Dam Inspection for Mirror Pond Dam 2009

Dam-Inspect-Letter-B-99-Jul-21-09-1-HeaderJuly 21, 2009

Gregg Sheerer
Pacific Power
201 SW Columbia Ave
Bend, OR 97702

Re. Dam Inspection for Mirror Pond Dam (Bend Hydro Project, File B-99)

On April 27th, Jeremy Giffin (Watermaster) and I inspected Mirror Pond Dam. A field form is attached. It was great having someone there to discuss issues with and ask questions. These complementary dam inspections are done as part the State of Oregon’s Dam Safety Program. This dam has similar issues to what was observed in a 2005 inspection (Letter dated Octobler 10, 2005) which included the following key issues:

  • There was considerable seepage and some spalling along the downstream slope of the dam along the spillway area along the center part of the dam (upstream of island area)(Figure 1).
  • The sluice gates in the turbine bays had considerable leakage (Figure 2).
  • The stop logs were in generally poor condition.
  • Some of the cribs were really pushing a great deal of water out along the left side (spillway portion of the dam and make shift repairs had been done to some) (Figure 3).

I would suggest having the damaged concrete examined in greater detail by a concrete expert considering the seepage that is forming there. Some of the cribs along the spillway section are nearing the end of their functional life and should be prioritized and repaired over time. Please keep us in the loop on the current repairs that are going to be done.

Please let me know if you have any questions. We look forward to continued mutual cooperation to insure the safety and stability of this dam.

Sincerely;

E. George Robison, PhD
Dam Safety Coordinator
george.robison@state.or.us
Ph. 503-986-0840
Fax. 503-986-0902

c. Jeremy Giffin – Watermaster OWRD, Barry Norris – State Engineer OWRD

 

Figure 1. Concrete damage upstream of island (note seepage in places).
Figure 1. Concrete damage upstream of island (note seepage in places).
Figure 2. Leakage near turbine area on far right side of dam.
Figure 2. Leakage near turbine area on far right side of dam.
Figure 3. Excessive water moving thru one of the cribs.
Figure 3. Excessive water moving thru one of the cribs.

Source: Dam Inspect Letter B-99 Jul 21-09

Related: Dam Inspection Summary 2012