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PollutionEngineering October 2012 : Page-18

ENVIRONMENTAL AND DIRECT PUSH DRILLING TECHNOLOGIES Drill more holes. Gather more data. Spend less money. This is a reality and not a dream. T By Thomas D. Dalzell, CWD, Director of Environmental Research for AMS Inc. The purpose of environ-mental drilling is: 1. To identify the type, level/concentration and extent of contaminated soil. 2. To determine details regarding the subsurface lithologic condition. 3. To evaluate if groundwater has been impacted or has the potential to be impacted by contamination. 4. To sample groundwater and/or install long-term groundwater monitoring wells. 5. Successful cleanup/remediation of contaminated soil and groundwater. 6. Obtain site closure – the documenta-tion for, and final approval of, successful cleanup of the contamination for which the investigation and cleanup was caused. 7. Ultimately, the goal is in protect-ing and/or restoration of groundwater resources. Above is a PowerProbe 9500-D direct push drilling rig mounted on a trailer. Direct push drilling technology Direct push drilling technology (direct push) allows the use of a wide variety of direct push tooling (DP tooling) and instrumentation that can be advanced into a subsurface lithology. This is conducted 18 Pollution Engineering OCTOBER 2012 using a combination of the static weight of a direct push rig, hydraulic down pressure, and rapid hydraulic hammering. For some direct push instrumentation, such as cone penetration testing, rapid hydraulic ham-mering is not used. Direct push can be used when subsur-face soil/lithology is unconsolidated and displaceable, such as sand silt, clay or small gravels. Compared to other types of drill rigs, the benefits of direct push for envi-ronmental drilling are: small volume of/ or no cuttings (unwanted waste material); DP tooling is easy to handle and main-tain; proper decontamination is easier; small volume of decontamination waste materials; no use of oils, greases, foams or anti-seize compounds; easier to mobilize/ demobilize, set up, operate and main-tain; and because the rigs are generally smaller, they are ideal for limited access and remote areas. The main activities are: soil sampling; groundwater sampling; soil gas sampling; installation of small diameter, pre-packed screen groundwater monitoring wells (direct push wells); installation of tempo-rary groundwater monitoring wells; geo-technical testing and sampling to be used in remedial design; pilot studies; remedial injections, installation of conventional remedial wells; and angle borings/direct push wells. Direct push equipment can be installed on trucks, track carriers, tractors, skids, trailers, ATVs/UTVs or can be stand-a-lone units. This provides great versatility in being able to collect samples from a variety of situations as needed with mini-mal destruction. Many direct push drill rigs have dual combination types of drilling such as direct push and augering. Having an auger capability on a direct push rig can enhance the capability and effectiveness of direct push. A simple example of this is to auger through a relatively shallow and thin hardpan and then telescopi-cally direct push for the remainder of the depth of the boring. By having multiple types of drilling, the rig can be more versatile in function-ality, unanticipated subsurface litholo-gies and changing scopes of work for capabilities, such as environmental drill-ing techniques, as well as geotechnical investigations. A direct push rig can be equipped with an auto drop hammer or

