Articles
Case Study Highlighting the Perils of Inadequate Wetstock Control By Steve Jones, Fairbanks Environmental Ltd the
• The site is unusual in so far as the
reconciliation process was completed
experiences of one site operator whose
tank farm is located behind a
at grade level, rather than at tank
site closed following the catastrophic
retaining wall, with the tanks being at
level.
failure of one of the tanks on site. The
a higher level than the forecourt.
- This is not unusual for a site with a
The
case
study
highlights
pressure
site operator has given his permission to publish this article in the hope that others will learn from his experience
• The tanks were installed between 1959 and 1963.
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
where
the
dispenser units are fed from all tanks. When using this method of reconciliation, if a problem with a
and ensure they have systems in place that will give early warning of tank leaks
system,
• The forecourt is supplied by means of
particular grade is identified then
a pressure system; with each tank
individual tanks or pumps could be
having a submersible pump within
isolated by means of the shut-off
the tank top man chamber.
valves, in order to identify the
• There is a series of shut-off valves
likely cause of the problem.
that could allow individual tanks or pumps to be isolated should the need arise.
• Due to the sudden and dramatic levels of loss experienced from Tank 1, following a tank overfill, this course
• Oil Company supplies the site from its
of action was not appropriate. As
Supply Terminal, with the tanks being
soon as the problem was identified
fed from a below ground offset fill.
Tank 1 was isolated, with the product
to the catastrophic tank failure.
being transferred to the other tanks.
In order to protect the identity of the
• The site has an above ground, high-
site the following changes have been
level manifolded, vapour recovery
• A tank test was arranged, and the
made to this report:
system, with a vapour-balancing
tank was found to be unable to hold
valve.
pressure.
The site name has been replaced with the name 'Leaking Garage Ltd.'
• A physical investigation of the area
The oil company name has been replaced with 'Oil Company' The Supply Terminal name has been
• The tank contents are measured by
around Tank 1 was performed, by
means of a hydrostatic gauge with
breaking
analogue read-out.
inserting a sampler into the sand
replaced with 'Supply Terminal'
out
the
concrete
and
back-fill.
Some dates have been changed
Findings • Following the identification of the problem a spreadsheet showing the
• There was no evidence of product detected by this method.
daily wetstock reconciliation data for
• A site audit was performed in order to
the period 01/04/03 to 06/11/04 was
assist with the quantification of
sudden wetstock loss following a
sent for analysis.
wetstock loss. All meters were within
delivery on the 30th October 2004.
- The fact that this data was so
trading standards guidelines, but all
There were reports of high levels of
readily available indicates that the
were found to be under dispensing.
vapour in a disused well some 60
information was being collected
- When taken into account the
meters off site.
and recorded in an appropriate
meter settings have the effect of
manner, rather than having to be
increasing
reconstructed
experienced.
Introduction Leaking
Garage
experienced
a
The purpose of this report is to identify
the
effectiveness
of
the
from
disparate
actual
losses
manual records. • Following the audit, and the results of
wetstock reconciliation procedure in place at Leaking Garages.
the
• The
data
showed
that
the
the both the pressure test on Tank 1
Site Details 43
