Design Notes:

28" to bottom of inlet to bottom of tank
26" to bottom of outlet from bottom of tank
Tanks are steel rebar reenforced
Manhole access to each compartment
4" PVC coupling cast in for inlet and outlet

Capacity: first compartment 333 gallon
Second compartment 167 gallon

Do not bury in traffic areas

Options:
Larger inlet and outlet
Size and location of vent
Cast iron ring and cover