Runoff from Rehoboth City Hall site went to lake

• The Rehoboth Beach City Hall construction project is underway.
• Heavy rains sent sediment from the building site to Lake Gerar.
• Additional measures to stop run-off have been established.

Additional measures have been put in place to stop sediment flow from the construction of the new Rehoboth Beach City Hall into Lake Gerar.

Contractors on Friday were pumping fresh clean water from the ground when a heavy rain hit, sending a combination of groundwater, rainwater and pale, brown sediment running off the property.

State environmental and the Sussex County Soil Conservation District officials were contacted with concerns that the sediment would harm the environmentally sensitive lake. Water from Lake Gerar ultimately flows into the Atlantic Ocean.

The pumping is done to dewater underground areas before and during underground construction in places where groundwater is near the surface. Dewatering is a common practice in low-lying Sussex County where the water table is close to the surface.

A call to contractor Whiting-Turner on Wednesday was not immediately returned.

Voters last summer approved a plan to demolish the existing City Hall and build a new structure, borrowing up to $18 million. The building at 229 Rehoboth Ave. was torn down in February.

The city and contractor shut down groundwater pumping on Friday.

Jessica Watson, sediment and stormwater program manager for the Sussex County Soil Conservation District, said an inspector visited the site Friday and additional controls were put in place that are designed to minimize future runoff from the construction site.

"These are concerns for any site," Watson said. "Hopefully, this has been resolved."

Michael Globetti, a spokesman for the state Department of Natural Resources and Environmental Control, said the city has both perimeter and storm drain controls for the City Hall construction project but the rain and dewatering combined caused the runoff.

Much of the runoff was captured, but some of the sediment did make it into Lake Gerar, Watson said.

"We had a bad rain that day," said Rehoboth City Manager Sharon Lynn. "All of the precautionary measures had been taken."

Lynn said the city also received complaints about the runoff.

"People were concerned," she said.

Among those who complained was long-time city resident and former commissioner Walter Brittingham. He said he was pleased that the conservation district addressed the runoff issue so quickly. Brittingham said his concern was that soil was running directly into the lake.

Lake Gerar, which is five blocks north of the construction site, is one of three freshwater lakes in Rehoboth Beach. The lake was once a freshwater wetland and activists like the late Mary Wilson Thompson believed it was a breeding ground for mosquitoes. In the 1930s, at her urging, the lake was cleared and deepened.

These days, runoff pollution is a major concern with each of the three freshwater lakes.

Lynn said that the rain was so heavy that the filter traps in place to catch sediment from the site couldn't remove all of the dirt particles.

The Soil Conservation Service asked that additional runoff controls be placed at the construction site, Watson said.

"It's being watched very closely," she said.

Reach Molly Murray at (302) 463-3334 or mmurray@delawareonline.com. Follow her on Twitter @MollyMurraytnj.