Briggsville Reservoir Report

Last Updated: December 5, 2025

Briggsville, also known as Lake Mason, is a gravity dam located in Marquette, Wisconsin, with a primary purpose of recreation.


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Summary

Completed in 1850, this dam stands at 14 feet tall and spans 250 feet in length, with a storage capacity of 850 acre-feet and a surface area of 856 acres. It is situated on the South Branch Neenah Creek and is regulated by the Wisconsin Department of Natural Resources, with permitting, inspection, and enforcement responsibilities falling under state jurisdiction.

The dam at Briggsville poses a high hazard potential, with a very high risk assessment rating of 1. Despite this, the condition assessment as of June 2019 was deemed satisfactory. The dam has undergone modifications in 1965 and 1993, with the last inspection conducted in May 2019. In the event of an emergency, it is crucial to have an effective Emergency Action Plan (EAP) in place, although details on its preparation and revision are not specified in the available data.

For water resource and climate enthusiasts, Briggsville offers a fascinating insight into the infrastructure that supports recreational activities while also highlighting the importance of proper maintenance and risk management for dams. Its location in a picturesque setting along the South Branch Neenah Creek adds to its allure, making it a valuable resource for both local residents and visitors to enjoy.

Years Modified

1965 - Other, 1993 - Other

Year Completed

1850

Dam Length

250

Dam Height

14

River Or Stream

SOUTH BRANCH NEENAH CREEK

Primary Dam Type

Gravity

Surface Area

856

Hydraulic Height

11

Drainage Area

37

Nid Storage

850

Structural Height

14

Hazard Potential

High

Nid Height

14
       
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.