This is a brief description of well drilling operations including water sampling procedures and equipment definition at the MMR.

There are several types of wells installed at the MMR for the ongoing remedial activities. These include monitoring wells to test groundwater contamination levels, piezometers to monitor groundwater levels, extraction wells to remove contaminated groundwater, reinjection wells to return treated or cleaned water to the ground, and recirculating wells, which treat contaminated water within one well. Photographs are linked to this web page to show viewers what some of the well drilling and sampling activities look like at the MMR.

Two main types of drill rigs are presently being used at the MMR. A sonic drill rig vibrates drill casing into the ground, creating a "borehole". Well casing is then installed in the borehole to create the well. Continuous soil core samples may be collected with this drilling technique.

The sonic drill rig shown here is set up to collect water samples while drilling to bedrock. Monitoring well 69MW1502, located on MMR property southeast of base housing, was installed in this borehole. A support truck with a blue tent for water sampling equipment and a platform for storing drill rig casing is backed up to the drilling end of the rig.

During well installation, soil samples are taken from the borehole. The purpose of soil sampling is to determine whether soil is fine or coarse. This information helps determine water flow and how remedies should be designed. A core of soil was collected continuously at this site from ground surface to bedrock to provide more information on the geology. The segment of core shown, representing the deepest portion of this core, is laid out as you would read text, with the shallowest section of core in the upper left, and the deepest section of core in the lower right. Mason jars, set in three cores, were used by the site geologist to mark different lithology. The particular section of the core shown in the photograph is taken right above the bedrock about 295 feet below the ground surface.

The other type of drill rig used at the MMR is a hollow-stem auger drill rig. The hollow-stem auger works like a corkscrew; a continuous string of augers is screwed into the ground to create the borehole. The first auger has sections of screen welded into it to provide water samples at various depths as the borehole progresses. The center of the auger is hollow so that water samples can be collected through it, and a well can be installed once the borehole is finished. The water sampling gear is located in a trailer behind the drill rig.

Both the sonic and hollow-stem auger drill rigs may be used to collect groundwater samples in a similar method. A submersible pump is lowered down the hollow center of the well casing or the auger to the zone to be sampled. An inflatable rubber packer located just above the pump is inflated to isolate the groundwater zone below that is to be sampled from accumulated water in the borehole. The pump is turned on, water is purged from the isolated zone, and then a sample of the groundwater is collected after the selected zone refills. The packer is deflated, the pump is removed, the drilling is advanced another 10 feet, and the process is repeated. Water samples are collected every 10 feet, if the geologic formation yields sufficient water, to provide a vertical profile of any contamination that might be present.
  

The pump and packer system, removed from the borehole, is stored in a drum for use at the next depth. The drum is filled with clean water, and the pump system is turned on to remove any potential contaminants from the sampling system. This water is then pumped through a granular activated carbon (GAC) filter system. Two hoses exit the top of the packer, the larger hose carries water to the surface to be sampled. The smaller hose contains the electrical wires that run the pump and the air hose used to inflate the packer.

Water that is purged from the well prior to sampling, and extra water collected during sampling, is contained in drums. The groundwater samples are then sent to an on-base laboratory for analysis. The excess water, temporarily stored in drums, is run through a series of three granular activated carbon (GAC) filters which remove any contaminants. The GAC system is sampled regularly from a port between the first and second GAC filters to confirm that all contaminants are being captured by the filter. The first GAC filter is replaced immediately if any contaminants are detected after the water passes through the first filter. Any remaining contaminants are filtered out by the second and third GAC filters.
                  

Prior to beginning any well drilling operations in a particular neighborhood, notices are sent to all potentially affected residents and telephone calls may be made to notify the nearby residents. Large signs are posted in the area to provide information to the public regarding the type of operation being conducted, the anticipated work schedule, and contact names and telephone numbers for further information. Typically, well drilling operations are conducted weekdays from 7:30 AM until 5:30 PM.

During all well drilling operations, specific procedures are followed for safety and environmental protection. The ground is covered with a geotextile layer and mulch to protect it from the heavy drilling equipment. A plastic liner is used to cover the area near the drill rig to prevent workers from potential splashing of groundwater. Drill rigs and associated equipment are surrounded with yellow caution tape to prevent unnecessary access to the immediate work site. All workers at the site must wear protective equipment including safety glasses, hard hats and steel-toed shoes.

For more information regarding these operations contact the AFCEE Community Involvement Office at 508-968-4678.