Spillway Modification

Fuse Plug Spillway Modification
Center Hill Dam

Partnering Lesson:

  • Hold follow-up Partnering sessions to keep Partnering concepts a viable tool.
  • Do not compromise the dispute resolution ladder.
  • Investigate and implement innovative approaches to overcoming obstacles.
  • Value engineering used with Partnering.

Project Description
The project schedule included milestones that coincided with flood seasons. During excavation of the existing saddle dam, which was later replaced with an erodable fuseplug, a calculated risk factor was built into the construction sequence. The flood protection level during the summer and early fall was lowered. Premature overtopping or failure of the saddle dam or fuseplug would have been catastrophic.

Project Challenges:

  • The contractor submitted and received approval of a VECP that involved redesign of the temporary retaining structure. This ultimately resulted in potential delays to first season work, and season-end flood protection.
  • The designed configuration of the concrete spillway apron due to somewhat differing site conditions required several design changes.
  • Overtopping concerns.
  • Unusual configuration of the fuseplug impervious core and gravel/sand filters.
  • The only available source for the gravel filter gradation was a glacier deposit several hundred miles from the project site.

Issue 1:
The initial partnering session was not well-facilitated. The project was far behind schedule before follow-up partnering sessions were held, and even those did not include an independent facilitator.

Follow-up partnering sessions were somewhat like workshops to determine strategies to implement damage control procedures. The resident engineer's effectiveness in resolving issues was threatened when at field level. The contractor began contacting the district office directly bypassing a necessary rung in the issue resolution ladder.

Issue 2:
Eventually, the partnering sessions, which included the designers, yielded innovations that resulted in achieving the project milestones. The project was completed not only on time, but slightly below the original budgeted cost, which was an added benefit. This was accomplished through continuing communication with the designers who worked cooperatively with the resident engineer to implement numerous cost and time reduction measures. Some of the innovations were contractor improvements on construction procedures, including use of laser-guided fill placement and grading equipment. Significant value engineering savings were also realized.

Benefits of Partnering:

  • Project was completed under budget and on time despite schedule acceleration.
  • Partnering sessions yielded several innovations in design and schedule.
  • Significant value engineering savings were realized.

Stakeholders:
Nashville District Operations Division, Prime Contractor, Southeast Power Association, TVA, lake users, downstream property owners/residents/businesses.