FPS Concerned at continuing above-inflation duty rises on red diesel

Case Study Highlighting the Perils of Inadequate Wetstock Control

By Steve Jones, Fairbanks Environmental Ltd

The case study highlights the experiences of one site operator whose site closed following the catastrophic failure of one of the tanks on site. The site operator has given his permission to publish this article in the hope that others will learn from his experience and ensure they have systems in place that will give early warning of tank leaks and prevent them from going undetected for a long period.

The site operator was making use of his POS sales data, tank gauge stock levels and back office PC to record wetstock reconciliation data. He was not using any 3rd party SIR system. A review of this wetstock data was conducted in order to determine if the losses could have been detected prior to the catastrophic tank failure.

In order to protect the identity of the site the following changes have been made to this report:

The site name has been replaced with the name 'Leaking Garage Ltd.'

The oil company name has been replaced with 'Oil Company'

The Supply Terminal name has been replaced with 'Supply Terminal'

Some dates have been changed

Introduction

Leaking Garage experienced a sudden wetstock loss following a delivery on the 30th October 2004. There were reports of high levels of vapour in a disused well some 60 meters off site.

The purpose of this report is to identify the effectiveness of the wetstock reconciliation procedure in place at Leaking Garages.

Site Details • The site is unusual in so far as the tank farm is located behind a retaining wall, with the tanks being at a higher level than the forecourt.

• The tanks were installed between 1959 and 1963.

• The forecourt is supplied by means of a pressure system; with each tank having a submersible pump within the tank top man chamber. • There is a series of shut-off valves that could allow individual tanks or pumps to be isolated should the need arise.

• Oil Company supplies the site from its

Supply Terminal, with the tanks being fed from a below ground offset fill.

• The site has an above ground, highlevel manifolded, vapour recovery system, with a vapour-balancing valve.

• The tank contents are measured by means of a hydrostatic gauge with analogue read-out.

Findings • Following the identification of the problem a spreadsheet showing the daily wetstock reconciliation data for the period 01/04/03 to 06/11/04 was sent for analysis. - The fact that this data was so readily available indicates that the information was being collected and recorded in an appropriate manner, rather than having to be reconstructed from disparate manual records. reconciliation process was completed at grade level, rather than at tank level. - This is not unusual for a site with a pressure system, where the dispenser units are fed from all tanks. When using this method of reconciliation, if a problem with a particular grade is identified then individual tanks or pumps could be isolated by means of the shut-off valves, in order to identify the likely cause of the problem.

• Due to the sudden and dramatic levels of loss experienced from Tank 1, following a tank overfill, this course of action was not appropriate. As soon as the problem was identified Tank 1 was isolated, with the product being transferred to the other tanks.

• Atank test was arranged, and the tank was found to be unable to hold pressure. • Aphysical investigation of the area around Tank 1 was performed, by breaking out the concrete and inserting a sampler into the sand back-fill.

• There was no evidence of product detected by this method. • Asite audit was performed in order to assist with the quantification of wetstock loss. All meters were within trading standards guidelines, but all were found to be under dispensing. - When taken into account the meter settings have the effect of increasing the actual losses experienced.

• Following the audit, and the results of the both the pressure test on Tank 1