|Sewer RehabilitationTechnologies Benefit from the Development of Standards
by Steve Henning
Well-maintained sewers help maintain public health. Chemical grouting offers one way to seal up older sewer and storm pipes, and the new ASTM Committee F36 on Technology and Underground Utilities will offer municipal engineers and others in the industry a much-needed standard for the specification of chemical grouting systems.
Sanitary sewer collection systems are a critical element in every citys infrastructure and consist of sanitary and storm collection systems, sanitary-storm combinations, and their appurtenances. They are designed to remove and transport wastewater to treatment facilities, making them key elements in the efficient and effective treatment of waste products. Over the past 100 years, sewer systems have been built using a variety of designs, techniques, and materials.
Sewer systems across the United States are leaking badly, with many of the older cities on the East Coast near, or in, a crisis mode. The counties that surround Pittsburgh, Pa., for instance, recently stated that they need 10 billion dollars to bring their sewer systems into compliance with U.S. Environmental Protection Agency regulations. Some municipal experts believe that restoring the sewer systems nationally will cost more than 500 billion dollars over the next 20 years. At a time when municipalities are facing shrinking budgets and are especially concerned with spending their limited resources as responsibly as possible, rehabilitation techniques that prolong the life of the systems while minimizing disruption to the public are highly desired. However, new wastewater treatment plants and sewer systems are often constructed instead of the existing sewer system being rehabilitated.
Chemical grout has been used to stop infiltration in sewer line joints, laterals, and manholes in the United States for over 30 years. The chemical grouting process has the advantage of minimizing disruptions to the general public while being performed. In most cases, the sewers remain in operation during the entire cleaning, televising, testing and grouting process without homeowners even being aware that rehabilitation is taking place. However, this is not the case when streets are dug up for the replacement of sewer systems. But although chemical grouting permanently reduces infiltration cost-effectively and with minimal disruption, it is not being used as often as it could be.
The Need for Standardization
A critical point in the acceptance and use of chemical grout has always been the lack of standardization in its application. The formation of Subcommittee F36.20 on Rehabilitation of Sewers Using Chemical Grouting Techniques will provide local governments, utilities, consulting firms, contractors and inspectors with the knowledge they need to confidently specify grouting as an approved rehabilitation technique. The standard practice being developed by F36.20 addresses the following issues:
Sewer line cleaning;
Sewer flow control;
Sewer pipe joint testing; and
Sewer pipe joint sealing.
The optical-fiber cable industry will also benefit from an ASTM standard. Sewer systems can be used to carry optical-fiber cables if the sewer pipes are structurally sound. If infiltration is discovered upon inspection, sealing the leaks in the sewer pipes with chemical grout allows for the installation of the optical-fiber cables. While the optical-fiber cable community has been quick to accept chemical grouting rehabilitation methods, the lack of a standard practice has hindered growth in their, as well as other, markets.
The elements of the proposed ASTM standard practice work closely with the new federal government Capacity, Management, Operation and Maintenance (CMOM) regulations and the Government Accounting Standards Board (GASB) Statement 34. The simultaneous arrival of the ASTM standard practice, once approved, along with the new government mandates, should provide needed guidance at a very appropriate time.
The new regulation, CMOM, requires the following of the nations underground utility managers:
Properly manage, operate and maintain, at all times, all parts of the collection system that you own or over which you have operational control;
Provide adequate capacity to convey base flows and peak flows for all parts of the collection system you own or over which you have operational control;
Take all feasible steps to stop, and mitigate the impact of, sanitary sewer overflows in portions of the collection system you own or over which you have operational control;
Provide notification to parties with a reasonable potential for exposure to pollutants associated with the overflow event; and
Develop a written summary of your CMOM program and make it, and the audit, available to any member of the public upon request.
The U.S. federal government also initiated Government Accounting Standards Board Statement 34 (GASB 34), which entails the largest changes in government accounting practices since the inception of the Generally Accepted Accounting Practice. GASB 34 identifies two approaches for reporting infrastructure assets, a standard depreciation approach and a modified approach. The modified approach requires that agencies use a system of asset management to manage and monitor the performance of the asset. Those agencies must maintain the asset at or above a minimum condition level. The agency is required by GASB 34 to identify minimum conditions, measure the asset condition, and allocate resources so that condition minimums are exceeded. If an assets condition is monitored and managed then the value of the asset should not be greatly depreciated.
Industry Enthusiasm for Standardization
Because these new regulations require proactive evaluation and maintenance programs, the need for standards has intensified. NASSCO, a national trade association consisting of municipal engineers, consulting engineers, contractors, chemical grout suppliers, and equipment manufacturers, is dedicated to setting standards for the rehabilitation of underground utilities. NASSCO has expanded by forming new divisions to focus on specific sectors of the underground rehabilitation market. The International Chemical Grouting Association (ICGA) was formed as a division of NASSCO to focus on chemical grouting. ICGA members are in complete agreement that their primary focus should be on obtaining an ASTM standard practice for the chemical grouting process. The ICGA membership believes that having an ASTM standard practice will be the best tool available to advance the use of chemical grouting since municipal and consulting engineers are very comfortable with ASTM procedures.
Due to the continuous rise of water treatment costs, it is much more cost effective to keep the water out of the system. With treatment rates of $1.00 to $2.00 per thousand gallons ($0.25 to $0.50 per cubic meter) of water, it does not take long to recoup savings by keeping infiltration to a minimum. A small leak of 1 gallon per minute (about 4 liters per minute) equates into 525,600 gallons (2000 cubic meters) of infiltration per year. The cost to treat that one leak ranges from $525.60 to $1051.20. Typically manholes are spaced every 300 feet (91 m) and pipe joints spacing is three to five feet (0.9 to 1.5 m). .Assuming three-foot (1m) joint spacing and each joint leaking the very small amount of only one-half gallon (about 2 L) per minute, the annual infiltration is 26,280,000 gallons (96 000 cubic meters). This one section results in the need to unnecessarily treat groundwater at a cost of $26,280.00 to $52,560.00 annually. Infiltration also increases the load on a treatment plant possibly causing illegal discharges to occur, or the increased load may actually require a new or expanded treatment plant.
Although the draft ASTM chemical grouting standard began with the development of sealing mainline sewer joints, it will soon be expanded to address sealing sewer laterals. U.S. EPA studies show that laterals allow 25 to 40 percent of the total groundwater infiltration into sewers, making the sealing of laterals with chemical grout a very hot topic due to its large contribution to infiltration.
When government agencies and the private service sector work together, the biggest beneficiary is the general public. The development of the ASTM standard practice for rehabilitation of sewers using chemical grouting will benefit everyone. The credibility of an ASTM standard further promotes governmental agency acceptance of the process, and because the sewer rehabilitation industry supports the development and usage of the ASTM standard it will be widely followed. //
Copyright 2002, ASTM