East Gwillimbury sits entirely in the Lake Simcoe watershed, and that shapes nearly every hydrogeological study in the town. Development applications have to show how much rain soaks into the ground before and after construction, and if the site cannot keep that infiltration, the owner may pay to make it up elsewhere. A hydrogeological study in East Gwillimbury is reviewed by Lake Simcoe Region Conservation Authority alongside the Town and York Region.
What this means for your project in East Gwillimbury
- Most studies here support subdivisions, site plans and severances in and around Holland Landing, Queensville, Sharon and Mount Albert, and construction dewatering for the servicing that comes with them.
- Lake Simcoe Region Conservation Authority reviews the groundwater and water balance work; York Region approves dewatering discharge to its sewers and reviews activities near its municipal wells.
- A larger development must show it keeps the same amount of water soaking into the ground after construction. If it cannot, LSRCA can require a fee for every cubic metre of shortfall.
- The local factor most likely to affect scope and cost: the post-development infiltration deficit. High groundwater or clay soils make it harder to infiltrate on site, which is when offsetting fees come into play.
East Gwillimbury groundwater data
Calculated from public provincial datasets for Town of East Gwillimbury. Each value names its source; links are under Sources at the end of the page.
| Median depth of wells with a water level | 25 m (3,081 records reporting depth and water level) |
|---|---|
| Median static water level | 6.7 m below ground (3,081 records reporting depth and water level) |
| Records reaching bedrock | 7.3% of all records with a depth |
| Well records | 4,976 records (all types) |
| Active Permits to Take Water | 20 permits; largest purpose categories: Farm uses 11 (10 + 1), Commercial 4, Industrial 2 |
| Active construction and dewatering permits | 1 of 20 active Permits to Take Water |
| Conservation authority | Lake Simcoe Region Conservation Authority (100% of area) |
| Provincial plan areas | Oak Ridges Moraine 19.7%; Greenbelt 77.3% of area |
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.
Lake Simcoe Region Conservation Authority covers the whole town in the provincial boundary data, and about 77.3% of East Gwillimbury is inside the Greenbelt outer boundary, with 19.7% in the Oak Ridges Moraine planning area. The median static water level in the town's well records is 6.7 m below ground. Agricultural takings are the largest group among the 20 active Permits to Take Water, and the permitted sources are split between groundwater and surface water.
What Lake Simcoe Region Conservation Authority asks for
Under memoranda of understanding with local municipalities, LSRCA reviews the hydrogeology in planning applications for major development in specific vulnerable areas. LSRCA's hydrogeology review page lists the policies that trigger a review:
| Policy | What it requires |
|---|---|
| Lake Simcoe Protection Plan, policy 4.8-DP | A water balance for all major development in the watershed, showing how stormwater management reduces runoff and increases infiltration. If low impact development is proposed, a scoped hydrogeological investigation of seasonal high groundwater and in-situ infiltration rates |
| Lake Simcoe Protection Plan, policy 6.40-DP | For major development in a significant or ecologically significant groundwater recharge area, a hydrogeological assessment and water balance showing the recharge function is protected, improved or restored |
| Source protection plan, policy LUP-12 | For major development in WHPA-Q2, mapped through York Region's Tier 3 water budget work, a hydrogeological assessment and water balance showing the existing water balance can be maintained |
| Oak Ridges Moraine Conservation Plan | For major development on the moraine, a hydrogeological assessment and water balance showing groundwater quantity and quality are maintained |
LSRCA expects the report to stand alone, so that any qualified person could reproduce the work without other documents, and names the Thornthwaite-Mather method with the ministry's 1995 infiltration factors as an accepted way to calculate the water balance. Applications next to a wetland, woodlot or watercourse may also need a catchment-based water balance for that feature. Hydrogeological support generally needs at least 12 continuous months of groundwater monitoring, including the seasonally high level.
