Site Investigation of Underground Storage Tank Contamination

Abstract

New regulations concerning the management of underground storage tanks (USTs) have resulted in increased awareness of environmental contamination resulting from leaking USTs. The objective of the typical underground storage tank investigation is to determine if any subsurface contamination has occurred as a result of tank or product line leakage, fuel spills or overfills. Soil contamination at underground storage tank sites is usually discovered during the removal and replacement of USTs. Techniques that can be used to detect the presence of soil contamination adjacent to existing USTs include soil vapor analysis, exploratory boring, and soil and ground water sampling. The lateral and vertical extent of contamination must be determined at any site which contains detectable quantities of contamination. Two common methods for determining the extent of contamination are over-excavation and borehole drilling and sampling. Boring design and location considerations include number of borings, borehole depth and spacing, and site sub -surface conditions. Differentiation between perched sub -surface water and aquifers is critical. Once an appropriate boring plan has been established, then a sampling and analysis plan must be adopted that meets the needs of the particular investigation. The determination of the extent of contamination at an underground storage tank site is the first step leading to site closure and remediation.