This includes the elevation of the site and the type of soil. The importance of good drainage makes a site on high ground preferable unless other factors rule it out. Moisture is one of the greatest natural threats to the contents of a cache. Swam p muck is the most difficult soil to work in. If the site is near a stream or river, ensure that the cache is well above the all-year- high-water mark so that it will not be uncovered if the soil is washed away.