When infiltration falls short: recharge offsetting
LSRCA's Water Balance Recharge Offsetting Policy applies across the watershed to plans of subdivision and condominium, site plans involving major development, and consents. It has applied to applications deemed complete after July 1, 2015 inside WHPA-Q2, and after January 1, 2019 elsewhere in the watershed. Agricultural uses, accessory structures and a single detached house on an existing lot are exempt.
The order of preference is clear. The developer should mitigate the infiltration deficit on site; if density is the problem rather than soils or groundwater, LSRCA asks for redesign to be considered. Only after all reasonable efforts can the deficit be made up on another property under a development agreement, or by paying a recharge offsetting fee, which LSRCA uses for projects such as stormwater pond retrofits. The fee is calculated on the annual infiltration deficit in cubic metres; the 2023 schedule set it at $100 per m³ plus a 15% administrative fee, adjusted each year for inflation.
This is where a good hydrogeological study saves money. Measured infiltration rates and seasonal high groundwater levels decide how much low impact development a site can support, and every cubic metre infiltrated on site is one that does not have to be offset.
Municipal wells and York Region approvals
The Town distributes water, but York Region owns and operates the wells. According to the Town's 2025 annual reports, the Holland Landing, Queensville and Sharon system receives groundwater from two Regional wells in Holland Landing and four in Queensville, plus a blend of Lake Ontario water and groundwater through Newmarket, and Mount Albert is supplied by three Regional wells in the community. Industrial, commercial, institutional and multi-unit proposals in wellhead protection areas may need a York Region source water protection permit before the Town can treat the application as complete.
For construction dewatering, East Gwillimbury is a primary approval municipality under York Region's sewer use bylaw: the Region runs any application to discharge to its infrastructure, charges an application fee and a monthly monitoring fee, and needs up to six weeks to review a complete package. The Region's shared hydrogeological terms of reference set the report contents; our page on Vaughan and York Region describes them.
Hydrogeological study cost in East Gwillimbury
| Study | Starting point | Full span |
|---|---|---|
| Site plan or rezoning hydrogeology | $12,000 – $18,000 | $12,000 – $150,000 |
| Water balance for a planning application | $3,000 – $5,000 | $3,000 – $14,000 |
| Infiltration testing for LID | $2,500 – $4,000 | $2,500 – $14,500 |
| Construction dewatering report | $9,000 – $14,000 | $9,000 – $62,500 |
| Lot severance hydrogeology (D-5-4 / D-5-5) | $5,500 – $8,500 | $2,500 – $17,500 |
These are indicative ranges based on typical scopes, the same province-wide ranges the estimator uses, not prices specific to East Gwillimbury. Locally, the work is reviewed by the Town of East Gwillimbury, York Region and Lake Simcoe Region Conservation Authority and, for water takings, the ministry, and the scope they ask for is what moves a quote. The infiltration deficit, and whether it can be kept on site or has to be offset for a fee, moves the scope most. Excludes well drilling, government application fees and HST. The province-wide cost breakdown shows what each range includes.
Projects that need a hydrogeological study in East Gwillimbury
- Subdivisions and condominiums. Hydrogeological assessment, Thornthwaite-Mather water balance and infiltration testing for low impact development, with offsetting where a deficit remains.
- Site plans with 500 m² or more of building. The Lake Simcoe Protection Plan water balance applies, even on a single commercial lot.
- Consents. The offsetting policy names consent applications, and rural lots also need the provincial D-5-4 and D-5-5 work.
- Servicing construction. Trench and shaft dewatering with York Region primary approval where water goes to Regional infrastructure.
Working with a hydrogeologist in East Gwillimbury
LSRCA generally expects 12 continuous months of groundwater monitoring, including the seasonal high, to support a planning application in East Gwillimbury, so install monitoring wells as early as the site plan allows. The water balance then decides whether infiltration can be kept on site; if it cannot after all reasonable efforts, LSRCA's offsetting policy allows compensation elsewhere or a fee. Send the consultant soil and geotechnical information first, because clay and a high water table are what usually limit on-site infiltration in a hydrogeological assessment in East Gwillimbury. The Professional Geoscientists Ontario register lets you confirm that the person signing an East Gwillimbury water balance is licensed.
