Unger-Bill Dam Reservoir Report
Last Updated: December 12, 2025
Unger-Bill Dam, located in Farmington, Oregon, is a privately owned structure that plays a crucial role in irrigation along the Tualatin River.
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Summary
Built in 1968, this earth-type dam stands at a height of 39 feet and has a storage capacity of 97 acre-feet. With a normal storage capacity of 80 acre-feet, the dam covers a surface area of 5.2 acres and serves a drainage area of 0.27 square miles.
Managed by the Natural Resources Conservation Service, Unger-Bill Dam is regulated by the Oregon Water Resources Department and undergoes regular inspections to ensure its safety and functionality. The dam features a slide gate outlet system and has a significant hazard potential, although its condition assessment is currently not rated. Despite this, the dam continues to provide vital irrigation water for the surrounding area and contributes to the region's water resource management efforts.
With the support of local authorities and the dedication of its owners, Unger-Bill Dam remains a key infrastructure for water supply and agricultural needs in Washington County, Oregon. Its presence highlights the importance of sustainable water resource management and the essential role that dams play in supporting local communities and ecosystems amidst changing climate conditions.
Year Completed |
1968 |
Dam Length |
530 |
Dam Height |
39 |
River Or Stream |
TUALATIN RIVER, TRIB TO |
Primary Dam Type |
Earth |
Surface Area |
5.2 |
Hydraulic Height |
34 |
Drainage Area |
0.27 |
Nid Storage |
97 |
Structural Height |
40 |
Outlet Gates |
Slide (sluice gate) |
Hazard Potential |
Significant |
Nid Height |
40 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Tualatin River Near Dilley
|
1360cfs |
Willamette River At Newberg
|
64600cfs |
East Fork Dairy Creek Near Meacham Corner
|
21cfs |
Fanno Creek At Durham
|
49cfs |
Fanno Creek At 56th Ave
|
4cfs |
Columbia Slough At Portland
|
5cfs |
Dam Data Reference
Condition Assessment
SatisfactoryNo existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.
Hazard Potential Classification
HighDams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.
Unger-Bill Dam