About this Project

The Valley Creek Watershed project was initiated to mitigate hydrologic and hydraulic impacts associated with the planned widening of US Route 202 in Chester County, Pennsylvania. The project focused on the Valley Creek and Little Valley Creek basins in Tredyffrin and East Whiteland Townships, regions characterized by karst terrain, sensitive groundwater systems, and flood-prone stream corridors.

AEG provided comprehensive engineering and environmental services during both the preliminary and final design phases. Our team surveyed and assessed all drainage and stormwater structures along the seven-mile highway corridor to determine if replacements or modifications were needed due to the highway expansion. AEG then developed a GIS-based watershed-wide assessment, identifying public water supplies, groundwater resources, soils, geology, floodplains, and the impacts on surface water hydrology.

This data guided the development of stormwater Best Management Practices (BMPs), such as wetlands, stormwater treatment ponds, and infiltration facilities, to boost baseflow recharge and enhance water quality. AEG identified 23 potential mitigation sites through field reconnaissance and spatial analysis, which were then verified with site testing to determine their suitability for wetland treatment, stormwater detention, and retention.

Floodplain and natural channel restoration using fluvial geomorphologic techniques was proposed to reduce erosion in vulnerable areas. About 2,500 feet of stream was restored and stabilized through natural channel design and bioengineering methods, along with additional improvements benefiting a nearby municipal park.

AEG’s services included:

• DEP Chapter 105 / ACOE Section 404 joint permit coordination
• Environmental impact assessment and NEPA documentation
• Floodplain analysis and stream restoration design
• Wetland delineation and mitigation
• Erosion and sediment control planning
• Post-construction stormwater management
• Construction oversight

This project demonstrates AEG’s ability to combine engineering, environmental science, and regulatory compliance to provide sustainable infrastructure solutions in complex watershed environments.