Past vs Past Perfect

While writing a paper for my English class, I couldn't decided whether past or past perfect tense was needed. It's basically about how a guy whose house is destroyed because the government wants to build a freeway over it:

Walking towards where my house was built, I see that only my mailbox had survived the wreckage, while I try to salvage all I could. Looking through my mail, I see a letter from the government telling me kindly that they are going to build a freeway where my house had once stood. Attached is a sum of money reimbursing my devastating loss, but it could not account for the number of generations who had once lived there.

Basically, I can't decide if there following are correct. It's supposed to be in present tense. (The guy is currently standing at the wreckage.)

1) "had survived"

2) try to salvage all I "could"

3) where my house "had once stood"

4) but it "could" not account

5) number of generations who "had once lived" there

Please provide some sort of explanation. Thanks!

You say that you want to cast your narrative in the present tense.

Consequently, these actions and perceptions —your guy's— occur in the “narrative present”, and so should be in the present tense:

I see ... I try ... I can ... I see ... they are going to build* [because you are reading this in the narrative present] ... it can

This, since it started in the past but continues into the narrative present, could be in either the present or present perfect:

house survives or has survived ...

The rest are events or states which occurred before the narrative present and therefore should be in simple past:

house was built ... house stood ... generations lived

Put them together:

Walking towards where my house was built, I see that only my mailbox has survived the wreckage, while I try to salvage all I can. Looking through my mail, I see a letter from the government telling me kindly that they are going to build a freeway where my house once stood. Attached is a sum of money reimbursing my devastating loss, but it cannot account for the number of generations who once lived there.

You use past perfect only if you are locating an action at some time before a specific event in the past—for instance, if you cast your narrative in the past, the pasts in the last version would become past perfects:

Walking towards where my house had been built, I saw that only my mailbox had survived the wreckage, while I tried to salvage all I could. Looking through my mail, I saw a letter from the government telling me kindly that they were going to build a freeway where my house had^† once stood. Attached was a sum of money reimbursing my devastating loss, but it could not account for the number of generations who had^† once lived there.

*Yes, I know this is called future tense — but it's formed here with a present-tense auxiliary. I would call the auxiliary's tense non-past and the construction a future mode, but I'm eccentric.
^†Actually, nobody will object if you cast these in the simple past, since the adverb once effectively locates the standing before the narrative past.