A hydrogeological study in Toronto is very often about the foundation. The City does not allow new buildings to send groundwater to the sanitary sewer over the long term, so most applications need a hydrogeologist to establish how high groundwater rises on the site and what the building will do with it, during construction and afterwards. The report goes to the City's Development Engineering staff with the development application.
What this means for your project in Toronto
A hydrogeological study in Toronto usually turns on the foundation: the City reviews how the building will manage groundwater, and the province handles construction dewatering, usually through an EASR registration.
- Most Toronto projects that need a hydrogeologist have a basement, underground parking or a deep excavation. Expect a groundwater review for the foundation design and, during construction, a dewatering assessment.
- The City reviews the foundation side through Development Engineering under its Foundation Drainage Policy. The province handles the water taking, usually through an EASR registration.
- A new building cannot send groundwater to the sanitary sewer over the long term. It has to manage groundwater on site or meet strict conditions for a storm sewer.
- Pumping water into a City sewer during construction needs a separate discharge permit or agreement, and the City asks for applications 8 to 12 weeks ahead.
- The local factor that most affects scope and cost: how high groundwater rises on your site. That level decides whether the building needs a watertight foundation, and setting it takes monitoring wells and a record of readings.
Toronto groundwater data
Toronto groundwater data reflects a built-up city, and the panel leaves out well depths because most well records with a recorded use are test holes, monitoring wells or dewatering wells.
Calculated from public provincial datasets for City of Toronto. Each value names its source; links are under Sources at the end of the page.
| Median static water level | 7.6 m below ground (1,064 records reporting depth and water level) |
|---|---|
| Well records | 60,457 records (all types) |
| Active Permits to Take Water | 183 permits; largest purpose categories: Dewatering 48, Dewatering Construction 42, Construction 22 |
| Active construction and dewatering permits | 116 of 183 active Permits to Take Water |
| Conservation authority | Toronto and Region Conservation Authority (99.5% of area) |
| Provincial plan areas | Greenbelt 6.4% of area |
| Sewer discharge | Private water, including construction dewatering, needs a City permit or agreement before it is discharged to any sewer (City of Toronto) |
Source: Well Records (Water Well Information System), MECP (WWIS_2026a), retrieved 2026-10-14.
Source: Permit to Take Water, MECP (PermitsToTakeWater_26-01), retrieved 2026-10-14.
Source: Conservation Authority Administrative Area, Ontario GeoHub, retrieved 2026-10-14.
Source: Oak Ridges Moraine (ORM) Planning Area, Ontario GeoHub; Greenbelt Outer Boundary, Ontario GeoHub; Niagara Escarpment Plan Boundary, Ontario GeoHub; retrieved 2026-10-14.
Figures count records inside the municipal boundary that report a value; well locations and values are as submitted by well contractors, and MECP notes inaccuracies exist. How these figures are calculated.
The numbers tell the story of a built-up city. 116 of the 183 active Permits to Take Water are for construction or dewatering, and many more construction takings are registered on the EASR, which this dataset does not include. The city also has 60,457 well records, and nearly all of those with a recorded use (93.4%) are test holes, monitoring wells or dewatering wells rather than water supply wells, so their depths say little about any one site and the panel leaves them out.
The Foundation Drainage Policy
Toronto Water's Foundation Drainage Policy, released November 1, 2021 and amended October 1, 2026, applies to development applications, including Planning Act applications and cases where a zoning requirement must be met, but not Committee of Adjustment applications. Its stated aim is to preserve sewer capacity for sanitary sewage and stormwater and to protect watercourses and Lake Ontario from the effects of foundation drainage. The core rules:
| Situation | What the policy allows |
|---|---|
| Long-term foundation drainage to the sanitary sewer | Not permitted (policy 4.1) |
| Drainage from groundwater in a confined aquifer | Not permitted to any City sewer (4.2) |
| Structure entirely above the Maximum Anticipated Groundwater Level | Infiltrated stormwater may go to the storm sewer, or the combined sewer where there is no storm sewer, with a stormwater management report and, for combined sewers, a servicing report (4.3) |
| Long-term discharge that includes groundwater | Only to a dedicated storm sewer, meeting Chapter 681 Table 2 limits without pre-treatment (except TSS), at no more than 3 L/s/ha (sites over 0.7 ha) or 2 L/s (0.7 ha or less) in dry weather (4.4) |
| Brownfield sites | Discharge conditions require either no potentially contaminating activity on the site or a Record of Site Condition confirming risk management measures (4.3, 4.4) |
Everything else has to be managed on site. The policy lists the options: build above the Maximum Anticipated Groundwater Level, discharge groundwater into infiltration galleries, reuse it in greywater systems, or build a watertight foundation. Exemptions for long-term discharge are at the sole discretion of the General Manager of Toronto Water, where a qualified professional shows on-site management is not technologically feasible and discharge is needed to avoid hazardous impacts.
