A development hydrogeological study describes groundwater conditions across a proposed subdivision, condominium, site plan or rezoning, predicts how the development will change them, and sets out how the effects will be managed. Ontario municipalities and conservation authorities ask for it as a supporting study with the planning application. It is prepared by a licensed hydrogeologist (P.Geo.) or professional engineer (P.Eng.), and the report must be signed and stamped; who can sign a hydrogeological report explains the engineer exception and how to check a licence.
Who asks for it, and when
The municipality is the approval authority, and the request usually comes during pre-consultation as part of the list of studies for a complete application. Conservation authorities often carry out the technical review: the Lake Simcoe Region Conservation Authority (LSRCA), for example, reviews hydrogeology for its member municipalities under a memorandum of understanding, focusing on whether infiltration is maintained from pre- to post-development.
In some areas provincial plans add requirements. On the Oak Ridges Moraine, section 26 of the Oak Ridges Moraine Conservation Plan requires a hydrological evaluation with applications for development or site alteration within the minimum area of influence of a key hydrologic feature, and section 24 requires a water budget and water conservation plan for certain major development applications. LSRCA describes the practical result as a hydrogeological assessment and water balance showing how groundwater quantity and quality will be maintained.
What it covers
Terms of reference vary, but Barrie's published terms of reference are representative. It groups the work into three parts:
| Part | Typical content |
|---|---|
| Existing conditions | Topography, drainage, geology and soils; boreholes and monitoring wells; private well survey; aquifer properties, water levels and flow direction; surface water features; water quality; source water protection; recharge areas |
| Impact assessment | Changes to groundwater levels, baseflow and quality; water balance; temporary and permanent dewatering; effects on drinking water aquifers and wellhead protection areas; contaminant migration; flowing conditions |
| Mitigation | Maintaining infiltration and groundwater quality; monitoring program; contingency plans |
On private services, the same study carries the D-5-4 and D-5-5 assessments described on the severance study page, at subdivision scale.
For a section-by-section reading guide, see what’s in a hydrogeological report; for how this study relates to the foundation investigation, see hydrogeological study vs geotechnical report.
Monitoring is the long pole
Most of the calendar time goes into groundwater level monitoring, because reviewers want the seasonal high water table rather than a single reading. Published minimums include:
- LSRCA: generally at least 12 continuous months of monitoring data, including the seasonally high groundwater elevation.
- Hamilton, mid-rise and high-rise: biweekly manual readings in all on-site wells for at least three months, longer where highly porous deposits are expected.
- Hamilton, low-rise subdivisions: continuous data logger readings with monthly manual checks for at least two years before a detailed design application.
Hamilton's urban hydrogeological study guideline also sets the number and depth of wells: at least five for multi-residential and commercial sites with below-grade structures, screened 2 m below the lowest structure, plus one deeper well.
Our guide to how long a hydrogeological study takes collects the published monitoring minimums and approval times.
Development hydrogeological study cost
Site area, servicing and the length of monitoring set most of the price.
| Answer | Indicative range |
|---|---|
| Starting point (Under 1 ha, Municipal water and sewer, Single round) | $12,000 – $18,000 |
| Site area | |
| Under 1 ha (starting point) | $12,000 – $18,000 |
| 1 to 5 ha | $19,000 – $29,000 |
| 5 to 20 ha | $31,000 – $47,000 |
| 20 ha or more | $48,000 – $72,000 |
| Servicing | |
| Municipal water and sewer (starting point) | $12,000 – $18,000 |
| Private wells and septic | $15,500 – $23,500 |
| Groundwater monitoring period | |
| Single round (starting point) | $12,000 – $18,000 |
| Seasonal, 3 to 6 months | $15,500 – $23,500 |
| 12 months | $19,000 – $29,000 |
| Full span across all answers | $12,000 – $150,000 |
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.
Ways to keep it in check
- Install monitoring wells during the geotechnical drilling program.
- Start monitoring early, before the plan is final, so the clock runs while design continues.
- Confirm the scope with the municipality and conservation authority before field work.
Useful to have before scoping
- Pre-consultation notes or the list of required studies
- Concept or draft plan, with proposed basement depths
- Servicing approach: municipal, private, or a mix
- Geotechnical, environmental or earlier hydrogeological reports for the site
Why studies are sent back
Barrie is explicit that an incomplete study, one by an unqualified author or one without adequate analysis makes the application incomplete. The recurring problems are short monitoring records, a missing water balance, no private well survey where wells exist nearby, and dewatering estimates that do not match the final foundation design.
Worked cost examples
Each example runs the estimator's own calculation on a realistic set of answers.
-
Urban infill under one hectare, municipal services, one monitoring round$12,000 – $18,000
Site area: Under 1 ha · Servicing: Municipal water and sewer · Groundwater monitoring period: Single round
The base case. A short program can work where the agency accepts limited monitoring, for example a slab-on-grade building well above the water table.
