TARP: Chicago's Deep Tunnel & Reservoir System
This overview was generated with AI from the public sources listed below and checked against them before publication. It has not had a complete human fact-check — treat it as a starting point and follow the sources.
18 sourced claims on this page, none individually verified yet — turn on “Sources in the text” to see each one.
How this atlas is made · What “last verified” means · What “source-checked” means · The full record behind this page
Fifty years and more than $3 billion of tunnel halved overflow days. In July 2026 the McCook reservoir sat all but full while 311 logged about 400 flooded basements: the bottleneck is the street sewers.
what does this mean?
The strongest source is the operator's or the city's own reporting — an official report, dataset or press release. It grades who did the looking — not how well the project went. All four grades →Part of 1001 Smart Cities — 1,216 documented projects · 🏙️ 7 more in Chicago · 🌊 Flood resilience guide · 🌱 Environment projects
The Metropolitan Water Reclamation District — a county agency, not the city — has built TARP since 1975: 110 miles of tunnel 150 to 300 feet down, feeding reservoirs that now hold over 11 billion gallons. MWRD publishes reservoir fill levels on a public live map. Overflow days fell from about 100 a year to 50; McCook Stage 2 has slipped to 2032.
📊 Impact
MWRD reports combined sewer overflows fell from an average of 100 days a year to 50 once the tunnels came online, and that overflows in the Thornton Composite Reservoir's service area have been eliminated since 2020. TARP has captured over 1 trillion gallons of combined sewage since 1981, about 140 billion of it by McCook Stage 1 alone by June 2026. The district also says the tunnel system captures about 85% of the combined-sewer-overflow pollution from its service area. All figures are the district's own; no independent evaluation was found.
🎓 Lesson
Capacity is not protection. Fifty years and more than $3 billion halved overflow days, but in July 2026 McCook sat between 96% and 100% full while 311 logged almost 400 complaints of water in basements — the neighbourhood sewers, which handle about 2 inches of rain before flooding is likely, not the tunnels, are the bottleneck.
Sources
Show 3 more sourcesShow fewer
📅 How old is the evidence?
Two clocks, kept apart: when this entry’s sources were published, and what has happened to its record in the atlas. Documented span: since 1975. 4 of 8 sources carry a publication date, from 15 August 2025 to August 2026.
When the sources were published
- Metropolitan Water Reclamation District of Greater Chicago (MWRD) · utilityMWRD — issues update on the Tunnel and Reservoir Plan, 15 August 2025 (authority)
- WBEZ Chicago · pressWBEZ Chicago — Deep Tunnel nearly full after days of heavy rain, 6 July 2026 (press)
- Smart Cities Dive (Industry Dive) · pressSmart Cities Dive — with extreme rainfall overwhelming Chicago's sewers, the city tries a new approach, July 2026 (trade)
- MWRD — TARP Status Report, second quarter of 2026 (August 2026)
Show your work What this page rests on and what it can’t tell you · all 18 claims with their sources · the forensic record
Evidence file · public beta 18 addressable claims, 8 source dossiers, one permanent baseline. The file is unreviewed — an AI-assisted structural migration, not a human or expert endorsement. Every revision keeps a permanent copy under revision history.
Inspect the claims, one by one — verbatim text, sources and caveats for all 18
The text below is copied verbatim from the published record. Each claim names the source dossiers that carry it; caveats stay attached to the claim they qualify.
