Hillsborough is enlisting the help of its residents to protect local waterways and the waters of San Francisco Bay by addressing several key issues that contribute to an overburdened sanitary sewer system. (Storm sewers that are designed to capture rain water are a separate infrastructure system.)
Inflow and Infiltration Sanitary sewer mains and laterals often become cracked or damaged when tree roots break into the line. Inflow is then created when groundwater enters the sewer system through the damaged pipes. During wet weather events, inflow and infiltration can increase sewer flows by 300 percent, leading to SSOs and unpermitted discharges at the Burlingame and San Mateo wastewater treatment plants. That is why it is important that public mains and private laterals be inspected and maintained.
Preventing Excess Storm Water in Sanitary Sewers Storm water entering the sanitary sewer system can cause sanitary sewer overflows (SSO) during wet weather events. While Hillsborough is working with other jurisdictions and regulators to expand treatment capacity, Town officials have identified capacity problems in the sanitary sewer collection system such as insufficent flow capacity in the Crystal Springs/El Cerrito Sewer Trunk. This has caused SSO's on 700 block of El Cerrito every winter. In the past 12 years more than $19 million has been spent to repair and upgrade sewer mains and trunk lines. As a result of a Cease and Desist Order (R2-2009-0020) the Town has been ordered to complete more than $13 million in capital improvements over the next 5 years.
As part of the Cease and Desist Order the Town in currently in the process of video inspecting every public sewer main and studying the hydraulic model of the system to determine the areas with the worst storm water issues. Unfortunately, the video inspections are revealing numerous defects within the 100 miles of sewer mains; some require immediate repair while others can be addressed through capital improvement projects over the next 10 years. By November 2011, the Town will submit a 5 and 10 year capital improvement plan to the Regional Water Quality Control Board. This will be subsequent to the Town's first comprehensive evaluation to the entire system.
Video of Public Main* *It should be noted there were no above ground signs this public main was damaged. The logitudinal crack suggests further failure of ther main will occur in the future. This video was made during dry weather. During wet weather it is highly likely ground water infiltration is occurring from this crack and break. There are no roots in this main because it was treated with an herbacide and cleaned prior to video inspection.
Longer Video
As with the other video, no above ground indication that sewer main was obstructed was known in advance of video inspection. The root masses in this main cause some surcharging within the main. Whereever roots are found in a public main or private lateral, in wet weather inflow of storm waters will also be found. The amount of gravel in this main suggests that an upstream section of the pipe is broken, and allowing dirt/rocks to enter the main.
Sewer Laterals Another key factor in solving the problem is the maintenance and repair of sewer laterals, the lines that run from each residence to the sewer main. Literature regarding sanitary sewer systems suggest between 40-60% of all inflow and infiltration enters through sewer laterals. When laterals become cracked or damaged by tree roots, groundwater seeps into the sewer lines during wet weather, the system becomes overloaded and leads to SSOs and unpermitted discharges into the Bay. It can also lead to sewer backups in residences. This is where residents can do their part to solve the problem by having their sewer laterals inspected and repaired or replaced if necessary.
Inside a Lateral*
*This short video shows the interior of lateral in Hillsborough that has been affected by root intrusion, and subsequently ground water infiltration. Made in summer 2010, the video is stopped because of the break in the lateral pipe and ground water leaking into the sanitary sewer. This ground water infiltration occurs 24 hours a day, every day of the year. Again there was no sign above ground that this defect existed, and the resident's sewer lateral was not causing any backups at the home.
If residents are having their laterals serviced to clear roots on a regular basis, they should consider having their lateral repaired or replaced. Several technologies exist where laterals can be lined with a non-corrosive material or injected with foam to prevent root intrusion. Call the Public Works Department for more information about qualified plumbing contractors at 375-7444. $0 $0 The Town continues to evaluate the most effective manner in which to ask residents to inspect and repair their sewer laterals in the coming years.
How You Can Help Avoid putting fats, oils or egg shells down the sink or garbage disposal. Grease is a major cause of sewer stoppages.
If you plant trees in your yard, avoid planting them near your sewer lateral. Root intrusion damages mains and laterals. Town crews can help you located the sewer lateral on your property.
Do not flush plastic materials of any kind down the toilet, including feminine hygiene products or wrappers. These can clog lines, cause backups and damage pumps.
Flush only toilet paper down the toilet. Paper towels and other paper materials do not degrade quickly and can cause backups.
The Town provides free pop-up covers for residential sewer clean-outs. Town crews can help you find your clean out.
