Risk of Underground Storage Tank Petroleum and Hazardous Chemical Release After the Implementation of the 1988 and 2015 Federal UST Technical Requirements

Abstract

Underground Storage Tanks (USTs) are commonly used to store regulated petroleum and hazardous chemicals, but they also may pose a substantial threat to the environment. A UST release, which occurs when the contents of a UST spill or leak into the environment, is one of the greatest threats that a UST system poses. Therefore, in response to the environmental and human health risks from USTs, the U.S. EPA introduced UST technical requirements in 1988 and 2015 that regulate how UST systems are constructed, operated, and maintained. However, there is little information on the effectiveness of these requirements in reducing the risk of release. To calculated risk of release for the USTs regulated under the 1988 and 2015 regulations, I used the UST performance measures reports that contains release and active UST data For my analysis, risk of release is defined as number of releases per active UST. To estimate the effect of the UST technical guidelines on the risk of release, I used the Mann-Whitney U statistical test to compare the retrospective risk of release between the UST facilities regulated under the 1988 and 2015 technical standards. Results indicate that the risk of release for the USTs regulated under the 1988 regulations was significantly greater than the risk of release for the USTs under the 2015 requirements (P < 0.01). The average risk of release per regulated UST was 0.010 for the USTs regulated under the 1988 technical standards, and 0.005 releases/tank for the USTs regulated under the 2015 technical standards. The median risk of release per UST was 0.007 for the 1988 regulated USTs and 0.005 for the 2015 regulated USTs. The relative risk of release per UST for the 1988 regulated USTs in comparison to the 2015 regulated tanks was 2.0 using average risk and 1.4 using median risk. Furthermore, I used the Kruskal Willis Rank-Sum statistical test to compare the UST risk of release between the 10 EPA regions and found that the risk of release between the regions was different (P < 0.01). Some factors that may have influenced the risk of release in this analysis include UST equipment age, release prevention methods, release detection methods, operator training, UST maintenance requirements, and UST facility compliance rates. Further studies on the efficacy of the approved release detection and release prevention methods in reducing releases can help determine which regulatory requirements had a significant role in risk reduction. Additionally, an investigation into the state-managed UST programs in regions with greater risk of release can help determine why the risk of release between EPA regions varies. Tracking and analyzing the risk of UST release, and determining what factors influence this risk, can provide useful data for the regulatory efforts of the EPA and local regulatory agencies.