Multilevel Groundwater Monitoring
The Basics
If you want to solve a three dimensional contaminant problem, you need to understand the three dimensional distribution of hydraulic head and contaminant concentrations.
One of the problems faced by environmental scientists and engineers is that it is extremely expensive to collect subsurface data. As a result, these professionals are often tasked with characterizing a site to develop a conceptual model with a paucity of data. Furthermore, contaminant and hydraulic head measurements taken over large screened intervals may not provide useful information, if the predominant flow regimes and contaminant loading are in specific hydrogeologic units.
Environmental professionals have also come to realize that significant contaminant mass may reside in low permeability strata. Understanding the contributions of contaminant flux from low K units as a function of time is not easy.
Thus, we need a cost-effective way of collecting data spatially and temporally.
The Company Dajak Represents
Schlumberger Water Services manufactures the Westbay multilevel groundwater monitoring system. The system allows you to collect groundwater samples and measure the formation's hydraulic pressures from multiple depths within a single drill hole. The costs related to understanding the formation’s 3D flow field become far more reasonable. Typical installed systems are at depths ranging from 75 to over 4,000 feet.
The Westbay multilevel groundwater measurement system provides a unique solution as the sampling device can collect discrete samples and make head measurements from aquitards and permeable units with little difficulty.
The following are important reasons to consider using Westbay:
- Reduce costs: You drill a single borehole to collect multilevel data, eliminating clusters of wells terminating at various depths. Furthermore, there are no regulatory requirements to purge well volumes prior to sample collection.
- Increase knowledge: You gain a better understanding of the site’s 3D flow field, as you can now get piezometric data from significantly more depths without the attendant costs of drilling more wells. The incremental cost of an additional measurement zone at any depth, which, in essence, is actually the same as installing a new conventional well to that depth, is usually less than $3,000. Thus, adding 5 zones to a Westbay well costs between $10,000 and $15,000.
- Improve data quality: You collect unique groundwater samples at multiple depths under in-situ pressure conditions, thus reducing VOC losses. Also, because the pressure transducer is readily accessible (it resides in the wire-line tool), it is easy to calibrate and maintain. Further, you can conduct all of the hydraulic tests that you can perform on conventional wells. These features are unique to the Westbay System.
- Insure defensibility: You can verify the integrity of the well and sampling and measurement methods during every step of operations.
Applications include:
- DNAPL investigations
- Aquifer Storage and Recovery studies
- Landfills, mining sites and nuclear waste repositories
- Characterization of CERCLA and RCRA sites
The Westbay System provides outstanding three-dimensional data. You gain a detailed understanding of the site hydrogeology and features of the contaminant plume. This knowledge is invaluable in the design and implementation of remediation systems.