The active coal ash basin at Duke Energy's H.F. Lee plant will be removed from maps designating the floodway of the Neuse River's 100-year flood plain should the state approved revised maps.

Duke isn't the only property owner that would be affected by the revised maps -- four residential structures would be added to the flood plain while another eight would be removed.

Altogether, 16 structures would be added and 12 others removed.

All of the property owners affected by the change need to check with their insurance carriers, said Marl Schillinger of Geosyntec Consultants.

A floodway is the Federal Emergency Management Agency-designated part of the flood plain where development is generally prohibited.

For Duke Energy the change will mean the company would be able to build in the area removed from the map, Schillinger said.

Property owners affected by the modified map will be notified by letter later this month and will have 90 days from that time to direct comments or question to the Wayne County Planning Department.

They may also want to hire their own surveyor to determine if they are indeed inside the flood plain, Schillinger said.

The maps would become effective following the 90-day period.

The process, referred to as a Letter of Map Revision, has gone through state, city and county review and the notifications are anticipated to be sent this month following final state approval.

Schillinger Tuesday morning told Wayne County commissioners that Duke Energy had hired the firm in order to correct historical errors in FEMA maps that incorrectly placed the coal ash basin in the floodway.

The error dates back to the late 1970s, he said. Those maps do not reflect construction of the coal ash basin since it was constructed from 1978 to 1980, he said.

There have been no new discharges into the coal ash basin since late 2012, he said.

"Why we are removing this from the flood plain is the active basin is about 15 feet higher than the surrounding grade and about eight to nine feet higher than the 100-year water surface elevation," Schillinger said.

That is significantly higher than the flood elevations, he said.

FEMA hydraulic maps and models were reviewed and improved topography data from Duke and state surveys used to update models and maps in the vicinity of the active basin, he said.

The results indicated a 16-inch decrease in flood plain elevations and modified flood plain limits based on the improved topography, he said.

That study adds 28 acres to the flood plain, but takes out 150 acres so overall there is a net decrease in acreage, he said.

Overall, the map reflects a decrease in the overall flood plain area of seven acres in the county and city of Goldsboro and the majority of the modified flood plain area is in agricultural lands or on Duke property.

Wayne County Manager George Wood asked Schillinger what the net effect of the changes would be.

"The net effect is essentially the limits of the flood plain along about a two-mile stretch (of the Neuse River) have been revised," Schillinger said. "Overall, more land is being taken out of the flood plain although there are some sections that are being added."

Wood asked if it removed any restrictions on the Duke property.

"Yes," Schillinger said. "We realized this active basin was in the floodway where any work is prohibited. So this would allow use of that area in the future."

Commissioner Ed Cromartie asked if the changes would negatively impact residents' insurance or ability to get insurance.

Residents no longer in the floodway would not be required to have flood insurance, but if they decided to get it anyway then the cost would be less, Schillinger said.

However, owners of the four residential structures added to the map will need to evaluate getting flood insurance if the property is backed by a federal loan, Schillinger said.

Property owners who may have additional information or data showing they are not within the flood plain would need to work with their individual insurance providers, he said.

Cromartie asked if it impacted people affected by Hurricane Matthew.

FEMA has not incorporated the new information so it would not account for any recent storms, Schillinger said.

"I must admit, I am a little confused," Commissioner Joe Daughtery said. "If I am understanding correctly, Duke has retained you to actually go in do an analysis of the flood plain basically from their property. That being said you found several errors... you (are) basically stating that the flood maps provided by FEMA are not necessarily accurate?"

Schillinger the maps are "pretty well calibrated" with periodic updates. The last major one was in 2005 and preliminary maps released in 2014 have not yet been finalized.

However, Daughtery said that based on the new findings, the older maps do not sound very accurate to him.

Daughtery asked County Planner Chip Crumpler how a property owner within the 100-year flood plain would know if the maps are accurate.

"You have the same right or option to challenge the map with a Letter of Map Revision," Crumpler said. "The biggest thing is if you have a federally backed mortgage, you are required to have flood insurance if that structure is in a flood zone.

"Some of these properties were removed. If they had federal-backed mortgages, that requirement would no longer be on them. However, there were some properties added that if they had federally backed mortgages, they will now be required to have or obtain flood insurance."

Wood asked if people who were on the "bubble" would still not be better off to carry flood insurance particularly in light of Hurricane Matthew, a 500-year storm.

Crumpler said that was correct.

"In fact, a couple of the ones that were added flooded during Hurricane Matthew," he said. "They have been mitigated or applied for mitigation grant program."