South Side

BIG THOMPSON RIVER-TR· Larimer, Colorado· Built 1921· Earth· 31 ft tall
Significant Hazard Irrigation Private

Key Takeaway

South Side is classified as significant hazard in Colorado. It was completed in 1921 and is 105 years old. Its primary use is irrigation. Significant hazard means failure could cause economic or environmental damage. Learn more.

Physical Details

Dam Height 31 ft (taller than 68.6% in CO)
Dam Length630 ft
Dam TypeEarth
Max Storage1.0K acre-ft
Normal Storage658 acre-ft
Surface Area66 acres
Drainage Area4 sq mi
Max Discharge4,930 cfs
Year Completed1921 (105 years old)
NID IDCO01195

Safety Information

Significant Hazard

No probable loss of human life, but can cause economic loss, environmental damage, or disruption of lifeline facilities.

Hazard potential describes downstream consequences of failure, not the dam's current condition. What does this mean?

Emergency Action Plan: Yes
Last Inspection: August 3, 2021
State Regulated: Yes
Regulatory Agency: DWR

Ownership

SOUTH SIDE RESERVOIR COMPANY (STEVE MCMILLAN, TREA

Private

Nearby Dams

Frequently Asked Questions

What is the hazard classification of South Side?

South Side is classified as Significant Hazard. No probable loss of human life, but can cause economic loss, environmental damage, or disruption of lifeline facilities. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.

Who owns and operates South Side?

South Side is owned by SOUTH SIDE RESERVOIR COMPANY (STEVE MCMILLAN, TREA (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

When was South Side built?

South Side was completed in 1921, making it 105 years old. Many U.S. dams were built between the 1930s and 1970s during a period of major infrastructure investment.

What is the primary purpose of South Side?

South Side serves the following purposes: Irrigation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.

How tall is South Side?

South Side has a dam height of 31 ft. Dam height is measured from the natural streambed at the downstream toe to the top of the dam, and may differ from the visible height.

When was South Side last inspected?

South Side was last inspected on August 3, 2021. Inspection dates indicate when a formal review occurred, not the results of that inspection.

Data from the National Inventory of Dams (NID) maintained by the US Army Corps of Engineers. Dam conditions may have changed since the last update. This site is not affiliated with USACE. Do not use for emergency planning — contact your local dam safety program.