Point Loma Wastewater Treatment, above ground. More lies below.
Deep below the City of Coronado lies a labyrinth pipes and pumps that moves what we flush or drain away. Occasionally a putrid smell will surface, as gases, like methane, build up in the pipes and have to be vented to prevent cracks. Otherwise, few of us think about it. Recently, the City of Coronado has launched a city-wide sewer system inspection aimed at keeping it that way.
Cracks are something you never want to see in a sewer system, for no matter how deep you bury the muck, it will find its way to the surface. When that happens, it can become a public health issue. To make sure that the Coronado sewer system does not crack, the city has initiated a Wastewater Management Project to inspect the entire system and ensure that all components remain in good working order. The previous system-wide inspection was ten years ago.
The inspection will have minimal impact on residents. “Most of the lines are in alleys; it won’t take more than a quarter of an hour to inspect each,” said Ed Walton the city’s Director of Engineering. Crews will examine the system by lowing a camera through a manhole and then follow the pipes to the next manhole. “It will be checking to see if there any of the joints are misaligned or if there are cracks in the pipes,” Walton said.
Crews will also be looking for other types of problems or potential problems. Tree roots working their way into sewer joints can cause damage, for example. The roots are looking for water and are not deterred by water containing a few ‘extra ingredients.’ In fact, they prefer it that way. “Trees love wastewater,” said Walton.
Aging of the pipes is another factor. The sewer system dates back to the founding of the city, 100 years ago. Over the years, the piping has changed as new subdivisions were added – Country Club, the Shores, the Cays – and new materials became available. As a result, the city’s 46 miles of sewer lines are a mishmash of clay, copper and polyvinyl chloride (PVC).
An example of a sewage pipe, on display at the Wastewater Treatment Plant in Point Loma
The oldest of these are the clay pipes which Walton says “have served us pretty well, but they have a tendency to crack and have more joints,” said Walton. Joints are vulnerable to tree root invasions. The newest pipes, made of PVC, have a number of advantages – the pipes are lighter, more flexible and cheaper to install, according to Walton.
Once the waste goes into the pipes a combination of gravity and mechanical force pushes it to a transfer pump near the old ferry landing. From there the sewage flows under San Diego Bay to the Wastewater Treatment Plant in Point Loma. There, the waste is separated, chemically treated, and released into the ocean some 4.5 miles offshore.
Gravity and force are the common ways to move waste in San Diego County municipalities. Coronado’s system, though, is unique in the number of pump stations required. Because Coronado is flat and a portion of it is below sea level, pump stations play a bigger role in moving the waste then they do in other communities. “You need a certain about of [downward] slope, for gravity to work,” Walton said. So while the City of Le Mesa has only one pump station, Coronado has 16 different stations buried 20 to 30 feet below the surface throughout the city. There are three principle pumps in Coronado: Glorietta Bay, the Transbay, and the Cays. Like sewer lines, pump stations need to be maintained. The Glorietta Bay Pump station is currently undergoing repairs to its wet well and pumps rails, which have cracks in the cement due to gases in the waste.
Along with the inspection and repairs, the city is also proposing a rate increase to $48.75 from $31.64 for single-family units by fiscal year 2018-2019. The rates for multi-family units will jump to $39 from $25.31. The increases take place gradually over a three-year period beginning next year, with a three-dollar increase each year. The city last raised rates in 1994. In a letter sent to homeowners, the city claimed the increase was “necessary to continue to fund the annual operating costs and allow the city to continue its pay-as-you-go practice for funding major capital improvement (replacement) projects to the sanitary sewer system.” A public hearing on the rate increase is scheduled for the city council meeting on July 15. The council meeting begins at 4pm.
The rate increase, however, is not connected to the new project, according to Walton. “It will get us caught up with the capital improvement projects we have now,” he said. “The upcoming study will help the city identity future needs.” The city is expending time and revenues to project a system that most folks don’t know about or even want to think about. “But that’s point,” Walton said. “You’re not supposed to be aware of it,” he said. “If you are aware of it, there’s a problem.”
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Gloria Tierney
Staff Writer
eCoronado.com
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