Innovative solution to stormwater management pond sediment could save billions

In 2004, the City of Waterloo hired Francine Kelly-Hooper, Ph.D., to evaluate its stormwater management (SWM) pond sediment. The chemistry results determined the sediment would need to be landfilled, with an unplanned cost of $50,000. Even more alarming, the City would need to find $10 million to dispose of sediment at many other SWM ponds as well. Francine was concerned how this unplanned cost might drain funding from community programs that benefited her friends, neighbors and public programs. And so began the research that would define her career.

Thousands of stormwater management (SWM) ponds protect against floods and treat water in urban developments. Rainfall and snow runoff flows over lawns, rooftops and pavements before settling into SWM pond basins. These ponds control stormwater release, protecting communities from flooding and improving water quality. Suspended soil particles and contaminants settle into the ponds, becoming sediments.

Determined to change the system and find a sustainable alternative, Francine first had to investigate the contaminants. She and the client approached the Ontario Ministry of Environment to raise the red flag:

Sediments must be removed to maintain flood control and water quality treatment efficiencies. But, where to put them? This is a challenge as owners spend thousands to millions of dollars on disposal fees, disposal trucks emit carbon emissions and the world is running out of landfill space.

With funding under way, Francine conducted the sediment quality survey of 371 samples from 121 ponds over 17 years. The study aimed to:

• Characterize contaminant sources and concentrations
• Complete ecotoxicity, leachability and pore water tests to see if the sediments could be reused (i.e., beneficial reuse)

She tested sediments for toxic substances, nutrients, carbon and particle size. She also tested earthworms, grasses and trees for ecotoxicity.

Initial results found petroleum hydrocarbons (PHCs) in most sediments. But Francine questioned whether the PHCs came from algae, plants and waterfowl droppings. Her research determined that most of the PHCs came from asphalt particles rather than natural organic sources.

Never one to back down from a challenge, Francine pursued a 7-year Ph.D. to prove the sediment contamination was contained in asphalt particles. Every sample had low or undetectable contaminants. Further, the PHCs and PAHs in the samples came from asphalt. Plants and earthworms thrived in the asphalt-contaminated sediments, with no toxic impacts.

She demonstrated that SWM pond sediment should be managed as a valuable resource for beneficial reuse, rather than as a toxic waste. This finding, combined with her sediment plant growth and earthworm toxicity trials, has led to the only beneficial reuse approvals of its kind in Canada.

Unfortunately, the current legislation makes SWM pond sediment beneficial reuse difficult. Francine helps organizations work through the system to find sustainable outcomes.

For example, she helped the Ontario Ministry of Transportation save $3.3 million in landfill disposal fees for a highway construction project. The sediment was reused as landscaping material on highway offramp sites. Another project reused sediment as topsoil at the Grand River Conservation Authority’s Burford Tree Nursery. Both projects demonstrating excellent plant growth.

Francine offers suggestions for others looking to change the status quo:

• Collaborate wherever you can. Bring as many stakeholders to the table as possible. Provide opportunities to find common ground and solutions that benefit everyone.
• Describe the community benefits. The tree nursery manager was skeptical about Francine’s motives for reusing the sediments. However, the manager agreed to participate in the project after hearing Francine’s history and goal to save the community’s financial resources.
• Emphasize the cost savings and environmental benefits. Francine estimates her beneficial reuse work has saved her clients at least $8 million. Eliminating unnecessary trucking to landfills has reduced carbon emissions as well.

Francine’s research won an Environmental Innovation Award from the Environmental Services Association of Alberta, among other awards. Learn more about Francine Kelly-Hooper, Ph.D., GHD’s new Canadian Sediments Lead, and her work at Battelle’s Sediments Conference from January 9-12 in Austin, Texas.