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Record

Thomas J. O'Brien Lock and Controlling Works

Thomas J. O'Brien Lock and Controlling Works listed High as its hazard class, with no published condition assessment, as of October 30, 2026, according to the National Inventory of Dams.

Federal ID IL01013, in Cook, Illinois. The NID counts it as a dam record.

Hazard class and condition, each as the NID defines it

Hazard class

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.”

The NID defines the field: “Category to indicate the potential hazard to the downstream area resulting from failure or mis-operation of the dam or facilities. It reflects probable loss of human life and impacts on economic, environmental, and lifeline interests. The hazard potential does not speak to the condition of the dam or the risk of the dam failing.”

Condition

Condition Assessment
Not published: the condition assessment is not provided to the NID
Condition Assessment Date
Not given

“Dams for which the condition assessment is not provided to the NID.”

The NID defines the field: “Assessment that best describes the condition of the dam based on available information.”

A condition the NID does not publish is not a rating, and it says nothing either way about the dam.

The record, as the NID prints it

Each field is under the NID’s own label, with the unit the label names. A date later than the file’s own is printed as the NID prints it. The record’s own date is September 24, 2026; the file’s is October 30, 2026.

Identity

Federal ID
IL01013
NID ID
IL01013
Is Associated Structure?
No
Number of Associated Structures
0
Dam Name
Thomas J. O'Brien Lock and Controlling Works
Other Names
Lake Calumet
Former Names
Tj O'Brien Lock

The NID gives no value for this record: Other Structure ID.

Location

State
Illinois
County
Cook
City
Chicago
The NID’s meaning: the nearest downstream city, town or village most likely to be affected by a flood if the dam failed.
Latitude
41.652139
At the dam’s centerline, in decimal degrees.
Longitude
-87.567111
At the dam’s centerline, in decimal degrees.
River or Stream Name
Calumet River
Congressional District
Illinois, Congressional District 02

The NID gives no value for this record: Distance to Nearest City (Miles); American Indian/Alaska Native/Native Hawaiian.

Where the record comes from

Source Agency
US Army Corps of Engineers
State or Federal Agency ID
IL01013
Data Last Updated
September 24, 2026

Owners and designers

Owner Names
USACE - Chicago District
Owner Types
Federal
Primary Owner Type
Federal
Designer Names
CELRC

Purpose and regulation

Primary Purpose
Navigation
Purposes
Navigation;Other;Flood Risk Reduction
State Regulated Dam
Yes
State Jurisdictional Dam
Yes
State Permitting Authority
Yes
State Inspection Authority
Yes
State Enforcement Authority
Yes
Federally Regulated Dam
Yes
Federal Agency Owners
US Army Corps of Engineers
Federal Agency Involvement Funding
US Army Corps of Engineers
Federal Agency Involvement Design
US Army Corps of Engineers
Federal Agency Involvement Construction
US Army Corps of Engineers
Federal Agency Involvement Regulatory
US Army Corps of Engineers
Federal Agency Involvement Inspection
US Army Corps of Engineers
Federal Agency Involvement Operation
US Army Corps of Engineers
Federal Agency Involvement Other
US Army Corps of Engineers
Non-Federal Dam on Federal Property
No
Non-USACE Dam with USACE Flood Control Storage Authority (Section 7, Flood Control Act of 1944)
No

The NID gives no value for this record: State Regulatory Agency; Built Under the Authority of the Secretary of Agriculture; NRCS Watershed Dam Authorization.

Structure and size

Primary Dam Type
Concrete
Dam Types
Concrete;Other;Rockfill;Gravity
Core Types
Metal
Foundation
Soil
Hydraulic Height (Ft)
9
Structural Height (Ft)
37
NID Height (Ft)
37
NID Height Category
25-50 feet
Dam Length (Ft)
430
Volume (Cubic Yards)
4,600
Year Completed
1960
Year Completed Category
1960-1969
NID Storage (Acre-Ft)
9,700
Max Storage (Acre-Ft)
9,700
Normal Storage (Acre-Ft)
0
Surface Area (Acres)
0
Drainage Area (Sq Miles)
250
Max Discharge (Cubic Ft/Second)
2,200
Spillway Type
None
Spillway Width (Ft)
0
Number of Locks
1
Length of Locks (ft)
1,000
Lock Width (Ft)
110
Outlet Gate Type
Other Controlled1;Slide (sluice gate)4

The NID gives no value for this record: Dam Height (Ft); Years Modified; Length of Secondary Lock (Ft); Secondary Lock Width (Ft).

Inspection, status and emergency action plan

Last Inspection Date
April 5, 2022
The most recent periodic or comprehensive inspection before the submitting agency sent its data to the NID.
Inspection Frequency
5
The scheduled interval between inspections, in years.
Operational Status
Under Investigation, Planning, Permitting, or Design for Remediation
Operational Status Date
November 20, 2025
EAP Prepared
Yes
EAP Last Revision Date
April 30, 2020

Inundation maps

Inundation Maps Added to NID?
Yes

The NID’s file records whether inundation maps were added and holds no link to them, so this page links none. The National Inventory of Dams viewers are the NID’s place to look.

The NID lists no other record under this record’s NID ID.

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Sources

Compiled automatically from National Inventory of Dams — national CSV by a checked SQL query · Editor: Kian O'Connor · How this site is built

Data retrieved