Overview

The Town of Cary is exploring the use of a reservoir aeration system to provide better water quality near its water supply intake in Jordan Lake. By "mixing" the water in Jordan Lake that is treated by the Cary/Apex Water Treatment Facility, the Towns of Cary and Apex will be able to maintain their high levels of service in providing reliable and safe drinking water to customers while holding down costs of treating the Jordan Lake supply and provide more flexibility to treat water during droughts.

Details

The Towns of Cary and Apex co-own a water treatment facility that withdraws water from Jordan Lake and provides high quality drinking water to residents and businesses in Cary, Apex, Morrisville, RDU, and RTP South.

Water quality in Jordan Lake can vary with the depth of the lake. During the warm weather months, Jordan Lake stratifies causing warm oxygen rich water to exist near the lake surface and cooler, oxygen poor water to sink to the lower lake depths. When lake levels are lower - typically from drought or increased withdrawals - the Towns have to use the lower intake. Variable water quality can pose water treatment challenges,  including taste issues and odors, increased blue green algae levels, low dissolved oxygen, and elevated levels of dissolved iron and manganese.

The proposed water quality enhancement project would utilize an aeration system that will slowly "mix" water from the surface and water from the lower depths by gently moving the oxygen-rich surface water down to the lower level. This mixing will result in better circulation in the lake for overall improved water quality. The aeration system would be located on the lake near the US 64 bridge and Farrington Road.

Benefits

The proposed Jordan Lake Aeration System supports the Town’s commitment to providing a high level of service to our citizens while preserving and protecting our environment by:

• Reducing drinking water taste and odor problems
• Improving water treatment plant reliability during maximum production
• Lowering operating costs by providing more consistent and better water quality
• Improving aquatic habitat

The aeration system will not only benefit the communities who use the lake as their drinking water source, but will also benefit those who enjoy it for recreation and business as well as the creatures that live in and around the water.

The US Geological Survey began monitoring Jordan Lake water quality in April 2012 at multiple locations and depths for such parameters as temperature, dissolved oxygen, iron, manganese, and algae. If the project is approved and the Towns decide to implement the proposed aeration system, USGS will continue to monitor Jordan Lake water quality for two years following installation. USGS would then evaluate the water quality benefits of the system.

Timeline

The US Army Corps of Engineers is conducting an environmental review of the proposal, including an Environmental Assessment (EA) for the proposed water quality enhancement project. The purpose of the EA is to ensure the environmental consequences of the proposed water quality enhancement project are considered and available to the public. The environmental review process will continue throughout 2012.

Assuming the project is approved, the mixing system would likely be installed in spring of 2014.

Environmental Review

The US Army Corps of Engineers sent a scoping letter on September 30, 2011. The scoping period concluded on November 9, 2011.

The next step in the process is preparation of a draft Environmental Assessment addressing the comments received during the scoping period.

Questions regarding the environmental review should be directed to Michael Hosey at (919) 542-4501, extension 26.

Budget

The total FY 2013 proposed budget for the project is $2.54 million, which is funded by utility capital revenue sources. This budget includes the $1.75 million previously approved, plus a proposed FY 2013 increase of $790,000 to allow for anticipated increases in material costs, currency exchange rates between the United States and Australia, and US Geological Survey water quality monitoring and evaluation.

The proposed Jordan Lake Aeration System is a more cost effective alternative for addressing the water quality issues associated with lake stratification than the water treatment process improvements that would otherwise be necessary at an estimated cost of $6.9 to $15.3 million.

More on Aeration Systems

Lake aeration technologies have been used in North Carolina, as well as in several locations throughout the United States and internationally. These systems have been used in water supply lakes, recreational lakes and multi-purpose reservoirs similar to Jordan Lake.

The proposed system for Jordan Lake, ResMix™, is manufactured by WEARS Australia.

Read the Jordan Lake Aeration System staff report.

Contact

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