Engineering for Dam Repairs | Design, Permitting and Construction Observation
Due to corrosion of an 11-foot diameter riveted steel penstock that extended through the earthen berm portion of the dam, the integrity of the earthen berm was jeopardized. This was evident from sink holes that had developed within the berm near the penstock. Verdantas' experience in geotechnical engineering and permitting and our ability to look at the “big picture” enabled us to perform simultaneous engineering evaluations, seepage mitigation design and permitting, as well as construction oversight and support during implementation of the work.
Achievements
IDENTIFIED SEEPAGE THROUGH THE EMBANKMENT AS THE CAUSE OF OBSERVED SINK HOLES – Verdantas performed a subsurface investigation through the dam embankment, and our observations of the embankment materials confirmed seepage as the primary cause of sink holes.
DESIGNED SEEPAGE MITIGATION – consisting of improving the dam embankment by installing a low permeability geosynthetic clay liner along with new rip rap armoring to prevent erosion and scour. Prepared design plans identifying the extent of improvements, required materials, construction methods, etc.
SUCCESSFULLY PERMITTED THE PROJECT THROUGH STATE AND FEDERAL AGENCIES – The project included obtaining the necessary permits (Massachusetts Chapter 253 Dam Safety Permit, Wetlands Protection Act permit and Notice of Intent, and Remediation General Permit for construction dewatering). In addition, Verdantas prepared an Emergency Action Plan for Construction Activities as required by the Chapter 253 permit.
OVERSAW CONSTRUCTION ACTIVITIES AND ADDRESSED PROJECT CHANGES AS ENCOUNTERED – Verdantas performed regular inspections of the construction activities to verify compliance with the design plans and permits. Construction efforts resulted in the need to modify the design as unexpected conditions were encountered, and Verdantascommunicated these changes to the owner and permitting agencies to maintain compliance and successfully complete the project.
Scope of Services
- Geotechnical Engineering
- Site Investigation
- Dam Embankment Seepage Analysis and Remedial Design
- State and Federal Permitting
- Construction Oversight
Client
IndustrialLocation
MACapability
Civil InfrastructureServices
Site EngineeringRelated Projects
An existing roof vent arrangement was allowing rainwater to enter the Pot Room. Alden supported efforts to develop a roof vent geometry to eliminate the intrusion of rain water. The purpose of the CFD study was to ensure that the roof vent modification did not increase pot room temperature levels beyond specified limits for workers in the plant.
To evaluate the existing and proposed Pot Room arrangements, thermal and fluid flow profiles in the immediate vicinity of the pots were determined based on air flows through the plant floor and wall mounted vents. The detailed CFD model was developed from plant drawings to include all major basement, pot room and roof venting geometries. The surrounding ambient environment was included with quiescent atmospheric conditions and average ambient temperature. Thermal losses form the pots to the pot room air and from the pot room to the environment were included in the analysis. The results of the CFD modeling showed that the proposed modification to the roof venting arrangement was acceptable and would not increase the temperature in the worker-occupied spaces by more than 2 degrees F.
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Civil Infrastructure
Smelter Pot Room Roof Ventilation System
Read how a CFD study ensured that a roof vent modification did not increase pot room temperature levels beyond safe levels
Plant McDonough, owned and operated by Southern Company, has experienced excessive siltation at the makeup water intake. The intake uses cylindrical wedgewire screening within an intake originally designed for much larger, once-through cooling water flows. Flow modeling was performed to provide a viable passive solution to reducing the sediment accumulation at the intake. To model the geometric details of the system accurately, a field survey was performed prior to the flow modeling efforts. The flow study included both CFD modeling and scale physical modeling.
For this investigation, Alden developed a 1:20 scale live bed physical model. This model was extremely well tuned to reproduce the behavior of bed load sediment. Even with the very fine crushed walnut shell particles, however, it was challenging to reproduce the behavior of suspended load. The use of a high fidelity CFD model, therefore, proved extremely useful for this project, in that suspended load is generally very accurately tracked with CFD models, which are not well validated for bed load simulation. By using the two together, the two extremes of sediment transport are captured, and developing a solution that covers this range has a high likelihood of success.
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Civil Infrastructure | Hydrology Hydraulics and Fluids
Plant McDonough Intake Modification
CFD and physical model study to assist in the evaluation of a solution to reduce the sediment accumulation.