Amla has a fat taproot, so as long as you preserve that im sure the plants will be healthy. Its pretty hardy for poor growing conditions.
When you say sewer line, is it a city sewer line or a septic field line? if city, is it a larger sewer line or the one connected to your home? The city line materials, especially modern ones, are generally sturdy enough that most plants wont be an issue. Depending on the material of the line (if known) and soil conditions, citrus planted nearby may be fine, perhaps consider a cherry as they are shallow-rooted.
If youre talking septic, based on my own experience and understanding from working in that field, dont plant near it or on it. In addition to many potential health risks, the costs to repair/replace septic systems is bonkers.
Finally, my personal suggestion for something with shallow roots in your zone would be either Yauopon holly (Ilex vomitoria), beautiful plant with leaves that can be prepared for a great tea, or Southern Bayberry (Myrica cerifera), in addition to smelling good, would be awesome to graft some Yangmei in the next few years as scions become more readily available.
It's a city one. I thought the sewer lines were deeper, but apparently my friend who planted the Citrus hit it, so it's a shallow one. What soil conditions do you need to know? We have clay here. Do you know what materials I should ask about? I can probably call my local MUD that info.
Thanks for the suggestions. I'm considering papaya (last year store fruit was terrible, so I need to plant some) too. There are definitely options, but I would need to shift my plans around and prefer to not need to. The Citrus would be kept small, so I can cover it during winter, so I'm debating trying it anyhow.