Drilled Well vs Dug Well — Which Is Right for Ontario Properties?

Renfrew County's Two Geological Zones

To understand well types in Renfrew County, you need to understand the ground beneath your property. The county straddles two distinct geological regions that profoundly affect how groundwater is found and accessed:

Canadian Shield (north Renfrew County): Hard Precambrian granite and gneiss underlie most of the northern county — from Pembroke northward through Deep River, Petawawa, and into the Madawaska Valley toward Bancroft's fringe. Water in Shield terrain is found primarily in fractures within bedrock. Drilling deep into these fractures is the only reliable way to access sufficient yield for residential use.
Ottawa Valley sedimentary zone (south Renfrew County): Limestone, dolostone, and sandstone laid down in an ancient sea underlie the southern county — from Arnprior through Renfrew town and westward. Sedimentary rock is more porous, water tables are typically shallower, and productive aquifers can often be reached at 100–200 feet.

This geological divide is the primary reason well costs, depths, and appropriate well types differ significantly within the same county.

Drilled Wells — The Standard for New Installations

A drilled well uses a rotary or percussion drilling rig to bore a 6-inch diameter hole into bedrock. A steel or PVC casing is inserted and sealed with grout to prevent surface water from entering around the outside of the casing. A submersible pump is set below the water level inside the casing to deliver water to the home.

Depths in Renfrew County: 100–200 feet in the sedimentary south; 200–400+ feet in the Shield north. Depth drilled is determined by the contractor based on water yield encountered — drilling typically continues until sufficient yield is confirmed.

Key advantages of drilled wells:

Penetrates below the water table and into bedrock fractures — protected from surface contamination by depth and grout seal
Consistent year-round yield in most cases; not affected by seasonal surface conditions
Long casing life (50+ years for steel); meets Ontario Regulation 903 requirements
Only practical option for Shield-zone properties

For all new residential well installations in Renfrew County, a drilled well is the strongly preferred and typically required approach. The Ontario Ministry of the Environment, Conservation and Parks (MECP) requires all new wells to be installed by a licensed water well contractor, which in practice means drilled well construction under O. Reg. 903.

Dug Wells — Older Technology, Limited Use Cases

A dug well is a large-diameter hole (typically 3–4 feet across) excavated by hand or machine to reach the water table — usually 20–50 feet deep. It is lined with concrete tiles or stone to prevent collapse and has a concrete cap.

Dug wells draw water from the shallow, unconfined water table rather than from bedrock fractures. This makes them:

Susceptible to surface contamination: Runoff, agricultural chemicals, septic system effluent, and animal waste can enter a shallow water table relatively easily. Dug wells require a water-tight seal at the surface and regular water quality testing.
Subject to seasonal fluctuation: Dug wells may run low or dry during summer droughts or extended dry periods, because they depend on a water table that fluctuates with precipitation.
Lower yield: Dug wells produce water by seepage from the surrounding soil — suitable for lower-demand uses but inadequate for modern household demand in most cases.

Dug wells are rarely installed for new construction in Renfrew County today. However, many older rural properties — particularly those built before the 1980s — still operate from dug wells. If you are purchasing a property with a dug well, thorough water quality testing and a structural assessment of the casing are important steps.

Bored Wells — An In-Between Type

A bored well is constructed using an auger rather than a drill rig. It is larger in diameter than a drilled well but narrower than a hand-dug well, and typically reaches 50–100 feet in depth — below most dug wells but above typical drilled well depths. Bored wells access the water table in unconsolidated materials (sand, gravel, till) rather than bedrock.

Bored wells are uncommon in Renfrew County today. In Shield terrain, the rock is encountered too quickly for augering to be practical. In the sedimentary south, the preference is for drilled wells into bedrock aquifers for their reliability and contamination resistance.

What This Means for Your Property

For a new rural property in Renfrew County, plan on a drilled well as your default. The geological zone of your specific property determines depth and cost ranges. Properties in the northern Shield zone should budget for deeper wells and higher per-foot costs.

If you're purchasing a property with an existing dug or bored well, consult a licensed water well contractor about whether the existing well meets current standards or whether conversion to a drilled well is advisable given yield, contamination, or structural concerns.