Can you tell me a bit more about how much sunlight this area receives?  

Direct sun, with a couple of tall walnut trees giving little shade. 

Planting in and around a septic field can be challenging as multiple needs and desires are often in conflict with each other. While grass is the best option followed by herbaceous plants, such as perennials, bulbs, and ornamental grasses many people want taller plants for a privacy screen or aesthetic value.  In this case, it is best to choose shrubs with less aggressive root systems; examples include boxwoods, hollies, arborvitae, and azaleas (there are some azalea varieties that get tall).  Although all of these are not as aggressive as many other trees and shrubs, it is still recommended that they be planted at least 10 feet away from drain field lines or at the very least between drain field lines. I always like to suggest that rather than planting a uniform line of one type of plant, that a mixed border including several of types of plants has some advantages. If one or more plants of a particular type gets a disease or does not do well the other species of plants are not affected. It is also easier to replace a single plant without disturbing the look of the entire border. In addition, the variety has an interesting and pleasing look.

The following links will provide you with additional information on landscaping in a septic drainfield area.

https://agriwaste.com/landscaping-your-septic-drainfield/

https://vtechworks.lib.vt.edu/bitstream/handle/10919/48282/426-617_pdf.pdf