clm-35e3497fcff2d510
descriptive
a county agency, not the city
Sources carrying this claim
clm-b9f41ba0708fc4e7
quantitative
has built TARP since 1975
Sources carrying this claim
clm-3a6fa1fbb924c8f6
quantitative
110 miles of tunnel
Sources carrying this claim
clm-408dfb0463afc209
quantitative
150 to 300 feet down
Sources carrying this claim
clm-e0443c6cbfbf3f93
quantitative
feeding reservoirs that now hold over 11 billion gallons
Sources carrying this claim
clm-22590ba1b87e22c8
descriptive
MWRD publishes reservoir fill levels on a public live map
Sources carrying this claim
clm-aabe815e3d8110a4
quantitative
Overflow days fell from about 100 a year to 50
Sources carrying this claim
clm-e76203669ab1a602
quantitative
McCook Stage 2 has slipped to 2032
Sources carrying this claim
clm-c7d492567020dc23
quantitative
MWRD reports combined sewer overflows fell from an average of 100 days a year to 50 once the tunnels came online
Sources carrying this claim
clm-defd61cb87509e8c
quantitative
overflows in the Thornton Composite Reservoir's service area have been eliminated since 2020
Sources carrying this claim
clm-3f6df8c1e62feada
quantitative
TARP has captured over 1 trillion gallons of combined sewage since 1981
Sources carrying this claim
clm-7a4d30b183b648d8
quantitative
about 140 billion of it by McCook Stage 1 alone by June 2026
Sources carrying this claim
clm-d2e4d532034512d6
quantitative
the tunnel system captures about 85% of the combined-sewer-overflow pollution from its service area
Sources carrying this claim
clm-f0f94e0a0b868a48
descriptive
All figures are the district's own; no independent evaluation was found
Sources carrying this claim
clm-4435ec2225107b69
quantitative
Fifty years and more than $3 billion halved overflow days
Sources carrying this claim
clm-f39f38a0ed70d7b8
quantitative
in July 2026 McCook sat between 96% and 100% full
Sources carrying this claim
clm-5bee81a65b0d4f79
quantitative
311 logged almost 400 complaints of water in basements
Sources carrying this claim
clm-f20a91e569a4825d
quantitative
the neighbourhood sewers, which handle about 2 inches of rain before flooding is likely, not the tunnels, are the bottleneck
Sources carrying this claim
Forensic record — source dossiers, gaps, hashes and the exact revision this page renders
This layer records what is known about each source, what is still missing, and the exact snapshot this page is rendering. A missing date, archive or hash stays visible as missing.
Awaiting operator and domain-expert review; publication of this revision implies neither.
sha256:f73abad17a695d8ea7600f0271c7bf5694141c6f4b80e8f020e39bdb81a4415e
- 18
- of 18 claims mapped
- 8
- source dossiers
- 3
- publication dates recorded
- 0
- archives linked
- 0
- exact locators
- 0
- content captures hashed
Governance facts carried by the record
- Operator
- Metropolitan Water Reclamation District of Greater Chicago (MWRD), a county-wide agency separate from the City of Chicago
- Actor types
- utility
- Funding model
- public
- Funding description
- MWRD, with federal cost-sharing through the US Army Corps of Engineers
- Cost
- $3.861bn total programme cost (MWRD status report, 30 June 2026)
- Ownership
- Not recorded
- Decision rights
- Not recorded
- Exit conditions
- Not recorded
8 source dossiers
MWRD — Tunnel and Reservoir Plan (TARP) (authority, operator)
- Stable source ID
src-80e956e9e0d826da- Publisher
- Name not classified · mwrd.org
- Type / language
- web-page · language not classified
- Published
- Not recorded
- Updated
- Not recorded
- Source last checked
- No source-level check date
- Record last verified
- 2026-10-05
- Dossier created
- 2026-10-05
- Retrieved copy
- No local capture recorded
- Archive
- No archived copy linked
- Content hash
- No captured content hash
- Locator
- Descriptive only — not page/paragraph exact
Open the recorded source note
Operator page. Carries the scale and the outcome figures sentence-level: 'four tunnel systems totaling 110 miles of tunnels, 8 to 33 feet in diameter and 150 to 300 feet underground'; 'The system currently has a capacity of more than 11 billion gallons for combined sewage and stormwater'; 'since the first portions of the system were put in operation in 1981, TARP has captured over 1 trillion gallons of combined sewage'; 'CSOs have been reduced from an average of 100 days per year to 50'; Thornton eliminating CSOs in its service area since 2020. Reservoir dates: Majewski 1998, Thornton 2015, McCook Stage 1 2017.
