Loading Bay

A loading bay is a patch of ground built hard enough that a delivery vehicle can drive on, stop, turn and be unloaded without sinking in or churning the ground to ruts. Its whole value is that it stays usable in wet weather. It is built to a design load, the weight on one wheel it has to take without failing, of at least about 1800 kg (4000 lb). It sits at the end of a route a loaded vehicle can travel, and hands straight off to where material is stacked.

The build is layers and each has a job. The sod and soft material are stripped off, and no deeper: a pad dug into a hollow collects water, so the finished surface has to sit above the ground around it. Next comes geotextile, a tough fabric sheet laid over the soil to stop the stone above working down into it and the soil pumping up into the stone. It is specified by weight, at least 6 ounces per square yard and 8 to 10 where machines drive, and covered within two days because sunlight destroys it. Then 150 to 200 mm (6 to 8 in) of crushed angular stone, compacted. Angular matters, because broken faces lock together under a wheel where rounded gravel rolls. About 50 mm (2 in) of fine material finishes it, laid to a crown so water sheds in every direction at a slope of 1 to 2 percent.

Failure is always mud, by four routes: digging too deep so the pad collects water, leaving the fabric out or specifying it too light, compacting too little so the layers mix under traffic, and too little slope so a soft spot forms in the crown. A subgrade left wet by any of these heaves when it freezes. Clean water from upslope or a roof is turned around the outside so it never crosses the pad, and what runs off goes onto planted ground. Top up the fine layer every three to five years without scraping into the stone beneath, keep the diversion and crown clear, and keep the pad empty: a bay used for storage is not available as a bay.