Legacy Sediment

Why Legacy Sediment Matters

At the heart of the Blue Green Connector Project is the excavation of more than four million pounds of “legacy sediment” along the Little Conestoga Creek. Legacy sediment is soil that has eroded from high points and washed down to settle in valley bottoms and streams, then becoming trapped behind thousands of dams built by early settlers to harness water-power for grain and lumber mills. Legacy sediment has accumulated rapidly over the past 300 years due to human activities. You can learn more about research on legacy sediment from the Chesapeake Watershed Initiative at Franklin & Marshall College.

Why Removal is Necessary

Restoring natural function: Over time, legacy sediment buildup has buried an ancient floodplain that persisted for thousands of years, disrupting its ability to manage water and support native ecosystems. Removing legacy sediment restores water’s natural flow, increasing water storage, while enhancing growth of vegetation, carbon storage, and habitat stability.
Improving water quality in local and regional watersheds: Legacy sediment removal helps to reduce phosphorus and nitrogen in streams, two pollutants that degrade water quality and aquatic ecosystem health. Their removal directly benefits the Little Conestoga Creek and contributes to cleaner water in the Conestoga and Susquehanna Rivers and the Chesapeake Bay.

Reducing flood risk and protecting property: Legacy sediment can worsen flooding by creating high, steep stream banks, and causing a high speed water channel during flooding. Its removal helps slow the water, allowing it to soak into the ground and be stored on site. It can also lessen the effect of floods to local homes, roads, and farms – and neighbors downstream as well.
Expanding native plantings: Some trees are removed during excavation in order to restore historic wet meadows within the floodplain. New native trees are planted along with a diverse mix water-loving perennial flowers, native grasses, and shrubs to support healthy habitat and manage water naturally.

Before and After – Legacy Sediment Removal

Restoration of the floodplain involves removing legacy sediment and adding native plants and trees. This is a return to conditions similar to those that existed here for thousands of years. Read our Frequently Asked Questions.

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Before and After - Legacy Sediment Removal

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Does Removing Legacy Sediment Really Make a Difference?

Yes! This project will remove 4 million pounds of sediment, 1,541 pounds of phosphorus, and 7,752 pounds of nitrogen from the Little Conestoga Creek, preventing them from polluting the water and traveling downstream to pollute the Susquehanna River and the Chesapeake Bay. By creating gradual slopes, we can improve access and the floodplain’s ability to function.

Connections between the creek and groundwater springs act to cool water temperatures during the summer and warm them during cold winter months, which provides temperature stability for fish and other aquatic animals.

By establishing a biodiverse native plant community, we can filter pollutants, reduce erosion, and support a healthy ecosystem. Native wildflowers, grasses, trees, and shrubs will provide wildlife habitat and beautify the greenway.

It is our hope that the Blue Green Connector project serves as a catalyst for further restoration efforts along waterways in Lancaster County, helping to clean water and restore our environment!

Additional Resources

Dive deeper into the stories, science, and impacts of restoration with these additional resources — from interactive maps to initiatives that connect our local work to a healthy Chesapeake Bay.