Best Practices for Sewer Inspection and Cleaning
- • Using the latest technology, map out the entire system of sewer lines, pumping and lift stations, manholes, etc., and record all known information from previous studies and complaints about problem areas throughout the system.
- • Determine if mosquitoes are breeding in the various catch basins of the combined sewers or storm sewers and if so immediately contact the local health department for appropriate control measures.
- • Sewer line inspections should be conducted at low-flow times, preferably between midnight and 5 AM or if necessary when the sewers are temporarily plugged to reduce the flow. Inspections can be conducted with: closed-circuit television which, because of the late night hours when the operators are less efficient and may possibly lead to errors due to inattention or fatigue; cameras where the pictures of the inside of the pipes may be done haphazardly and therefore not provide a comprehensive view of the problems; visual inspection and recording of the problems, which is fine for large sewer pipes but in smaller sewer pipes only allows the individual to see what is happening close to the manhole; lamping used in low priority pipes laid 20 years ago or less, which is the lowering of a camera into a maintenance hole and then positioning it in the center of the manhole frame and the sewer and taking pictures of the surrounding area; and the use of mirrors to reflect images of the inside of the pipes. Innovative acoustic technology using portable equipment can be used for smaller diameter pipes of 12 inches or less. This can give you information within a few minutes about blockages and save substantial amounts of money and time in the testing process. (See endnote 37.)
- • Use grease traps from businesses and in some cases homes to trap the grease before it can get into the sewer line. It is essential to clean the grease traps regularly and dispose of the material in an appropriate manner to avoid contaminating the land or water.
- • Insist that industries trap and treat most of the effluent before it is allowed to enter the sewer line.
- • Use mechanical techniques for breaking up grease deposits, cutting roots, and loosening debris and removing it from the inside of the sewer pipe. This can be accomplished either through rodding, which consists of using an engine, rods, and blades to break up and cut debris and remove grease and other substances, or using a bucket machine with open hinge jaws to scrape the material off of the pipe into the bucket and disposing of the contaminated contents of silt, sand, gravel, and biosolids.
- • Use hydraulic techniques which scrub the interior of the pipe and increase the flow in the sewer line. This helps remove floatables and some sand and grit. It can be accomplished by using a threaded rubber cleaning ball that scrubs the inside of the pipe, by introducing a heavy flow of water into the sewer line through the manhole, or directing high velocities of water against pipe walls.
- • Use chemicals only as a last resort in the sewer lines, and be certain that the material safety data sheets have been reviewed in order to not cause additional problems when trying to control roots, grease, odors, corrosion, insects, and rodents.
- • Monitor the flow of the fluid within the sewer lines at various points in the collection system to determine if there are obstructions and deposits which may be slowing down the fluid.
- • Determine if there are frequent sewage overflows from the system and record them along with the weather conditions at that time. The maintenance of good records is essential to aid in establishing a proper maintenance schedule and to avoid violating environmental laws.
- • Establish emergency repair crews with all the necessary available equipment and materials as well as procedures to be followed in the event of an emergency.
- • When sewer lines are repaired, the laterals should be repaired if feasible at the same time.
Best Practices in Sewer Line Replacement (See endnotes 33, 34)
The traditional method of digging up old, deteriorating, and cracked sewer lines and replacing them is an extremely expensive and time-consuming process. The latest methods are called trenchless sewer rehabilitation which uses: pipe bursting, or in-line expansion; slip lining; cured- in-place pipes; and modified cross-section liners.
• Pipe bursting occurs when a special tool forces the pipe to burst and thereby opens it up.
An expansion head is pulled by a special machine through the old pipe and replaces the old pipe with the new pipe, which is immediately behind the expansion head. It is necessary after the pipe bursting to reroute the flow and reconnect laterals to the new pipe.
- • Slip lining is the placement of a liner of smaller diameter inside the existing pipe. It is necessary to grout between the liner and the old pipe to prevent leaks and provide a seal for the space between the new liner and the old pipe.
- • Cured in-place pipe is a process where a flexible fabric liner coated with a special heat setting resin is inserted into the existing pipe and cured under pressure to form a permanent liner.
- • Modified cross-section lining consists of using a new flexible pipe deformed in shape and inserted into the original pipe. The liner is pulled through the existing pipe and is heated and pressurized to conform to the original pipe shape.
All of these techniques may be useful in replacing the damaged and deteriorated existing pipes. Wastewater Treatment Systems
(See endnote 3, and Chapter 11, “Sewage Disposal Systems” for specifics)