Q. What is a CSO?
A. Combined Sewer Overflows (CSOs) are an overflow of sewage and stormwater into Puget Sound. They occur as a direct result of stormwater entering the sanitary sewer system. Stormwater entering the sanitary sewer system uses the available system capacity and as the pipes fill and wastewater pump stations reach their capacity a CSO event can occur.
Q. What is inflow and infiltration (I/I)?
A. Inflow and infiltration (I/I) are terms used to describe the ways that groundwater and stormwater enter the sanitary sewer system. Inflow is water that enters the sewer through direct (improper) connections, such as roof downspouts, driveway and foundation or curtain drains. Infiltration is groundwater that leaks into the sewer system through cracks in the service lateral or mainline pipe, manhole or separated pipe joints.
Q. Why is I/I water a problem?
A. Rainwater belongs in the stormwater system or on the surface of the ground, and not in the sanitary sewer system. When rainwater enters the sanitary sewer system it takes up valuable capacity in the sewer system. It is then conveyed and treated like sanitary waste which increases operation costs for the collection and treatment systems. Too much rainwater often causes sewer backups and overflows when it rains.
Q. What is a sanitary sewer system?
A. A sanitary sewer system is a collection of pipes located in the streets and easements that are designed solely to transport wastewater away from the sanitary fixtures inside homes, businesses and industry and convey it to the wastewater treatment plant. This system protects public health by removing human and industrial wastes so it can be properly treated.
Q. What is a stormwater system?
A. A stormwater system is a collection of catch basins, and pipes located in streets and easements that are designed to transport rainwater away from streets, homes and businesses. The potential for flooding is greatly reduced by collecting and moving water away from these areas, which protects public and private property and reduces the threat to human health and life. Stormwater pipes are usually much larger than sanitary sewer system pipes because they are designed to carry larger amounts of water.
Q. What is an improper connection to the sanitary sewer system?
A. An improper connection permits rainwater from sources other than sanitary fixtures to enter the sanitary sewer system. That rainwater should be going to the stormwater system or allowed to soak into the ground without entering the sewer system.
Q. What are some different types of improper sanitary sewer connections?
A. Some examples of improper connections include, but are not limited to: downspouts, groundwater sump pumps, foundation drains, curtain drains and driveway drains.
Q. Why is it important for everyone to remove improper connections?
Removing improper connections will significantly reduce the flow of rainwater into the sanitary sewer system which reduces the operation and maintenance cost for the wastewater system. By removing rainwater from the sanitary sewer system, the possibility of combined sewer overflows will be greatly reduced and the need for new system upgrades, to handle this extra water, will be avoided.