Here is a page from someone who is not close enough to help you with the work. But the advice article
may give you a really good idea about what kind of questions you should ask landscapers to see what they understand or not.
Drainage and Soil Information and Tips
Be sure to read it all the way through.
Really shows why some folks pay for drains that don't do the job. I think some people are just hiring contractors who do not know what they are doing.