Pumped groundwater cannot simply go into a municipal sewer. A groundwater discharge permit, or a longer-term discharge agreement, is the municipality's approval to send private water to its storm, sanitary or combined sewers, and it is granted on the strength of hydrogeological data: how much water, for how long, and what is in it. That data is assembled by a licensed hydrogeologist (P.Geo.) or professional engineer (P.Eng.).
Dewatering discharge permits and permanent drainage
During construction
Water pumped to keep an excavation dry, typically for months. Toronto issues a short-term permit when discharge will finish within about a year and the fee will not exceed $20,000.
After construction
Water collected by a building's foundation drainage for its whole life. Toronto issues an agreement for perpetual discharge, granted for terms of up to one year and renewable.
Those definitions come from the City of Toronto, which requires a sewer discharge permit or agreement before any private water is discharged: groundwater, surface water, construction dewatering, and rainwater or stormwater mixed with construction material. Other municipalities have their own by-laws and thresholds, and some are stricter about the permanent case.
Private water discharge: municipal rules differ
- Toronto. All private water must meet the Sewers By-law limits, with separate tables for sanitary/combined and storm sewers. The City can restrict volumes and flow rates where sewer conditions warrant.
- Hamilton. The City of Hamilton's urban hydrogeological study guideline says Sewer Use By-law 14-090 only permits construction dewatering with advance approval and does not permit long-term post-construction drainage to a Hamilton sewer. Developments must either be watertight or keep at least 1 m between the seasonally high water table and the lowest point of the structure.
- Barrie. The City of Barrie's hydrogeological study terms of reference note that dewatering discharge to municipal storm or sanitary sewers needs a separate application under the Sewer Use By-law.
- Durham Region. In Clarington and the rest of the Region, the Region's sewer use by-law allows groundwater into its sanitary sewers only with written authorization.
For any other municipality, the starting point is the sewer use by-law and the contact in its water or environmental services department.
What the hydrogeologist provides
- Seasonal high water table. Water levels from monitoring wells over the period the municipality requires, which decides whether permanent drainage can be avoided.
- Discharge rates. Construction dewatering volumes in litres per day and peak flow, and the long-term inflow to foundation drains if the building will not be watertight.
- Water quality. Groundwater samples analysed for the by-law parameters, compared with the limits for the sewer you plan to use.
- Treatment. Where results exceed the limits, the treatment approach the discharge will need.
- Supporting report. Signed hydrogeological report for the municipal application.
Timeline
Work back from the date pumping has to start. Monitoring wells go in first, then water levels over the period the municipality expects and a sampling round for the by-law parameters, with laboratory turnaround. The application follows: Toronto asks for completed applications at least eight to 12 weeks before the planned start of discharge, and discharge cannot begin until the permit or agreement is in place. Where treatment is needed, its design and delivery belong in the same schedule.
Dewatering discharge permit cost
Basement depth and whether you need temporary discharge, permanent drainage or both drive the scope.
| Answer | Indicative range |
|---|---|
| Starting point (1 level, Temporary (construction)) | $3,500 – $6,000 |
| Basement levels | |
| 1 level (starting point) | $3,500 – $6,000 |
| 2 levels | $4,500 – $8,000 |
| 3 or more levels | $5,500 – $9,500 |
| Discharge type | |
| Temporary (construction) (starting point) | $3,500 – $6,000 |
| Permanent (foundation drainage) | $4,500 – $8,000 |
| Both | $5,500 – $9,500 |
| Full span across all answers | $3,500 – $15,500 |
Each row changes one answer and leaves the others at the starting point. Indicative ranges, rounded to the nearest $500. They exclude well drilling, government application fees and HST. Final scope is confirmed by the hydrogeologist after reviewing your site.
Contaminated groundwater adds treatment design and more sampling. Municipal discharge fees, which in some cities are charged by volume for sanitary or combined sewers, are separate and not included in the range.
Bring these to the first conversation
- Foundation drawings with the lowest slab, sump and footing elevations
- Whether the building is designed as watertight or with perimeter drainage
- The geotechnical report and any existing monitoring wells
- Environmental site assessment results, if any
- The construction start date and dewatering period
Why discharge approvals get held up
- Sampling left too late. No lab results means no application.
