April 1, 2008More than 18 million manholes dot America’s landscape. These weak but essential links in today’s sewer systems provide an important window into our underground infrastructure. Enduring tremendous wear and tear everyday, manholes have become a vital component of trenchless technology rehabilitation.
NASSCO, the leading organization for the trenchless
technology industry, recognized the importance of maintaining and repairing manholes years ago when it introduced the Manhole Assessment and Certification Program (MACP). This training and certification program was designed to provide new standards for inspecting and evaluating the condition of manholes and other structures in the sewer system.
“The demand for MACP training is constant and growing,” said NASSCO executive director Irv Gemora. “The number of firms that are inspecting manholes seems to be increasing based on the inquiries that come to the NASSCO office for MACP training. The response of people who are MACP trained and certified is very positive and re-confirms our belief that this program is very much needed.”
Since introducing the MACP course in the fall of 2006, NASSCO has trained approximately 2,000 trenchless technology professionals. MACP helped expand the success of NASSCO’s Pipeline Assessment and Certification Program (PACP), first introduced in 2002. PACP revolutionized the industry by providing common standards for the inspection coding, evaluation, user training and exchange of information about the condition of pipelines in the nation’s wastewater systems. NASSCO’s PACP program is now recognized in North America as the standard for assessing the condition of pipelines. The manhole program was a logical next step.
“With more than 20 million manholes, many of which are in poor condition, manhole renewal is one of the fastest growing segments of the sewer rehabilitation industry,” said NASSCO technical director Gerhard Muenchmeyer. “Like sewers, manhole defects are indicators of the manhole’s condition and service life expectancy. The Manhole Assessment Certification Program (MACP) training is an industry standard method for identifying and coding manhole defects, in a common format, so that the owner can track the deterioration of the manholes and make renewal decisions based on predictable deterioration patterns.”
NASSCO provides the MACP training as part of the PACP training class at no additional cost. For those who have been PACP trained and certified before the MACP was introduced, NASSCO provides MACP training at no charge in several ways. NASSCO provides free MACP training and certification at the three major trade shows: WEFTEC, UCT and No-Dig. Every PACP class scheduled anywhere in the United States will offer free MACP training on a space available basis to all who pre-register for it. NASSCO considers this free MACP training as part of its commitment to re-invest back into the industry.
Design Considerations of Manholes
Manholes endure tremendous wear and tear both on the cover and inside. As a result, it’s important to consider these factors when designing a manhole.
- The cover must provide an easy entry into the manhole, yet provide a water tight seal after the cover is replaced.
- Ground level components must have adequate structural strength to resist damage from mowing equipment, traffic, soil movement, erosion, snow removal equipment, wide temperature excursions etc.
- Extraneous water from surface runoff (inflow) or groundwater (infiltration) must be prevented.
Manholes must also be resistant to powerful deterioration mechanism such as erosion, hydrogen sulfide corrosion and other corrosive chemicals that may be introduced into the system from businesses and industries.
MACP Coding enables individuals to record:
- Construction features and attributes of each manhole component including material, type and dimension.
- Data necessary to estimate the rate of (I/I)
- Any structural or O&M defects
By recording dimensional data, individuals can then effectively select and estimate rehabilitation methods. Data is collected on each of the components of the manhole. Starting from the manhole cover to the frame on which it sits and then to the chimney. Data on material, size and shape along with a listing of defects found on each component is noted. The same data collection continues down to the cone (or corbel in brick structures) to the manhole wall and then down to the bench and channel. Pipe connections to and from the manhole are noted and inspected for defects.
Manholes and the Wastewater Collection System
Due to their exposure to traffic, corrosion, soil movement and other normal wear and tear, manholes experience a high risk of damage. As a result, poor access to manholes can greatly impair the effectiveness of the entire collection system.
Michele V. Brier is a freelance writer and owner of a marketing communications and public relations consulting business. She frequently writes about the trenchless technology industry.