MIL-HDBK-1021/6 (YD), DEPARTMENT OF DEFENSE HANDBOOK AIRFIELD PAVEMENT DESIGN FOR FROST CONDITIONS AND SUBSURFACE DRAINAGE (15 APR 2000) [SUPERSEDING DM-21.06]., This handbook presents criteria for the design of subsurface drainage systems and frost protection for airfield pavements. Included in this handbook are criteria for subsurface exploration as it relates to frost and drainage, frost protection, design alternatives for subsurface drainage, and suggested details for subsurface drainage design.