The San Antonio Water System announced its sewer-monitoring devices have alerted them in time to prevent more than 200 sewer spills since being put into use.

The devices are called Smart Covers and are attached to the manhole covers of sewer pipes.

The unit shoots a 24-inch sonar beam over the sewage channel below, sending data about every six minutes to satellite receivers around the city.

SAWS Superintendent Shawn Dorn said if the unit detects a rise in the level of the water below, it sends out an alarm via text message and to a website, letting SAWS know to send a crew.

“As it comes up, it starts to sends alarms saying there's something wrong with our system,” Dorn said.

He said installing these unites started as a pilot program in 2009.

"We have about 178 units that are currently installed and to date, they've saved over 214 spills,” Dorn said. “In the month of December, which was our record month, we saved 20 spills alone from Smart Cover unit."

Recently crews responded to a neighborhood north of downtown when a Smart Cover alarm sounded. They found a partially blocked sewer and were able to remove debris before a spill occurred.

The units cost $4,200 each, with $360 per-year monitoring costs -- but they can save hundreds of thousands of dollars in headaches.

“You have the EPA, you have the TCEQ and the EAA that are constantly looking at the spills,” Dorn said. “The remediation of a spill far outweighs the cost of just having the unit in the ground itself.”

But Smart Covers are not installed on all manhole covers.

In November 2013, SAWS crews were called to a sewer spill in Salado Creek where a 66-inch sewer line was clogged with debris.

Before that, a spill near Mission Road in May 2013 had some 100,000 gallons of sewage flowing into the San Antonio River near Mission Concepcion.

But Dorn said there could have been many more spills if it were not for the use of the Smart Covers.

For more information on the company that makes the smart cover, Hadronex, click here.

For a list of recent stories Brian Mylar has done, click here.