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VADOSE ZONE SAMPLING METHOD BENEATH SINGLE-SHELL TANKS AT THE HANFORD SITE, WASHINGTON (DRILLING AND SAMPLING IN A HIGHLY

RADIOACTIVE ENVIRONMENT)

H. A. Sydnor CH2M Hill Hanford Group

K. D. Reynolds, M. G. Gardner Duratek Federal Services, Inc.

ABSTRACT In the summer of 2000, a successful drilling and sampling project was performed to assess the highly radioactive contaminated vadose zone adjacent to and beneath the 241-SX-108 Single-Shell Tank (SX-108 SST) located at the Hanford Site in Washington State. The drilling and sampling effort was designed to retrieve contaminated samples where cesium-137 concentrations could be at a theoretical maximum concentration of 108 pCi/g. Handling of drill cuttings at this concentration was not an option, because dose rates to workers would have been several R/hr. A special drill rig and drilling and sampling system were designed, constructed, and fully tested to advance a casing string at an angle to collect periodic samples without damaging the SX-108 SST, generating any unnecessary wastes, or exposing workers to excessive radiation. The drilling method used was a driven closed-end casing with a removable tip. An industry standard diesel pile driver was selected to advance the casing. A removable internal drill string was designed to provide access for sampling tools and to provide additional energy to the tip of the drive casing during its advancement. The drill rig used a remote-controlled articulating mechanical arm to maneuver casing and split-spoon samplers, avoiding direct worker contact with contaminated components or samplers. A lead shielded split-spoon sampler was designed to reduce personnel exposure from samples as the sampler was extracted from the borehole and placed in shipping containers. To further reduce dose rates, the sample size was limited to the minimum volume required for laboratory analysis. Sample intervals were selected based on existing samples and geophysical logs from adjacent wells. Because of casing and drilled lengths and the drill rig wrench design, samples were physically constrained to one sample per 5 ft of advancement. Seventeen intervals were selected for sampling and 16 samples were successfully retrieved. Overall, sample recovery was 80%. The borehole was advanced at a 30 degree angle with a total distance of 172 ft (149 vertical ft). These techniques provided exceptional contamination control, minimized worker exposure, and provided representative soil samples. The maximum dose rate measured was 2 R/hr at 4 in. from the sampler and 14 R/hr on contact with the sample material. Doses received by workers were well under administrative guidelines. The techniques deployed were extremely successful and provided results that were not achievable utilizing standard practices. These techniques have far reaching applications and can provide viable alternatives for collecting characterization data during site investigations where high levels of radiological or other types of dangerous contamination are present. INTRODUCTION Retrieving highly radioactive soil samples from contaminated environments is often difficult and sometimes impossible using conventional technologies. This is also true for soil characterization activities in hazardous waste sites; therefore, the development of new techniques that specifically address


the problems of obtaining soil samples in highly radioactive and/or hazardous waste contaminated environments are desirable. Within the U.S. Department of Energy (DOE) complex, numerous sites are undergoing characterization, yet proven and regulatory agency-approved techniques are not available. The primary problem associated with these soil characterization efforts is the potential for release of contamination from the sampling activities to the surrounding environment. Uncontrolled releases of this type can result in contaminating personnel and equipment as well as spreading airborne contamination. This is of great concern to regulatory agencies and creates permitting restrictions that can severely constrain field-sampling methodology choices. In response to these issues, the DOE Office of River Protection Vadose Zone Project, which is operated by CH2M Hill Hanford Group (CHG), was tasked with the responsibility to develop and deploy drilling and sampling techniques that would meet both project objectives and regulatory permitting requirements. The initial objective was to retrieve soil samples from beneath an underground radioactive waste storage tank, which required a borehole being placed at an angle of up to 45 degrees from vertical. The feasibility of drilling and sampling using an angle driven (slant) closed-bottom casing method was investigated. The benefits of this technique are as follows: • A slant borehole can intersect contaminant plumes beneath surface and subsurface structures that

vertical boreholes cannot reach. • Driving closed-bottom casing eliminates the use of conventional drill cuttings circulating mediums

