The Ramparts is a walkway which follows the course of the River Boyne and the old Boyne canals (in places) Ultimately the intention is to have a walk/cycleway the whole way from Navan to Drogheda however this is a long way from fruition 
The existing sections are as follows;
1) A hardpack track starting in Navan and heading east towards Slane (there is an older series of caches along here)
2) A hardpack track starting in Slane and heading east towards Drogheda (there are 3 older caches along this section)
3) A grassy trail leading from Slane back west towards Navan (this series of caches is along this section)
If you park at the carpark coordinates at the Slane Bridge on the N2 you head towards the weir following the trail the whole way following the River Boyne. This is a completely flat walk along a grassy trail. When the series was placed (in the midst of a summer heatwave) the terrain was dry and easy but I cannot say what it will be like when the weather is less pleasant 
This is a linear walk so remember for every step you take you must return by the same route 
At this section of the route you will be quite literally undercover, under tree cover anyways The cache is hidden up the slope near the lowest point of the tree cover. If your GPS is struggling under the trees the hint will hopefully help. The cache is a small tupperware container containing log and pen though best to byop just to be on the safe side. Please replace cache and its cover exactly as found.