Tualatin Basin Water Supply

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Our communities rely on Hagg Lake/Scoggins Dam

The safety, security, and reliability of Hagg Lake/Scoggins Dam is critical to Washington County's community health and water supply.  With the potential future threat of a major earthquake and our growing population, we need to modify Scoggins dam to protect the public and meet our community's long-term water needs.

Learn more about the project

OPTION 1 Dam Modification & Raise

OPTION 2 Existing dam

OPTION 3 Downstream dam

Option 1 modifies the existing dam at its current location to provide needed safety improvements so it could withstand a major earthquake

Water Surface Elevation: 303.5 feet

Option 1 modifies the existing dam at its current location to provide needed safety improvements so it could withstand a major earthquake

Water Surface Elevation: 303.5 feet
This option does not provide increased water storage
Legend Dam location Current Full Reservoir Water Surface When Full

Option 2 modifies and raises the existing dam providing needed safety improvements and additional water storage

Water Surface Elevation: 321 feet

Option 2 modifies and raises the existing dam providing needed safety improvements and additional water storage

Water Surface Elevation: 321 feet
Provides an additional 21,000 acre feet of water storage (An acre-foot is the volume of one acre of surface area to a depth of one foot and equals 326,000 gallons.)
Legend Dam location Current Full Reservoir Water Surface When Full

Option 3 incudes a new dam downstream where the valley is narrower. Because the dam is downstream, it can store more water without raising the water level.

Water Surface Elevation: 303.5 feet

Option 3 incudes a new dam downstream where the valley is narrower. Because the dam is downstream, it can store more water without raising the water level.

Water Surface Elevation: 303.5 feet
This option provides an additional 50,000 acre feet of water storage (An acre-foot is the volume of one acre of surface area to a depth of one foot and equals 326,000 gallons.)
Legend Dam location Water Surface When Full

Our growing water supply

Key Resources

2016 TBWS Brochure 2012 TBWS Brochure » View all documents

Document archive View past documents, including design and public involvement resources.

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