(e.g., water, drilling mud, air, etc.). • Driving closed-bottom casing eliminates generating contaminated drill spoils at the surface. BACKGROUND The Hanford Federal Facility Agreement and Consent Order (1) addresses cleanup at more than 2,000 waste disposal and unplanned release sites on the Hanford Site in Washington State. Some of these sites are treatment, storage, and/or disposal (TSD) units that have been grouped into waste management areas (WMA) for purposes of groundwater monitoring. Included in the WMAs are 149 single-shell tanks (SST) that are TSD regulated under Washington’s Hazardous Waste Management Act and it’s implementing requirements. Through the Single-Shell Tank Program Vadose Zone Project, CHG has the responsibility for characterizing the vadose zone around the SSTs that received high-level radioactive waste. Several tanks have leaked releasing radioactive waste into the subsurface environment. The data quality objective process for the SX Tank Farm WMA identified the following questions: • How far beneath the tanks does contamination extend? • What quantity and type of contaminants have been released from the tanks? • What chemical reactions between the contaminants and the soil column may have impacted waste

migration? • How stable are the contaminants?


• Under what condition would the contaminants move with inf iltrating moisture through the vadose zone to groundwater?

A slant borehole beneath the SX-108 SST was selected in the data quality objective process because the tank leak volume was estimated to be one of the largest in the SX Tank Farm and the leaked waste contained significant quantities of high-level radioactive waste. Cesium-137 is the primary contaminant of concern in the vadose zone and could be at a theoretical maximum concentration of 108 pCi/g. The method of driving a closed-bottom casing and sampling ahead of the casing as it is advanced was determined to be the only viable method for successfully retrieving these highly contaminated samples. STATEMENT OF THE PROBLEM Installing angle (slant) boreholes is standard practice in the drilling industry, as is the construction industry method of driving closed-bottom casings and pilings both vertically and at an angle. Standard drilling practices include removing soils as the drill pipe and/or casing is advanced. Soil samples are collected either by coring as the drill string is advanced, driving split-spoon samplers or drive barrels ahead of the advancing casing, or from drill cuttings returned to the surface. Driving casing and routinely sampling ahead of the casing through a removable tip has never been applied successfully nor attempted in a highly contaminated radioactive environment. The following issues arise when attempting this method: • Providing adequate force to advance a closed-bottom casing of the required diameter for sample

retrieval to the identified depth. • Developing a removable tip system that can withstand the drive forces and designing a mechanism

that is capable of being removed and reinserted for multiple sample collections as the casing is advanced.

• Protecting personnel from expected high-radiation dose rates from soil samples. The environment in which this drilling and sampling method was to be deployed provided additional constraints. The slant borehole location was selected in an attempt to intercept the highest contamination levels, which placed the borehole site near the center of the SX Tank Farm. Due to the proximity of the adjacent tanks, tank infrastructure of piping and electrical supply, and dome loading restrictions, the placement of drilling and support equipment within the specific coordinates was situated to ensure tank integrity and safety. Proper alignment of the slant borehole was critical to avoid underground utilities that transfer waste, that provide raw water and electrical power to the facilities, and to avoid the tank. The borehole was positioned and aligned to ensure the probe would pass a safe distance from the bottom of the tank and still intersect the estimated high concentration portions of the leaked waste. In addition, the drilling and sampling methods selected ensured worker exposures were as low as reasonably achievable (ALARA). As previously stated, it was because of the anticipated high contaminant concentrations that the method selected for constructing the slant borehole was by driving a closed-end casing. The advantage of this method is that no cuttings would be brought to the surface during well construction and no circulation medium would be required. Additionally, at the anticipated contaminant concentration levels, a closed-end driven well would be the only drilling method allowed when considering air emission permitting standards provided in the Notice of Construction(2).