MWRD — TARP Reservoir Levels (authority, the data layer)
- Stable source ID
src-8f31e8b33b7e0558- Publisher
- Name not classified · mwrd.org
- Type / language
- web-page · language not classified
- Published
- Not recorded
- Updated
- Not recorded
- Source last checked
- No source-level check date
- Record last verified
- 2026-10-05
- Dossier created
- 2026-10-05
- Retrieved copy
- No local capture recorded
- Archive
- No archived copy linked
- Content hash
- No captured content hash
- Locator
- Descriptive only — not page/paragraph exact
Open the recorded source note
This is the measurement layer the entry rests on: a public interactive map of live reservoir fill levels, with a full-screen view and a live camera on McCook. The page states no update interval or units, so the entry claims only that fill levels are published live, not any accuracy or frequency.
- Claims linked
MWRD — issues update on the Tunnel and Reservoir Plan, 15 August 2025 (authority)
- Stable source ID
src-db5fbe1ffae9ee27- Publisher
- Name not classified · mwrd.org
- Type / language
- web-page · language not classified
- Published
- 2025-08-15
- Updated
- Not recorded
- Source last checked
- No source-level check date
- Record last verified
- 2026-10-05
- Dossier created
- 2026-10-05
- Retrieved copy
- No local capture recorded
- Archive
- No archived copy linked
- Content hash
- No captured content hash
- Locator
- Descriptive only — not page/paragraph exact
Open the recorded source note
Currency source, and the correction that matters: 'The current estimate for McCook Stage 2 going online is now Dec. 31, 2032.' Consent decree entered 6 January 2014 originally required mining complete by 31 December 2028 and operation by 31 December 2029; the delay is attributed to a slowdown in Chicago-area stone demand. Also: McCook Stage 1 'has already captured approximately 130 billion gallons'; Stage 2 brings McCook to 10 billion gallons; the system serves 3.1 million people across Chicago and 36 suburban municipalities.
- Claims linked
WBEZ Chicago — Deep Tunnel nearly full after days of heavy rain, 6 July 2026 (press)
- Stable source ID
src-5fa5fe5b043f01a9- Publisher
- Name not classified · wbez.org
- Type / language
- web-page · language not classified
- Published
- 2026-07-06
- Updated
- Not recorded
- Source last checked
- No source-level check date
- Record last verified
- 2026-10-05
- Dossier created
- 2026-10-05
- Retrieved copy
- No local capture recorded
- Archive
- No archived copy linked
- Content hash
- No captured content hash
- Locator
- Descriptive only — not page/paragraph exact
Open the recorded source note
Counterweight and 2026 currency, sentence-level: 'The McCook reservoir in southwest suburban Bedford Park fluctuated between 96% and 100% full' after 'more than 8 inches of rain over the past 30 days'; 'The city's 311 system received almost 400 complaints about water in basements and nearly 600 reports about flooded streets between Thursday and Monday afternoon.' Also carries the independent view: 'Experts say that Deep Tunnel isn't enough to prevent flooding.'
- Claims linked
Ven Te Chow Hydrosystems Laboratory, University of Illinois — Tunnel and Reservoir Plan (academic, boundary source)
- Stable source ID
src-5b22692946ae6eed- Publisher
- Name not classified · vtchl.illinois.edu
- Type / language
- web-page · language not classified
- Published
- Not recorded
- Updated
- Not recorded
- Source last checked
- No source-level check date
- Record last verified
- 2026-10-05
- Dossier created
- 2026-10-05
- Retrieved copy
- No local capture recorded
- Archive
- No archived copy linked
- Content hash
- No captured content hash
- Locator
- Descriptive only — not page/paragraph exact
Open the recorded source note
Boundary source, and the reason this entry claims no automation: 'The MWRDGC now desires to develop a new, updated and enhanced computer model for each TARP system, to allow real-time control of the TARP systems.' Real-time control is a stated goal of a modelling research programme, not a documented operating system. Earlier models 'were based on design, rather than as-built specifications for the system and are now outdated.'
