There is nothing wrong with your soil, although the fact it has a high clay content means it may hang on to water for longer, which is not a bad thing for plants, but will make good conditions for slugs and snails because they need moisture. Snails hibernate during winter, but when active, they lay eggs; each one can lay up to 80 eggs each time,and these hatch out into tiny snails which also will lay eggs eventually. I'm afraid its probably time to resort to chemicals to reduce the population if the baby snails are becoming active - in the UK,I would use slug pellets which are coloured blue and contain either metaldehyde or methiocarb. Both of these chemicals are toxic to snails,but also toxic to bird and aquatic wild life; overuse or excessive application is a major problem,where people put so many down the soil appears blue, but a light sprinkle once or twice a year should reduce the snail and slug population without creating toxicity problems. There are more organic slug and snail treatments,but these are not usually as effective - it rather depends what treatments are available where you live as to the choices you have. Otherwise, an old remedy was to sink small containers filled with beer into the soil - slugs and snails like the beer,fall in when trying to drink it, and die, probably in a state of inebriation.
Other home control methods are listed here Organic Slug & Snail Control, but are not so effective as using slug pellets.
