Mike,
From what I understand, there are three companies who build wirewound concrete tanks in Ohio. They can be found at: www.preload.com, www.natgun.com and www.concretetank.com.
You should be able to find details of construction on those sites. I don't know much about tendon tanks.
Good Luck
I would suggest a circular prestressed concrete tank and separating the inlet from the outlet 180 degrees. The inlet pipe should rise above the floor to a level below the normal operating range. The outlet pipe should be just above the floor. If additional mixing is required there are various...