In the Southern Hemisphere, where the June solstice is known as the shortest day of the year, it marks the first day of astronomical winter, but the middle of winter in meteorological terms.
Backfill refers to products or materials used to fill excavations. The most common form is composed of a mixture of gypsum and calcium bentonite. Apart from filling holes, one of the primary purposes is to mantle sacrificial anodes under the ground.
Backflow is the undesirable reversal of flow of nonpotable water or other substances through a cross-connection and into the piping of a public water system or consumerâs potable water system. There are two types of backflow; backpressure and backsiphonage.