Rock Island Lake Dam Reservoir Report
Nearby: Glen Lake Dam Morris Lake Dam
Last Updated: December 10, 2025
Rock Island Lake Dam, located in Sparta, New Jersey, was completed in 1940 and serves as a recreational resource in the area.
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Summary
This private earth dam stands at 19 feet tall and spans 500 feet in length, with a storage capacity of 61 acre-feet and a drainage area of 0.09 square miles. Despite its primary purpose being recreation, the dam is also state-regulated by the New Jersey Department of Environmental Protection, with regular inspections conducted to ensure its safety and compliance.
The dam's condition assessment is rated as poor, with a significant hazard potential, indicating the need for potential maintenance and risk management measures. The last inspection took place in November 2021, with a frequency of every 2 years. While the dam has not been modified in recent years, emergency action plans have been prepared in the past to address any potential risks or incidents. With its location in Sparta Township and proximity to the Sparta Glen-TR river or stream, Rock Island Lake Dam remains an important structure for both recreational and safety purposes in the region.
Overall, Rock Island Lake Dam stands as a significant earth dam in Sussex County, New Jersey, contributing to the local landscape and offering recreational opportunities for residents and visitors. As a state-regulated structure with a history dating back to the 1940s, the dam plays a crucial role in water resource management and public safety in the area. With ongoing inspections and assessments, efforts are being made to ensure the dam's continued functionality and compliance with regulatory standards, highlighting its importance for the community and the environment.
Year Completed |
1940 |
Dam Length |
500 |
Dam Height |
19 |
River Or Stream |
Sparta Glen-TR |
Primary Dam Type |
Earth |
Surface Area |
11 |
Drainage Area |
0.09 |
Nid Storage |
61 |
Hazard Potential |
Significant |
Nid Height |
19 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
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