• Site Survey
• Coastal and Geotechnical Analysis
• Regulatory Coordination
• Alternative Formulation and Evaluation
• Preparation of Construction Plans
• Full time Construction Observations
• Meetings/Presentations
Challenge
The Erie County Water Authority (ECWA) provides drinking water to more than 550,000 people in New York State. The Lake Erie facility experienced significant shoreline erosion and damages to existing outfalls in the last couple of years. Partial repairs to the main outfall were performed in 2016, but they need to be revisited. The active upper erosion slope setback was over 2 feet per year.
Lake Erie is subject to extreme water level variations due to induced seiches (up to 8 feet), and therefore a robust design solution needed to be implemented
Solution
ECWA selected GZA for survey and geotechnical data collection, Coastal and Geotechnical analyses, formulation of repair/improvement alternatives with construction cost estimates, preparation of final construction plans, regulatory coordination and full-time construction observations. The project construction was completed by September 2024.
The upper slope (glacial till composition) was be regraded and a new stone revetment was provided, with a reinforced concrete toe anchored to the existing shale bedrock. One concrete outfall pipe was replaced; other repairs included utility pipes, access stairs and a new vertical concrete wall.
The GZA team investigated the condition of the shale bedrock and found the depth of competent bedrock (where steel anchoring dowels were installed to secure the reinforced concrete toe). Coastal protection was also provided, with excavated large armor stone anchored to the bedrock at the toe of the slope.
Benefit
The GZA team carefully planned and designed the proposed improvements providing shoreline and outfall protection and significantly reducing the periodic maintenance.