Piscataway Basin Asset Protection and Stream Restoration Projects

Hazen conducted hydrologic evaluation and Stream Stability Assessments utilizing Watershed Assessment of River Stability and Sediment Supply methodologies (WARSSS) for each site to document the existing stream conditions and identify the potential stable form. Risk of damage to sanitary assets (manholes, sewer pipes, etc.) was completed in the field to identify and prioritize stream restoration and asset protection project sites.

We developed asset protection and stream restoration designs for each site based on Priority I-IV stream adjustments to restore stable channel form and function while providing cost-effective long-term protection for existing sanitary infrastructure. The Natural Channel Design approach was backed with engineered hydraulic stream flow modeling and incorporated hard and bio-engineered features to stabilize the channel and provide aquatic and riparian ecological uplift. A variety of stream revetments were used including step pools, stone grade controls, vegetated geolifts, imbricated stone walls, J-vanes, engineered riffles, log drop pools and stone cascades. Extensive planting plans were created for each project area.

All necessary permits including 401/404 Waters of the US and wetlands permits and 100-year floodplain permitting were procured. The plans complied with the Maryland Forest Conservation Law and exceeded local grading and sediment and erosion control requirements.

Hazen provided construction management and on-site technical expertise to WSSC. Hazen worked closely with project stakeholders to ensure construction met the design intent, visiting active project areas to review completed work, on-going installations, and discuss scheduling. Where required, Hazen evaluated changes to field conditions and provided design redlines to ensure constructability and long-term stability.

Project Outcomes and Benefits

• Identified and prioritized stream restoration and sanitary asset protection project sites.
• Developed designs for each site to restore stable channel form and function while providing cost-effective long-term protection for existing sanitary infrastructure; natural channel design methods utilized extensively in lieu of more costly sanitary sewer removal and replacement.
• Provided streamlined construction management support and observation services, with typical 24-hour or less turnaround on needed field engineering decisions.
• Provided detailed cost estimates to capture the full cost of site access, site preparation (clearing and grubbing, erosion and sediment control, etc.), construction of design, site evacuation, and planting.
• Worked collaboratively with client and contractors to understand and implement the design. No change orders were issued during construction.
• Design submittals and construction schedules were completed on-time.