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NASSCO introduces manhole assessment program.

New standards for inspecting and evaluating the condition of manholes and other structures for accessing sanitary sewer systems soon will be complete, says Irv Gemora executive director of NASSCO, a national association dedicated to establishing and implementing standards for rehabilitation of underground utilities.

The new Manhole Assessment and Certification Program (MACP) expands the success of the NASSCO Pipeline Assessment and Certification Program (PACP) which has been in effect since 2002. PACP was the first program to provide common standards for inspection, coding, evaluation, user training and exchange of information about the condition of pipelines in the nation's wastewater systems. The manhole program is the next logical step, says Gemora.

"MACP will complement PACP in the vital task of effectively addressing defects in our sanitary sewer systems," adds Gemora.

"The MACP manual is in draft form and will be completed very soon. Plans are to begin teaching the trainers early in 2006 so full-scale training can begin for public works personnel, engineers and contractors."

MACP is being developed by a NASSCO committee co-chaired by Rod Thornhill, P.E., White Rock Consultants, Dallas, TX, who also is secretary of NASSCO, and Gerry Muenchmeyer, P.E., Muenchmeyer Associates, New Bern, NC, and president of NASSCO.

Understanding manholes

Manholes are essential to sewer systems, yet there has never been industry standards for inspecting and assessing their condition, says Thornhill. To simplify the inspection and assessment process, MACP uses PACP terminology whenever possible.

"However," he adds, "manholes have unique features and components not found in pipelines. These components have their own set of defects that are not adequately described by the PACP defect code list. The MACP addresses this by creating component defect codes that are unique to manhole components--examples are vented covers or defective frame seals."

Thornhill points out manhole structures are more susceptible to groundwater infiltration and surface water inflow than sewer pipelines that are buried below the surface. Manholes must provide access at the ground level, where they are subject to damage from mowing equipment, traffic or environmental conditions such as frost heave in cold climates.

"Manholes must have covers that are easily removed and re-sealable to prevent surface water inflow," Thornhill continues. "Manholes also must extend downward to the pipes where the manhole will be exposed to other detrimental factors such as hydrogen sulfide corrosion or groundwater infiltration. Manholes are also usually constructed of several different components such as covers, frames, cone sections or walls. These different components are often of dissimilar materials that must be built in such a way that the interface between components is structurally sound and watertight."

To identify locations of manhole defects, MACP treats the manhole as a vertical pipe with distances referenced from the manhole rim down to the defect. Locations around the manhole recorded by clock position, with the outgoing pipe designated as 6 o'clock. Defects inside the pipes connected to the manhole are coded the same as other pipe defects using the PACP codes.


Thornhill says that lessons learned during development of PACP have been a great asset in establishing manhole standards.

"Much of the time and effort with PACP was the development of a standard database for storing data," says Thornhill. "The same approach will be used for storing and exchanging MACP data. MACP will include a condition rating based on the severity of defects encountered. A condition rating will be assigned to each component as well as an overall condition rating for the manhole. This will provide the ability to know if one component is defective, but otherwise the manhole is in good shape."

In addition, NASSCO will develop a process to certify manhole inspection software similar to the PACP software certification process now in use.

"By standardizing manhole condition assessment standards and software programs, utilities, engineers, and contractors will see the same benefits proven by PACP," Thornhill concludes.

Muenchmeyer adds that assistance from the industry is needed in the form of good clear photographs showing typical manhole defects which will be used as illustrations during training of MACP.


Manhole Assessment & Certification Program: Irv Gemora, NASSCO, (410) 486-3500, or circle #373
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Title Annotation:Rehabilitation TECHNOLOGY
Author:Griffin, Jeff
Publication:Underground Construction
Date:Dec 1, 2005
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