Gross Reservoir Report

Last Updated: December 5, 2025

Gross Dam, located in Boulder, Colorado, is a concrete structure completed in 1955 primarily for water supply purposes.


°F

°F

mph

Wind

%

Humidity

Summary

With a height of 340 feet and a storage capacity of 46,200 acre-feet, it serves as a vital resource for the surrounding area. Situated on South Boulder Creek, this dam is regulated by the Colorado Department of Water Resources and inspected by the Federal Energy Regulatory Commission to ensure its safety and functionality.

The dam's high hazard potential and moderate risk assessment underscore the importance of proper management and maintenance. Despite its age, Gross Dam continues to fulfill its role in water supply management, with a maximum discharge capacity of 10,000 cubic feet per second. The presence of an uncontrolled spillway and a spillway width of 160 feet further demonstrate the dam's robust design and preparedness for potential emergencies.

As a key component of the water infrastructure in the region, Gross Dam plays a critical role in water resource management and climate resilience. Its location in Eldorado Springs, surrounded by the natural beauty of Boulder County, highlights the intersection of human-made structures with the environment. With its impressive specifications and regulatory oversight, Gross Dam stands as a testament to the importance of sustainable water resource development in the face of changing climatic conditions.

Year Completed

1955

Dam Length

1050

Dam Height

340

River Or Stream

South Boulder Creek

Primary Dam Type

Concrete

Surface Area

413

Hydraulic Height

350

Drainage Area

92.8

Nid Storage

46200

Structural Height

340

Hazard Potential

High

Nid Height

350
       
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.