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1. How does the Wastewater Collection System Work?

If it goes down your drain, it goes in the system. Whether it’s a commercial use or residential, if it goes down your toilet, shower or sink drain, it will end up at the treatment plant for processing. We call this wastewater.

Once the wastewater goes down the drain, it enters the property’s sewer lateral which then connects to the City’s public sewer main. Once the wastewater reaches the sewer main, it makes its journey to the Laguna Treatment Plant, located on Llano Road via larger “trunk sewer” lines.

Wastewater enters the Laguna Treatment Plant through a pipe system from urban homes, businesses and industry. Solids removed from rural septic systems are combined with the wastewater at the head of the treatment plant.

The pipe system depends largely on gravity. A gentle slope in increasingly larger pipes moves wastewater to the plant. Tanker trucks bring septic wastes to the plant for treatment. Each day these two sources contribute 18 million gallons of wastewater to the plant, which also accommodates additional water during storms.

The sewer system is different from the storm drain system. The City’s storm drains are not designed for “wastewater” and the storm drains do not go to the treatment plant, but to creeks and waterways.

2. Where does our wastewater go?

The Santa Rosa Water Reuse Plant (located on Llano Road) takes wastewater from homes, businesses and industry located within the city of Santa Rosa along with the other partners in the Santa Rosa Subregional Water Reuse System. Over 500 miles of underground pipes brings our wastewater to the treatment plant where water goes through three stages of treatment prior to disinfection, storage, and reclamation. The recycled water that leaves the Water Reuse Plant is a high quality, tertiary-treated water that is safe for many reuse options.

3. What is inflow and infiltration?

Inflow and infiltration are terms used to describe the ways that clean groundwater and/or storm water flow into the wastewater system, due to cracked sewer lines, leaky manholes or through erroneously connected storm drains. Most inflow comes from storm water and most infiltration comes from groundwater.

Inflow is surface water that enters the wastewater system through improper connections, such as catch basins, yard, roof and footing drains, downspouts, groundwater sump pumps, and through holes in manhole covers. Inflow typically occurs as a result of storm events. Peak inflow occurs during heavy storm events when storm sewer systems are full, resulting in backups and ponding.

Infiltration is groundwater that enters the wastewater system through holes, breaks, joint failures, connection failures and other openings in the pipe. Infiltration amounts often exhibit seasonal variation in response to groundwater levels. Storm events can trigger a rise in groundwater levels and increase infiltration flows. The highest infiltration flows are observed following significant storm events or following prolonged periods of precipitation when the ground is saturated with water.

4. Why is inflow and infiltration a problem?

Inflow and Infiltration belongs in storm sewers or on the surface of the ground, and not in the wastewater system. When it gets into the wastewater system, it must be treated like sanitary waste and this raises costs. Too much often causes sewer backups and overflows when it rains.

5. What is an erroneous connection to the wastewater system?

An erroneous connection allows water from sources other than sanitary fixtures to enter the wastewater system. Instead of entering the wastewater system, that water should be going to the storm sewer or allowed to soak into the ground. Some examples of erroneous connections include downspouts, groundwater sump pumps, foundation drains and drains from driveways.

6. How does Santa Rosa Water identify inflow and infiltration?

Television Inspection

Water crews guide portable television cameras through the wastewater system pipes to determine any sources of inflow or infiltration.

Smoke Testing

Filling the wastewater system lines with smoke and watching where it emerges can identify many sources of inflow. The smoke is kept from entering buildings by the drain traps required on all sanitary fixtures and drains. It will emerge from the sewer stand-pipe vents on the roof of buildings, from improper connections such as downspouts, and it may also emerge from holes in the ground that lead to leaks in sewer lines.

Flow Monitoring

Santa Rosa Water can monitor the amount of water flowing through wastewater system by inserting special measuring devices into the sewer lines. If the flow increases during rainstorms, it's a sure sign of infiltration.
Smoke Testing (PDF)

7. How can inflow and infiltration be prevented?

There are many methods and technologies that are available to remove and/or reduce Inflow and Infiltration. When Inflow and Infiltration is identified, the City of Santa Rosa Utilities department works to eliminate it. Utilities crews repair leaking manholes and replace cracked or broken pipes. We also identify problems on private property, such as missing clean out caps and improper connections.

2006 Inflow and Infiltration Study

8. What are Sewer backups/blocks and how are they prevented?

Sewer overflows and backups can cause health hazards, damage homes and threaten the environment. The most common cause of the overflows is sewer pipes becoming blocked by grease or foreign materials. Grease usually enters the sewer system through the kitchen sink. Grease is found in items such as meat fats, lard, cooking oil, food scraps and dairy products. The grease sticks to the sides of the pipes on your property and in the streets. Over time, build-up can cause a block in the entire pipe. Foreign materials also contribute to overflow by entering through unsecured clean-out caps and broken sewer laterals. What this may mean to you is: •Raw sewage overflowing in your home or your neighbor’s home; •An expensive and unpleasant cleanup; •Raw sewage overflowing into streets, yards, parks and creeks; •Potential contact with disease-causing bacteria; and •An increase in repair and maintenance costs for the City of Santa Rosa, which causes higher sewer rates for customers. What can you do to help? The easiest way is to keep grease and foreign material out of the sewer in the first place and if you have an issue or happen to see an overflow in progress, call immediately! How can you do this? Never pour grease down the sink or toilet. Place all cooking grease and oil in a sealed container and dispose in the trash. Scrape grease and food scraps off of cooking surfaces and put them into the trash for disposal. Do not put grease down the garbage disposal. Garbage disposals do not keep grease out of the system, they only shred material into smaller pieces. Put in sink strainers to collect scraps and place scraps in the trash. Secure all sewer clean-out caps and repair any broken sewer laterals. Call the City of Santa Rosa, Environmental Services Section at (707) 543-3369 if you have any questions.

Additional overflow information is available on the California Integrated Water Quality System (CWIQS) project website.