Sanitary Sewers

Sanitary Sewer:

A sanitary sewer is a separate underground carriage system specifically for transporting sewage from house and commercial building sewer laterals to treatment or disposal. Sanitary sewers serving industrial areas also carry industrial wastewater.

Sanitary sewers are operated separately and independently of storm sewers, which carry the runoff of rain and other water which wash into city streets.

Sewer Lateral:

A sewer lateral is the pipeline that connects the property to the local sanitary sewer main. The sewer lateral is owned and maintained by the property owner including any part which may extend into the street or public right-of-way.

Sewer Main:

A sewer main is a utility pipe that carries wastewater from the connected laterals to the wastewater treatment plant (via sewer force or gravity main). In the City of Racine, smaller diameter pipes, 18 inches or less are owned, operated and maintained by the City of Racine. Larger diameter pipes called interceptors are owned, operated and maintained by the Racine Wastewater Utility. 90% of the sanitary sewers in the City are owned and maintained by the City of Racine department of Public Works and not the Wastewater Utility. The City of Racine contracts with the Racine Wastewater Utility to perform triannual cleaning of their sewer system. The Wastewater Utility also responds to City residents for the City of Racine under a maintenance contract for that service. All costs associated with maintenance of the City owned system are paid for by the City and its ratepayers through sewer rates.

Sewer Force Main:

A force main is a pressurized main pipe which can carry sewage counter gravitationally (from lower to higher elevations). A force main pipeline carries wastewater from a sewage lift station to other pipes further along in the system. The word "force" refers to the fact that the pipeline is under pressure, rather than relying on gravity to move wastewater.

Force mains are used to convey wastewater from a lower to higher elevation, particularly where the elevation of the source is not sufficient for gravity flow.

Gravity Main:

Gravity mains are large networks of underground pipes that convey wastewater from individual households to a centralized treatment facility using gravity. The system is designed with many branches. Typically, the network is subdivided into primary (main sewer lines along main roads), secondary, and tertiary networks (network at the neighborhood and household level). Gravity mains do not require onsite pretreatment or storage of the wastewater. Because the waste is not treated before it is discharged, the sewer must be designed to maintain self-cleansing velocity (i.e. a flow that will not allow particles to accumulate). A constant downhill gradient must be guaranteed along the length of the sewer to maintain self-cleaning flows.

Sanitary Lift Station:

When a downhill grade cannot be maintained, a lift station must be installed. Primary sewers are laid beneath roads, and must be laid at depths of 5 to 9 feet to avoid damages caused by traffic loads.

A lift station pumps or lifts the waste stream from low lying areas to higher lying areas, so gravity can carry the flow to the treatment plant. Some areas must be pumped because the gravity areas are not possible.

Checks are performed on each station daily and records are maintained for run time on pumps and for flow calculations. Maintenance procedures and general house keeping are also performed at each station. Checks are done on backup generators for readiness in case of power outages. For stations without built-in generators staff has portable generators which can be set up to operate the pump station.

All of the stations are on a SCADA tracking and alarm system. Computers monitor wet well levels and pump operation. If a pump fails, an alarm is sent to the wastewater plant for the operator to respond to, to have a member of the field operation fix the problem. The system also keeps historical data to be used for reporting purposes.

Sanitary Manholes:

Periodically, a vertical pipe will run up from the main to the surface, where it is covered by a manhole cover. Manholes allow access to the main for maintenance purposes.

Access manholes are placed at set intervals along the sewer, at pipe intersections and at changes in pipeline direction (vertically and horizontally). The primary network requires rigorous engineering design to ensure that a self-cleansing velocity is maintained, that manholes are placed as required and that the sewer line can support the traffic weight. As well, extensive construction is required to remove and replace the road above. Manholes are installed wherever there is a change of grade or alignment and are used for inspection and cleaning.

Sanitary Sewer Maintenance:

The City of Racine has a maintenance and cleaning program to keep the sanitary sewer system operating efficiently and to minimize the number of calls for service. The City contracts with the Wastewater Utility to provide this maintenance program for them. Some problem areas in the City are cleaned more frequently than others.

