SUBSURFACE OIL DETECTION AND DELINEATION IN SHORELINE SEDIMENTS

Abstract

An American Petroleum Institute (API) Oil Spill Research and Development (R&D) Project was designed to evaluate current practice and prospective developing technologies for the detection and delineation of subsurface oil in shoreline sediments. One product of the study has been the production of a Field Guide to support planners and responders during a spill response in which subsurface oil is known or suspected in beaches (API Technical Report 1149-2, September 2013). This job aid includes a step-wise process for the development of a subsurface oil survey design and a survey plan. Generally accepted technology for emergency response level detection and delineation of subsurface oil on shorelines has advanced only slowly in the last 40 years. Current practices typically consist of visual observations using excavations, various coring techniques, water jetting, and use of UV lights. Other tactics have been tested, but most did not increase the speed or quality of data collection. These procedures are labor intensive and time consuming, particularly when large areas are involved or repetitive surveys are necessary. In addition, typically, current practices rely on small horizontal samples, which may not be adequate to detect or define subsurface oil if the distribution is discontinuous. The key attributes of the basic current and developing technology strategies are horizontal delineation, vertical delineation, survey speed, the description of oil characteristics, and relative costs. Analysis of these attributes strongly suggests that no single currently accepted technique is likely to be applicable to all situations that may be encountered and that a combination of current practice and developing technology may be effective in providing better subsurface resolution at a quicker rate and with a more efficient commitment of resources. Developing technologies have a real potential to provide procedures that can either accelerate the collection of subsurface data or allow for continuous horizontal detection and delineation. Some of the developing technologies, in particular, service dogs, electromagnetic, and surface vapor measurements, show significant potential for achieving operational status with minimal additional testing and trials and so represent a realistic potential for short-term (months to years), high value gains.