a heavy concentration of grease, the boro’s staff jets the sewer line with a jet/vacuum combination truck, using Jet Power II, a sewer degreaser made by Duke’s Root Control, Inc. in Syracuse, N.Y.
Sometimes the problems inspectors find reside in the manholes themselves. Manhole construction defects can contribute to road sinkage and to groundwater inflow and infiltration (I/I) problems. Water can enter a manhole through cracks, holes, and improperly installed invert pipes (the lowest part of the manhole).
John believes every new manhole should be inspected initially, then every eight to 10 years thereafter. “New manholes, especially the new precast ones, should be good for 10 years,” he says.
a manhole may be caused by poor initial construction or by shifting of the
surrounding earth. “Earth may shift around manholes for many reasons,”
John says. “During construction, a backhoe may have filled improperly,
leaving a void. In some areas, poor soil, standing water, or improper
installation can cause pipes to crack and break.”
In some of Bergenfield’s oldest manholes, which are as old as the community, iron ladder rungs installed in the brick sides of the shafts to facilitate entry have rusted or corroded away. Such rungs are made of hard rubber in newer manholes. “We don’t replace rungs in older manholes because to install them we would have to break the integrity
of the manhole walls, causing leaks,” John explains.
Manholes periodically become stopped up when solids accumulate on the bench located on a manhole’s floor, on the floor itself, and on rungs and sidewalls.
“Visual inspection tells us when cleaning is required and why a manhole is backed up,” John says. “Our inspectors are trained to watch for animals and bugs, to smell and test for gases, and to evaluate the color of the sewage. Black sewage has been there a long time
and indicates problems. Lighter-colored sewage means it’s fresher and is moving through on a regular basis.”
The nature of the sewage flow helps to locate the problem. If the flow is choppy and sporadic, building up and spitting out, the backup may be upstream of the manhole in question. If the sewage enters a manhole smoothly and exits in a choppy manner, the obstruction is likely to be in that manhole.
“Today everyone doing manhole inspections follows international precautions and confined-space regulations,” John says. “We wear protective clothing and no longer clean with our bare hands. All inspections are done from ground level, and when we do have to enter manholes, we follow the proper precautions.
of the confined-spaces rules and regulations, we don’t encourage anyone
besides our trained workers, or the trained workers of our subcontractors
or public utilities, to enter our manholes.”
Building a database
The initial boro-wide manhole inspection cycle started Nov. 1, 2002, and finished June 30, 2004. Its purpose was to create a database of information on the manhole system and to systematically find, open, and repair each manhole cover in the city, says John.
“We found some manholes no one knew existed, and some we thought existed were non-existent,” he notes. Some recorded manholes were covered over in the streets, and others were buried in grassy easements. Every one had to be found and cleared. All manhole covers are now accessible.
For each manhole, Public Works employees compiled a two-page paper record and a one-page cumulative location sheet. John created the paper forms from three sources:
• The boro’s utility authority.
• Information he gleaned by attending seminars sponsored by the New Jersey Water Environment Association on sewer maintenance.
• Professional in-service classes offered by the Department of Environmental Sciences at Rutgers - The State University of New Jersey.
“We are deciding how we want to enter and store the data from these paper records in the boro’s computer system,” John says. The inspections involved a total of 1,478 manholes. “We found defects in 1,165 manholes,” says John. “We replaced two cracked or broken manhole covers and will be replacing 57 rims.” Other results of the inspection program:
• 794 manholes required new tar due to street cracking/manhole sinking.
• 479 manholes showed evidence of inflow/infiltration problems.
• 244 manholes needed cleaning.
• 436 manholes had rusted or corroded rungs.
• Four manholes had vermin or odors.
The inspection results gave the Boro of Bergenfield staff a sound basis on which to build a maintenance and repair program. That program, in turn, helps John and his staff keep the sewer system functioning properly, limit I/I, and deliver cost-effective service to the boro’s taxpayers.
© Cleaner March 2005