Two options were identified for collecting the contaminated sediment samples from a closed-end driven borehole. These options included collecting driven split-spoon samples ahead of the borehole casing or collecting sidewall samples during borehole decommissioning. Driving a split-spoon ahead of the casing was selected as the primary method based on anticipated success rates. Previous efforts at developing sidewall sampling methods had met with limited success and were therefore only considered as a contingency or “last chance” option. Because of anticipated radiation levels and sampler size restrictions, standard split-spoon sampling equipment could not be used for the proposed slant borehole. The split-spoon sampler was specially designed to limit sample volume and provide a portion of the estimated necessary radiation shielding internal to the sampler. Collecting split-spoon samples ahead of the borehole casing would be achieved by removing the drive tip at predetermined locations of interest, collecting the split-spoon sample, and reinstalling the drive tip to advance the slant borehole to the next sampling location. The advantage of collecting a split-spoon sample ahead of the casing is the ability to collect a representative sample of sufficient size for laboratory analyses and to recover an undisturbed sample from a known depth. Several uncertainties existed with this sampling methodology at the SX-108 SST. The primary uncertainty was the potential exposure resulting from handling hot samples, because the actual concentrations of radionuclides were unknown. Additional uncertainties include sample handling in the laboratory and potential transportation problems when moving the samples from the field to the analytical laboratory. Limitations associated with collecting split-spoon samples from the slant borehole included sampling without the benefit of prior knowledge of the precise location and concentrations of contaminants prior to sampling, and because of engineering and design constraints, the sampling frequency was restricted to 5-ft intervals. Because of these limitations, the details of the sampling plan were developed with the understanding that the samples would be collected at regular intervals -- based on casing addition lengths, the rig power wrench dimensions, and that each sample had the potential to be highly contaminated. APPROACH A team was formed to develop the drilling and sampling techniques required to accomplish the objectives. The team included CHG, Duratek Federal Services, Inc., Northwest Operations (DFSNW), Resonant Sonic International (RSI), CH2M Hill Hanford, Inc., (CHI) and Pacific Northwest National Laboratory (PNNL). CHG provided project objectives and goals, regulatory permit documentation, and support personnel for work performed inside the SX Tank Farm. DFSNW was the technical lead for implementing project goals, designing drilling and sampling methods, field deployment, and providing project oversight during operations. DFSNW selected RSI as a teaming partner for project implementation and operation support. RSI provided the rig fabrication and assisted in casing and tool design and testing, as well as providing personnel for field operations. CHI provided drilling engineering support during the design phase, testing and evaluation of the samplers, drilling tool, and control systems design and development. PNNL determined minimum soil sample volumes required for analysis efforts and performed the analyses of recovered materials. Lessons learned from previous tank farm vadose zone characterization activities managed by DFSNW identified a need to provide adequate testing prior to actual deployment into a contaminated environment. For this reason, a full “demonstration” phase in an uncontaminated soil environment outside the SX Tank Farm was incorporated into the schedule. The purpose of this demonstration was not only to test the methodology of retrieving sediment samples from beneath the selected tank, but also to develop operational procedures and provide hands-on training to members of the team that would be performing the actual tasks of driving casing and collecting samples.


To protect workers from the anticipated high radiation levels, minimize waste disposal costs, and meet a relatively short design, testing, and deployment schedule, a decision was reached to utilize the simplest configuration of available tools and methodologies. This action resulted with the following: • Diesel pile driver and mast assembly that could be set from 0 degree vertical to a 45 degree angle and

was mounted centrally on a trailer for driving the casing. • Threaded heavy wall (.5 in. thick) large diameter casing (7 in. outside diameter [OD]). • Removable tip held in place by an inner rod assembly that extended to surface (i.e., utilizing no

mechanical latching mechanisms). • Specially designed internally shielded small diameter sampler sized to provide the maximum amount

of sample material for analysis and not exceed DOE allowable dose rates. • Mechanical articulating arm for remote handling of the drill tools and samplers Techniques and tools were identified, designed, developed, and tested during the demonstration phase. Based on results of the demonstration, final tool and procedure modifications were made. The selected techniques were then deployed into the SX Tank Farm (Fig. 1).

Fig. 1. Multiple Angle Drill Rig Setup in SX Tank Farm

DESIGN AND IMPLEMENTATION Successfully achieving the project objectives required design and fabrication of a drive casing with a removable tip, shielded split-spoon sampler, and mechanism for directional control. The drill system was


designed to accommodate the techniques developed, provide multiple angle deployment, and support remote handling of drill tools and samples. Directional Control As previously noted, controlling the direction and entry angle of the probe was critical because of potential impacts to the tanks and tank farm infrastructure. Because of drill rig motions caused by casing advancement, which is the result of the casing hammer impact, a method to anchor the drill rig to the precise selected point of casing entry and angle was required. Additionally, the drilling platform height periodically needed adjustment to align the power wrenches to compensate for casing height changes and to adjust the alignment of the drive head and pile driver with the casing and drill pipe. Because of these movements and adjustments, an immobile anchor point was required. The anchor also allows for accuracy when aligning the drive mechanisms and provides a stable platform for the casing jacking equipment for removal of casing, as well as stabilizing the rig. To meet these needs, a concrete filled steel anchor block was designed for SX Tank Farm deployment (Fig. 2).

