ADU Sewer Connection

[David W.]

Orange County CA. I have an existing structure approx 14X12 we are considering converting to a ADU in 2020. The structure is 20' from the rear lot line. The building has gas, electrical sub panel, water but no sewer connection. Connecting a sewer line to the primary residence is problematic due to elevation and trenching into the house slab for 35', across a bedroom, hall and bath. It would also require a waste sump and pressurized line to move uphill.

The rear of the lot terminates onto the neighboring street, in the same development.  A new connection to the rear street is 20' and downhill but would require cutting the sidewalk and opening the street.  I just replaced a 50' sewer line on a rental in Texas, $6,500 including permit. The TX project did not require cutting into the city sidewalk or street. 

Back to Orange County CA, if the city will permit, what is the ballpark cost?  I have no idea if this is a 12k or 50k project in California.