Five steps to take today to make the most of your drilling program

Five steps to take today to make the most of your drilling program

Understanding the hydrogeologic conceptual model of a site and quantifying potential future impacts to water resources is required for permitting and ultimately makes mining possible. Rachael Peavler, PG, PMP, a hydrogeologist and project manager at Stantec, offers the following tips for getting the most out of any drilling program:

1. Document Groundwater Conditions

A preliminary evaluation of groundwater conditions is best determined early on in the life of a mine – ideally in the exploration stage. Unfortunately, in the drive to please shareholders and raise funds, some exploration companies are more focused on drilling for metals than collecting the information for a hydrogeologic conceptual model. But this can be short-sighted and can hinder the company when they apply for environmental permits, or further into the operation, when they wish to expand.

The smart approach is to collect as much groundwater information as possible during exploration drilling. While this information may only be qualitative in nature, its significance in guiding future data collection shouldn’t be overlooked. If groundwater conditions are not documented during drilling, the hole is abandoned and the opportunity is gone. If groundwater is not encountered, this should be documented. If groundwater is encountered, what depth was it encountered; did estimated flow rates change with depth; was the borehole artesian and at what depth?

2. Consider Local Geologic Conditions

To best understand the impacts to water resources over the life-of-mine, you want a solid understanding of the controls on groundwater flow. At many mine sites, one of the primary controls on groundwater flow is faults and fracture systems. The in-house geologist(s) often has the best knowledge of the site’s geologic conditions, although the geologic data is generally viewed from the lens of mineral resources, rather than the potential to influence the movement of groundwater. With a small shift, the geologic data collected from borehole logs can be more than a geologic block model:  it can also be the basis for a preliminary hydrogeologic conceptual site model, particularly when viewed in conjunction with groundwater information recorded by drilling contractors.

Fault characteristics that should be documented include the thickness and extent of fault gouge, clay-infilling, fracturing, and voids. This is often done to some extent with the Rock Mass Rating (RMR) system and in some mines is incorporated into a geotechnical block model for fracture density. If this is the case, it will assist in developing the preliminary hydrogeologic conceptual site model.

3. Install Monitoring Instrumentation or Wells

Taking advantage of exploration boreholes to install downhole instrumentation or piezometers can save hundreds of thousands, if not millions of dollars in later drilling costs. The cost of material and the time for installation is commonly a fraction of the time and cost of drilling. Furthermore, the data collected from these locations can be directly input into a site’s conceptual or numerical groundwater model and be used in support of environmental permitting.

Information gathered from Step 1 and 2 above, along with surface water information, can guide selection of these monitoring locations. Effort should be made to collect groundwater levels or hydraulic heads across various lithologic units, faults, and depths. Each instrumented hole should be equipped with a data logger. The higher frequency of data collected from a data logger will be worth the investment, and it will minimize the number of trips to site to manually collect measurements. Higher frequency data can be used to evaluate for seasonal trends, affects from nearby drilling, or pumping from water-supply wells.

4. Monitor the Water-Supply Well

Monitoring the conditions of your onsite water-supply well provides considerable insight to your groundwater flow system for a negligible cost, depending on the well’s proximity to your site. Commonly, the hydrogeologist will plan a pumping test as part of baseline characterization and impacts analysis for water resources. The hydrogeologist will use data from the pumping test to estimate aquifer parameters and evaluate the degree of hydraulic connection across lithologies and faults. Pumping tests are often logistically challenging and can be expensive to execute. However, data collected from your onsite water-supply well, and surrounding instrumentation installed as part Step 3, can be used to optimize the pumping test and obtain more meaningful data. In some cases, data collected from your onsite water-supply well can even substitute for data collected from a formal pumping test.

Your water-supply well should be equipped with a flow meter and totalizer and be designed with two down-hole sounding tubes. An appropriately rated pressure transducer installed in one of the sounding tubes and the second sounding tube can be used for taking manual depth to water measurements. Data should be documented on a regular basis.

5. Identify a Water Resources Steward and Champion

Identifying a water resources steward and a champion in the early stages of your project is critical. Optimally, the water resources steward is the hydrogeologist(s) who will drive the overall water resources program: data collection, data analysis, conceptual/numerical model development, and impact analysis. The water resources champion is an internal person who recognizes the importance of this information and will promote planning and budgeting for the water resources program.

Doing hydrogeological work early on will help predict potential water resources issues related to operation, expansion, or closure. It can also increase the value of a mining property, which is always helps attract investors and potential acquirers. Working with a skilled hydrogeologist throughout the mine-life can also prevent missed opportunities for data collection, reduce permitting timelines, and assist in reporting during the various stages of operation. Failing to do that early water work properly can mean costly permitting delays and add-ons like unexpected dewatering systems or treatment plants. This is especially true in the United States when federal money or lands are involved, which triggers environmental assessments based on the National Environmental Policy Act (NEPA).

Racheal Peavler of Stantec will speak about groundwater studies and successful permitting at the AEMA annual meeting at 8 am on Wednesday, December 5, 2018 in Spokane Washington.