Study of Maine Cathodically Protected Underground Storage Systems

January 2001
Marcel Moreau Associates, for Maine Department of Environmental Protection

pass/fail ratiby year of installtion chart

Background Purpose of This Study

View or Download Report - in pdf format

Appendix: Data Summary Report - in pdf format

BACKGROUND EXCERPT

Since 1985, all new or replacement storage systems installed in Maine have been protected against corrosion by using nonmetallic construction materials such as fiberglass or by using cathodic protection (CP) to prevent corrosion of metallic storage system components. At present, some 1,812 cathodically protected steel tanks are installed in the ground in Maine. This represents just under one third (31%) of the tank population of approximately 5,900 tanks.

DEP regulations have required annual monitoring of cathodically protected storage system components since 1985. Results of the monitoring are required to be kept for three years by the owner of the storage system. In recent years, the DEP has encouraged tank owners to send the results of this monitoring to the DEP, but there is no regulatory requirement to do so.

Because only a small percentage of cathodic protection monitoring results are voluntarily submitted to the DEP, there is little data available on how the cathodic protection systems on these storage tanks are faring. There is anecdotal evidence indicating that significant numbers of tanks are failing to meet established criteria for cathodic protection. In addition, there are rumors that some cathodic protection monitoring is not being conducted according to proper procedures. As a result, there is little reliable information concerning the corrosion protection status of Maine's cathodically protected storage system population.

PURPOSE OF THIS STUDY

The purpose of this study is to answer the following questions:

What percentage of cathodically protected storage tanks meet established criteria for cathodic protection?
How do CP test results from this study compare to CP test results from certified tank installers?
Is there a relationship between the corrosion protection status of the storage tank and the manufacturer of the tank?
Is there a relationship between the corrosion protection status of the storage tank and the capacity of the tank?
Is there a relationship between the corrosion protection status of the storage tank and the installer of the tank?
Is electrical continuity a significant factor in the failure of cathodic protection systems?
What is the compliance rate with cathodic protection monitoring record keeping requirements?

Based on the answers to these questions, the study is to evaluate:

Whether currently established testing procedures are adequate to fully evaluate the CP status of underground storage tanks;
Whether the data indicate that any specific category of tank (e.g. size, age) should be watched more carefully than the general population, and
Whether modifications to the annual cathodic protection monitoring program should be made to improve its effectiveness.