Conducting Subsurface Environmental Investigations in Urban Watersheds - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 134

4.2.6 Feasibility Study
A feasibility study is conducted after the nature and extent of contamination have been
defined. The timing of this study corresponds with the risk assessment if contamination is
present at sufficient levels to justify the possibility of remedial action. Selecting the most
appropriate remedial technology or technologies—if more than one is necessary—is a key
objective of the feasibility study. Technology selection can be evaluated within this frame-
work: (1) the nature and extent of contamination at a specific site; (2) the future intended
land use or uses; (3) the results of the risk assessment; and (4) other sites conditions, if
present (USEPA 1988; New York State Department of Environmental Conservation 2009).
A feasibility study evaluates many different methods and technologies to reduce con-
taminant risk. Some cases may not involve a specific technology, but include alternatives
such as institutional controls and deed restrictions. The purposes of institutional controls
are to restrict or prevent access to areas posing exposure risk, or to reduce the risk of acci-
dentally spreading any of the remaining onsite contamination. Examples of institutional
controls include
• Vapor barriers
• Pavement
• Maintaining building structures
• Drainage control
• Access restrictions
• Fencing
• Constructing other physical barriers
Common examples of deed restrictions include special handling of materials if they are
disturbed and restricting the use of surface water or groundwater.
As part of a feasibility study, a bench scale and/or pilot level test is conducted using a
particular remedial technology to evaluate its effectiveness as applied to real site condi-
tions, contaminants, and on-site geologic and hydrogeologic conditions. A bench scale test
involves collecting samples of contaminated material from a site and conducting tests in
the laboratory under controlled conditions. The samples are then used to assess the effi-
cacy of the particular technology, and if successful, additional engineering and design
data for the pilot test are collected.
A pilot test is larger in scale than a bench scale test and is conducted in situ (at the site
of the contamination). Results from the pilot test are used for final engineering design,
dosing (if used), and evaluating the time required to complete remediation. Information
obtained from the bench scale and pilot tests assist in selecting and designing a remedial
technology.
4.2.7 Remedial Investigation
Remedial investigations represent the range of actions taken at a site of environmental
concern, and typically represent a combination of the Phase I ESA, Phase II Investigation,
Risk Assessment, and Feasibility Assessment outcomes. Remedial investigations generate
large amounts of geological and hydrogeological information about the area, and often the
region being investigated, but often require two or more years to complete and may cost
several million dollars. These time and cost factors dictate that these investigations are