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.
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