One of the key measures of water quality at the Yadkin Project is the level of dissolved oxygen (DO) in the water being released from the dams. 

 

APGI is committed to helping improve the water quality in the Yadkin Project lakes and the Yadkin River. Recent data shows that new technology installed by APGI at Narrows Dam in 2008-2009 continues to improve DO levels downstream of the dam. 

 

Water quality within the Yadkin Project lakes is generally considered to be good or fair. One significant challenge comes from runoff – soils and sediment that flow from neighboring communities into the Yadkin River add nutrients. High levels of nutrients lead to increased algae production and can result in lower DO levels.

 

State Regulation
Water quality at the Yadkin Project is regulated by the NC Department of Environment and Natural Resources, Division of Water Quality (DWQ).

 

The Yadkin Project is subject to the following state standards related to DO levels: a minimum of 4.0 mg/L (measured instantaneously) and a minimum of 5.0 mg/L (daily average).

 

Once the 401 and the final FERC license are finalized, additional upgrades in equipment and operation will provide additional DO enhancement and higher levels of DO throughout the project to meet North Carolina’s standards regarding minimum levels of DO.

 

Monitoring Dissolved Oxygen Levels
APGI closely monitors DO levels in the tailwaters of each dam. The monitors record DO and temperature data every 15 minutes, 7 days a week, between May 1 and November 30, the time when DO concentrations are of greatest concern. The monitors in the Narrows and Falls tailwaters have been operating since 2001; monitors to the Tuckertown and High Rock tailwaters were added in 2003.

 

Controlling Hydrilla on the Yadkin Project Lakes

 

Alcoa is cooperating with North Carolina’s Aquatic Weed Control Program to control the growth of hydrilla, an invasive aquatic weed, on the Yadkin Project lakes.   After hydrilla was observed growing in Badin and Tuckertown lakes, Alcoa asked for assistance from the Aquatic Weed Control Program to implement control measures to reduce the areas of infestation and prevent widespread growth.

 

Alcoa worked with the Aquatic Weed Control Program, the NC Wildlife Resources Commission (NCWRC), and others to develop a Badin Lake Hydrilla Extirpation Plan. The Plan outlines a management approach that includes chemical (herbicides) and biological (grass carp) controls, vegetation surveys, and hydrilla tuber monitoring.

 

The short term goal of the Plan is to minimize the spread of hydrilla on Badin Lake and the long term goal of the Plan is to extirpate hydrilla from Badin Lake entirely.  Alcoa and the Aquatic Weed Control Program made the first application of an aquatic-use herbicide on Badin Lake in May 2012.  Additional herbicide applications on Badin Lake are planned in 2012.

 

Alcoa and its partners are also making preparations to introduce grass carp into Badin Lake later in 2012.  Grass carp are sterile fish that preferentially feed on hydrilla.  Because grass carp will also eat other submersed vegetation, such as water willow, Alcoa is working with NCWRC to construct exclosures, which will be placed in the lake to protect native aquatic vegetation.

 

Alcoa and the Aquatic Weed Control Program are also planning an extensive survey for hydrilla on Tuckertown Lake in 2012.

 

In March 2012, APGI provided DWQ with a report summarizing the level of DO measured in the Yadkin Project tailwaters since 2007. The report indicates that water coming into the Yadkin Project at High Rock has relatively low levels of DO. But DO levels significantly improve at Narrows Dam, where APGI installed new technology in 2008-2009 to increase the presence of DO. That improvement is maintained until the water exits the Yadkin Project at Falls Dam.

 

Data gathered to date in 2012 demonstrates that the technology installed at Narrows is continuing to improve DO conditions at both Narrows and Falls. APGI initiated the 2012 monitoring season on May 1, 2012 and will monitor DO in the tailwaters of each dam through November 30, 2012.


 

The graph above shows the daily average DO concentrations measured in each of the Yadkin Project tailwaters for the 2012 monitoring season. Water released at Narrows Dam is indicated by the green line; water released at Falls Dam is indicated by the purple line.

 

See graphs of:

1Generating units not equipped with dissolved oxygen enhancing technology.

2Data undergoes a quality assurance/quality control review prior to being presented herein.
3The daily average DO data plotted in this graph is the average of the instantaneous DO readings measured from midnight to midnight.