In English, verbs usually follow subjects. When this order is reversed, make the verb agree with the subject, not with a noun that happens to precede it.

The subject is silos; it is plural, so the verb must be stand.

In sentences beginning with there is, there are, there was, or there were, the word there serves only as a placeholder; the subject follows the verb.

The subject, positions, is plural, so the verb must also be plural.