Milton combines urban areas supplied with Lake Ontario water with a rural and escarpment landscape on private wells, and its own municipal groundwater supply showed in 2025 why nitrate matters: a well was shut down when it exceeded the drinking water standard. A hydrogeological study in Milton may have to satisfy Halton's private servicing guidelines, the Town's requirements and Conservation Halton's review at once.
What this means for your project in Milton
- In urban Milton, studies support subdivisions and buildings with basements or underground parking: groundwater levels, construction dewatering and where pumped water can go.
- In rural Milton, development has to stand on its own private well and septic system, and Halton's guidelines call for a two-stage study proving both work.
- The Town now holds the former Regional Official Plan; Halton Region comments where its water and wastewater systems are involved; Conservation Halton and, on escarpment land, the Niagara Escarpment Commission also review.
- The local factor most likely to affect scope and cost: nitrate. Septic systems are assessed against 10 mg/L at the property limits, and lot sizes follow from that calculation.
Milton groundwater data
Calculated from public provincial datasets for Town of Milton. Each value names its source; links are under Sources at the end of the page.
| Median depth of wells with a water level | 20.1 m (3,470 records reporting depth and water level) |
|---|---|
| Median static water level | 5.8 m below ground (3,470 records reporting depth and water level) |
| Records reaching bedrock | 61.4% of all records with a depth |
| Well records | 7,189 records (all types) |
| Active Permits to Take Water | 19 permits; largest purpose categories: Commercial 7, Construction 2, Dewatering Construction 2 |
| Active construction and dewatering permits | 6 of 19 active Permits to Take Water |
| Conservation authority | Conservation Halton (84.1% of area); Grand River Conservation Authority (15.4% of area) |
| Provincial plan areas | Greenbelt 66.2%; Niagara Escarpment Plan 21.3% of area |
| Sewer discharge | Groundwater to Regional sanitary or combined sewers only with the Commissioner's written authorization (Halton By-law 2-03) (Halton Region) |
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.
Under the escarpment and the till plain, Milton's wells usually find rock: 61.4% of records with a depth reach bedrock, and wells with a water level have a median depth of 20.1 m, with water standing about 5.8 m down. Growth shows in the permits, where 6 of 19 active takings are for construction or dewatering. The watershed splits between Conservation Halton (about 84.1%) and Grand River Conservation Authority (about 15.4%).
Milton's water supply and the Walker's Line well
Halton Region's 2025 Milton water system report describes two supplies that do not normally mix: Lake Ontario water from the Regional lake-based system, and groundwater from wells. The groundwater system had two well fields, Kelso and Walker's Line. After nitrate in the aquifer supplying Walker's Line rose during 2025, with a treated result of 10.6 mg/L on May 29 against the 10.0 mg/L standard, the well was removed from service and decommissioned in August 2025. Four wells at Kelso now supply the groundwater system, with greensand filtration for manganese and chlorination.
The report does not say what caused the increase. For anyone planning development, though, it shows why nitrate gets so much attention here: it is the parameter Halton's septic impact calculations are built around, and the one that took a municipal well out of service.
Halton's guidelines for private wells and septic systems
Halton's Guidelines for Hydrogeological Studies and Best Management Practices for Groundwater Protection (version 1.0, 2014) set the minimum content of studies for development on individual wells and septic systems. They were written as Regional Official Plan guidelines; since July 1, 2024 that plan is a local plan of each Halton municipality, so ask the Town how it applies them. Under the plan, development outside serviced areas must be self-sustaining on individual services, and communal water or sewage systems are not permitted for development in designated private servicing areas.
| Stage | When | What it must show |
|---|---|---|
| Stage 1, preliminary | Before draft plan, severance or official plan amendment approval | Adequate, sustainable potable or treatable water; no disruption to neighbouring wells or natural features within 250 m; septic impacts acceptable at the property limits; allowable density |
| Stage 2, final | Before registration (not for two lots or fewer) | A well with adequate supply on each lot, no adverse effect on neighbouring wells in test pumping, and Stage 1 findings still valid |
The method is set out in detail. Test wells are pumped for at least six hours, with three for sites up to 15 ha and more for larger sites. Septic impact uses a direct dilution calculation: a house of up to four bedrooms is assumed to produce 1,000 L/day of sewage carrying 40 g/day of nitrate-nitrogen, and the recharge falling on the lot must dilute that to 10 mg/L or less at the property limits. Nitrate removal treatment is not credited in that calculation. Systems over 10,000 L/day need a hydrogeological report showing the off-site increase stays at 2.5 mg/L at the property boundary.
Dewatering in urban Milton
Construction dewatering is registered on the EASR or covered by a Permit to Take Water, and the discharge needs the sewer owner's approval. For Regional sanitary sewers, Halton's Sewer Use By-law 2-03 prohibits groundwater unless the Commissioner authorizes it in writing, so most projects plan for storm discharge with water quality testing, or design to reduce dewatering.
