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In many parts of Milwaukee's north side, residents are faced with two major problems: the threat of flooding and vacant houses abandoned during the foreclosure crisis.

In what Ald. Jim Bohl called "out-of-the-box thinking," the city is exploring the idea of using the basements of foreclosed and abandoned homes as cisterns of sorts to hold stormwater during heavy rains.

The idea is the brainchild of Erick Shambarger, deputy director of the city's Office of Environmental Sustainability. Although a long way from becoming reality, the concept — dubbed BaseTerns — and the possibility of a pilot project received a warm reception Wednesday by the city's Public Works Committee. There is talk of a pilot project next year.

"We have to do something to address these extreme weather events," Shambarger said.

A feasibility study prepared by HNTB Corp. for the city concluded that using vacant basements could manage larger amounts of stormwater better than other strategies such as rain barrels; help protect other, occupied homes from basement backups; provide a source of water for urban agriculture; and help the city adapt to a changing climate.

The study looked at three different ways to convert the basement into a storage facility. "Each of the three basement conversion options appears to be a cost-effective approach to help reduce combined sewer overflows," the study said.

In each scenario, the new structure — with the rest of the home removed — would be covered with topsoil to prevent public hazards. In addition, the study noted that different north side locations might be suitable only for capturing roof runoff from other homes, while other locations might only be usable for capturing storm water from streets and alleys.

The stormwater would be delivered to the BaseTerns in one of two ways. One would direct roof water from adjacent homes to rain barrels, which would then direct the water to the BaseTern. The other possibility would take advantage of gravity to direct stormwater on streets and alleys to the BaseTerns.

Each BaseTern would operate independently; they would not be linked.

The idea has a certain beauty to it because of the convergence of two major issues afflicting residents on the north side. The flooding of July 22, 2010 caused extensive damage, especially in areas of the north side near Lincoln Creek. On the northeast side, one rain gauge that day measured 8.31 inches of water in 24 hours; another gauge measured 3.74 inches of rain in an hour.

In 2010, the city's call center received 11,600 reports of water in basements.

Those same areas also happen to have been hit the hardest by the foreclosure crisis with hundreds of vacant and abandoned homes. Converting basements of homes set to be demolished into BaseTerns also would reduce the costs of demolition.

The idea under consideration would be a complement to a plan by the Milwaukee Metropolitan Sewerage District to spend $140 million to control flooding on the north side.

The HNTB study used a city-owned foreclosed home in the 3000 block of N. 21 St. to study the feasibility of converting a basement as a storage facility. Its conclusion: it would be "technically feasible, both strategically and operationally. The converted basement can be used for rainwater harvesting, stormwater detention, groundwater recharging, or a combination."

How much water can an old basement store? According to the study, anywhere from 13,400 to 40,000 gallons, the equivalent of 243 to 807 55-gallon rain barrels.

The cost? According to Shambarger, the cost to convert a basement would run anywhere from $30,000 to $70,000.

Ghassan Korban, the city's commissioner of Public Works, told committee members that his department would need to study the proposal further.

"They have to be strategically located," Korban said. "And the basement has to be in good shape."