Fig. 2. Drawing of Anchoring Point (Box)

The anchor box incorporated an 11-in. outside diameter starter casing aligned at 30 degrees from vertical and an angled face on which to position the casing jacks, as well as points for attachment to the rig trailer. The starter block required placement precisely on the point calculated for clearance of underground obstructions and for the guide tube of the anchor block to be oriented correctly. This directional precision was required to guide the probe so that the direction and angle of the probe forced the advancement path to pass through the “clearance or target window”. The target window was based on safety calculations to minimize potential impact to the tank integrity and to pass through the calculated high contamination zone targeted for sampling. Due to the rigidity of the casing, the probe essentially follows a straight path with only minor incremental deviations during advancement. This “straight path” was proven during the demonstration and deployment by using a borehole gyroscope. Three-dimensional calculations based on review of the tank design drawings, plume mapping based on nearby vadose zone wells, ground-penetrating radar studies, and tank infrastructure drawing reviews determined the optimal ground location for probe entry. This point was marked by using a global positioning satellite (GPS) and the anchor block/guide device was placed and re-measured with the GPS system.


Casing and Removable Tip The casing was selected to withstand the driving force of the drill rig mounted ICE 40S diesel pile driver, which delivers approximately 35,000 ft/lb of force at a 30 degree angle (manufacturer estimate). The casing selected to withstand this high degree of force was P-110 grade carbon steel, 18 cm (7-in.) OD by 13 cm (5 13/16-in.) inside diameter (ID) with a pin pile thread. The majority of the casing string was composed of 5-ft joints with several 1, 2, and 3 ft joints for positioning adjustments for the proposed sampling intervals. The thread pattern was selected to withstand the expected driving force as well as the maximum pull back capacity of the selected casing jacks. Tests were conducted on the threading by the manufacturer to substantiate the calculations. During the demonstration prior to in-farm work, and during deployment activities in the SX Tank Farm, no problems were encountered with handling or torquing the casing. The casing was torqued to the manufacturer’s specifications (5,000 ft/lb). Following removal of the casing from the borehole after the demonstration and for the portion of casing removed during the in-farm activities, the extracted portion of the casing string was visually inspected. No deformation of the casing bodies from the large driving forces was observed and no casing thread or casing shoulder damage was evident. The basic goal was to acquire sediment samples by using a split-spoon advanced ahead of the casing as it was advanced beneath the SX-108 SST. To accomplish this, the closed-bottom casing was driven at an angle and to deploy the sampler, the casing shoe was designed to accommodate a removable tip. When a sampling interval was reached, the tip was removed and the sampler was inserted and advanced. This removable tip design had to meet several requirements to be considered a successful and viable method. The removable tip had to be easily removed and re-inserted, remain in place while the casing was driven, and withstand the forces while being driven (e.g., not deform and become locked in place). The tip was designed as an insertable “plug”, which eliminated elaborate latching mechanisms. Industry research indicates that latching mechanisms are prone to failure upon repeated reuse because of accumulated dirt and debris, wear, and tip and mechanism deformation. During driving operations, the casing and drive tip were driven together as a single unit. The tip was held in place by using an inner string of pipe, which also served as a deployment string for the split-spoon sampler. A special drive head was fabricated that allowed adjustments for matching the length of inner drill string with the total casing length. This provided for the ability to place the inner string in compression from the impact of the hammer simultaneously with the outer casing. This compression held the tip in place while driving without the need for latching mechanisms. The design proved to be very effective for driving as a unit. The adjustable drive head easily aligned to the top of the casing. The tip did not show signs of wear or damage when removed during the demonstration or during the deployment. The casing shoe was undamaged when removed from the slant borehole during the demonstration. The casing shoe and a portion of the drive casing were not retrieved during the actual deployment because of the high level of contamination remaining on the interior and exterior of the pipe. The drive tip was removed and re-inserted 11 times during the demonstration and 17 times during the deployment. Difficulties were experienced during the first two removals of the tip during testing. Camera surveys were run to determine the cause of the difficulty. Wear marks on the interior of the casing, the tip, and drill string indicated the need for improved centralization of the tip and bottom hole assembly to facilitate insertion and removal. To meet this need, closer tolerance centralizing devices were fabricated and inserted into the drill string. Additionally, observation of fine material caked to the tip following removal, as well as material packed in the shoe opening, as recorded by the camera surveys, indicated the need for wiper o-rings. Two separate design modifications were tested and the final selected design utilized a dual set of oversized


