Northern Virginia Stream Restoration Bank

WSSI solved two problems at once, improving community natural areas and offering the stream impact credits needed to offset development, by establishing the first stream mitigation bank in Virginia and restoring more than 11 miles of stream channels. In the process to create the Northern Virginia Stream Restoration Bank, WSSI worked with federal and Virginia regulatory agencies to pave the way for more stream mitigation banks across the Commonwealth.

The Challenge

Northern Virginia’s development projects needed a way to compensate for impacts to streams in the watershed. At the same time, eroding stream banks were undermining trees and trails, exposing utility lines, and polluting streams in the established Reston community. WSSI’s solution at the intersection of the two issues generated two more challenges: sculpting a regulatory framework for stream mitigation banking and educating Reston stakeholders about the benefits of stream restoration.

Our Solution

WSSI worked with the Reston Association (RA) to designate more than 11 miles of highly degraded stream channel and opportunities for channel restoration, riparian planting, and ecosystem improvement. Given that RA owns complete subwatersheds, this community was a perfect candidate for this large stream restoration project; WSSI was able to restore entire streams from the top of the watershed down to the mouth of the receiving lakes.

Simultaneously, we worked closely with the U.S. Army Corps of Engineers (COE), the Virginia Department of Environmental Quality (DEQ), and other regulatory agencies to develop the guidelines and requirements that make up the Mitigation Banking Instrument for this stream mitigation bank – the first of its kind in the Commonwealth – and laid the foundation for future stream mitigation banking in Virginia.

Together with federal and state agencies, WSSI developed a “currency” (Stream Credit Units or SCUs) for assessing stream impacts and required mitigation. The resulting “Virginia Stream Impact Assessment Manual” (SIAM) formed the basis for the “Unified Stream Methodology” (USM) developed by the COE and DEQ for use throughout Virginia.

WSSI employed a comprehensive outreach campaign to engage the community. We conducted more than 100 meetings for the community and with local plan approval authorities. WSSI’s outreach extends to the annual community fishing event for children, displays for the Reston Museum, and interpretive signage throughout the NVSRB corridors.

WSSI conducted all of the initial natural and cultural resource investigations, collected stream geomorphology data, and completed the design and modeling along with the regulatory process. During construction, WSSI provided inspections and oversight as well as stakeout and as–built surveys. We are responsible for 10 years of post–construction monitoring and maintenance to ensure successful restoration, including geomorphic, riparian, and benthic macroinvertebrate community measurements. All of the stream channels have exceeded their success criteria, and many have completed the 10–year benchmark.

Stream restoration in NVSRB included connecting the channel to the floodplain to restore natural processes. Our design has resulted in an additional 25 acres of valuable overbank wetlands in the project corridor!