How to Prevent Sanitary Sewer Overflows
Reliable wastewater infrastructure is one of the most important environmental assets a city can have. Without proper maintenance, our wastewater collection systems struggle to support the growth of our modern cities and increase the risk of environmental disasters like Sanitary Sewer Overflows (SSO). The EPA defines SSOs as a release of raw sewage from collection systems into the environment, and can be caused by blockages, line breaks, sewer design defects and power failures.
Bay Area Sewer Overflows
From October 2018 – March 2019 there were 446 SSOs reported in the Bay Area, which spilled a total of 3.7 million gallons of untreated sewage onto city streets and into creeks or the bay. Untreated sewage in public waterways exposes people to bacterial infections and destroys ecosystems of plants and animals. The high amount of rain the Bay Area received last year pushed the capacity of our collection systems, most of which date back to the 1950’s, but in San Francisco more than 70% of the system is over 100 years old.
With approximately 7.8 million people living in the Bay Area, the region’s wastewater infrastructure needs to operate at full capacity to support the sustainable growth of the region. Replacing old collection systems is too time consuming and expensive, but with proper inspection, cleaning, and maintenance the condition of many of these pipes can be improved before a disaster occurs.
Developing a Plan
The first step in assessing the condition of a pipe is a closed-circuit television (CCTV) inspection to understand if there are problematic defects or blockages. During a CCTV inspection, technicians send robotic crawlers into pipes to videotape their condition and record where defects are using specialized software. Once the condition of the pipe has been assessed, a team of inspection technicians will use the data collected from the CCTV inspection to develop a plan to improve the condition of the pipe. The most common defects are typically related to system design, which can reduce the flow capacity of a pipe due to a build-up of thousands of pounds of sediment and debris.
Depending on the size of the pipe, the best methods to remove debris are hydro-jetting with a combination jet-vacuum truck or a similar proprietary system that has the ability to vacuum large amounts of debris. Establishing a maintenance schedule that involves routine inspection and cleaning prevents pipes from degrading and improves their flow capacity, decreasing the chance of an SSO during wet weather months. Municipalities should have a routine maintenance schedule for their collection systems to ensure due diligence in protecting environmental and public health.
Protecting the Environment
The Bay Area’s population has grown at a rapid rate over the last few decades, but much of its wastewater and stormwater infrastructure has not been updated since the beginning of the 20th century. Since the region’s collection systems are so old, routine inspection, cleaning, and maintenance of collection systems is crucial in preventing SSOs that harm the environment and public health.