- Wrong sewer. Planning for the storm sewer without checking that its stricter limits can be met.
- Permanent drainage assumed. In municipalities that do not allow it, a design built around foundation drains has to change.
- Incomplete applications, which in Toronto's words take longer to process.
Worked cost examples
Each example runs the estimator's own calculation on a realistic set of answers.
-
Townhouse block, one basement level, construction only$3,500 – $6,000
Basement levels: 1 level · Discharge type: Temporary (construction)
A short dewatering period and a single sampling program. The base range covers water level data, discharge estimates and comparing results with one by-law table.
-
Mid-rise, two levels, construction dewatering$4,500 – $8,000
Basement levels: 2 levels · Discharge type: Temporary (construction)
Deeper excavation means more inflow to estimate and usually more monitoring wells to sample.
-
Three levels, construction dewatering then permanent drainage$9,000 – $15,500
Basement levels: 3 or more levels · Discharge type: Both
Two applications with different durations and, in cities such as Toronto, different instruments: a short-term permit and a long-term agreement. Long-term inflow to foundation drains has to be predicted as well as construction rates.
What the municipal reviewer checks
- Seasonal high water table, supported by the monitoring period the municipality asks for
- Daily discharge volumes and peak flow rate, for construction and, if relevant, the long term
- Laboratory results compared with the correct by-law table: sanitary/combined or storm
- Treatment proposed for any exceedance, and how it will be confirmed
- Discharge location and connection on the site plan
- Duration of discharge, which decides permit or agreement in Toronto
- In Hamilton, proof that the building is watertight or keeps 1 m above the seasonally high water table
Discharge permit or EASR registration?
| Aspect | Sewer discharge permit or agreement | EASR registration |
|---|---|---|
| Question answered | May this water go into the sewer? | May this water be taken from the ground? |
| Issued by | The municipality | Self-registered with the Province |
| Main evidence | Water quality against by-law limits; volumes | Water taking report and discharge report |
| Small takings | Still required for any private water to the sewer | Not required at 50,000 L/day or less |
Where this study is commonly required
Location pages with local requirements, groundwater data and the agencies involved, by region:
Discharge permit questions
Is a dewatering discharge permit the same as an EASR registration?
No: the EASR registration (or a Permit to Take Water) is the provincial permission to take the groundwater. The sewer discharge permit or agreement is the municipality's permission to put it into its sewers. A dewatering project often needs both, and the same hydrogeological data supports both.
Why does it matter whether the water goes to the storm or the sanitary sewer?
The limits and fees differ. In Toronto, for example, water sent to the sanitary or combined sewer is charged a fee based on volume, while there is no fee for the storm sewer but its contaminant limits are stricter, according to the City's discharge page.
Can a new building drain groundwater to the sewer permanently?
Only in some municipalities: Toronto issues long-term agreements for permanent private water drainage systems. Hamilton's sewer use by-law does not permit long-term post-construction drainage to its sewers, so buildings there must be watertight or sit at least 1 m above the seasonally high water table.
What tests does the groundwater need?
The parameters listed in the municipality's sewer use by-law for the sewer you plan to use. Samples come from monitoring wells on the site, and results are compared with the by-law tables. Where a result exceeds a limit, a treatment system is designed before discharge is approved.
How early should I apply?
Earlier than most people expect. Toronto asks for completed applications at least eight to 12 weeks before the planned start of discharge, and incomplete applications take longer. The groundwater quality results have to be in hand before you apply.
Related studies
- Construction Dewatering Assessment
Groundwater inflow estimates and dewatering rates for excavations, basements and servicing trenches.
- Permit to Take Water & EASR
Work out whether a water taking needs an EASR registration or a Permit to Take Water.
- Groundwater Monitoring & Annual Reporting
Water level and water quality monitoring programs, baseline private well surveys and annual reports.
- Hydrogeological study cost guide
Ranges for every study type, side by side.
Sources
- Discharge permits and agreements for private water (opens in a new tab), City of Toronto.
- Hydrogeological Study (Urban): development application guidelines (last updated February 13, 2026) (opens in a new tab), City of Hamilton.
- Hydrogeological Study: terms of reference (2026) (opens in a new tab), City of Barrie.
- Sewer Use By-law 55-2013 (opens in a new tab), Region of Durham.