Where the hydrogeologist comes in
In Toronto the hydrogeologist sets the Maximum Anticipated Groundwater Level from monitoring wells, and that one level decides which branch of the Foundation Drainage Policy applies to the building.
Every branch of that table depends on one number: the Maximum Anticipated Groundwater Level, which the policy defines as the estimated top of the saturated zone from site-specific monitoring, with an allowance for seasonal and multi-year fluctuation. Setting it takes monitoring wells and a record of water levels collected to the City's Foundation Drainage Guidelines. From there the hydrogeological work answers whether the lowest slab sits above that level, what the groundwater quality is against the Chapter 681 limits, how much water a drained foundation would collect, and whether the site draws on a confined aquifer, which closes off sewer discharge entirely.
On a deep site the answer is often a watertight design, and the hydrogeological study then shifts to supporting the construction dewatering that builds it.
Construction dewatering in Toronto
Construction dewatering in Toronto usually needs two approvals side by side: an EASR registration for taking the groundwater, and a City sewer discharge permit or agreement for where the water goes.
Two approvals usually run side by side. The province regulates the taking: construction dewatering of more than 50,000 litres of groundwater on any day is registered on the EASR, backed by a water taking report and a discharge report. The City regulates where the water goes: Toronto requires a sewer discharge permit or agreement before private water is discharged to a storm, sanitary or combined sewer. Permits cover discharge that will finish within about a year with fees under $20,000; agreements cover long-term discharge. The City asks for completed applications eight to 12 weeks before discharge starts, and water sent to sanitary or combined sewers is charged by volume.
The City's Hydrological Review terms of reference
Toronto's Hydrological Review terms of reference set the minimum contents of the City's groundwater report, from monitoring wells and water levels to a pumping test and baseline water quality.
Toronto calls its groundwater report a Hydrological Review. The City's development guide publishes terms of reference for it (August 2018): it may be required for a zoning by-law amendment, plan of subdivision, consent or site plan, and it is built around the quality and quantity of groundwater a development may send to City sewers. The minimum contents are specific enough to scope from: at least five monitoring wells, at least 2 m below the lowest proposed floor, with one reaching 10 m below it; water levels every two weeks for at least three months, six readings or more; a pumping test of at least 24 hours where applicable; and baseline water quality for every Chapter 681 parameter, analyzed by an accredited laboratory. The review must give flow rates and daily volumes for both construction dewatering and long-term foundation drainage.
It has to be signed and stamped by a licensed P.Geo. or exempted P.Eng. (our article on who can sign a hydrogeological report in Ontario explains the exemption), and the author completes the Hydrological Review Summary form and attaches it; the form says a review missing any listed item is treated as incomplete.
Hydrogeological study cost in Toronto
Hydrogeological study costs in Toronto follow the province-wide ranges, and on most Toronto sites the scope is driven by construction dewatering, sewer discharge and the foundation drainage decision.
| Study | Starting point | Full span |
|---|---|---|
| Dewatering assessment for construction | $9,000 – $14,000 | $9,000 – $62,500 |
| Discharge permit and foundation drainage | $3,500 – $6,000 | $3,500 – $15,500 |
| Hydrogeological study for development | $12,000 – $18,000 | $12,000 – $150,000 |
| Permit to Take Water study (long-term taking) | $12,000 – $20,000 | $5,500 – $31,000 |
These are indicative ranges based on typical scopes, the same province-wide ranges the estimator uses, not prices specific to Toronto. Locally, the work is reviewed by the City of Toronto and Toronto and Region Conservation Authority and, for water takings, the ministry, and the scope they ask for is what moves a quote. On deep sites, how high groundwater rises against the lowest slab decides whether the building needs a watertight foundation, and setting that level is what drives the monitoring. Excludes well drilling, government application fees and HST. The Ontario cost guide breaks each range down.
