Coal Ridge Waste Dam #1 Reservoir Report

Last Updated: December 5, 2025

Coal Ridge Waste Dam #1, also known as Sand Hill Lake, is a privately owned structure located in Weld County, Colorado, near the city of Platteville.


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Summary

Built in 1954 for irrigation purposes, this earth dam stands at a height of 31 feet and has a hydraulic height of 25 feet. The dam has a storage capacity of 1189 acre-feet, with a normal storage of 591 acre-feet and a surface area of 81 acres.

With a significant hazard potential and a satisfactory condition assessment as of July 2020, Coal Ridge Waste Dam #1 is regulated by the Colorado Department of Water Resources. The dam has an uncontrolled spillway with a width of 242 feet and a maximum discharge rate of 9290 cubic feet per second. The structure has been modified in 2001 for hydraulic purposes, and regular inspections are conducted, with the last one taking place in July 2020.

For water resource and climate enthusiasts, Coal Ridge Waste Dam #1 presents an interesting case study of a private irrigation dam in Colorado. Its location near the South Platte River and its association with recreational activities make it a vital part of the local water management infrastructure. With a moderate risk assessment and a history of satisfactory condition, this dam serves as a reminder of the importance of maintaining and monitoring such structures to ensure the safety of both the surrounding community and the environment.

Years Modified

2001 - Hydraulic

Year Completed

1954

Dam Length

2720

Dam Height

31

River Or Stream

SOUTH PLATTE RIVER-OS

Primary Dam Type

Earth

Surface Area

81

Hydraulic Height

25

Drainage Area

3

Nid Storage

1189

Structural Height

31

Hazard Potential

Significant

Foundations

Soil

Nid Height

31
       
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.