Federal and state/provincial  laws require underground storage tank (UST) systems to have leak detection. One of the available leak detection methods is Statistical Inventory Reconciliation (SIR). SIR has the advantages of being inexpensive and being able to detect leaks as well as fuel management issues and other forms of product loss (e.g., meter calibration problems, delivery errors, evaporation and theft). With SIR, a trained professional uses sophisticated computer software to conduct a statistical analysis of inventory, delivery and dispensing data.

Clearstone Engineering Ltd.'s SIR  software is designed to efficiently process fuel inventory data for many sites at a central location in a very sensitive and accurate manner.

Two types of analyses are performed:

Daily checks for sudden statistically-significant loss trends, and

Monthly analyses for less pronounced loss trends.

The first test is designed to detect larger loss trends as soon as possible (e.g., within a few days of initiation). The latter type of analysis is designed to detect smaller loss trends (especially leaks) that might otherwise go unnoticed. In both cases, the objective is to identify real loss trends, quantify the loss rate, and diagnose the probable cause or causes.

As part of the analysis report, each tank system receives a tightness rating, namely:

Pass - no statistically significant loss trend is detected.

Monitor - the minimum detectable loss rate is greater than the regulatory limit of 18.2 L/d and no statistically-significant loss trend is detected.

Investigate - a statistically significant loss rate is detected.

In the last case a quantitative estimate for the loss rate is provided.

The specific types of errors that may be detected and quantified for a given tank system are as follows:

Dipping Errors (i.e., worn dip sticks or incorrect striker-plate height).
Dip-Chart Errors (e.g., wrong tank type, tilt, rotation, or dimensional errors in the diameter, length, or dip port position).
Delivery Errors.
Pump Calibration Errors.
Unexplained Losses or Gains.
Incorrect Inventory Adjustments.
Data Entry Errors.
Temperature Effects.
Evaporation Losses.
Leakage.

Clearstone's SIR system has a leak detection performance capability of 0.10 US gallons per  hour with 95 percent confidence and less than 5 percent probability of a false alarm. Use of this service minimizes the risk of costly site remediation by providing reliable and affordable leak detection on an ongoing basis. Furthermore, it identifies other potentially costly operational problems.