Austell mayor wants 5-mile tunnel to spare city from future floods

By Ralph Ellis

The Atlanta Journal-Constitution

Austell Mayor Joe Jerkins is proposing a 5-mile tunnel be built to protect the Cobb County town from another devastating flood.

Jerkins says the tunnel could divert overflow from Sweetwater Creek, which flooded Sept. 21 and damaged about 700 homes in Austell. He estimates the project would cost about $100 million.

Cobb County Commission Chairman Sam Olens said he’s interested but not ready to commit. He wants county engineers to study reports submitted by the Army Corps of Engineers after previous floods in Austell. The corps would be deeply involved in building a tunnel.

“We want to make sure the proposal would have the support of the Corps of Engineers,” Olens said Thursday. “That’s probably nine figures [in cost] so that couldn’t happen without federal assistance.”

Jerkins thinks the tunnel should start near Perkerson Mill Road, run for about five miles and empty south of I-20 into Sweetwater Creek. The tunnel would not be needed until the creek overflows.

Jerkins favors a tunnel because the Corps of Engineers earlier studied Austell flooding and didn’t propose any changes.

Pat Robbins, a spokesman for the Army Corps of Engineers, said the agency looked at the Austell flooding problem, most recently in 1995, but decided against taking any action because "the benefits must exceed the cost." Among the solutions studied were channel cleaning, which included dredging; building a levee; buying up residences and businesses; and enlarging an area underneath a bridge. He declined to comment on the tunnel idea.

Jerkins said Austell is vulnerable to flooding because several creeks empty into Sweetwater Creek. The creek begins in southwest Paulding County and runs through southwest Cobb before going south into Douglas County and emptying into the Chattahoochee River. Its winding course also contributes to flooding.

Jerkins said studies show the creek drops about 10 feet per mile before reaching Austell, where it flattens out and drops at 1 foot per mile.

Floods hit Austell in 1990 and 2005, but the 1990 flood was minor in comparison to the 2005 and Sept. 21 floods, Jerkins said.

The 2005 flood went 3 feet over the flood plain, damaged about 100 houses and was considered a 100-year flood. The Sept. 21 flood went 14 feet over the flood plain and damaged about 700 homes and 50 businesses. It has been classified as a 500-year flood.

City leaders have said they didn’t take more drastic steps after the 2005 flood because of the low probability that two massive floods would occur four years apart.

Cobb County recently completed a $114 million, 9.5-mile sewage transport tunnel that runs from Indian Hills in East Cobb to a treatment plant on the Chattahoochee River, said Cobb water system director Stephen McCullers. The tunnel has an 18-foot diameter.

The county just started digging a 6.5-mile, $305 million sewage transport tunnel in south Cobb that has a 27-foot diameter. The cost includes treatment equipment.