Missouri Water Science Center


Riverfront Site, New Haven, Missouri—Photos and Caption
Monitoring well TW-G along the bank of the Missouri River at Operable Unit 1. Sampling of monitoring well TW-G along the bank of the Missouri River at operable unit OU1 just before the well is submerged by the rising river on May 17, 2002. The large snag on the right is the top of the boat ramp. This well monitors the downgradient end of the PCE plume in the alluvial aquifer emanating from the Front Street building about 600 feet southwest of the well.
Careful sampling during the drilling of a shallow monitoring well at operable unit OU2 detected the presence of a dense non-aqueous phase liquid (DNAPL) in fractures between 16 and 20 feet deep. Analysis the DNAPL (black fluid) indicated that it was pure tetrachloroethene (PCE). Drilling Sample detects a dense non-aqueous phase liquid.
Installation of new Waterline to the high school. Flushing of the new waterline to the high school, New Haven, Missouri The USEPA cooperated with City of New Haven and the Kellwood Company during the installation of a new water line to the high school to ensure that contaminants from OU2 did not affect the water quality in the line. No contaminants were detected in soils during the installation of the water line or in water from the line after its installation.
This type of drill rig is used to install wells in areas where contamination is known or suspected to exist at high levels. Well casing can be installed as the borehole is being drilled. This technology has been used for more than 100 years, but generally has been replaced by faster air-rotary methods. Essentially, a heavy bit is suspended on a cable, raised a small distance, and dropped to break up the rock. A bailer is used every 3 to 5 ft (feet) to remove the rock cuttings.

This method is slow (20 to 40 ft per day) but no air compressors are needed (potential source of contaminants themselves), and little water is added while drilling. The lack of additives to the borehole enables U.S. Geological Survey (USGS) personnel collect high-quality samples every 5 ft of depth--providing a vertical distribution of tetrachloroethene (PCE) in the bedrock aquifer. In addition, the method is clean and cuttings can easily be placed in drums for removal.
Cable Tool Drilling Rig photo

Cable Tool Drilling Rig sampling    Cable Tool Drilling Rig bit
This may be not be pretty and it is slow, but it provides for good samples.
Air Rotary Drilling Rig set up

Air Rotary Drilling Rig set up
Very fast, but can be messy and difficult to get a vertical profile of contamination.
Nearly all public-and domestic-supply water wells are drilled using air rotary methods. This type of drill rig is used when there is little to no contamination is suspected and is used primarily to install the deeper bedrock wells. A large air driven hammer bit on the end of a hollow string of drill pipe is use to break up the rock. The compressed air is used to blow the rock cuttings and ground water up the borehole and onto the surface. Hundreds of cubic feet of air per minute at several hundred pounds per square inch pressure are required.

Air rotary drilling is fast (hundreds of feet per day) but can be messy. A problem with the method is the large volume of waste generated during drilling. You may see large dumpsters or roll-off containers placed next to the drill rig to catch the drill cuttings. Water is pumped from the containers and disposed in the sanitary sewer system each day. The large volume of air used strips PCE and other VOCs from the water making it difficult to determine the vertical profile of PCE in the bedrock. To avoid this problem, water samples are collected from the borehole at the beginning of each day.

For deeper holes such as were drilled at the grade school and at the Kellwood site, an extra compressor (red trailer on the right in top photo) is needed.
In unconsolidated sediments such as in the Missouri River alluvium at operable unit OU-1, direct-push technology is used to collect soil and ground-water samples. Clockwise from the top left corner shows a GeoprobeTM truck-mounted direct-push drill rig that was used to collect ground-water samples along the Missouri River.

The geoprobeTM pushes threaded steel rods into the ground using a hydraulic hammer. At the desired depth, a 4-ft long well screen at the bottom of the rods is opened and a plastic tube inserted from the surface (middle photo).

A small pump is used to remove a water sample from the temporary well, and the screen is pulled. The process repeated at various depths. Using this technology, the vertical distribution of PCE in the alluvial aquifer at various locations can be determined.
Direct-Push Soil Sampling and Wells-geoprobe well Setting    Direct-Push Soil Sampling and Wells-geoprobe inside

Direct-Push Soil Sampling and Wells-geoprobe water sampling

Direct-Push Soil Sampling and Wells-geoprobe inside-G60
Temporary wells allow the vertical profile of PCE to be determined in soft sediments. Technique used extensively at OU-1 (Riverfront site).
Tree Core extraction.

Tree Core Sample Collection.

You are what you eat, and a tree is no different. Technique used extensively at all operable units.
Drilling monitoring wells or collecting subsurface soil samples is costly and can be a great nuisance to property owners. The USGS has been researching the use of tree- core samples as a means of determining if subsurface soils or shallow ground-water at a site are contaminated. The technique is fast and inexpensive.

Trees pull moisture from the ground and with that moisture any dissolved contaminants. Volatile organic compounds such as PCE also may be absorbed by the trees roots from soil gases.

A core sample from the tree trunk is placed in a sealed glass vial and analyzed for PCE and other VOCs. The plume of contaminated ground water in the alluvium at the Riverfront Site (OU-1) was initially discovered by analyzing tree core samples.

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