Boling Dome, an underground rock structure that contains petroleum, sulfur, and salt, is on the western bank of the San Bernard River almost entirely in Wharton County (at 29°18' N, 95°56'W). It is oval in shape and ranges five miles east-west and three miles north-south, encompassing 5,500 acres. The Boling Dome caprock mantle of minerals is shallow, 383 feet below the surface. Another 120 feet through caprock, at the center of Boling Dome, is the salt dome itself, about 500 feet below the surface. Its outer edge requires up to 5,000 feet of drilling before reaching salt. The entire Boling Dome area is seventy-five feet above sea level. Salt domes in Texas have been of particular geologic significance because of their mineral production. Most of them are located on the Gulf Coast between the lower Colorado and Neches rivers. They have also been used for product storage and disposal.
Sulfur production at the Boling Dome is from the crest of the caprock to deep down the southeast flank of the cap. The first well went into production in March 1929, using the Frasch method for removal (pumping steam into the ground to melt the sulfur, then pumping the liquid sulfur out). The sulfur reserve covers more than 1,500 acres. This reserve, owned by Texasgulf, Incorporated, once produced more sulfur than any other sulfur mine in the world. By the time the mine closed in 1993, 80.8 million long tons of sulfur had been removed. The first oil well at the dome went into production in December 1925. As of 1989 the Boling field had produced 6,246 million cubic feet of natural gas and 25,635,836 barrels of oil. Over 8,000 wells had been drilled to mine the sulfur reserve, and 12,000 wells for oil and gas. In addition, at the Boling Dome, Valero, Incorporated, operates three gas-storage caverns in the salt stock, with a combined volume of 7.5 million barrels.
Spacing between the boreholes for sulfur wells is about 100 feet; the sulfur holes, with the 12,000 additional injection wells for oil and gas, produce a highly porous zone that affects the integrity of the dome. On August 12, 1983, a sinkhole approximately 250 feet in diameter and twenty-five feet deep, formed suddenly over the crest of the Boling Dome on Farm Road 442 three miles north of Boling, collapsing the roadway. Water filled the ditch. In early drilling records such as those that the Gulf Production Company kept for a well drilled near the middle of the sinkhole in 1927, there is evidence that an underground cavern once extended over 100 feet vertically but apparently collapsed. Several other sinkholes have occurred over the Boling Dome, a condition that is becoming common at other salt dome sites where sulfur and oil are produced.
Two communities, Boling and Newgulf, are located at the Boling Dome. Their existence is due directly to the production of sulfur and oil from the dome. Newgulf is a Texas Gulf Sulphur (now Texasgulf) company town that has largely depopulated since the Texasgulf mine closed in 1993, and Boling is located at the intersection of State Farm roads 1301 and 442.