o-rings. This modification effectively sealed out fine materials from wedging into the gap between the tip and shoe. No further problems were experienced when removing or re-inserting the tip during testing or during the deployment. Casing Advancement In order to advance the large diameter casing selected (7 in. OD), an ICE 40S diesel pile driver was utilized. This equipment was selected because of the la rge amount of force delivered per blow (40,000 ft/lb in a vertical configuration) and because of the ease of operation and low maintenance requirements for operation within the contaminated environment. This pile driver provided adequate force in the demonstration and in the deployment to drive the casing at the predetermined 30 degree drive angle. The target depth of 150 ft vertical depth and 183 ft total casing length for a demonstration and 144 ft vertical and 173 ft total casing length for the SX-108 SST characterization deployment were easily achieved. During both the demonstration and actual deployment, the probe angle drifted up from the targeted 30 degree angle during driving. The starting angle was 30 degrees, drifted to approximately 40 degrees from vertical at completion for the demonstration, and changed only minimally from 30 to 30.5 degrees during the in-farm operation. Proper alignment and rig stabilization were determined to be essential at the initiation of driving to ensure proper angle of penetration. Greater care and increased operational knowledge used during the deployment resulted in the close adherence to the planned probe path. During the testing demonstration and the SX Tank Farm activities, the path of the probe was documented by deploying an in-hole gyroscopic measurement system. This system was only used to document the probe path because the method of casing advancement does not allow for steering or adjusting the drive direction, once started. The hammer performed as expected and required very little repair and maintenance during both the demonstration and deployment. Blow counts vs. time and advancement were recorded and, as expected, varied over depth. Charting the blow counts at the various depths exhibits influence from geologic conditions, but are not directly correlateable nor are the blow counts useful as engineering data for formation evaluation. This is the result of the design of the hammer, which applies increasing impact force up to a maximum as resistance to the advance of the tip increases. Remote Handling of Casing, Samplers, and Drill String The final design of the rig was a platform (trailer), hammer, and mast assembly, which incorporated a remote-controlled handling arm. This extremely useful safety feature reduced worker exposures to lifting/ergonomic hazards and reduced the time spent handling the contaminated drill pipe. The handling arm was included for manipulating, lifting, and removing sections of the casing and the drill string (pipe) as well as for the samplers. In addition to health and safety, this arm was an important factor as a timesaving engineering improvement. Each time a sample was taken, the drill string was removed (with the sampler at its head) and then re-assembled and lowered to the bottom of the hole. After a sample was advanced ahead of the casing shoe, the drill string was removed, the sampler sleeved and packaged, and the drill string was reassembled with the drive point and re-inserted. Handling of the very high dose rate split-spoon samplers at surface was also done by the remote arm, which was utilized to hold the samplers while they were removed from the drill string and to place the samplers directly into shielded transportation containment. By using the remote arm to perform the direct lifting of the drill string components and to secure and move the high dose rate samplers, workers did not handle potentially contaminated materials directly, thereby reducing exposure (Fig. 3).


Fig. 3. Adding Pipe with Manipulator Arm (shown above), and Remote Handling Sleeved Contaminated Pipe (shown below).


