Last week’s heavy rains caused nearly 400,000 gallons of sewage-tainted stormwater to gush out of 16 points along Waco’s sewer lines and overwhelmed the capacity of the central sewer plant.

The extent of the overflows surprised city officials, but the problem was all too familiar.

Since 1992, the city has spent about $2 million annually replacing and repairing old sewer infrastructure, including some 20 miles of sewer mains, city officials estimated.

But the recent heavy rains have revealed vulnerabilities of a system in which some pipes are a century old.

“There are ongoing problems with all older sewer collection systems,” city utilities director Ricky Garrett said. “You don’t ever really finish. You have to keep identifying areas you need to shore up.”

The city had similar overflow problems during heavy rains this past fall and on Jan. 29, when city crews had to respond to 19 overflows.

In 2007, the city had a series of wastewater overflows that resulted in a $54,000 fine from the Texas Commission on Environmental Quality.

TCEQ officials said it’s unlikely the recent overflows will result in fines because there was little environmental impact and the city is complying with an agreement with the state to make sewer improvements.

Water seeping into pipes

Garrett said the problem is not so much wastewater flowing out of leaky pipes but stormwater flowing in.

The public collection system and private yard lines have thousands of cracks, holes and loose joints where water can enter, he said.

When the ground is saturated, standing water finds its way into those pipes, overloading the system further down and causing overflows at manholes, Garrett said.

Most of the overflows this time were in North Waco.

The rush of tainted stormwater can occasionally spill out at sewer pump stations and even wastewater treatment plants.

In the January and February rainstorms, the central treatment plant downstream from LaSalle Avenue was overwhelmed, causing some untreated water to overflow.

Garrett said that has happened only a few times since the city took control of the sewer plant in 2004, and he blamed it on unusually wet conditions.

“I really think when you have the kind of rain we’ve been getting with these El Niño weather patterns,” he said, “big sewer systems just aren’t made for that, especially ones that are more than 100 years old. At some point, you just get supersaturated.”

Garrett said several projects now in the works will prevent overflows:

* An upcoming expansion of the central sewer plant, complete with a holding tank for heavy flows, will help process stormwater more quickly and prevent it from backing up in lines upstream and popping manhole covers.

* A major new sewer interceptor line along Flat Creek also will relieve pressure on sewer mains in the central city.

* The replacement of a major sewer line along Martin Luther King Jr. Boulevard, now under way, should reduce overflows along that line.

* The city recently completed a study of the Landon Branch watershed in West Waco and is developing a plan to prevent overflows at the Landon Branch pump station, which sometimes overflows into a tributary of Lake Waco.

Garrett estimated that 40 percent of the stormwater infiltration comes from privately owned lateral lines in people’s yards.

Property owners are required to repair their own lines, but Garrett said past efforts to enforce that law ran into problems in low-income areas.

“There were people who could just not afford it,” he said. “Trying to be draconian wasn’t very smart. But we do have to tackle it one way or the other. A whole lot of our stormwater comes from private laterals.”

In 2002, the city replaced laterals at 81 homes, mostly in the Brook Oaks area, at a cost of about $100,000.

Since then, Garrett said there has been no focused effort to fix the private lines, but the city often repairs them in the course of repairing public lines.

jbsmith@wacotrib.com

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