ESTCP Direct Push Monitoring Well Study- The CRREL Test Site
Louise Parker, William Major, Mark Kram, Timothy McHale, and Marty Gildea

Our direct-push (DP) study was designed to compare analyte concentrations and water quality parameters in samples taken from DP monitoring wells with those from co-located conventionally installed monitoring wells to determine if well installation affected values. The US Army Engineer Research and Development Center’s Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, NH was selected as a test site. The CRREL site is located on Glaciofluvial, and Glaciolacustrine deposits and is heavily contaminated with trichloroethylene. This site was selected to test the capabilities of this technology in more challenging terrain.
In phase 1of this study, three ½-in. diameter DP (Geoprobe) wells were installed at depths of 116 to 138.5 ft using a truck-mounted unit. After using a larger probe rod to collect soil samples in the first well, 2.125-in OD probe rods were used to push to depth in the other two. Nine-ft sections of pre-packed well screen were attached to the anchor point, the drive rods were retracted to allow the natural formation to collapse above the screens. After collapse occurred, bentonite slurry was pumped in to the annulus using Geoprobe technology and the remaining rods were removed. The wells were developed by surging and purging using a check valve. Installation went very quickly. As an example in one well, it took 65 minutes to push to depth (128 ft).
However, attempts to recover a ground water sample were plagued by a series of problems. We were not able to get the ½-in Prism pumps (sold by Geoprobe) to the depth needed for sampling in some wells. We tried several solutions but found that having our machine shop remove ~10/1000th of an inch from the pump’s diameter worked best. In addition, the pumps would not deliver water to the surface. The developer found that with this system, a high pressure (~120 to 126 PSI) was needed to overcome differences in head. (The depth to ground water is between 95 and 125 feet and the depth of the pumps from the water surface was ~10 to 15 feet.) With a redesigned controller that allowed higher pressures, the pump was able to deliver water at a reasonable flow rate but lost capacity after half an hour. The lost capacity was due to condensation of water in the airline and a drying column was added to correct this. Currently, we are able to sample two of the wells but continue to have problems with the air compressor running constantly and water condensate in the air line.
In phase 2 of this study; three ¾-in Geoprobe DP wells were installed. Again, installation went very quickly. We tested two 3/4-in diameter pumps, the Sample Pro Bladder pump developed and sold by QED and the MPB bladder pump developed by Innovative Sampling Systems, Inc. and sold and distributed by Durham-Geo Slope Indicator. Both pumps performed well in these wells, with higher flow rates produced by the MPB pump. Although both pumps hung up in some wells, we were again able to correct this problem on the MPB pumps by removing a small fraction of the diameter of the pump.
With funding from the Army Environmental Center, we have been able to test additional bladder pumps. Although this work is on-going, we have tested a ½-in pneumatic bladder pump, developed by Innovative Sampling Systems, Inc., that performed well at our site.
With respect to the long-term performance of the DP wells, we are concerned whether the stainless steel used in the pumps and screens and the steel used in the anchor point can withstand the corrosive conditions at our site. We will be examining the pumps for signs of rust and monitoring for leached metals such as manganese, cadmium, chromium, and iron during the second phase of this study.