In AA&E storage facilities, why must drainage structures be secured if they cross the fence line and meet certain size requirements?

As an additional security measure in an AA&E storage facilities, securing drainage structures must be considered if their cross section is greater than 96 inches and any dimension is greater than 6 inches, they must be barred and welded at the intersections to prevent any human from crawling into the area.

Explanation:

U. S. national security relys on ensuring DoD sensitive or classified assets such as classified material, arms, ammunition, and explosives (AA&E) and nuclear weapons, in properly safeguard facilites and storage containers, voiding DoD assets loss or compromise and additional to supplemental intrusion detection systems and guard patrols, security lighting, communications, fences and clear zones, drainage structures, key control, and other security measures required to protect AA&E.