Lake Grinnell Dam dam
Lake Grinnell Dam
Lake Grinnell Dam, located in Sussex, New Jersey, is a privately owned earth dam that serves primarily for recreational purposes. Built in 1900, the dam stands at a height of 12.1 feet and stretches 195 feet in length, creating a reservoir with a storage capacity of 150 acre-feet. The dam is situated on the Wallkill River-TR, within the jurisdiction of the New Jersey Department of Environmental Protection, which regulates its operation, inspection, and enforcement.
Despite its age, Lake Grinnell Dam has been flagged for significant hazard potential and poor condition during its latest inspection in April 2021. The dam's Emergency Action Plan (EAP) status is currently unknown, and risk assessment and management measures are yet to be determined. With a drainage area of 2.7 square miles and a maximum discharge capacity of 30 cfs, the dam poses a potential risk to downstream communities in the event of a failure. As such, it is crucial for the dam's owners and regulatory agencies to prioritize maintenance and monitoring to ensure public safety and the integrity of the structure.
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.
- 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.
- 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.
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, environmental 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.
Plan around the weather
Same NOAA / yr.no feed Snoflo's iOS app uses. Watch the precipitation column on the meteogram -- rain on the basin upstream typically lifts inflow 24-72 hours later.
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
5-day forecast table
Every 3 hours, broken out across temperature, snow, rain, humidity, and wind. Each cell is colour-coded relative to the column min/max.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day temperature & precipitation
Daily temperatures, snow, and rain projected over the next two weeks.
Nearby streamflow gauges
USGS streamgauges around Lake Grinnell Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Eb Paulins Kill Near Lafayette Nj | 16 cfs | → |
| Green Pond Brook At Picatinny Arsenal Nj | 2 cfs | → |
| Pequest River At Huntsville Nj | 17 cfs | → |
| Green Pd Bk Bl Picatinny Lk At Picatinny Ars Nj | 2 cfs | → |
| Musconetcong River At Outlet Of Lake Hopatcong Nj | 13 cfs | → |
| Pequannock R At Macopin Intake Dam Nj | 14 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Lake Grinnell Dam.
Boat launches
- West Shore Drive Stillwater Township
- Jefferson Lake Road Sussex County
- Winding Waters Trail Town Of Warwick
- Dell Avenue 9, Netcong
- Mcdade Recreational Trail Delaware
- Greenwood Lake Turnpike Ringwood
Track Lake Grinnell Dam in the Snoflo app
Save this dam as a favorite and get the local NOAA / yr.no forecast plus regional flow context wherever you are.
About Lake Grinnell Dam
Where does the data for Lake Grinnell Dam come from?
Structural and regulatory data come from the U.S. Army Corps of Engineers' National Inventory of Dams (NID). Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.
How often is the report updated?
NID structural data refreshes annually as the Corps publishes updated assessments. The weather forecast refreshes throughout the day.
What does the Significant hazard rating mean?
The Corps of Engineers' hazard potential classification grades probable consequences if the dam fails: High = probable loss of human life; Significant = no probable loss of human life but possible economic loss / environmental damage; Low = no probable loss of human life, only minor economic / environmental losses. See the Dam Data Reference card above for the full definitions.
What's "% of normal"?
The current storage value compared to the historical average storage on this calendar day. 100% = right on average; values above 100% mean above-normal storage (wet year); values below mean below-normal (dry year or drought).
Can I get alerts when storage crosses a threshold?
Yes -- alerts are managed in the Snoflo iOS app. Favorite this dam, set a threshold, and you'll get a push the moment conditions cross.
Other water bodies near here
Snoflo-tracked reservoirs and dams within driving distance of Lake Grinnell Dam.