Sitla - Sienna Hills Reservoir Report

Last Updated: December 15, 2025

Sitla - Sienna Hills is a privately owned dam located in Washington County, Utah, designed for flood risk reduction along the Grapevine Crossing Wash.


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Summary

The dam is regulated by the Utah Division of Water Rights and is subject to state jurisdiction, permitting, inspection, and enforcement. With a hydraulic height of 17.7 feet and a structural height of 26 feet, Sitla - Sienna Hills has a low hazard potential and is currently not rated for its condition assessment.

Although the dam's completion year, storage volume, and other specific details are not provided, it is known to have a normal storage capacity of 15.9 acre-feet and a maximum discharge of 847 cubic feet per second. The dam is primarily made of earth materials and spans a length of 330 feet. Despite its low hazard potential, the dam undergoes inspections every five years to ensure its structural integrity and compliance with safety guidelines. Overall, Sitla - Sienna Hills serves as a vital infrastructure for flood risk mitigation in the region.

Dam Length

330

River Or Stream

GRAPEVINE CROSSING WASH

Primary Dam Type

Earth

Hydraulic Height

17.7

Nid Storage

15.9

Structural Height

26

Hazard Potential

Low

Nid Height

26
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No 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

High
Dams 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.