Using verb tenses correctly

I'm trying to keep this descriptive essay in the past tense. I bolded the words of my concern (and italicized the ones I believe are in the right tense) in the following passage:

As a result of the floor containing thousands of small holes, looking down through them yielded the sight of the rushing waters of the Merrimac River. Passing by this intense stream invoked a fear of falling into the violent, rushing waters.

What my question comes down to is: Are those verbs that end in -ing considered past tense, as well as those ending in -ed? If not, how should I re-write this passage?

Solution 1:

Containing can be replaced with which contained (past tense) without any change in meaning, so that is compatible with the past tense.

Looking and Passing are gerunds, that is, they are nouns formed from verbs. Since all nouns are compatible with the past tense, so are the gerunds you used.

Also, as a result of the floor containing lots of small holes sounds unnatural. I would instead write since the floor contained lots of small holes.

Solution 2:

No, they are not. They are not tenses at all. Words in ‘-ing’ derived from verbs are called variously gerunds, present participles and verbal nouns, depending on their role in the sentence, although they are frequently described simply as ‘-ing’ forms. The two verbs in italics, on the other hand, are in the past tense, and they are enough to show that the scene is set in the past.