Soil Sampling As previously stated, the objective was to collect soil samples that were directly impacted by the leaking of high-level waste from the SX-108 SST. The implication from this objective was that the retrieved samples could have extremely high dose rates. The calculated rates indicated that cesium concentrations could be as high as 108 pCi/g. The design of the driving mechanism and rig assembly produced restrictions on the ability to sample. The restrictions were the result of the following: • Height of the rig platform from ground surface • Dimensions of the starter/anchor block • Design of the hydraulic wrenches for tightening and breaking of the pipe and casing connections • Travel length of the mast for moving the driving mechanism. These restrictions required that the targeted sampling points be at least 5 ft apart. Other increments would have required a significant amount of time to complete equipment redesign. To stay within the available budget for field expense and laboratory analysis and to meet the deployment and completion schedule, a decision was reached to prepare a sampling plan that limited the overall number of sampling attempts. To accomplish this, the sample plan required 17 samples to be collected at 5-ft and 10-ft intervals. The initial sample point was selected level with the bottom of the tank, and sampling was to continue at 5-ft intervals through the zone projected to be directly impacted by the tank waste. Below that interval, the sampling decreased to a sample every 10 ft for the portion of the vadose zone that was thought to have been affected by movement of contaminates subsequent to the leak. From a worker exposure and transportation requirement standpoint, the expected high dose rates produced restrictions on the volume of soil that could be safely brought to surface. To accommodate these issues, the strategy was to limit the recovered volume to meet the projected laboratory needs. The minimum volume of material necessary to perform the planned analysis was calculated. To allow for safety margins, that volume was doubled and an inner sleeve diameter and length was selected that would contain the estimated volume. Dose rate calculations utilizing the highest concentration of cesium expected were run to estimate the expected worker exposure or dose rates. This expected dose rate was compared to the allowable exposure rates for workers who would be required to handle, package and transport the sample, as well as the laboratory limits. Additional considerations for the overall sampler design included proper sizing for passing through the opening in the casing shoe and withstanding drive forces that were to be applied. Subsequently, a sampler was designed that used the shielding effects (thickness) of the following: • Stainless-steel sample liners (.035 in.) • Carbon steel split tube that held the liners (.25 in.) • Additional lead shielding (.375 in.) • Outer body of the sampler (375 in.). The above components resulted in a sampler that had a 3.875 OD and collected a sample in a set of two liners that had 1.93 in. ID and were each 6 in. long. Because of the remote handling system and the immediate capping and containerization of the samples, field personnel were not able to verify sample recovery in the field. Following retrieval at surface, all samplers (with the exception of Sample #6) were immediately shipped to the PNNL 300 Area Laboratory


for breakdown, sample recovery, and analysis. Sample #6 remained in the SX Tank Farm from June 28, 2000 to July 5, 2000 (7 days) due to a general area evacuation for safety concerns caused by a range fire on the Hanford Site. Various problems were encountered during the 17 sampling attempts beneath the SX-108 SST. The most common problem involved the breakage of fingers on the retaining baskets in the sampler bodies. Even though the fingers were parting from the ring and, in some cases, the ring was driven up into the sampler, the recovery rates with the exception of Sample #2 were acceptable to meet laboratory analysis needs. The overall average recoveries including Sample #2, which had no recovery, was 80.2% (see Table I for individual sample recovery percentages).

Table I. Sample Field Data Sample # Date Targeted

Angle/DepthVertical Depth

Sample Depth/Angle

Vertical Depth

Recovery Field Dose Rate for Containerized Sample

1 6/13/00 63.5 55.0 63.2 - 64.2 54.50 80% 3 mR/hr2 6/14/00 73.5 63.7 73.2 - 74.0 (refusal) 63.00 0% 15 mR/hr3 6/19/00 78.5 68.0 78.2 - 79.2 67.30 ≈ 80% 100 mR/hr4 6/20/00 83.5 72.3 83.2 - 84.2 71.50 93% 40 mR/hr5 6/21/00 88.5 76.6 88.2 - 89.2 75.70 88% 100 mR/hr6 6/28/00 93.5 81.0 93.2 - 94.2 79.90 83% 180 mR/hr - 800 mR/hr window open

7 7/6/00 98.5 85.3 98.2 - 99.2 84.10 90% 200 mR/hr8 7/10/00 103.5 89.6 103.2 - 104.2 88.30 88% 5 mR/hr - 100 mR/hr window open