Projects that need a hydrogeological study in Toronto
Mid-rise and tall buildings with underground parking, brownfield redevelopment, infill on small lots and linear infrastructure are the Toronto projects that typically need a hydrogeological study.
- Mid-rise and tall buildings with underground parking. The foundation drainage decision, construction dewatering registration and sewer discharge permit all apply, often on the same field data.
- Brownfield redevelopment. The policy ties any discharge to either no history of potentially contaminating activity or a filed Record of Site Condition, so groundwater quality work and the environmental site assessment have to line up.
- Infill on small lots. Sites of 0.7 ha or less face the flat 2 L/s dry-weather cap if groundwater discharge is permitted at all, which pushes many toward watertight designs.
- Linear infrastructure. Sewer, watermain and transit work that dewaters along a corridor, where the EASR lets several construction sites on one project be treated as one.
What City reviewers look for
City reviewers in Toronto look for a supported Maximum Anticipated Groundwater Level, a professional opinion on the lowest structure, groundwater quality against Chapter 681 and the dewatering and stormwater documents.
- Monitoring well records long enough to support the Maximum Anticipated Groundwater Level, collected to the Foundation Drainage Guidelines
- An opinion from a P.Eng. or P.Geo. on whether the lowest structure sits above that level
- Groundwater quality compared with Municipal Code Chapter 681, Table 2
- Whether any groundwater comes from a confined aquifer
- A stormwater management report, and a servicing report where a combined sewer is involved
- Brownfield status, and a Record of Site Condition where one is needed
- For dewatering, the EASR documents and the sewer discharge application
The policy also reserves the City's right to peer review submitted studies.
Conservation authority and source protection
Toronto and Region Conservation Authority covers almost all of the city (99.5% of the land area in the data panel), and about 6.4% of the city lies inside the Greenbelt outer boundary. None of Toronto is in the Oak Ridges Moraine or Niagara Escarpment plan areas.
Unlike many communities outside the city, Toronto's drinking water does not come from municipal wells: the City's 2025 drinking water annual report describes a system of four water treatment plants. Their vulnerable areas are intake protection zones, set out in the Toronto and Region Source Protection Area assessment report under the CTC Source Protection Plan. Wellhead protection rules are therefore a smaller part of Toronto work than foundation drainage and dewatering.
Near ravines and wetlands, TRCA's water balance guidelines for natural features, part of its 2012 Stormwater Management Criteria, call for a water balance showing that the feature's water levels and seasonal wet periods will be maintained after development.
Working with a hydrogeologist in Toronto
Before scoping a hydrogeological assessment in Toronto, gather the architectural sections showing the lowest slab, any geotechnical report and the site's environmental history, because the Foundation Drainage Policy decision turns on the groundwater level against that slab. City Development Engineering staff review the foundation drainage side with the application. Sewer discharge during construction is a separate permit, and Toronto asks for those applications eight to 12 weeks before discharge starts, so the dewatering estimate has to be ready early enough to file it. The person who signs a Toronto foundation drainage or dewatering report can be confirmed on the public register of geoscientists or, for an engineer, in PEO's online search of licence holders.
Contractors in Toronto can follow the EASR dewatering registration steps for the provincial filing alongside the City's sewer discharge permit.
Toronto questions
Can a new Toronto building drain groundwater into the sanitary sewer?
No new Toronto building may drain groundwater into the sanitary sewer over the long term. The City's Foundation Drainage Policy says long-term discharge of foundation drainage to the sanitary sewer is not permitted, and drainage from confined aquifers is not permitted to any City sewer. The building has to manage groundwater on site, for example with a watertight foundation, or meet the conditions for discharge to a dedicated storm sewer.
What is the Maximum Anticipated Groundwater Level?
The Maximum Anticipated Groundwater Level is the estimated upper level of the saturated zone, based on site-specific monitoring plus an allowance for seasonal and multi-year fluctuation. That is the definition in the City's Foundation Drainage Policy, and the level is determined under the City's Foundation Drainage Guidelines. If a P.Eng. or P.Geo. shows the lowest part of the structure sits above that level, the foundation drains only infiltrated stormwater and the storm sewer route becomes available.