If the application in East Gwillimbury is a lot severance rather than a subdivision, our guide to severance studies explains when a study is needed.
East Gwillimbury questions
What counts as "major development" for the Lake Simcoe water balance rules?
It depends on the policy. LSRCA's Water Balance Recharge Offsetting Policy explains that under the Lake Simcoe Protection Plan it means buildings of 500 m² or more, and under the source protection plan's LUP-12 policy it means 500 m² or more of impervious area. The policy applies to plans of subdivision and condominium, site plans involving major development, and consents.
What happens if our site cannot infiltrate as much water after development as before?
LSRCA expects the deficit to be mitigated on site first, for example with low impact development. Only where that is not possible after all reasonable efforts, typically because of a high water table or clay soils, does offsite compensation come in: infiltrating on another property, or paying a recharge offsetting fee to LSRCA. Deficits of 100 m³ a year or less are excluded.
How much is the LSRCA recharge offsetting fee?
When the LSRCA Board approved the current schedule on May 26, 2023, the fee was $100 per cubic metre of annual infiltration deficit plus a 15% administrative fee. The policy says the fee is reviewed every year and adjusted for inflation, so ask LSRCA for the current rate. Where the phosphorus offsetting policy also applies, the greater of the two requirements is used.
Who approves construction dewatering discharge in East Gwillimbury?
York Region approves construction dewatering discharge in East Gwillimbury, one of the five municipalities where it runs the application itself. The Region's sewer use page lists an application fee, a monthly dewatering fee, a volumetric fee for sanitary discharge and lab costs for its own samples, and a review time of up to six weeks.
Where does East Gwillimbury's drinking water come from?
East Gwillimbury's drinking water comes mostly from York Region wells. The Town's 2025 reports say the Holland Landing, Queensville and Sharon system receives groundwater from two Regional wells in Holland Landing and four in Queensville, blended with Lake Ontario water and groundwater supplied through Newmarket, and the Mount Albert system draws from three Regional wells in the community.
How long does groundwater monitoring take for an LSRCA review?
LSRCA says hydrogeological support for a planning application generally needs seasonal groundwater levels from at least 12 continuous months of monitoring, including the seasonally high groundwater elevation. Starting monitoring early is the simplest way to keep the application on schedule.
Studies for East Gwillimbury sites
- Water Balance Assessment
Pre- and post-development water budgets for planning approvals and low impact development design.
- Development Hydrogeological Study
Groundwater assessments that support subdivision, site plan and zoning applications.
- Infiltration Testing (LID)
In-situ infiltration testing used to size low impact development stormwater features.
- Construction Dewatering Assessment
Groundwater inflow estimates and dewatering rates for excavations, basements and servicing trenches.
- Hydrogeological study cost guide
Ranges for every study type, side by side.
Near East Gwillimbury
Sources
- 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.
- Hydrogeology (planning application reviews) (opens in a new tab), Lake Simcoe Region Conservation Authority.
- Water Balance Recharge Offsetting Policy (May 1, 2023) (opens in a new tab), Lake Simcoe Region Conservation Authority.
- Source Water Protection Permit (Section 59 Notice) (opens in a new tab), York Region.
- Sewer Use Permits: Temporary Dewatering Discharge Program (Sewer Use Bylaw No. 2021-102) (opens in a new tab), York Region.
- Terms of Reference: Hydrogeological Report (Development Application Supporting Studies, June 2024) (opens in a new tab), York Region.
- Public Register (registered members) (opens in a new tab), Professional Geoscientists 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.
- 2025 Annual Report: Holland Landing, Queensville and Sharon drinking water system (opens in a new tab), Town of East Gwillimbury.
- 2025 Annual Report: Mount Albert drinking water system (opens in a new tab), Town of East Gwillimbury.