{"id":528,"date":"2015-02-03T16:45:29","date_gmt":"2015-02-03T21:45:29","guid":{"rendered":"http:\/\/www.solinst.com\/onthelevel-news\/?p=528"},"modified":"2018-03-21T09:54:51","modified_gmt":"2018-03-21T13:54:51","slug":"high-resolution-site-characterization-multilevel-systems","status":"publish","type":"post","link":"https:\/\/www.solinst.com\/onthelevel-news\/groundwater-sampling\/multilevel-monitoring\/high-resolution-site-characterization-multilevel-systems\/","title":{"rendered":"High-Resolution Site Characterization With Multilevel Systems"},"content":{"rendered":"

Within the last few years, the U.S. EPA added a new focus area on high-resolution site characterization (HRSC) to their Contaminated Site Clean-Up Information (CLU-IN) website<\/a>.<\/p>\n

The U.S. EPA’s definition of HRSC is: \u201cHigh-resolution site characterization (HRSC) strategies and techniques use scale-appropriate measurement and sample density to define contaminant distributions, and the physical context in which they reside, with greater certainty, supporting faster and more effective site cleanup.<\/p>\n

In other words, the more spatially and temporally diverse your data sets are \u2013 the more representative they are of the actual site conditions. Using technologies that collect data from zones that are more closely spaced together provides a higher resolution picture of the subsurface. This gives you a better understanding of how to go about remediating a contaminated site.<\/p>\n

The new HRSC section is very helpful \u2013 it describes what HRSC is, why it should be used, and how it is conducted. It offers tools and techniques for performing high-resolution site characterization, case study examples, and training and support options.<\/p>\n

However, it is missing what many in the hydrogeological industry would consider an important part of the tools and techniques discussion\u2026Multilevel Systems (MLS).<\/p>\n

Note: <\/em>There is a brief mention of continuous packer\/liner sampling systems (another term for a specific type of system that can be used for multilevel monitoring), but very little detail is provided.<\/em><\/p>\n

Multilevel Systems, also often referred to as engineered nested wells, are installed in a single borehole, but are constructed with multiple ports to provide samples and hydraulic head measurements from many isolated depths within the single borehole. With a series of MLS, a contaminated site\u2019s groundwater can be assessed on a four-dimensional scale: level, type, and lateral and vertical extent of contamination \u2013 this is high-resolution site characterization!<\/p>\n

Solinst manufactures two types of Multilevel Systems. The Waterloo Multilevel System<\/a><\/strong> and the CMT Multilevel System<\/strong><\/a>.<\/p>\n

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The Model 401 Waterloo Multilevel System Components<\/p><\/div>\n

Solinst has manufactured the Model 401 Waterloo Multilevel System, since 1984. The System uses modular components of various casing lengths, sampling ports, and optional packers that are connected to form a sealed casing string. This design gives excellent flexibility, allowing placement of ports and packers to suit borehole logs. Pumps and\/or transducers can be dedicated to each port. All instrument tubing and cabling is contained within these modules and collected at the top of the system at a wellhead manifold. The Waterloo System is ideal for long-term monitoring in bedrock and cased boreholes, and has been used to depths of 1000 ft. (300 m).<\/p>\n

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Since 1999, Solinst has manufactured the Model 403 CMT Multilevel System. The CMT System consists of continuously extruded polyethylene tubing with seven or three separate channels running the length of the tubing. Monitoring zones are mechanically created and sealed off, one in each separate channel at different vertical intervals. CMT offers in-field design flexibility, is low cost and easy to install. The number of monitoring ports, port locations, install depths, and monitoring strategy, can all be accommodated and finalized on site. The 7-Channel System is 1.7″ (43 mm) and the 3-Channel is 1.1″ (28 mm). They are ideal for shallow applications in narrow diameter boreholes.<\/p>\n

What are the advantages of using Multilevel Systems in High-Resolution Site Characterization?<\/h2>\n

These multi-port systems are engineered with hydraulically isolated short-screened intervals. The seals between zones are reliable, overcoming issues of cross-contamination between aquifers or between different layers within the same aquifer (which are noted issues with cluster and nested wells). The shorter screened intervals provide the true groundwater chemistry at each zone and eliminate the issue of chemistry and head being averaged across long screens (typical of conventional wells).<\/p>\n

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Comparing Long-Screened Well Data with Multilevel Well Data<\/p><\/div>\n

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Comparing Multlevel Systems to Clustered and Nested Wells<\/p><\/div>\n

There are numerous other application advantages to using MLS technology:<\/p>\n