For many years, the world's longest borehole was the Kola Superdeep Borehole in Russia. Drilling began with test bores to assess the viability of a deep borehole. Groundwater use through deep borehole drilling has somewhat eased the effects of drought. In 1986, Southampton began pumping heat from a geothermal borehole through a district heating network. In such cases the fracturing may extend only a few feet from the borehole. Each will use teeth to cut into the surface in order to create a borehole. Borehole temperatures are used as temperature proxies. In terms of true vertical depth, it is the deepest borehole in the world. Core recovery parameters describe the quality of core recovered from a borehole. A tool that measures the diameter of the borehole, using either 2 or 4 arms. Gravel of a certain size and shape for use in the borehole must be located. In practice the effect on borehole temperature is believed to be generally small. No signs of life were detected from the sixth borehole. The deepest research well in the world, the Kola superdeep borehole, is deep. The deepest research well in the world, the Kola Superdeep Borehole (KSDB-3), is deep.