Groundwater Sampling & Laboratory Testing Services
In a Phase II ESA and many other site investigations, a key piece of site characterization involves groundwater sampling and analysis.
AEL arranges for a drill rig to visit the site to drill a monitoring well. Monitoring wells are drilled deep into the ground to reach the groundwater, a depth which can vary depending on specific site features from just a few metres or much deeper (100 metres or more). This can take anywhere from an hour to days, depending on the depth and the type of material being drilled through.
Once the monitoring wells are installed, AEL’s experienced team members take samples according to specific sampling protocols. Water samples are then sent to a certified laboratory to be analyzed for a variety of parameters, depending on the site conditions.
Standard Procedures for Well Sampling
Water quality samples are taken to establish the water quality at each sampling point and to obtain bacteriological information as part of a bioremediation program (if required). Special care must be taken to ensure that the sample taken from a well is representative of the water at that location and that the sample is not altered or contaminated by the sampling and handling procedures. AEL use only dedicated samplers and tubing to sample wells. Any non-dedicated equipment (i.e. water levels tapes, the bladder pump housing if used) are all thoroughly cleaned with residue free detergent, and triple rinsed with distilled water after each well.
The Importance of Well Development in Groundwater Sampling
Well development involves pumping a large volume of water out of the well for disposal. Wells are developed before sampling after they installed to ensure that the water sampled is representative of the site conditions (e.g., free of drilling fluids, cuttings, or other materials introduced during well construction).
Representative water is assumed to have been obtained when pH, temperature, and specific conductivity readings stabilize on the Horiba U-10 (water quality checker) and the water is (generally) visually clear of suspended solids. Typically, the AEL team will purge a minimum of 3 well volumes, or until the well is dry. If a low-flow method is employed, purging is complete when readings from a water quality monitor are within 10% of each other (based on US EPA standards).
Ensuring Proper Development
An important factor in developing a well is that work be started slowly and gently and be increased in vigor as the well is developed. Most methods of well development require the application of sufficient energy to disturb the filter pack, thereby freeing the fines and allowing them to be drawn into the well. The coarser fractions then settle around and stabilize the screen. Low-flow purging and sampling is used whenever possible. Purging and sampling methods include inertial lift, peristaltic pump, bailer or bladder pump. All purge water is collected and stored on-site until arrangements can be made to remove, in accordance with appropriate legislation.
All wells are sampled directly into laboratory prepared containers, pre-charged with preservative by the lab where necessary. Only samples for metals analysis are field filtered.
As per O. Reg. 153/04, at least 1 duplicate sample is obtained per 10 samples taken, and a trip blank, prepared by the lab, is submitted for analysis of VOCs whenever VOCs are sampled.
On-Site testing of groundwater can include PHCs and PAHs (by UVF) and metals (by XRF).
The lab preforms its own QA/QC procedures and calculations, which are reviewed by AEL. In addition, AEL preforms calculations on duplicate samples taken, to ensure the samples are representative and not influenced but outside factors.