# Presentation: 193311

## Clark Fork-Flathead-Pend Oreille Basin

## Pend Oreille River

## Box Canyon Dam

- Pend Oreille Public Utility District
- on the Pend Oreille River near Ione, WA
- first licensed by FERC in 1952
- built/started operating in 1955
- run-of-river, 60 MW hydroelectric dam
- 4 turbines, 4 spill bays
- 55 mile long reservoir backs up to Albeni Falls Dam
- discharges into Boundary Dam reservoir

## FERC License & Water Quality Certification

- FERC issued new 50 year license in July 2005
- state Water Quality Certificate went into effect then (issued February 2003)
- required plan to reduce dissolved gas levels caused by spills at dam
- gas levels of 140% + recorded downstream at high flows
- goal to meet state standard of 110% saturation up to 7Q10 high flow
- 7Q10 flow ~ 112,800 cfs

## Box Canyon Dam

- FERC license requires:
-  backwater effect of </= 2 feet at Albeni
-  don't flood Cusick (reservoir at 2041' elevation or below)
-  at flows >= 68,000 cfs, start removing spillway gates to meet these requirements
-  at 90,000 cfs, all spillway gates are up
-  so, no power & no spill

## Box Canyon Dam (higher flows)

## Box Canyon Dam (lower flows)

## Box Canyon TDGP Abatement Plan(draft)

- Upgrade Turbines
- Put in Auxiliary Spillway Bypass
- Modify Spillway Gate Settings
- considered/eliminated several other options
- all measures to be put in place by 10 years after Ecology/PUD agree on plan

##  Turbine Upgrades

- Upgrade all 4 turbines
-  new high efficiency runners
-  rewind generators
-  60 MW to 90 MW rated capacity
-  27,400 cfs to 32,400 cfs maximum water flow through turbines

##  Turbine Upgrades

-    current condition
-  gas-generating flows between 27,400 cfs- 80,000/90,000 cfs: 25%- 26.6% of time
-     after upgrade
-  gas-generating flows between 32,400 cfs- 80,000/90,000 + cfs:  17.5 %- 19% of the time

## Auxiliary Spillway Bypass

- auxiliary spillway located in forebay channel between the dam and the powerhouse
- redesign to bypass flows around dam & decrease spill over the dam
- 3 bays controlled with stoplogs
- replace stoplogs with vertical steel gates
- water would be discharged beneath the gates

## Box Canyon Dam- Diagram

## Auxiliary Spillway Gates

- 27 foot high gates
- pass up to 27,600 cfs
- up to 60,000 cfs with no spill, no added gas
- 	flows between 60-000 cfs- 80,000/90,000 cfs:
-       3.5 %- 5% of the time
- gate size determined considering:
- gas reduced vs. cost
- characteristics of forebay channel
- backwater effects upstream
- capacity of gate hoist system

## Gas Production- turbines + gates

- turbine	aux. gate	time          max. mixed    max. gas
-  flow                flow                spilling         gas               spillway

| 27,400 | 0 | 26.6% | 128.7% | 138.7% |
| --- | --- | --- | --- | --- |
| 32,400 | 0 | 19% | 128.5% | 137.6% |
| 32,400 | 27,600 | 3.8% | 123.9% | 137.2% |

## Spillway Gate Settings

- modify gate configuration to reduce gas
-  preliminary work in 2002
-  needs further testing
-  considerations:
- gas reduction
- dam safety- balancing flow to minimize structural vibration
- operational constraints

## Spillway Gate Settings

## Monitoring 

-  forebay and tailwater fixed stations
-  April (March?)- mid-July, 15 minute intervals
-  until compliance demonstrated at expected range of flows
- possibly:
- turbine tailwater- following upgrades
-  auxiliary spillway tailwater- once finished
- downstream grid- if not in compliance after all measures in place