You do NOT need a civil engineer in San Diego City or County if the retaining wall is under 7 feet. See link here http://www.sandiego.gov/development-services/industry/pdf/infobulletin/ib221.pdf (links seems to indicate 6feet but the plans in the permit office have specs to 7ft) If you go to the office for a permit (you need one to build retaining wall more than 3 feet) they have detailed specs on walls up to 7 feet. They are pre-approved engineering plans for retaining walls provided they are 7 feet or less. You can construct a retaining wall over 7 feet but if you do then you have to have your own custom engineering performed. Having the pre-approved plans saves a lot. Make sure the mason/builder follows the plans exactly. The inspecters are sticklers on retaining walls. I have 3ft wall (with fill at base of hill) and then a 7ft wall which cuts into the slope.
At a 2 to 1 slope this provides an extra 20feet of depth to the yard. FYI it took 20 cubic yards of concrete (that is 2 full trucks) just to pour the footings of the concrete wall. The specs they provide seem overkill but I don’t worry about the wall as a result.
