Sheldrake Lake Aeration Project
by Frank Hope and Rich Campbell
As part of the Water Quality Committee report to the WRWEO 2004 AGM, Dr. Pat Lane presented a progress report on the Sheldrake Lake Hypolimnetic Aeration Project. In summary, the operation has overcome many minor difficulties encountered during operating trials last year, and it is hoped that we will be able to conduct a formal evaluation in the course of a full season of operation this year. Additional funds are being sought for improvement to optimize operations and pay for follow-up water quality analysis.
Tim McGee gave a report on behalf of the Hunting and Fishing Committee concerning the fish habitat restoration implications associated with the project. He noted with satisfaction anecdotal reports by nearby residents concerning improvements in the water quality associated with our efforts, and addressed the possibility of re-stocking the lake with native brook trout after the habitat is restored.
Based on a 1985 recommendation by the Halifax Soil and Water Conservation Society, WRWEO has embarked on an ambitious project to restore the fish habitat in Sheldrake Lake. Like many heavily-settled lakes in the watershed, Sheldrake becomes oxygen deficient at deep levels each summer due to external nutrient loading, mainly from fertilizers and faulty septic systems.
Sheldrake Lake is typical of the small shallow lakes on the Chebucto Peninsula, where residential developments along the lake shore can have drastic effects on the aquatic ecosystem unless natural buffer zones are maintained to limit the amount of nutrients entering the lake.
In fact, Sheldrake Lake was developed some time ago with only minimum set backs and lawns extending to the waterside, and now seems to be suffering the consequences. Seasonal oxygen levels at depth are depleted to the point that they no longer support the fish that once thrived in the lake, and algae as well as other aquatic plants are spoiling the lake for swimmers.
This hypolimnetic aeration project (referring to increasing oxygen levels in the deep layers of the lake) was developed by Dr Ken Ashley of UBC and the BC Department of the Environment. It is based on a design specially configured to match the characteristics of the lake and involves removing nitrogen from air and pumping the resulting relatively oxygen-rich gas to the bottom of the lake in such a way that it remains dissolved in the water at a deep level.
Although this technique has been used to remediate much larger lakes across North America, this pilot project is the first time it has been attempted on a lake this shallow. An extensive water sampling program is already underway to support a scientific evaluation of the project, and providing all goes well, this technique will be used to restore the fish habitat in several other lakes in the Province that share similar characteristics.
The result could be, for example, to allow survival of fish and other aquatic species that would otherwise not survive in the lake. However, the ultimate solution to the problem is to eliminate phosphate run-off from the human population surrounding the lake, and the human population upstream of the lake.
One of the important purposes of the project has been–through the sheer visibility of what’s being done, and the discussions it provokes–to raise local awareness of the connection between what residents do, and the life of the lake. It is hoped that this action pro-coupled with improved residential practices such as the use of phosphate-free detergents, less fertilizer and regular pumping of septic systems, will restore a healthy natural environment in this headwater lake of the Woodens River Watershed.
The project has required extensive water-quality data gathering and analysis; construction, by volunteers from the local community, of a shed to house the equipment; purchase and assembly of the oxygen generating and pumping equipment, as well as deployment of the weighted air hose and diffuser.
These efforts have been led by Tim McGee, John Matthews, Dale Conrad and Frank Hope. In addition Dr. Anthony Fielding has been taking water quality samples to validate the project and ensure compliance with Department of Fisheries and Environmental requirements. The $40,000 budget for this project was raised through an intensive fundraising effort led by Tim McGee by generous donations from a variety of agencies, including Eco Action, Department of the Environment, TD-Canada Trust Friends of the Environment, NS Power (Emira), the Bronfman Trust, ELJB Foundation, NS Wildlife Federation, Three Brooks Development, HRM and the Sheldrake Homeowners Association.
This project to bring the lake back to life is on track but not without extra expense and many, many hours of volunteer work.
New permits needed to be secured, the ventilation of the shed changed through new ducting, new hose laid from the shed to the aeration device and then repaired, several monitoring stations checked and remarked, the use of complex monitoring devices learned, and more.
There have been several attempts at breaking into the shed, none successful. We have notified the RCMP, asked NS Power to replace burnt out lights, and taken steps to find a way to insure the contents under government contracts.
The good news is that the various bugs are being worked out of the system. We will have some preliminary data on the effects of aeration this year (as required by our contract) and will be ready to run the system through the critical summer months this year from start to finish.