Water Well Journal
Issue link: http://read.dmtmag.com/i/482464
custody forms and the laboratory pro- viding details of the QA/QC as part of the reporting. The standard recognizes two broad classes of parameters for analyses: mi- crobial and others. A good starting point to identifying such parameters of inter- est is the U.S. EPA's website, the local health department that permitted the well, and industry trade groups such as the National Ground Water Association and the American Water Works Association. International users of the ANSI/NGWA standard may select parameters and standards identified by their respective National Health Agency and the World Health Organization. For dedicated monitoring wells, the parameters to be monitored usually in- clude those contaminants that are char- acteristic of the groundwater plume. Other parameters that may aid in the interpretation and understanding of the geochemistry should also be included. The standard provides additional de- tails regarding microbial sampling and analyses. Section 10.2 describes sample collection for microbial analyses. Mi- crobial analyses are very important for potable wells, especially for those that can be regarded as under the influence of surface water. Such water samples should be collected in sterile sample bottles and "shall not have residual chlorine present." Per the standard, "sampling shall be performed during or immediately fol- lowing construction and development" by qualified personnel. Even though the standard was primarily devoted to water well construction, the standard subcom- mittee provided for post-construction sampling because groundwater quality may change with time. As such, the standard recommends subsequent peri- odic sampling to monitor water quality. The National Ground Water Association recommends that private water well owners have their wells checked and tested by a professional contractor every year to ensure water safety. Analytical results from periodic post- construction sampling will determine the continued suitability of the well for its stated purpose. When the purpose of the well is to be changed (for example, converting an agricultural well to a do- mestic well), it may require re-sampling and analyses of additional parameters that fit that purpose. It is important to keep proper records of analytical results from periodic sampling. Permanent Well and Test Hole Decommissioning This section of the ANSI/NGWA standard reflects the importance of proper well and test hole decommis- sioning. So often once a well has outlived its useful purpose, it is left unattended—out of sight, out of mind. But an abandoned well is as big a hazard to the groundwater reservoir as a poorly constructed well. In fact, most of the abandoned wells were constructed during a time when construction standards were either ab- sent or inadequate for providing mini- mum protection to the aquifer from groundwater contamination. In addition, when a test hole is drilled for the pur- pose of investigating for groundwater and is not properly decommissioned, the test hole becomes an unstable environment that is a direct conduit to the groundwater reservoir. Proper decommissioning involves several key components in order to restore the integrity of the subsurface geology needed to support the natural filtration of the water cycle. This in- volves learning as much about the well and well site as possible. Historical research requires a search of well logs in the area to determine the potential for multiple aquifers, confin- ing units, and possible sources of con- tamination. Interviewing the owner to learn as much as possible about the use and performance of the well is a good tool. Measurement of the well or test hole to determine the static water level is key. Choosing the correct grout for the decommissioning is important for suc- cessful abandonment of test holes in particular. The test hole environment is often an uncased boring exposed to the natural conditions of the ground both above and below the static water level. In order to restore the natural filtration of the ground, you need to match up the type of grout that performs best under the site conditions. A test hole that has encountered high concentrations of chlorides would not be a good environ- ment to use bentonite grouts, as salts have the ability to degrade bentonite- based grouts. As always, be sure the decommis- sioning method you use accomplishes the goal of protecting the aquifer and groundwater resources and is not just for filling the casing so someone or something doesn't fall in the well. When a well or test hole is properly de- commissioned, the protective conditions of the site should be restored to condi- tions to where the well or test hole never existed. Stuart A. Smith, CGWP, is a hydrogeologist with Ground Water Science LLC in Poland, Ohio. Babs Makinde, PE, D.WRE, is a professional licensed engineer in California. Tom Christopherson is the manager of water well standards for the State of Nebraska Department of Health and Human Services in Lincoln, Nebraska. WWJ DACUM Codes To help meet your professional needs, this article covers skills and competen- cies found in DACUM charts for drillers and pump installers. DO refers to the drilling chart. The letter and number im- mediately following is the skill on the chart covered by the article. This article covers: DOB-1, DOG-3, DOG-4, DOG-9, DOG-10, DOH-1, DOH-6 More information on DACUM and the charts are available at www.NGWA.org. WWJ April 2015 21 Twitter @WaterWellJournl It is very important the water sampling and analyses follow the proper protocol and be defensible.