Well Monitoring Installation: What to Expect and Costs

What a Monitoring Well Actually Is

A groundwater monitoring well is a small-diameter pipe installed into the ground so that water samples and water-level readings can be taken from a known depth over time. On a contaminated site, monitoring wells are how you find out whether contamination has reached groundwater, how far it has moved and whether it is getting better or worse. They are the eyes of almost every groundwater investigation.

What It Costs

A single standard monitoring well in British Columbia typically costs $2,000 to $8,000 installed. The spread is wide because the number depends heavily on depth, drilling method and access. A shallow well in soft ground beside a road is at the low end. A deep well through rock in a tight location is at the high end. Most investigations need several wells, so budgeting per well and then multiplying is the sensible approach.

On top of installation, plan for the ongoing cost of sampling. Each monitoring event, where a technician visits and collects samples for laboratory analysis, generally runs a few hundred dollars per well per visit once lab fees are included.

The Installation Process

Step one, drilling. A drill rig advances a borehole to the target depth. Common methods are hollow-stem auger for softer ground, sonic drilling for speed and difficult soils and air rotary for rock. The method affects both cost and how quickly the work goes.

Step two, well construction. A slotted screen is set across the zone to be monitored, with solid casing above it. Clean sand is placed around the screen and a seal of bentonite is placed above to stop surface water from running down the outside of the well.

Step three, completion. The well is finished with a protective cover, either flush with the ground or in a stick-up casing, and then developed by removing fine sediment so it yields clean, representative water.

Step four, survey and baseline. The well location and elevation are surveyed so that water levels from different wells can be compared, and a first round of samples establishes the baseline.

When Monitoring Wells Are Required

In British Columbia, groundwater monitoring is commonly required when a Phase II Environmental Site Assessment finds contamination that could affect groundwater, when a site is going through the Contaminated Sites Regulation process, or as a condition of ongoing management at an industrial site. A qualified environmental professional designs the network so that it actually answers the regulatory question, which usually means wells both upgradient and downgradient of the contamination. Our post on the difference between Phase I and Phase II assessments explains where monitoring fits in.

Keeping the Data Defensible

Monitoring only has value if the record holds up. Sample dates, chain of custody, laboratory results and water levels all have to be tracked consistently, sometimes over years. Gaps in that record are exactly what an auditor or a buyer's lawyer will find. NVES uses EnviroLog to keep sampling and chain-of-custody records organized and audit-ready. If groundwater monitoring is part of your site, see how the record is kept.