Environmental And Direct Push Drilling Technologies

Thomas D. Dalzell

Drill more holes. Gather more data. Spend less money. This is a reality and not a dream.<br /> <br /> The purpose of environmental drilling is:<br /> <br /> 1. To identify the type, level/concentration and extent of contaminated soil.<br /> <br /> 2. To determine details regarding the subsurface lithologic condition.<br /> <br /> 3. To evaluate if groundwater has been impacted or has the potential to be impacted by contamination.<br /> <br /> 4. To sample groundwater and/or install long-term groundwater monitoring wells.<br /> <br /> 5. Successful cleanup/remediation of contaminated soil and groundwater.<br /> <br /> 6. Obtain site closure – the documentation for, and final approval of, successful cleanup of the contamination for which the investigation and cleanup was caused.<br /> <br /> 7. Ultimately, the goal is in protecting and/or restoration of groundwater resources.<br /> <br /> Direct push drilling technology<br /> <br /> Direct push drilling technology (direct push) allows the use of a wide variety of direct push tooling (DP tooling) and instrumentation that can be advanced into a subsurface lithology. This is conducted using a combination of the static weight of a direct push rig, hydraulic down pressure, and rapid hydraulic hammering. For some direct push instrumentation, such as cone penetration testing, rapid hydraulic hammering is not used.<br /> <br /> Direct push can be used when subsurface soil/lithology is unconsolidated and displaceable, such as sand silt, clay or small gravels. Compared to other types of drill rigs, the benefits of direct push for environmental drilling are: small volume of/ or no cuttings (unwanted waste material); DP tooling is easy to handle and maintain; proper decontamination is easier; small volume of decontamination waste materials; no use of oils, greases, foams or anti-seize compounds; easier to mobilize/ demobilize, set up, operate and maintain; and because the rigs are generally smaller, they are ideal for limited access and remote areas.<br /> <br /> The main activities are: soil sampling; groundwater sampling; soil gas sampling; installation of small diameter, pre-packed screen groundwater monitoring wells (direct push wells); installation of temporary groundwater monitoring wells; geotechnical testing and sampling to be used In remedial design; pilot studies; remedial injections, installation of conventional remedial wells; and angle borings/direct push wells.<br /> <br /> Direct push equipment can be installed on trucks, track carriers, tractors, skids, trailers, ATVs/UTVs or can be stand-alone units. This provides great versatility in being able to collect samples from a variety of situations as needed with minimal destruction.<br /> <br /> Many direct push drill rigs have dual combination types of drilling such as direct push and augering. Having an auger capability on a direct push rig can enhance the capability and effectiveness of direct push. A simple example of this is to auger through a relatively shallow and thin hardpan and then telescopically direct push for the remainder of the depth of the boring.<br /> <br /> By having multiple types of drilling, the rig can be more versatile in functionality, unanticipated subsurface lithologies and changing scopes of work for capabilities, such as environmental drilling techniques, as well as geotechnical investigations. A direct push rig can be equipped with an auto drop hammer or conventional Standard Penetration Test hammer, also sometimes referred to as blow count testing. Having a dual combination type and capability drill rig there can greatly extend sampling capabilities with just one drill rig.<br /> <br /> For environmental drilling activities, it is important to know and understand the site facilities, underground utilities, have a work plan or job specification, use applicable standard operating procedures (SOPs), whether they be from ASTM International, customer specific requirements, regulatory requirements (federal, state and local) or other. It is possible that the entire project is a combination of all of the mentioned SOP contributors.<br /> <br /> As with all drilling and subsurface contamination, there is a risk of danger to human health and safety. All potential dangers, conditions, and considerations must be identified with a work plan and worker health/safety plan.<br /> <br /> A work plan/sampling plan contains any known prior site information that was gathered to help the investigators conduct a proper investigation. Some valuable information could be history of the site, such as any information available about the source, age of release and previous subsurface contaminants on or adjacent to the subject site. The plan should include proposed soil boring and groundwater monitoring well locations. It should describe how samples are to be collected and prepared for submittal to an appropriate analytical laboratory for analysis. Also in the work plan, details about overhead and underground utilities must be included along with how to cut concrete or asphalt, the sample collection plan (depth, interval, quantity to initially be submitted, volume for analysis required, quality control), field monitoring and laboratory analysis.<br /> <br /> Laboratories can be either conventional or mobile.<br /> <br /> Soil sampling <br /> <br /> Soil sampling with direct push can be: single tube, dual tube, piston sampler, telescopic drill and sample or other, depending on the scope of work and subsurface conditions.<br /> <br /> Groundwater sampling<br /> <br /> Prior to installation of direct push wells, groundwater samples can be collected through a variety of DP tooling. There are several types of retractable groundwater samplers that are made for sampling groundwater where there are contaminants dissolved in the upper/ highest level of the groundwater table. There are also groundwater samplers for determining the conditions of the groundwater when a contaminant is possibly sinking within the groundwater table.<br /> <br /> If it is not possible or practical to sample through DP tooling, temporary groundwater monitoring wells can be installed. If a long-term groundwater monitoring program is needed to be started at the site, direct push wells can be installed. In addition, where it is not possible or practical to install long-term groundwater monitoring wells, temporary wells can be installed. Monitoring wells can be flush mounted if needed.<br /> <br /> Direct push groundwater monitoring wells <br /> <br /> Direct pushed wells are approved and accepted by federal and state regulatory agencies and ASTM International has several methods and procedures directly related to the use and installation of direct push wells. The sizes of direct push wells range from 0.5 to 2 inches nominal inside diameter (ID). The practical achievable depth is based on lithology and the desired well ID size. Generally, the average depth is less than 80 feet below ground surface (bgs); although it is possible to install direct push wells over 100 feet bgs depending on conditions.<br /> <br /> They can be secured exactly like conventional wells and the development of the pre-packed section can be a simple surging method. They can be used to calculate gradient magnitude and direction and there is a variety of small-diameter instrumentation that can accurately take depth measurements, measure useful parameters, and collect samples.<br /> <br /> Once a subject site has been properly characterized, a precise and strategic remedial investigation can be conducted. Depending on the contaminant type, subsurface lithology, and applicable regulatory requirements, a remedial action plan can often be drafted based on the initial site investigation alone. If a pilot study needs to be conducted to determine the radius of influence for a particular remedial action, it can also be conducted with a direct push drill rig.<br /> <br /> Once a remedial action has been completed, verification borings can be quickly and accurately conducted with a direct push rig to confirm of the success of clean up or if additional remedial activities need to be conducted to restore the site prior to requesting case closure.<br /> <br /> In general, the limitations are the inefficiency in direct push activities at depths greater than 100 feet bgs and lithology. Direct push should not be used in bedrock and other consolidated subsurface lithologic formations.<br /> <br /> This article only describes the general advantages and basic capabilities of direct push for environmental drilling. It does not describe many important details and regulatory requirements that need to be taken into account prior to beginning any field activities of environmental drilling.<br /> <br /> Thomas D. Dalzell, CWD is the director of environmental research at AMS Inc. For more information, send an email to tom@ams-samplers.com or call (208) 226-2017, ext. 113.

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