|Protecting Ground Water and Vadose Zones
ASTM International Subcommittee D18.21
Ground water is one of the most important resources on the earth. People depend on ground water for drinking as well as many other uses. In the United States, nearly half the population depends on ground water as a drinking water supply. Almost 95 percent of rural drinking water and 80 percent of the public water supply systems in the United States depend on ground water.1,2
Although the use of ground water is increasing and has doubled from 1970 to 1985, ground water resources in populated and agricultural areas have declined and are threatened by poor industrial practices. These practices have included the release of organic and inorganic compounds such as petroleum compounds, solvents, gas additives, perchlorates and heavy metals into ground water supplies.
With major environmental legislation passed in the 1970s and 1980s, environmental site characterization activities have increased dramatically. Although legislation initially focused on surface water and air quality, later actions, including the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Environmental Response and Compensation Act (CERCLA), have provided protection for ground water. These laws frequently prescribe ground water monitoring, cleanup, and protection.3
The U.S. Environmental Protection Agency estimates there are more than 30,000 hazardous waste sites in the United States. Of these, 1,200 sites are on the EPA national priority list (CERCLA). There are also many thousands of underground storage tank sites where releases have been suspected. The cost of environmental site investigation and restoration is a very large domestic expenditure. The U.S. EPA will spend in excess of $150 billion and the U.S. Departments of Defense and Energy will spend $1 trillion on sites in the next 20-30 years.
In response to the demand for standards for environmental site characterization, ASTM International Committee D18 on Soil and Rock created Subcommittee D18.21 on Ground Water and Vadose Zone Investigations. Other committees such as D19 on Water, D34 on Hazardous Waste, and E50 on Environmental Assessment, Risk Management, and Corrective Action have also developed standards on water and the environment.
HISTORY OF SUBCOMMITTEE D18.21
Subcommittee D18.21 was formed in the 1980s. While activity was slow at first, it increased dramatically in the early 1990s when Ivan Johnson (U.S. Geological Survey, honorary member of D18, and currently a 50-year member of ASTM) obtained funding from the EPA, the Department of Defense (Navy) and the U.S. Geological Survey. The subcommittee grew to almost 300 members in the mid-1990s. With the support of federal funding, this group of ground water professionals, who were concerned about proper testing standards generated about 90 standards, on the testing, sampling, and modeling of ground water and pore fluids.
Subcommittee D18.21 was developed to address the sampling, testing and monitoring of ground water and the unsaturated zone of soil or rock above the groundwater. The first order of business was to address ground water monitoring. One of the most important standards was ASTM D 5092, Practice for Design and Installation of Ground Water Monitoring Wells. Monitoring wells are almost always needed for hazardous waste, Superfund, or underground storage tank sites. Hundreds of thousands of monitoring wells have been installed since the 1970s. Table 1 shows a listing of important ground water monitoring well standards.
At the same time, activity was ongoing in Subcommittee D18.01 on Surface and Subsurface Characterization, which was developing standards on environmental site characterization and geophysics. These standards are used extensively in hazardous waste and ground water quality investigations.
Several symposia were held which concentrated on ground water sampling. The STPs generated from these D18 activities include STP 1053, Ground Water and Vadose Zone Monitoring (Editors: Nielsen/Johnson); STP 1118, Current Practices in Ground Water and Vadose Zone Investigations (Editors: Nielsen/Sara); STP 1288, Subsurface Fluid Flow (Ground-Water and Vadose Zone) Modeling (Editors: J.D. Ritchey, J.O. Rumbaugh); and STP 1415, Evaluation and Remediation of Low Permeability and Dual Porosity Environments (Editors: Sara/ Everett).
The early work of Subcommittee D18.21 was to develop guides and practices. The guides were written to provide users with the methods available and their advantages and disadvantages. A listing of key guides from the ground water and vadose zone committee are given in Table 2.
After the development of guides, practices on the specific sampling methods were developed. Practices address each of the many components of ground water sampling events to help ensure that the highest quality samples are submitted to laboratories for analysis. The quality of information obtained from the lab analyses can only be as good as the quality of the samples collected and submitted from the field. The standards are incorporated into site-specific sampling and analysis plans, and the acquisition of representative samples and the accuracy and precision of sampling efforts can be assured.
Because samples are often analyzed at the parts-per-million or parts-per-billion level, even minor errors in sample collection and handling procedures can introduce either positive or negative bias in ground-water sample chemistry. Simple things, like poor housekeeping practices during sampling events, can result in the introduction of surface contaminants into monitoring wells and into samples, which can result in the detection of artificially high contaminant levels in samples (positive bias). Positive bias can make it appear that ground water quality is worse than it actually is and may result in the expenditure of significant financial resources to clean up a site that may not be contaminated. Negative bias, which may be caused by something as simple as improper placement or operation of a sampling device, may result in either the failure to detect contaminants entirely or in the detection of contaminants at concentrations well below actual concentrations. This can make it appear that the water is safe for consumption when, in fact, it may not be.
