Print this page Print this page

Environmental Investigation and Remediation of a Hazardous Waste Site

Part 5 - Results and Implications of Phase 2 Investigations

Samir G. Khoury, Ph.D., P.G.


Course Outline

This course, Part 5: Results and Implications of Phase 2 Investigations, briefly reviews the key points of the previous courses in the sequence (Parts 1 through 4), and presents the results of the Phase 2 investigations. This phase of work started with the preparation of an accurate topographic base map of the waste disposal site and its vicinity on which all data collected in the field were plotted for analysis and interpretation. Three additional monitoring wells were installed around the waste disposal site to collect geologic, hydrologic and chemical data. Permeability measurements were performed in these wells and groundwater samples from most of the wells were analyzed to detect any contaminants that may be present.

A down gradient groundwater investigation was initiated with the installation of two monitoring wells at the base of the slope west of the waste disposal site. One of the wells was screened in the soil that overlies the bedrock, while the other was screened in the bedrock. Contaminants were detected in the well with its screen in the soil above the bedrock, while no contamination was detected in the well with its screen in the bedrock. The investigation was then extended into the floodplain of the Creek.

The floodplain was investigated by the Hydropunch™ technique. This technique provided a fast and relatively inexpensive method to collect a large amount of information to determine the presence or absence of groundwater contaminants within the floodplain. The distribution of contaminants was determined up to the edge of the Creek, located down gradient and to the west of the waste disposal site. Three surface water samples from the Creek were also collected and analyzed.

An evaluation of the results led to the recommendation to perform an environmental and public health assessment (Risk Assessment), the preparation of a conceptual engineering study to evaluate appropriate options for the control of the contamination (Feasibility Study), and the implementation of the corrective action plan (Engineered Remediation).

This course includes a multiple choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the end of Part 5, the student should be able to understand how and why the initial field investigation conducted around the waste disposal site during Phase 1 (Part 4) was extended in both the up-gradient and down-gradient directions. The student should also be able to follow how:

More specifically the student should be able to follow and understand how the following Phase 2 investigations were conducted:

 The student should be able to follow how the collected data were:

The student should also recognize the tradeoffs made between the desire for the collection of more data and the budgetary constraints imposed by the nature of the project. The continuing role of the regulatory agencies in the process is also followed throughout this phase of work.

Intended Audience

This series of courses is intended for environmental engineers, environmental scientists, geotechnical engineers, civil engineers, engineering geologists, environmental geologists, hydrologists and other individuals who are interested to learn how environmental investigations are conducted.

Benefit to Attendees

Students who take this series of courses will learn how environmental problems are investigated; feasibility studies conducted and engineered remediation implemented. These steps are taken to prevent the spread and migration of contaminants to the accessible environment, thus protecting the health and safety of the population and stopping the otherwise inevitable and continual degradation of the environment.

Course Introduction

A research institute (“Institute”) operated a small (0.65 acre) hazardous chemical and radioactive waste burial facility on its campus for about 20 years, starting in the 1960s. All waste buried at the site resulted from the use of radioactive elements and chemicals in research experiments. Waste brought to the disposal site was in both solid and liquid form, and the liquids were in various types and sizes of containers. The waste was placed into narrow trenches dug into the soil at the burial site. The trenches were about 8 to 12 feet deep. Once waste reached about 4 feet from the surface, dirt was used to fill the trench.

When the site was decommissioned and no longer used, it was fenced, posted and locked. Minimal grounds maintenance was done until the State Radiation Protection Agency (State RPA) notified the Institute that they were to keep the fence clear of vegetation and the area within the fence mowed and free of trees. The following photo shows the waste disposal area after the site was decommissioned and the grounds maintenance started.

Fig 1

Figure 1: Decommissioned waste disposal site at the Institute

Yearly testing of soil, surface water and vegetation by the State RPA, following decommissioning of the site, showed no evidence of significant radioactive contamination outside the burial area. In the late 1980s the State RPA recommended that the Institute install a series of monitoring wells to allow sampling and testing of the groundwater. In response, and under the guidance of the State Groundwater Protection Agency (State GPA), the Institute installed five monitoring wells around the waste disposal site. The location of the five wells is shown on the following figure.