9 7/12/00 108.5 94.0 108.2 - 109.2 92.50 85% <.5 mR/hr10 7/14/00 113.5 98.3 113.2 - 114.2 96.60 75% <.5 mR/hr11 7/17/00 118.5 102.6 118.2 - 119.2 101.00 87% <.5 mR/hr12 7/18/00 123.5 107.0 123.2 -124.2 104.90 75% <.5 mR/hr13 7/20/00 133.5 115.6 133.2 - 134.2 113.10 70% <.5 mR/hr14 7/24/00 143.5 124.3 143.2 - 144.2 121.30 70% <.5 mR/hr15 7/25/00 153.5 132.9 153.2 - 154.2 129.40 100% <.5 mR/hr16 7/26/00 163.5 141.5 163.2 - 164.2 137.50 100% <.5 mR/hr17 7/27/00 173.5 150.1 171.2 - 172.2 143.99 100% <.5 mR/hr

Sample # 2 was lost in its entirety inside the casing during extraction. The zone that was attempted by Sample #2 was 63.7 ft below ground surface (73.2 ft pipe length). Based on local geology, this zone consisted of coarse to granular sand with minor small pebbles. It is moderately well compacted and appears to have very low moisture content. This combination of conditions has contributed to low recovery rates during previous sampling attempts at the demonstration site and at other drilling locations in and adjacent to the S/SX tank farms. The sampler refused after approximately 7 to 8 in. of advance and the advance that was made required prolonged operation of the downhole air hammer. During removal of the drill pipe and sampler, considerable effort was required to break the connections of the drill pipe immediately above the air hammer, sample crossover connection, and sampler. Based on high contamination levels found at the top of the casing, it was apparent that the material fell from the sampler into the casing during the attempts to break the last few connections. Subsequent to the loss of Sample #2 (estimated to have come from one of the highest contamination zones based on spectral gamma logging) use of the down-hole air hammer for driving of the sampler was discontinued. Because of air emission concerns, an up-hole air hammer was used in an attempt to drive Sample #3. The hammer was operated for approximately 4 minutes with only 0.15 ft of advance. This advance was accompanied by excessive vibration and the operation was discontinued. Subsequently, the diesel pile driver was used to complete the sampling activities for the remaining 15 sample attempts. During the driving of Sample #3 the sampler body and/or shoe threaded connection was apparently damaged and was unable to be opened at the laboratory. This sample was removed from the sampler by mechanically “digging” the material from the top end of the sampler, and due to this action became mixed. The recovery percentages for this sample were estimated by visual comparison to other sample volumes. Table I lists the sample numbers and associated information for the SX-108 SST deployment.


The split-spoon samplers were packaged and transported in accordance with requirements provided in Hanford Analytical Services Quality Assurance Requirements (3), DFSNW sampling procedures and U.S. Department of Transportation (DOT) regulations. As the samplers were recovered to surface, they were immediately sleeved in plastic and moved using the remote-handling arm from the drill rig floor to a transport container. Each sampler was immediately packaged in a DOT compliant shipping container and surrounded with blue ice to maintain sample temperature between 2 °C and 4 °C during transport. The shipping containers were sealed with custody tape and transported with a chain of custody, never leaving the custody of the shipper until arriving at the laboratory, where custody was relinquished. Because of a Hanford Site evacuation, due to a range fire, Sample #6 was the only sample that was not shipped immediately upon retrieval. Fig. 4 shows the remote-handling arm placing a sampler in a packaging container for shipping.

Fig. 4. Placing Sampler in Shipping Container CONCLUSION The development of the large diameter probe driving and sampling system provided a safe, fast, and economic methodology for sampling in a highly radioactive contaminated environment. Because a driven closed-end casing method produces no soil waste, this technique offers significant savings for waste disposal costs and a reduction in worker exposures to the highly contaminated soils. This large reduction in drilling waste is of great significance. Added to these advantages is the flexibility of the current design to accommodate placement of the probe at an angle. This allows for sampling under surface and sub-surface obstructions. In general, this technology was proven successful at SX Tank Farm and should be considered for other projects of this nature. Use of this technology has the capability to reduce worker exposures to contamination, provide economic methods to retrieve high-level waste samples from the sub-surface adjacent to and beneath potential leaking or past discharge sources, and to reduce the volume of waste generated.


