Cleaning up behind the tens of thousands of people who attended AquaPalooza on Lake Travis took just about a week.

Besides breaking down stages and vendor booths at mile marker 21 on Lake Travis, event organizers removed buoys and anchors from the water. Event organizers were in charge of all cleanup efforts.

Lower Colorado River Authority inspectors took to the water Monday morning and conducted one final cleanup check.

"We are using side-imaging sonar to look for any anchors or any that were left here doing the water event at AquaPalooza," explained LCRA Inspector Carroll Cowan.

Despite crowds leaving behind tons of trash, none was visible on the lake.

What was visible to the naked eye was not good enough for inspectors, who are charged with returning the Lake Travis to preconcert conditions.

To ensure quality, technology helped inspectors dig beneath the water's surface.

"Side-scanning imaging uses two precise beams that shoot down on either side of the boat under water. It acts like a flashlight," Cowan said. "If it hits something, it will reflect the shadow back up on the screen here. It is pretty precise. You can tell the difference between vehicles under water, trees, bridges, all kinds of stuff."

Cowan and his crew looked to see if any of the 150 concrete anchors were left under water. Anchors were used to create a makeshift parking lot to help boats park without colliding.

All the anchors, which weighed 2,500 pounds each, should have been removed by Monday. Cowan conducted sonar tests at different locations and depths that showed all were removed.

"So far, I haven't found any anchors or other big debris under the water," said Cowan. "Everything looks good, nice smooth bottom."

His test results were music to the ears of LCRA officials who spent months preparing and planning for this event.

"If you drove by it today, you would have no idea there were so many thousand people there just a week ago," said LCRA spokeswoman Clara Tuma.

Cowan said should LCRA inspectors find any anchors later in the week, event organizers will have a few days to clear them from the water, but he said he doubts that will be the case because organizers have GPS coordinators of each anchor's location.