Fig 2

Figure 2: Location of Initial Monitoring Wells Surrounding the Waste Disposal Site

About a month after installation, the State RPA collected groundwater samples from the five monitoring wells for radiological analysis. A year later, an additional groundwater sample was collected from Well No.3 for radiological and organic chemical analysis. The radiological analyses indicated that some of the groundwater samples in the immediate surroundings of the restricted area had elevated Tritium activities. It also appeared that organic chemical contamination might be present in the groundwater in the vicinity of the waste disposal area. Discovery of both chemical and radiological contamination outside the burial area fence prompted the State RPA to require the Institute to design and implement an extensive investigation program. The Institute issued an RFP to environmental and engineering firms to retain the services of a technical services consultant (Consultant). The winning bidder reviewed existing information and developed an estimate of the inventory of the waste disposed of at the site and evaluated existing soil, vegetation, groundwater and surface water test results. The Consultant issued a Preliminary Site Condition Report summarizing the results of these initial studies. The State RPA and other State Regulatory Agencies then requested a characterization of the geology and hydrology of the area and the collection of additional soil, groundwater and surface water samples for analysis, including the installation of additional groundwater monitoring wells, in order to determine the size, extent, and characteristics of the contaminant plume.

Because the waste disposal site contained both hazardous chemicals and radioactive isotopes, no additional field investigations could be started until a project-specific Health and Safety Plan was developed. A project-specific Quality Assurance Plan was also created, and the technical requirements were developed as part of the Sampling and Testing Plan. A set of Project Procedures was written to guide the field sampling and analysis programs that incorporated the requirements of each of the project plans. The relationship of the various plans, procedures and the field and laboratory activities is shown on the following flowchart.

Fig 3

Figure 3: Relationship of the Various Project Plans, Procedures and Field and Laboratory Activities

Part 4 of this course series reviewed the results of the Phase 1 investigations. This work included field and laboratory testing, data analyses, interpretations, and recommendations for the design of the Phase 2 work. Part 4 also reviewed the concerns and comments expressed by the various state regulatory agencies and the press coverage of the Phase 1 Report. The Phase 1 work provided additional insights with respect to:

One of the recommendations of Phase 1 was to initiate the Phase 2 field investigation program, including the performance of additional work in both the up-gradient and down-gradient directions. This approach was taken to verify the extent and configuration of the area considered up gradient, and therefore free of contamination, and to determine the extent and nature of the down gradient contamination.

The Phase 2 field investigations consisted of performing the following activities at the Site:

The Phase 2 data were evaluated, integrated with the existing information and interpreted to arrive at the recommendation to perform an environmental and public health assessment and prepare a conceptual engineering study to evaluate appropriate options to control the contamination.

Course Content

The course content is in the following PDF file:

Environmental Investigation and Remediation of a Hazardous Waste Site: Part 5 - Results and Implications of Phase 2 Investigations

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

Course Summary

This course presented the results of the Phase 2 Field Investigations, which started with the preparation of an accurate topographic map of the Site and its vicinity. Three borings were drilled around the perimeter of the waste disposal area to provide subsurface geologic information. Monitoring wells were then installed in these borings to provide hydrologic data; and groundwater samples were taken for radiological and chemical analysis.

Investigations in the floodplain west of the waste disposal site included installation of two clustered wells at the eastern edge of the floodplain and driving 10 HydropunchTM boreholes at selected locations within the floodplain for groundwater level measurements and the collection of groundwater samples for analysis. Surface water samples from the Creek were also tested for contamination.

The results of this work were published in the Phase 2 Investigation Report and reviewed by the Institute, their legal consultants and the State Regulatory Agencies. Comments were received and addressed by the Consultant.

The Phase 2 Investigation Report and all the previous work formed the basis for the recommendation to perform a health risk assessment, evaluation of engineering options for remediation of the site and the implementation of a corrective action plan. These topics are addressed in Part 6 of this course series titled: Risk Assessment, Feasibility Study and Engineered Remediation.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

Take a Quiz

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.