Issue Date: March 10, 2000
Revision Date: April 17, 2002

Linde Services Inc.
(originally listed as Tracer Research Corp.)

Tracer ALD 2000 Automated Tank Tightness Test

BULK UNDERGROUND STORAGE TANK LEAK DETECTION METHOD (50,000 gallons or greater)

Certification	Leak rate of 0.1 gph with PD = 100% and PFA = 0%.
Leak Threshold	A tank system should not be declared tight when tracer chemical or hydrocarbon greater than the background level is detected outside of the tank system.
Applicability	Gasoline, diesel, aviation fuel, fuel oil #4, waste oil.
Tank Capacity	Not limited by capacity.
Waiting Time	Ranges from 7 to 30 days (normally 2 weeks) after tracer is added to tank.
Tracer Dosage	Tracer is added to tank manually at tank fill or automatically using a metered injection pump at pipeline flowing into tank.  Manual dosage of tracer is based on tank size, product volume in tank, and frequency and volume of tank refills according to manufacturer's recommendations.  Automated dosage at pipeline flowing into tank is based on pipeline size and flow rate.  All tanks and piping downstream of the injection point are dosed with tracer compound.
Permeability	Soil permeability must readily allow tracer movement through the tank excavation backfill (greater than 1 Darcy).
Probe	Radius of influence of each tracer sampling probe is maximum 10 feet.  All tank surfaces must be within the zone of influence of a sampling probe.  Probes must be installed per Manufacturer's guidelines.
Groundwater	Depth to groundwater in tank excavation backfill must be determined.  For test method to detect a release of tracer chemical below groundwater, the hydrostatic pressure of product in the tank must exceed the hydrostatic pressure of groundwater during test.  To accomplish this, product level must be maintained at least 6 inches above groundwater for a minimum of 17 hours during the first three days following addition of tracer to the tank.  At the discretion of the regulatory agency, water ingress measuring devices may be used to supplement test method in high groundwater conditions.
Comments	The presence of a layer of water saturated soil, that is also frozen, above the location where a leak may exist, may inhibit the effectiveness of the method by impeding the transport of the tracer labeled product into the unsaturated zone. Groundwater above bottom of tank may limit effectiveness of test method (e.g. when applied to tanks containing water-miscible products or products whose specific gravity is greater than 1).  Test method may not be effective in some tank excavation backfill (such as clay) because it may plug holes in tank and retard tracer movement through the soil.  Third party evaluation of the ALD 2000 System tested the device's ability to collect a sample, transport sample through 2700 feet of 3/32 inch tubing, and analyze sample.  Sample collection, analysis, data storage, and alarm activation is controlled by system's computer.  Prior evaluations tested PD, PFA, leak threshold, dose, tracer movement through soil, and waiting times.

Linde Services Inc.	Evaluator: Ken Wilcox Associates
3755 N. Business Center Dr.	Tel: (816) 443-2494
Tucson, AZ  85705	Dates of Evaluation: 10/04/90, 06/19/99
Tel: (800) 394-9929	Evaluator: Control Strategies Engineering (out of business)
URL: www.praxairservices.com	Tel: Contact Praxair Services, Inc.
	Date of Evaluation: 05/92