Sewer cleaning using hydraulic or mechanical methods performed on a routine basis helps to remove accumulated debris in the pipe such as sand, silt, grease, roots and rocks. If debris is allowed to accumulate, it reduces the pipe capacity and a blockage can eventually occur resulting in overflows from the system onto streets, yards, basements, and into surface waters. The Racine Wastewater Utility has a full time crew assigned to cleaning the sanitary sewer mains.

Sewer Flushing:

The Racine Wastewater Utility uses high-pressure sewer Vactor jet trucks to clean the sanitary sewer system. To clean sanitary sewers the Utility uses high-pressure water to propel a jet nozzle at the end of a specialized hose through the sewer pipeline, breaking through obstructions and blockages. A flushing nozzle is installed on the end of the jet truck’s hose and the hose is lowered into the downstream manhole of the sewer section being cleaned.

This method uses high-pressure water to flush out stone, sediment or other unwanted material from the sewer. As the jet hose is rewound, high-pressure water cleans the sewer walls and back flushes all the debris.

Sewer Lateral/Tree Conflicts:

Residents occasionally submit complaints to the City indicating they have roots in their sewer lines causing poor drainage and other issues. 

Root growth into a sewer occurs where the sewer lines have been damaged by factors such as soil compaction and aging sewer laterals. The roots themselves do not cause the original sewer line damage but may result in blockages and further pipe breakdown.

Nutrients, oxygen and warm temperatures inside cracked or eroded pipes attract and encourage rapid root growth, filling the pipe with multiple hair-like root masses. The root mass inside the pipe then becomes matted with debris discharged from the residence or business. These root masses will expand and exert considerable pressure on the pipe resulting in further pipe breakdown or total collapse.  Pipes that are structurally damaged from severe root intrusion will require replacement and are the responsibility of the property owner.

Property owners may first notice signs of root intrusion through evidence of a slow-flowing drainage system.  This may take the form of gurgling noises in toilet bowls or the appearance of wet areas around floor drains. A complete blockage may occur if no remedial action is taken to remove the root masses.

The best way for a homeowner to prevent a blockage and/or damage to pipes is to keep the sewer lateral structurally sound. Homeowners may wish to hire a plumber to video the sewer lateral to determine its condition and if any repairs are needed.

It is also important to schedule regular cleaning of the sewer lateral. The common method of removing roots from sanitary sewer service pipes involves the use of augers, root saws, and high-pressure flushers. 

Should a blockage occur, the following list describes some of the treatments needed to correct the issue. 

• Root-Cutting/Hydro-Jetting: plumbing contractors have special equipment for removing obstructions from within a sewer lateral. In the case of roots, cutting or hydro-jetting alone is not a long-term solution to the problem. Roots will usually re-grow into the favorable environment of the damaged pipe.
  
  
• Chemical Root Inhibitors: some plumbing contractors can supply chemicals that kill roots and prevent re-growth into damaged sewer pipes, one example being Copper Sulfate. Foam that fills the entire inside of the pipe when applied is best. The foam kills all the roots inside the pipe, as well as roots in the soil surrounding the damaged area of the pipe. In addition to killing roots inside and around the pipe, the foam impregnates the surface of the pipe with a root inhibitor, creating a chemical barrier.
  
  
• Sewer Pipe Liners: sometimes it is possible to repair the damaged pipe itself, without excavating, through use of a cast-in-place liner. This system is inserted into the sewer lateral and essentially creates a new pipe inside of the damaged pipe. Lining is a long-term solution and generally has a minimum 50-year life expectancy.
  
  
• Replacement of Damaged Sewer Laterals: this is another long-term method of correcting a defective sewer lateral to prevent future root growth and blockage. In cases of extensive collapse or damage of sewer lateral pipes, this is likely to be the only effective solution. 

Grease:

One of the main causes of back ups from the sanitary sewer system is due to clogs in the sewer piping system from cooking oil and grease. This material solidifies in the sewer lines and restricts flow, sometimes completely.

Oil and grease enters our collection system most commonly through users pouring used cooking oil down a drain or during the cleaning operations at food service facilities. This not only clogs our sewer lines but can cause sewer to backup into your fixtures and facilities as well.