Here's a link to RI Department of Environmental Management.
Please let me know if I may be of any assistance.
How many bedrooms existing & are you increasing?
Soil conditions,, you cannot install a traditional ISDS,, now known as a OWTS in ground water that is within 2 ft of the surface.
How much land do you have to use for leeaching?
Some alterations can be permtted quickly, others that are more complex may require additional scurtiny at RIDEM,,
Contact Todd Chaplin PE at 508 379 1234 for additional information.
I have used his office on all my dealings with RIDEM,, Todd knows his stuff and will get it done.
Camara Excavation may also be qualified to design the new system,
Lyfort & Joel can prepare the plan & submit it to RIDEM if it's straight forward with no complex issues,, like a wel within 100 ft. Joel can be reached at 401 265 3363.
Hope this helps,
401 952 1953