Snow Caches (continued)

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

Construction and Storage (Pit Cache)

1. Remove debris from the site. Old sawdust, duff, slash, and other organic debris contain pathogens that may harm seedlings. This debris would decay, generating heat and melting the snow.
   
   
2. Prepare a sketch map of the cache layout showing seed lots and the order in which they will be removed.
   
   
3. Shovel or plow the snow from storage cells no more than a day or two before the trees are to be delivered. Leave a level, firmly compacted snow floor at least 2 feet thick. No debris should be between the ground and the snow.
   
   
4. Unload the delivery vehicle. Avoid dropping or mishandling the tree packages.
   
   
5. Stack the seedling packages as follows:
• Leave at least 1-foot spacing between rows.
• Leave at least 6 inches separation between packages within rows.
• Stack bags and boxes two high, crates four high, using 2- by 4-inch or 2- by 6-inch boards as separators between layers to maintain circulation.
  
  
6. Shovel snow into spaces between rows and stacks. Use only clean snow.
   
   
7. Shovel clean snow on top of packages.
   
   
8. A single sheet of plastic over the top of the cell will protect boxes made of kraft paper or cardboard from melting snow. Do not allow the plastic to lap over the sides of the cell where it would inhibit air circulation.
   
   
9. Place slats or sheets of 1/4-inch plywood over the top of cells, overlapping their edges. This layer (called the load distribution panel) will distribute the snow load.
   
   
10. Cover the distribution panels with a thick layer of snow. End loaders are the best machines for this task. Never run heavy equipment over the top of the snow cache. At least 4 feet or more of snow is needed to cover the cache.
    
    
11. Mark each end of the cells with long poles and tag lines.
    
    
12. Place at least 4 feet of snow around the sides of the cache. Do not use excessive force when placing snow with machines.
    
    
13. Insulate the snow cache. Cover the top and sides with at least a 5-inch layer of sawdust, shavings, straw, or commercial insulation. The complete snow cache should be covered with canvas in roof-shingle fashion from the bottom to the top. This cover will shed rainfall and drip from tree crowns, prolonging the cache's life.
    
    
14. Anchor the canvas cover with slabs or ropes. Install signs identifying the structure and its contents as Government property.