-
Subdivision of 1 to 5 hectares, municipal services, 12 months of monitoring$30,500 – $46,000
Site area: 1 to 5 ha · Servicing: Municipal water and sewer · Groundwater monitoring period: 12 months
Area and monitoring length multiply together. Twelve months matches what LSRCA generally expects, and it is the monitoring visits and data review that add most of the cost.
-
Rural estate lots on 5 to 20 hectares, private wells and septic, 12 months$65,000 – $97,500
Site area: 5 to 20 ha · Servicing: Private wells and septic · Groundwater monitoring period: 12 months
Private servicing brings the D-5-4 and D-5-5 assessments into the study, with test wells and pumping tests on top of a year of monitoring over a large site.
What the reviewer checks
- Author is a licensed geoscientist or exempted engineer; report signed, stamped and dated
- Every existing-conditions element in the terms of reference is covered, or its omission explained
- Monitoring record long enough to meet the agency's minimum and show the seasonal high
- Private well survey where wells exist nearby
- Water balance, if the site falls under a recharge, moraine or source protection policy
- Dewatering estimates that match the current foundation design
- Source water protection status of the site
- Mitigation, monitoring and contingency measures that follow from the impacts found
- A report that stands alone, so another qualified person can recreate the work
Development hydrogeological study or water balance assessment?
| Aspect | Development hydrogeological study | Water balance assessment |
|---|---|---|
| Question | What are the groundwater conditions, and how will the development affect them? | Will infiltration and recharge be kept up after development? |
| Field work | Boreholes, monitoring wells, water levels, sampling, sometimes pumping tests | Often desktop, plus infiltration and groundwater data where LID is relied on |
| Output | Existing conditions, impacts, mitigation, monitoring | Pre- and post-development budgets and the LID needed to close the gap |
| Relationship | Often includes the water balance as a section | Can be a stand-alone report where only recharge is in question |
Where this study is commonly required
Location pages with local requirements, groundwater data and the agencies involved, by region:
Greater Toronto and Hamilton Area
- Hydrogeological study Toronto
- Hydrogeological study Mississauga
- Hydrogeological study Hamilton
- Hydrogeological study Vaughan
- Hydrogeological study Richmond Hill
- Hydrogeological study Markham
- Hydrogeological study Brampton
- Hydrogeological study Caledon
- Hydrogeological study Milton
- Hydrogeological study Clarington
- Hydrogeological study East Gwillimbury
- Hydrogeological study King Township
- Hydrogeological study Whitchurch-Stouffville
- Hydrogeological study Halton Hills
Central Ontario
Eastern Ontario
Development study questions
Which applications usually need a development hydrogeological study?
It is set by each municipality. Barrie's terms of reference list official plan amendments, zoning by-law amendments, draft plans of subdivision or condominium, site plan control and community planning permits. Hamilton adds consents with an associated development or building permit, building permits and stand-alone dewatering applications.
How long does groundwater monitoring have to run?
Long enough to capture the seasonal high, and the minimum varies. The Lake Simcoe Region Conservation Authority says support for a planning application generally requires at least 12 continuous months of monitoring. Hamilton asks for three months of biweekly readings for mid-rise and high-rise sites, and two years of continuous logging for low-rise subdivisions before detailed design.
Will the municipality peer review the study?
Often: Barrie notes that a peer review may be required and that its cost is borne by the applicant. Conservation authorities also review studies on behalf of municipalities under agreements, as LSRCA does for its member municipalities.
Can the geotechnical consultant's boreholes be used?
Yes, if they were logged properly and fitted with monitoring wells at useful depths. Combining the geotechnical and hydrogeological drilling into one program is usually the cheapest approach, provided the hydrogeologist sets the well screens.
Does the study have to be updated if the plan changes?
Sometimes: Barrie's terms of reference require an updated report, or a letter from the author confirming the conclusions still hold, whenever the proposal is revised. Deeper basements or added density are the changes most likely to need new analysis.
What makes a submission incomplete?
Barrie states that a study that is incomplete, prepared by an unqualified author or lacking adequate analysis makes the application incomplete, and it is returned. The usual gaps are too little monitoring data and no water balance where one was required.
Related studies
- Water Balance Assessment
Pre- and post-development water budgets for planning approvals and low impact development design.
- Construction Dewatering Assessment
Groundwater inflow estimates and dewatering rates for excavations, basements and servicing trenches.
- Infiltration Testing (LID)
In-situ infiltration testing used to size low impact development stormwater features.
- Hydrogeological study cost guide
Ranges for every study type, side by side.
Sources
- Hydrogeology (planning application reviews) (opens in a new tab), Lake Simcoe Region Conservation Authority.
- O. Reg. 140/02: Oak Ridges Moraine Conservation Plan (opens in a new tab), Government of Ontario (e-Laws).
- Hydrogeological Study: terms of reference (2026) (opens in a new tab), City of Barrie.
- Hydrogeological Study (Urban): development application guidelines (last updated February 13, 2026) (opens in a new tab), City of Hamilton.