The guides and practices produced by D18.21 help ground water sampling field personnel avoid introducing error and bias into the ground water sampling process. To assist samplers in maximizing efficiency while in the field, and to get a sampling event started on the right track, the procedures outlined in
D 5903, Guide for Planning and Preparing for a Ground Water Sampling Event, should be followed. This guide provides samplers with organizational checklists to help make it easier to get all of the necessary sampling and support equipment ready for the trip to the field. By following this guide, samplers avoid delays in the field that can easily result from not having all of the required field gear, field quality control samples, or sufficient or correct sample containers for the parameters being sampled.
Subcommittee D18.21 also interacts with the other ASTM committees involved with the environment. For ground water sampling, the interaction and involvement of Committee D19 is critical.
STRUCTURE OF SUBCOMMITTEE D18.21
Subcommittee D18.21 is currently structured in the following sections:
• D18.21.01, Direct Push Technology This section develops new standards for subsurface investigations using new technologies. As opposed to large drilling rigs to penetrate the ground, new smaller, less intrusive, equipment is being developed. Special sensors have been developed to screen the subsurface for contamination.
• D18.21.02, Vadose Zone The vadose zone is the unsaturated zone above the ground water. At many sites ground water is very deep and the transport of contaminants through the unsaturated zone requires monitoring. Soil gas sampling above the water table became a good screening tool for UST sites. Vapor sampling is still critical today and new standards are being developed to evaluate human exposure to vapors.
• D18.21.03, Monitoring Well Construction, Drilling, and Sampling This section developed the key well construction standard D 5092 as well as guides for drilling wells and drilling and sampling of soils for testing of hazardous materials.
• D 18.21.04, Ground Water Sample Collection and Handling This section addresses the important procedures for collecting and assuring that ground water samples are tested correctly. Guidance is given on sampling, such as the new no flow sampling, and proper handling of groundwater samples. Purging and sampling devices are discussed along with proper quality assurance checks and sample preservation and treatment are presented. The ground water samples are then sent for chemical analysis, where Committee D19 performs testing of the samples.
• D18.21.05, Hydrologic Properties, Modeling, and Data Analysis This section has generated 22 standards on how to evaluate aquifer properties using field tests. These standards allow for the accurate determination of fluid flow in aquifers. More than 12 standards have been written on how to perform ground water modeling studies using the latest computer programs. Standards have been developed to alert users of important data elements to collect during sampling. The section also addresses unusual situations, such as monitoring in difficult limestone karstic geologic settings
• D18.21.06 Design of Ground Water Monitoring NetworksThe section addresses the challenges of designing groundwater monitoring networks to effectively detect a release from a known or permittedsource area. These standards address design of sampling programs based upon source characteristics or constituent migration potential as well as design of well systems and data analysis methods that provide consistent data sets for inter-well or intra-well data comparisons. The section continuously considers the environmental protection aspect of groundwater monitoring programs while seeking to minimize the financial impact of implementing a program that meets all regulatory requirements.
• D18.21.07 Ground Water Remediation This newly formed section is addressing methods for cleaning contaminated ground water. One of the first standards being developed is evaluation of Soil Oxidant Demand when treated with Permanganates.
ACCEPTANCE OF ASTM STANDARDS IN PRACTICE
When the earliest environmental legislation was being enacted, many old geotechnical or geo-hydrological testing methods were grandfathered as investigation methods in early guidance documents. As new methods were developed, they have been slow to be recognized. For example, many existing monitoring wells are sampled using the old three-well volume purge, and bailer sampling techniques, while new technology requires low flow samplings and dedicated sampling pumps.
While the EPA provides guidance on proper ground water contamination sampling, the individual states have control over testing methods. In accordance with U.S. Office of Management and Budget guidelines, the EPA has begun to incorporate ASTM standards into their guidance documents. The states have been slower to respond, however the Interstate Technology and Regulatory Council has been created to act as a clearinghouse to advise the states on acceptable new technologies.
There are currently around 150 members in Subcommittee D18.21. Qualified professionals are always welcome to join Subcommittee D18.21 in its standards developing activities. //
1 Nielsen, Gillian L. and David M. Nielsen, 2003, "How Safe is Your Drinking Water Supply," Standardization News, American Society for Testing and Materials, West Conshohcken, PA, May.
2 U S EPA, 1997, Water on Tap: A Consumers Guide to the Nations Drinking Water, Office of Water (4601), EPA Publication.
3 Practical Handbook of Environmental Site Characterization and ground Water Monitoring, Editor, David M. Nielsen, Second Edition, Taylor and Francis Group, Boca Raton FL, 2006. #815-K-97-0002, Washington DC, 22 pp.