Hydrogeological study cost in Milton
| Study | Starting point | Full span |
|---|---|---|
| Site plan or rezoning hydrogeology | $12,000 – $18,000 | $12,000 – $150,000 |
| Hydrogeological study for a severance | $5,500 – $8,500 | $2,500 – $17,500 |
| Dewatering assessment and EASR reports | $9,000 – $14,000 | $9,000 – $62,500 |
| Source protection study | $4,500 – $7,000 | $4,500 – $15,500 |
| Infiltration water balance assessment | $3,000 – $5,000 | $3,000 – $14,000 |
These are indicative ranges based on typical scopes, the same province-wide ranges the estimator uses, not prices specific to Milton. Locally, the work is reviewed by the Town of Milton and Conservation Halton or Grand River Conservation and, for water takings, the ministry, and the scope they ask for is what moves a quote. On rural lots, Halton's two-stage approach and its nitrate calculations decide how much testing a severance or subdivision needs. 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 Milton
- Urban subdivisions and mid-rise buildings. Groundwater levels, dewatering and water balance for Conservation Halton review.
- Rural severances and estate lots. Halton's Stage 1 study and nitrate dilution calculation, and Stage 2 for subdivisions of more than two lots.
- Escarpment properties. Hydrogeology alongside a Niagara Escarpment Commission development permit.
- Businesses near the Kelso wells. Source water protection review of activities that could affect the supply aquifer.
Working with a hydrogeologist in Milton
Since July 1, 2024 Halton Region no longer runs the planning review in Milton, so confirm with the Town who reviews the hydrogeology for your application and how it applies Halton's private servicing guidelines. Those guidelines work in two stages for rural lots: a preliminary study before draft plan, severance or official plan amendment, and a final one before registration. Conservation Halton comments on natural features. Send the consultant the lot layout and any well records so a hydrogeological assessment in Milton can deal with nitrate from septic systems, the parameter Halton's calculations are built around. Confirm that the person signing a Milton study is a practising P.Geo. through the list of registered P.Geo. members.
For a rural severance in Milton, our guide to severance studies explains how the well and septic tests fit together.
Milton questions
Why was a Milton municipal well taken out of service in 2025?
Nitrate: Halton Region's 2025 Milton water system report says rising nitrate levels were observed in the aquifer supplying the Walker's Line well during routine testing in the second quarter of 2025; a treated sample on May 29, 2025 measured 10.6 mg/L against the 10.0 mg/L standard. The well was removed from service and decommissioned in August 2025, and the Kelso well field increased production to make up the supply.
Does Halton Region still review hydrogeological studies for planning applications?
Its role has changed: since July 1, 2024, Halton has been an upper-tier municipality without planning responsibilities: the Regional Official Plan became a local plan of Milton, Halton Hills, Burlington and Oakville, and the Region is no longer an approval authority. It still comments on matters tied to its water and wastewater infrastructure. Confirm with the Town who reviews the hydrogeology for your application.
What does a privately serviced subdivision need in rural Milton?
Halton's hydrogeological study guidelines set a two-stage approach: a preliminary (Stage 1) investigation before draft approval to show adequate, sustainable water and acceptable septic impact at the property limits, and a final (Stage 2) investigation before registration to confirm a well on each lot. Severances and developments of two residential lots or fewer are exempt from the Stage 2 lot-by-lot well requirement.
How many test wells does a Stage 1 study need?
Under the Halton guidelines: three test wells for sites up to 15 ha, four up to 25 ha, five up to 40 ha, and one more for each additional 20 ha or part of it, each pumped for at least six hours. More may be needed where the hydrogeology is complex.
Can dewatering water go to the sanitary sewer in Milton?
Only with written authorization: Halton's Sewer Use By-law 2-03 prohibits discharging groundwater, storm water or uncontaminated water to a sanitary or combined sewer unless the Commissioner expressly authorizes it in writing, and water from a source other than the Regional water system needs written authorization regardless of quantity.
Is part of Milton on the Niagara Escarpment?
Yes: about 21.3% of Milton is in the Niagara Escarpment Plan area in the provincial boundary data, and 66.2% is inside the Greenbelt outer boundary. In the escarpment's area of development control, the Niagara Escarpment Commission issues development permits, and the Halton guidelines note that the Commission may have its own study requirements.
Studies for Milton properties
- Development Hydrogeological Study
Groundwater assessments that support subdivision, site plan and zoning applications.
- Severance Hydrogeological Study (D-5-4 / D-5-5)
Groundwater quality and well supply assessments for rural lot creation under MECP guidelines D-5-4 and D-5-5.
- Construction Dewatering Assessment
Groundwater inflow estimates and dewatering rates for excavations, basements and servicing trenches.
- Source Water Protection Risk Assessment
Assessments for activities proposed inside wellhead protection areas and other vulnerable areas.
- Hydrogeological study cost guide
Ranges for every study type, side by side.
Near Milton
Sources
- Sewer Use By-law No. 2-03 (opens in a new tab), Halton Region.
- 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.
- 2025 Milton Water System Annual Report (opens in a new tab), Halton Region.
- Guidelines for Hydrogeological Studies & Best Management Practices for Groundwater Protection (Regional Official Plan Guidelines, version 1.0, 2014) (opens in a new tab), Halton 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.
- Supporting Land-Use Planning: changes to Halton’s role in land-use planning (opens in a new tab), Halton Region.
- Development Permits (opens in a new tab), Niagara Escarpment Commission.
- D-5-4 Individual on-site sewage systems: water quality impact risk assessment (opens in a new tab), Government of Ontario (MECP).
- D-5-5 Private wells: water supply assessment (opens in a new tab), Government of Ontario (MECP).