Another sinkhole developed last Friday near Philadelphia related to underground drilling done to install the Mariner East 2 pipeline. The new sinkhole developed in Middletown Township (Delaware County), in Sleighton Park. Fortunately this latest hole was only about 18 inches in diameter, which is much better than a 15×15 foot hole that developed in September, also in Middletown Township (see Another Mariner East 2 Pipe Sinkhole Opens in Delaware County). However, the 18-inch hole fanned out to four feet wide and 30 feet deep underground. Sunoco immediately filled it with “flowable fill” (i.e. concrete)–to the tune of 48 yards of material.