- Claims linked
Wikipedia — Tunnel and Reservoir Plan (reference)
- Stable source ID
src-09b747e9e81d2eb5- Publisher
- Name not classified · en.wikipedia.org
- Type / language
- web-page · language not classified
- Published
- Not recorded
- Updated
- Not recorded
- Source last checked
- No source-level check date
- Record last verified
- 2026-10-05
- Dossier created
- 2026-10-05
- Retrieved copy
- No local capture recorded
- Archive
- No archived copy linked
- Content hash
- No captured content hash
- Locator
- Descriptive only — not page/paragraph exact
Open the recorded source note
Reference work, used only for dates and cost where MWRD does not state them: 'adopted in 1972, commenced in 1975, and completed and operational by 2006'; '109.4 miles of drainage tunnels ranging from 9 to 33 feet in diameter, up to 350 feet underground'; 'Across 30 years of construction, over $3 billion has been spent on the project.' Its reservoir capacities (Majewski 350 million, Thornton 7.9 billion, McCook Stage 1 3.5 billion gallons) and 2032 Stage 2 date agree with MWRD.
- Claims linked
Smart Cities Dive — with extreme rainfall overwhelming Chicago's sewers, the city tries a new approach, July 2026 (trade)
- Stable source ID
src-7bf429bb042b71fc- Publisher
- Name not classified · smartcitiesdive.com
- Type / language
- web-page · language not classified
- Published
- 2026-07-13
- Updated
- Not recorded
- Source last checked
- No source-level check date
- Record last verified
- 2026-10-05
- Dossier created
- 2026-10-05
- Retrieved copy
- No local capture recorded
- Archive
- No archived copy linked
- Content hash
- No captured content hash
- Locator
- Descriptive only — not page/paragraph exact
Open the recorded source note
The city's local answer to TARP's limits, and the source of the agency split: the $12 million Wing Storage pilot is 'a partnership between the Chicago Department of Water Management and the Metropolitan Water Reclamation District of Greater Chicago' — two vaults under West Side streets holding nearly 1.7 million gallons for more than 2,900 buildings, announced 8 July 2026. No sensors, monitoring or control layer is described; water is released back into the sewer as capacity frees up.
- Claims linked
MWRD — TARP Status Report, second quarter of 2026 (August 2026)
- Stable source ID
src-905f5de4a1f1d5ee- Publisher
- Name not classified · mwrd.org
- Type / language
- pdf · language not classified
- Published
- Not recorded
- Updated
- Not recorded
- Source last checked
- No source-level check date
- Record last verified
- 2026-10-05
- Dossier created
- 2026-10-05
- Retrieved copy
- No local capture recorded
- Archive
- No archived copy linked
- Content hash
- No captured content hash
- Locator
- Descriptive only — not page/paragraph exact
Open the recorded source note
Phase I's 110 miles of tunnel capture about 85% of CSO pollution from the service area; McCook Stage 1 has captured about 140 billion gallons; Stage 2 about 75% excavated and expected operational in 2032; total TARP cost $3.861 billion in contract-award dollars.
Known limits of this file
- Publisher names and source languages have not yet been classified; domains are recorded without guessing.
- Existing source notes are descriptive locators, not page- or paragraph-exact citations.
- A missing archive, publication date or content hash is shown as null rather than inferred.
- The project-level evidence grade ranks the strongest source in the entry; it is not a truth score for every claim.
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📎 Cite this project
1001 Smart Cities (2026). “TARP: Chicago's Deep Tunnel & Reservoir System” — Chicago, United States. The Smart City Atlas. https://1001smartcities.org/projects/chicago-tarp-deep-tunnel/ (last verified 2026-10-05). Data: CC BY 4.0.
The underlying data is free to reuse with attribution — see the open data page.
