Maintenance budgets are important because those who manage the collection systems manage infrastructure, assets, and people. In many instances these are aging assets in need of rehabilitation or new infrastructure replacing the aged infrastructure. These managers must set priorities, consider their alternatives, and make the most efficient use of their available resources.
Asset management plans should also be considered to help with optimizing the collection system performance. Since collection system managers are responsible for planning, design, construction, operation and financing of the collection system an asset management program is essential to receive the following advantages:
1. Makes decision making process clear to others
2. Provides consistent criteria for making those decisions, balancing critical needs and interests.
3. Minimize long term costs of system operation and maintenance
4. Define acceptable levels of customer service
5. Creates data and information processes to improve future decision making
6. Establishes roles, goals and metrics that can focus and motivate the organization toward more cost effective operation
Frequent system failures or lack of adequate performance and customer complaints may lead to unwanted political attention or regulatory enforcement issues. The asset management program will keep customers, decision makers, and employees in the know, and what the consequences may be if the mentioned issues are not done in a timely manner.
Maintenance and rehabilitation should occur based on predicted deterioration. There are several things that should be considered:
2. Performance of Assets
3. Operating costs
4. Financial position; revenues, balance sheet, cash flows
5. Required and anticipated levels of service
6. Methods of monitoring and measuring system performance
Case 1: Leaking problem In this case, the pipe is structurally sound and leakage is due to a problem with open or leaking joints. In this condition, chemical grouting provides the only cost- effective solution to the problem. Any other repair technique would be unnecessarily expensive since the only requirement is to stop the leaks, and no other method is less expensive than chemical grouting. A string line is often used in repair work on sewer sections to control the alignment of the sewer.
Case 2: Leaking and corrosion problem Corrosion is commonly encountered in wastewater systems. To be effective in this situation, the leakage should be eliminated using chemical grouting prior to any treatment of corrosion. However, grouting will not be an effective treatment to prevent further corrosion since it works outside the pipe. In this case, a combination of grouting the joints and lining, or coating, the pipe to prevent further corrosion would be the preferred engineering method of rehabilitation. If lining is chosen, the lateral reconnections should always be grouted to prevent water movement in the annulus and to seal the connection between the old pipe and the lateral.
Case 3: Leaking and partially deteriorated structural problem This is the most severe condition that could be encountered in the sewer system. Structural repair of the pipe or manhole is required. However, unless the leak is stopped prior to any structural repair (lining), the water will eventually find its way into the system at openings in the liner for each service connection and at manholes. Infiltration will flow through the annular space of the existing and newly installed pipe until if finds its way into the sewer line. If possible, the water leakage should be stopped or reduced using chemical grout prior to lining in the mainline and after lining at the service connections in order for the lining to be successful in stopping infiltration.
It is expected that city sewer systems in the United States will continue to be prone to infiltration problems due to deteriorated joints even though the pipes may remain structurally sound. The American Public Works Association’s National Statistical Survey showed that rubber rings (used in the form of plastic and compression gaskets) were historically the most widely used joining materials throughout the United States and Canada. These rubber rings were used with concrete and vitrified clay pipes which were built in short lengths, thus requiring more joints, which are subject to infiltration. The problem arises from the fact that there was no standard introduced for the rubber rings and standard composition until 1970. Recycled rubber had been widely used and, since the rubber used had no anti-bacterial agents, it is now being slowly eaten away and deteriorating with time.
Continued improvements in the collection system should be on going. It is important for municipalities to continue to move forward with inflow and infiltration projects as well as upgrade and maintain the existing systems. Grants are not as plentiful as they once were with tighter budgets on the state and federal levels and more cities and towns now have to fund the projects locally or borrow funds from various agencies to make the necessary repairs.
With the current state of aging infrastructure it is important to consider rehabilitation. Operation and maintenance logs should be kept to help make sure the collection system is working optimally. Maintenance records allow operators and
Wastewater Collection System Operator Certification Manual managers to keep track of repair/replacement work for equipment. These records also allow supervisors to develop more accurate maintenance budgets.
Sewer system rehabilitation is intended to reduce the flow of extraneous storm water into wastewater collection facilities. In order to determine the economic feasibility of sewer system rehabilitation, infiltration/inflow studies are conducted to quantify and locate sources of infiltration and inflow. Since these types of projects involves the rehabilitation and replacement of a collection system, it is important to characterize the activities usually undertaken to maintain the collection system. Information related to financing the rehabilitation of the collection system maintenance should be in the form of an annual budget or an asset management plan. It is important to consider a few things before starting a rehabilitation project. If you plan to hire contractors to do any of the work establish a municipal sewer construction contract. This will ensure that you will be covered on some very important issues. Things that should be included in the maintenance contract are:
1. Material performance clause
2. Performance test
3. Presence of a qualified inspector on-site