This mixed-use project combines community ecological benefits with economic development. Lime Spring Square, located in Lancaster, Pennsylvania, is a 98-acre development that surrounds 11.5 acres of restored floodplain. Floodplain restoration was chosen as the primary BMP for this project due to various benefits including peak runoff rate reduction, enhanced groundwater recharge, suspended sediment reduction and nitrogen and phosphorus load reductions.
“By virtue of its function and purpose, floodplain restoration enables the project to utilize the floodplain area in a storm water capacity. While the primary goal is restoration, the secondary benefit is that storm water management requirements for a development project can be met within a previously unutilized portion of a site," said Len Bradley, supervisor of engineering and associate at RGS Associates.
The floodplain project included the removal of sediment to reconnect the stream channel with the floodplain, the creation of large areas of interconnected wetland habitats and the rehabilitation of groundwater interchange. The project removed 38,500 tons of legacy sediment, created 8.5 acres of additional wetlands and provides pollutant reductions of approximately 5,773 pounds per year of nitrogen, 254 pounds per year of phosphorus and 400 tons per year of sediment, which meets the town’s obligations for its MS4 permit without using taxpayer dollars.
“Unlike many projects which assert positive environmental and hydrologic benefits, Lime Spring Square has robust monitoring equipment tracking the actual results of these improvements,” Bradley said. “Rate control, volume control, thermal mitigation, and macroinvertebrate species populations have all shown dramatic improvements from the pre-construction conditions.