Upper Watts Branch Stream Restoration – Design Implications and Lessons Learned During Construction
Paul Le Bel, PE
Hazen
Fairfax, Virginia
The City of Rockville retained Hazen, along with our design partner CPJ, to evaluate environmental and ecological conditions, identify opportunities for ecological restoration and uplift, and determine risk to exposed assets within the Upper Watts Branch Forest Preserve. The project team identified multiple ecological restoration opportunities including re-establishment of a forested wetland, and over 2,200 linear feet of stream restoration and outfall stabilization. Hazen developed stream restoration and asset protection 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, drinking water, and stormwater 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 ecological uplift. The reuse of naturally occurring on-site resources such as trees and streambed material was maximized to reduce the carbon footprint and environmental impact of the project. Construction began in July of 2017 and was completed in April of 2018. During construction, Hazen worked closely with the owner and contractor to ensure construction met the design intent. This presentation highlights several design and construction management strategies that proved successful during this project, including: (1) Scheduling – the importance of designer presence during the first installation of any structure type (e.g., toe wood, cross vane); (2) Communication – reporting mechanisms to provide both immediate/actionable feedback and record documentation; (3) Toe Wood Revetments – design implications for biological uplift and lessons learned during construction; (4) Reuse of Streambed Material (SBM) – development of site specific photo field guide for SBM identification and scoring (acceptable/non-acceptable); (5) Step Pool Storm Conveyance (SPSC) for Outfall Stabilization – design implications for sand bed retention and lessons learned during construction; (6) Reuse of On-Site Trees – wood budget development and implementation; (7) Hyporheic Zone Improvements – design implications for increased nutrient cycling and lessons learned during construction; and (8) Bedrock Triage – how to incorporate unanticipated bedrock and provide stable transitions. This presentation will identify challenges faced during design and construction, highlight lessons learned from those challenges, and discuss recommendations for future implementation.
About Paul Le Bel , PE
Paul Le Bel is a Water Resources Engineer with Hazen who specializes in analysis, design and construction oversight for stream restoration, asset protection and urban stormwater management projects. Paul works throughout the Mid-Atlantic region to provide stream assessment, design and construction phase services for time sensitive projects. Paul works extensively with owners and contractors during the construction phase to ensure design intent is met and appropriate guidance is provided for field adjustments. He works out of the Fairfax, VA office where he is frequently involved in projects that benefit the Chesapeake Bay.