Does the policy apply to a Committee of Adjustment application?
The Foundation Drainage Policy does not apply to a Committee of Adjustment application, which it expressly excludes. It applies to development applications, including Planning Act applications and cases where a zoning requirement has to be satisfied.
How much groundwater can go to a dedicated storm sewer?
A dedicated storm sewer can take up to 3 L/s of groundwater per hectare for sites over 0.7 ha, or 2 L/s for sites of 0.7 ha or less. Those are maximum dry-weather rates where long-term discharge of groundwater is permitted, and the water must meet the Table 2 limits in Municipal Code Chapter 681 without pre-treatment, except for total suspended solids.
Do I need a City permit for construction dewatering as well as an EASR registration?
Usually both: the EASR registration covers taking more than 50,000 litres of groundwater on any day. Separately, Toronto requires a sewer discharge permit or agreement before any private water, including construction dewatering, goes into a City sewer, and asks for applications eight to 12 weeks ahead.
Will the City check the hydrogeologist's work?
The City can check the hydrogeologist's work: the Foundation Drainage Policy reserves the City's right to peer review studies and reports submitted by the applicant. Application-specific questions go to the Development Engineering case manager.
What happens if the hydrogeological work is not done for a Toronto application?
Without the hydrogeological work, a Toronto application has no Maximum Anticipated Groundwater Level, the one number every branch of the Foundation Drainage Policy depends on. The City's Hydrological Review Summary form also says a review missing any listed item is treated as incomplete.
Studies for Toronto sites
- Construction Dewatering Assessment
Groundwater inflow estimates and dewatering rates for excavations, basements and servicing trenches.
- Groundwater Discharge Permits & Foundation Drainage
Approvals for discharging pumped groundwater to municipal sewers, during construction and over the long term.
- Development Hydrogeological Study
Groundwater assessments that support subdivision, site plan and zoning applications.
- Permit to Take Water & EASR
Work out whether a water taking needs an EASR registration or a Permit to Take Water.
- Hydrogeological study cost guide
Ranges for every study type, side by side.
Near Toronto
Sources
- Discharge permits and agreements for private water (opens in a new tab), City of Toronto.
- Well Records: Water Well Information System (WWIS_2026a) and county Well Record Data Reports (WW_Reports_2026a) (opens in a new tab), Government of Ontario (MECP), Ontario Data Catalogue.
- Permit to Take Water dataset (PermitsToTakeWater_26-01) (opens in a new tab), Government of Ontario (MECP), Ontario Data Catalogue.
- Conservation Authority Administrative Area (opens in a new tab), Ontario GeoHub.
- Oak Ridges Moraine (ORM) Planning Area (opens in a new tab), Ontario GeoHub.
- Greenbelt Outer Boundary (opens in a new tab), Ontario GeoHub.
- Niagara Escarpment Plan Boundary (opens in a new tab), Ontario GeoHub.
- Foundation Drainage Policy (released November 1, 2021, amended October 1, 2026) (opens in a new tab), City of Toronto, Toronto Water.
- Application Support Material: Terms of Reference, Hydrological Review (August 2018), in Building Toronto Together: A Development Guide (opens in a new tab), City of Toronto.
- Hydrological Review Summary (form, August 2018) (opens in a new tab), City of Toronto.
- 2025 Drinking Water System Annual Report (opens in a new tab), City of Toronto.
- Approved Assessment Report: Toronto and Region Source Protection Area (opens in a new tab), CTC Source Protection Region.
- Water Balance (Water Balance Guidelines for the Protection of Natural Features, incorporated into the 2012 Stormwater Management Criteria) (opens in a new tab), Toronto and Region Conservation Authority.
- Public Register (registered members) (opens in a new tab), Professional Geoscientists Ontario.
- Search for licence holders and engineering interns (opens in a new tab), Professional Engineers Ontario.
- Municipal Boundary - Lower and Single Tier (opens in a new tab), Ontario GeoHub.
- OHN Waterbody, 2M generalized layer (provincial hydrography dataset) (opens in a new tab), Ontario GeoHub.
- O. Reg. 63/16: Registrations under Part II.2 of the Act - Water Taking (consolidated to e-Laws currency date October 9, 2026) (opens in a new tab), Government of Ontario (e-Laws).