Poolside Retaining Wall

I need an engineering drawing / plan for a retaining wall to run along the length of our swimming pool area. Approx 20m long, 1.2m high, besser blocks. I can obtain more detailed information if needed. I'm told the plans are needed to ensure the footings are appropriate and potentially to submit to the council for approval, etc, and for a landscaper to then potentially construct the wall. Could you let me know if you can do this type of work, and an approximate cost for the drawings.
Regards,
Keith.