Noonday Creek Watershed Structure #17 Spillway Repair due

COBB COUNTY SOIL & WATER CONSERVATION DISTRICT

Noonday Creek Watershed Structure #17

Spillway Repair due to September 21, 2009 Flood

Structure #17 Emergency Spillway during September 21, 2009 Flood

678 South Cobb Drive, Suite 150 Marietta, Georgia 30060 www.cobbswcd.org


Noonday No. 17 Spillway After September 2009 Flood



Noonday No. 17 Spillway During Repair



Noonday No. 17 Spillway After Repair




PURPOSE OF STRUCTURE #17 The primary purpose of Noonday Creek Watershed Structure #17 is flood control. This structure is classified as a Category 1 structure by EPD’s Safe Dams Program who has determined that failure of the dam would result in a possible loss of life. Because of rapid growth in the area the drainage basin and downstream reaches have become developed with residential and commercial developments. Maintenance of this structure is essential to provide downstream protection of life and property.

HISTORY OF STRUCTURE #17 Structure #17 is an earthen embankment located on Tate Creek, a tributary of Noonday Creek. The structure was constructed in 1956 by the United States Department of Agriculture Soil Conservation Service. The dam is approximately 45 feet high and 550 feet long having an impoundment area of 23 acres. The emergency spillway is an earthen channel located on the North end of the dam. Funding for the project was supplied by the Watershed Protection and Flood Prevention Act. The dam and lake are located in both Cobb and Cherokee County.

THE STORM OF SEPTEMBER 21, 2009 The flooding that occurred on September 21, 2009 has been referred to as being of historical proportions. While we do not know the exact amount of rainfall that occurred in the Noonday Creek basin we do know that the emergency spillway for structure #17 was activated. The dam structure is designed to contain the runoff from the100 year storm without activating the emergency spillway. Due to the severity of the storm the spillway was eroded severely on the downstream section.

PLANNING FOR THE REPAIR OF THE EMERGENCY SPILLWAY The Cobb County SWCD entered into an agreement with the NRCS October 2009 for funds to repair the damage to the emergency spillway. Funds received from the NRCS would require a 25% match from the local sponsor (Cobb County). The Cobb County SWCD requested bids from 3 previously approved engineering firms to provide an analysis of the site, options for repairs, plans and specifications for the repairs, soils testing and supervision during construction. The prepared plans and specifications were reviewed and approved by all state and local agencies prior to construction. After the plan approval process was complete competitive bids were requested from 4 contractors. The low bidder was determined and work was started on November 10th 2010 and finished January 5th 2011.



REPAIR COSTS The following are costs associated with the repair of the damaged spillway. Engineering – Evaluation of options $ 8,500 Construction documents $ 7,500 Services during construction $ 15.000 Contractor - Spillway repair $ 285,000

Total = $ 316,000

Cobb SWCD Supervisor Volunteer hours: approximately 440 hours

PARTIES INVOLVED • Cobb County SWCD

• Natural Resources Conservation Service

• Georgia Soil and Water Conservation Commission

• Engineer of record- Walden Ashworth and Associates, Inc.

• Contractor- GEM Contractors, Inc.

Documents

Noonday Creek Watershed Structure #17 Spillway Repair due