Sewer Replacement - Help!

[Nicholas Q.]

I recently bought my first investment property, a duplex in Bremerton, WA.  When under contract, I had the sewer scoped and the company said there were some rocks in the line and worst case I would need to water jet the line to clean it out.  Shortly after purchase, the tenant called and said the sewer was backed up.  The plumber water jetted the line to get it flowing again, but when he scoped it, he said the water jetting is making the line worse because it is pulling rock and sediment into line at a break at some unknown location.

I have had several contractors look at the video and all said there is no way to clean the line for a trenchless repair and it will need to be replaced.  However, the sewer is 12 feet deep, runs underneath a set of concrete stairs and then 25 feet into a main city arterial.  No contract will even touch it because it is such a complex job due to the busy street.  They said even if they were to do it, it could cost $50-60K!!

I did happen to sign up for water backup insurance.  My insurance company said they "might" cover just the excavation portion of the job, but they require at least 3 quotes from different contracts first.  I can't even get one quote from a contractor for the full job.  One contractor wants to charge $10K just to dig up a 4 foot section for "exploratory purposes" before he can quote the full job.

I've spent 3 months researching and trying to find a path forward with no luck.  In the meantime, I am paying a plumber to regularly blowbag the line to keep it flowing.

Any recommendations for next steps would be greatly appreciated.