A good example of this would be a customer or contractor stepping into the already drained pond in the spring to do the annual cleanout. However, this person was just in the garage or shop where motor oil had been spilled recently and it is on their boots/shoes. Motor oil is very difficult to get off of surfaces as many of us know and that includes EPDM liner. This motor oil left on the EPDM liner can be not only harmful to the fish but also the EPDM liner. In some cases, it can even leave a hole in the liner if left long enough to have a severe reaction with the EPDM liner.
This is not meant to cause fear in using EPDM liner because EPDM liner is the best for pond use, but rather to raise awareness and knowledge. Pond installation and maintenance is very intricate and must be done correctly for care of the fish and beauty of the water feature. Please review this list of chemicals and their compatibility with EPDM liner and keep this in mind the next time you go to maintain or install a pond.