Tank Leak Detection Alaska Spring 2004
Leak Detection • Orientation • Basics • Automatic Tank Gauging • Interstitial Monitoring • Inventory Control/TTT • SIR • Other methods
Orientation • What do you have or use? • What does your leak detection system do? • Volumetric test • Inventory • Statistical • Presence/absence of something • Can you prove it is working properly? • Do you check your results periodically?
Basics • Must check for evidence of leaks every 30 days • Checking/testing equipment must be maintained • Equipment/method must be 3rd party evaluated and on the List of Leak Detection Evaluations for Storage Tank Systems by the National Work Group on Leak Detection Evaluations (NWGLDE) www.nwglde.org • Must keep records of leak tests • 2 months of Inconclusive/Invalid readings is a suspected release
Automatic Tank Gauge • Most common method in Alaska • Can run test when you want • Daily, weekly, monthly, continuously • Device must be 3rd party evaluated and on NWGLDE list. • Console and probes must be checked • Keep a copy of all printouts
ATG Common problems • Not enough fuel in tank during test • Test interrupted (fuel dispensed/delivered) • Test gets disabled • Paper/ink out • Probes go bad • Too much throughput, not enough quiet time • Older models had limits
Interstitial Monitoring • Double wall tanks • Interstice is space between inner and outer wall • Check the space electronically (sensor and console) or manually (stick and chart) • Electronic sensors must be on the NWGLDE list • Must check every 30 days • Must record results MONTHLY- examples Veeder-Root “Sensor Status Report”; EBW “Contact Report”; Incon “Line Compliance Report” or hand written log if display only (no printer)
Inventory Control & TTT • Stick tank every operational day • Reconcile daily • Track deliveries • Reconcile monthly • Calculate “leak” rate • Have a tank tightness test every 5 years. • State certified tester with current vendor certification • Test method on the NWGLDE list
Statistical Inventory Reconciliation • Take monthly inventory and have it analyzed by statistical company • A more sophisticated inventory control program • Gives you pass, fail or inconclusive • Statistical company method must be on the NWGLDE list
Bottom line An operator must be able prove every 30 days his or her tank (and piping) is not leaking more than 0.2 gallons per hour (slightly less than one quart) of product.