This sampling method provides several advantages over other known and tested technologies; however, the tight schedule for the design, assembly, and testing of this unique system resulted in progressing into the field deployment with some unresolved problem areas. A number of the problem areas were described previously. Pertinent advantages and problems proven or identified during the deployment are discussed below. Advantages: • Actual casing advance was very rapid with an overall average advance rate per foot of casing of

.84 min/ft. On the average, a 5-ft section of casing could be driven in 3 to 4 minutes. • Sampler advance was also very rapid with drive times ranging (on average) from 1 to 2 minutes for

12 to 14 in. of sampler advance. • The remote-handling manipulator provided excellent worker protection from exposure to high dose

rate radioactive and chemically contaminated samples. It also provided protection from injury due to lifting strain when handling drill pipe, casing, and other cumbersome and heavy drilling tools and equipment.

• The multiple angle capability of the drive unit allows it to be set to drive casing from vertical to

45 degree angles. This provides a large flexibility for placement of the unit to avoid surface obstructions and sample under targeted potential contaminate sources.

• When compared to standard drilling and sampling technologies, this methodology provides

significant reduction in generated waste requiring treatment and/or disposal. • Closed-end probe driving capabilities provide the potential ability to “plume chase” in an economical

fashion by using geophysical/remote sensing tools inside the casing. • As demonstrated from review of the gyroscope data, the methodology has been proven to achieve

specific targets within defined windows. Specific points in the subsurface can be identified and subsequently interrogated by using the probe for sampling or using remote sensing tools (e.g., spectral gamma, moisture, etc.).

• The simplicity of the driving unit design and downhole equipment proved to be extremely reliable. Problems: • The loss of Sample #2 inside the casing caused difficulty in meeting contamination control

requirements. The contamination introduced to the interior of the casing increased the trip times required to remove and replace the probe tip and samplers, added to the contamination control efforts at surface, and increased the total volumes of waste generated. The materials lost were subsequently “smeared” throughout the entire length of the casing providing such high levels of contamination in the casing that interpretation of geophysical information from certain zones was not possible. Efforts


to provide clean-up methods need to be resolved because sample loss is always a possibility when conducting subsurface work.

• In both the demonstration and deployment phases of this technology, certain geologic conditions

proved to be difficult if not impossible to sample with the samplers and driving techniques employed. This difficulty is primarily the result of grain size vs. sampler ID and sample moisture content, and the resultant exponential growth of sidewall friction as sample material is forced into the sample liner.

• This sampling method is only applicable to discreet point sampling due to casing length and

equipment design limitations. This pinpoint sampling requires accurate pre-planning to identify sample points before drilling. There is no feasible method to utilize this technology to acquire continuous samples with any certainty of high success rates.

• Failure of the fingers and retainer rings in the shielded sampler, and the loss of the Sample #2

indicates further development and testing of sampler design is required prior to future deployment and use of the present design.

• Because this work was conducted during the summer months, work rest regimens were imposed by

high ambient temperatures. These temperatures caused several work delays and work efficiency impacts. Many actions related to drilling and sampling do not conform well to artificially imposed work scheduling (e.g., 30 minutes of work followed by 30 minutes of shaded cool down). Future work under similar conditions require additional planning, engineering controls, or scheduling changes to lessen impacts and improve worker comfort and drilling efficiencies.

Overall, this project was an impressive success. The design for closed-end casing with removable tip was proven extremely reliable, experiencing no failures or problems during the deployment. No other design of this nature is available from industry and this system should be considered an engineering and operational achievement. The ability to drive casing (producing minimal waste) and acquire representative materials at predetermined intervals was proven an unqualified accomplishment. The remote handling devise provided a very high level of worker protection from ergonomic injuries and aided the project in fulfilling ALARA goals of reducing worker exposures to health threats from contaminates. There were no on-the-job injuries or worker exposures. The overall success of this project can be directly attributed to the combination of a simple design, a strong technical team, the demonstration testing prior to deployment, and the excellent teamwork and interaction between the subcontracting companies and SX Tank Farm operations personnel. Although the need for several improvements in tooling and methodologies has been identified, this method of casing placement and sampling is a viable alternative to standard techniques. REFERENCES 1. Hanford Federal Facility Agreement and Consent Order, Washington State Department of Ecology,

U.S. Department of Energy, and U.S. Environmental Protection Agency, Olympia, Washington (1994)

2. Notice of Construction, DOE/RL-99-34, U.S. Department of Energy, Richland, Washington (1999) 3. Analytical Services Quality Assurance Requirements, DOE/RL-96-68, Vol. 2, U.S. Department of

Energy, Richland, Washington (1996)

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