Dells Manor Reservoir Report

Last Updated: December 5, 2025

Dells Manor, located in Sauk County, Wisconsin, is a privately-owned dam with the primary purpose of recreation.


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Summary

Originally completed in 1929, this gravity dam stands at 24 feet tall with a hydraulic height of 16 feet. The dam has a normal storage capacity of 258 acre-feet and a maximum storage of 460 acre-feet, serving as a picturesque spot for water enthusiasts to enjoy activities on Dell Lake, also known as Lake Blass.

Managed by the Wisconsin Department of Natural Resources, Dells Manor is regulated, inspected, and enforced upon to ensure its safety and functionality. Despite its fair condition assessment, the dam poses a low hazard potential and has a very high risk rating of 1. Spring Brook, the river or stream it controls, has a drainage area of 6 square miles and can discharge up to 1500 cubic feet per second. With its controlled spillway and a surface area of 34 acres, Dells Manor remains a popular destination for visitors seeking outdoor recreation and water-based activities.

Although no major modifications have been reported in recent years, Dells Manor continues to be monitored with an inspection frequency of 10 years. The dam's emergency action plan (EAP) status is currently unknown, and there are no inundation maps prepared. As water resource and climate enthusiasts explore the beauty of Dells Manor and its surrounding area, they can appreciate the careful management and regulatory oversight that ensure both safety and enjoyment for all who visit this iconic site in Lake Delton.

Year Completed

1929

Dam Length

100

Dam Height

24

River Or Stream

SPRING BROOK

Primary Dam Type

Gravity

Surface Area

34

Hydraulic Height

16

Drainage Area

6

Nid Storage

460

Structural Height

24

Hazard Potential

Low

Nid Height

24
       
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.