Snow Caches (continued)

• Site selection
• Construction and Storage (Pit Cache)
• Construction and Storage (Culvert Cache)
• Inspection

Construction and Storage (Culvert Cache)

The following steps should be followed when constructing culvert snow caches and using them to store seedlings. Complete steps 1 through 7 during the fall and steps 8 through 10 when the seedlings are delivered.

During the Fall:

1. The concrete pipe should be at least 5 feet in diameter. The length and number of pipes depends on the type of tree packages and the volume of trees to be stored. If crates are used for storage, the pipes must be perforated to prevent the seedlings from drying out. The pipe does not have to be perforated if the trees are packaged in bags or boxes.
   
   
2. Place the culverts on log supports and stringers, about 2 to 3 feet above the ground to allow snow to build up below the culverts and to prevent heat transfer from the ground. Culvert snow caches depend on natural snow accumulation for cooling.
   
   
3. Place block supports inside the culverts to prevent them from collapsing. Spacing between the supports depends on the expected snow load.
   
   
4. Store insulation inside the culverts.
   
   
5. Install doors on the culverts, or place canvas covers over their ends.
   
   
6. Mark both ends of the culverts with long poles.
   
   
7. Position a ladder for descent into the culverts. Anchor the ladder to a tree if possible.

When Seedlings are Delivered:

8. Carefully transfer packages from the delivery vehicle to the culvert. Avoid mechanical shock to the tree packages. Store tree packages by the order in which they will be removed. Attach tag lines to packages in middle of culvert for easier removal. Provide 6-inch lateral spacing between packages. Use 2- by 4-inch boards or small diameter poles for vertical separation. Avoid overfilling culverts because this will reduce the culverts' cooling efficiency. Each tier should be no more than two packages high.
   
   
9. Close the entrance to the culverts.
   
   
10. You may wish to place additional snow over and around the sides of the cache to prolong its useful life. Insulate and cover the cache in the same fashion as for a pit-type snow cache. Post signs indicating that the facility is government property. (top)

Inspection

Inspect snow caches frequently to make sure snow hasn't melted, seedlings haven't been exposed, and that the cache hasn't been opened or vandalized. If trees are exposed, they should be inspected for dormancy and moisture stress. Trees that are no longer dormant should not be returned to the cache.

Removal

Snow caches should be entered from the north side. They should never be entered from the top. Any other method of entry will increase the rate of snowmelt. Avoid mixing insulation with snow during entry.

Entries can be shoveled or carved out of blocks along the tag lines. Chain saws are very effective for carving out blocks, so long as the seedlings are not exposed to exhaust fumes or petroleum products. Avoid damaging the seedlings when removing packages. After seedlings have been removed, the entry should be closed with snow and covered with canvas to maintain temperature and humidity. Thaw frozen seedlings slowly in shade. Cover them with a Space Blanket or tarp at night to prevent freezing. Do not handle frozen seedlings until they have thawed.