You might also investigate the possible use of the Easy Pro Multi-Vent system. http://www.easypropondproducts.com/InstructManuals/Multi Vent Flyer 7-09.pdf This could be an alternative to installing a French Drain. While I don't have any personal experience with this product, it does appear functional. I am sure that Easy Pro can give you referrals to contractors that have used it. Their phone number is 1-800-448-3873.