It is not nearly as much fun as buried treasure, but Lawrence City Hall leaders do have a growing issue that will involve burying lots and lots of money below the ground.

There are nearly 500 miles of waterlines buried below the surface in Lawrence. As the lines have started springing leaks at a record pace, a new report from City Hall is reminding leaders how much money it likely will cost to replace the aging infrastructure.

A new report estimates roughly 18 percent of all the waterlines in the city ought to be replaced between now and 2030, and it likely will cost a little more than $72 million in today’s dollars.

“I think it is pretty clear that from this point forward, we’re going to have to be more aggressive with our maintenance and replacement plans,” said City Commissioner Aron Cromwell. “That will probably impact future rates somewhat.”

The issue of aging waterlines hasn’t snuck up on City Hall leaders. City Manager David Corliss has talked frequently about making sure the city’s below-ground infrastructure doesn’t deteriorate to the point city streets did several years ago.

“This is another example of infrastructure that doesn’t heal itself,” Corliss said.

Staff members are highlighting the issue in a new report as the city deals with a record number of waterline breaks. New data shows the waterline breaks have increased by 80 percent from two years ago — rising from 100 in 2010 to 180 in 2011. Thus far this year, the city has responded to 160 breaks.

At times, the breaks have been disruptive to businesses and residents. Among the incidents the report details are:

• In July, there was a water main break that cut off water service to Del Monte’s pet food plant, the Kmart Distribution Center and other businesses and homes in northern Lawrence. Del Monte and Kmart shut down for the day, and the two businesses estimated they lost about $60,000 due to the work stoppage.

• A series of breaks along 23rd Street in August and October caused 22 businesses to close for up to six hours at a time during peak business times.

• In September, a water main break near 5200 Clinton Parkway left 108 residential customers without water service. The KU Tennis Center, which was hosting a tournament at the time, also was without service.

• On Sept. 24, the same line that broke in July near Del Monte’s pet food plant broke again. This time Del Monte estimated the down time cost the company a little more than $25,000, although Kmart kept its distribution center open by renting portable toilets and buying bottled water for employees.

Dave Wagner said the drought — which places stress on the water system through high demand but also through shifting soils — is a contributing factor to the large number of breaks. But he said the underlying issue is many of the pipes either have either reached the end of their useful life or are in harsh soil conditions that promote deterioration of metal pipe. The city for the past several years has been using plastic pipe instead of metal to combat the soil issues found in Lawrence.

“I think we do need to be more aggressive than what we have been in the past,” Wagner said of the city’s replacement strategy. “The good news is that our ability to assess what needs to be replaced is more accurate than it ever has been.”

Wagner said historically the city has spent, on average, about $1 million a year to replace waterlines in the city. Although the city’s master plan recommends the city replace the $72 million worth of water lines by 2030, it also says the city could feasibly stretch the replacement plan to 2045.

Wagner said he thinks it is more realistic to set a goal of having the aging pipe replace by 2045, but he said $1 million a year won’t be enough to accomplish that goal.

For the 2013 budget, the city tentatively has scheduled to replace about $3.3 million of poorly functioning water lines.

Whether the city can sustain that pace, though, without water rate increases will be a major question at City Hall. Cromwell said residents likely need to prepare for higher water rates in the future.

“Our rates have to be reflective of what it costs to provide the service,” Cromwell said. “If our costs go up because our system is aging, the rates will have to go up. But I remind people that sometimes it costs a little money upfront to save a lot of money in the future.”

City staff members last summer proposed a water rate increase that would have been between 4 percent to 6 percent, depending on several variables. But commissioners balked at that plan, and asked staff members to come up with a less aggressive proposal.

Commissioners haven’t yet been presented with a new rate proposal.

City Commissioner Mike Dever said he’ll want to examine several factors, including the size of the city’s reserve accounts, before he’ll commit to a rate increase.

“We have tried very hard to be wise about how we spend those rate dollars,” Dever said.

Cromwell said he also wasn’t advocating for dramatic rate increases to tackle the problem.

“We need to come up with an ongoing funding stream, but we don’t need to make this into some sort of emergency situation,” Cromwell said.