Environmental Services
Sanitary Sewer System
System Information
The sanitary sewer system carries wastewater from homes and businesses to the Water Pollution Control Plant for treatment. The Water, Sewer, and Streets Bureau is responsible for maintenance and operation of the 465 miles of sewer mains and 13,000 manholes which comprise the sanitary sewer system. The great majority of sanitary sewers in the County operate solely by gravity drainage flow, but there are 12 wastewater pump stations located in lower elevation areas of the County which pump wastewater through special sanitary sewers called force mains. The Water Pollution Control Plant operates and maintains these pump stations.
Maintenance Programs
There are several maintenance programs which are managed by the Water, Sewer, and Streets Bureau to ensure that the sanitary sewer system continues to operate effectively and efficiently, and to re-new the aging infrastructure. These programs include the grid program, trouble spots, grease spots, root control, TV inspection, and relining.
Grid Program: All sanitary sewers are flushed with a powerful water jet nozzle at least once every 4 years as part of the Grid program.
Trouble Spots: The trouble spots are identified segments of the system which have proven to be susceptible to accumulation of debris. These locations are visited on a 3 or 6-month cycle to be flushed.
Grease Spots: Grease spots are segments of the system which have been identified as being susceptible to an accumulation of grease and oils, which can restrict the capacity of the sewer. Similar to the Trouble Spots, these locations are maintained on a 3 or 6-month cycle. In addition to flushing the lines, a grease emulsifier is applied.
Root Control: Some sewer mains are susceptible to invasion of roots from vegetation, which can diminish the structural integrity and inhibit the flow capacity of the pipe. These sewers are placed on the root control program which annually routs the pipes with a mechanical saw and then flushes the pipes and applies a herbicidal foam treatment.
TV Inspection: The County owns two TV inspection trucks which include a remote control carriage mounted video camera which can be inserted into a sewer manhole and dispatched up a sanitary (or storm) sewer. The video camera is linked to the TV truck via a cable which transmits video to the truck and relays commands to the camera. The camera carriage can traverse sewers as small as 6” and the video camera itself can rotate and tilt to investigate any lateral, joint, or imperfection which is identified. The TV trucks generate a VHS recording which can be analyzed at a later date to identify cracks, dislodged pipe joints, locations of house lateral connections, flow conditions, and any other sewer characteristics.
Relining: The sewer main relining program is an annual Capital Improvement program performed by outside contractors and managed by the Water, Sewer, and Streets Bureau. Many compromised or failing sanitary (or storm) sewer mains can be 100% rehabilitated by a trenchless technology known as Cured-In-Place Pipe (CIPP). The process involves inserting a resin-impregnated felt liner similar to a sock into an existing sanitary sewer main through the manhole. Once the liner is in place, hot water is injected into the sock, and the heated water activates the resin material which is impregnated in the liner. As the resin is activated, it cures and forms into a solid plastic material which transforms the flexible liner into a rigid pipe which exhibits structural strength equivalent to a new sewer. Additionally, the new cured pipe provides a smooth and efficient flow channel which thoroughly renews the sewer without excavating the pipe. Once the pipe liner has cured, a robotic tool is inserted into the new pipe and is remotely directed through the pipe to cut out the lateral service connections, and the new pipe is placed back into service. The entire process typically requires 6-12 hours. The County’s Capital Improvement Program funds the relining program to replace approximately 1.5% of the sewer system annually, about 7 miles of pipe.
Questions about the sewer relining process? Review some Frequently Asked Questions for more information.
Emergencies
Emergencies 24-hour Emergency.....................................703-228-6555
If you experience a sanitary sewer backup, or suspect that there may be a problem with the sanitary sewer system, please call the DES Customer Service Call Center at 703-228-6570 during the day or 703-228-6555 after hours.
Billing & Customer service .........................703-228-6570
Tips for Residents
Many sewer backups are caused by failed or deteriorated service laterals, which are owned and maintained by the property owner. For a single family home, the sewer lateral is typically a 4” diameter pipe which connects the home’s plumbing to the sanitary sewer main, which is typically located in the street. Below are some helpful hints to protect your sewer lateral, home plumbing, as well as the sanitary sewer main:
- Do not dump fats oils or grease down the drain or into the toilet, as they may cool and solidify in the lateral. When the grease or oil solidifies in the lateral or sewer main, it restricts the pipe’s capacity. Oils and greases from cooking should be collected in a metal can, cooled, and ultimately thrown in the trash.
- Never dispose of any flammable or hazardous material down the drain or toilet. Discharge of these materials is not only damaging, but may be dangerous and illegal.
- Do not dispose of feminine sanitary products, paper products, or disposable diapers in the toilet. Instead, they should be wrapped and placed into a trash receptacle.
- Pour water or a mixture of water and vinegar into any floor drains or other drains which are not regularly used to keep the sewer trap full of water. This will prevent sewer odors and gases from entering your home.
- If you know the location of your sewer lateral, be careful to prevent any trees from growing near it. Tree roots can migrate towards a lateral and constrict it.
- Here are some other Disposal Tips for Residents.
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The TV inspection camera. This camera has treads on the side to let it crawl along the pipe. Also notice the three headlights for illuminating the interior of the pipes. |
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The inspection crew lowers the camera into the manhole opening of the sewer. |
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The operator watches the video monitor as the camera moves along the pipe. A video tape record of the survey is being made allowing later review. |
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The image is bright and clear. Any problems, such as a crack, bad connection, or blockage, are readily seen and recorded by the operator. |
