WorldWide Drilling Resource

Serving the Drilling Industry www.starironworks.com 257 Caroline Street Punxsutawney, PA 15767 800-927-0560 • 814-427-2555 Fax: 814-427-5164 SERVING THE WATER WELL INDUSTRY Need something special? Talk to us - we’ll make it happen faster than you think. 17 WorldWide Drilling Resource ® JUNE 2018 Sinkhole Reveals Unexplored Cave Compiled by Caleb Whitaker Associate Editor WorldWide Drilling Resource ® A 20-foot sinkhole emerged on a county street in Williamson County, Texas, revealing an underground cave which partially collapsed to create the fissure. The roof of the unexplored cave system crumbled because of the continual dripping of water from a pipe leak. Five chambers have been found in the cave so far. It starts at around the middle of Cambria Drive, around 20 feet west of the curb, then heads east about 200 feet. The height of the cave varies, reaching a height of approximately 22 feet near the entrance and an average height of 10-15 feet. There is 6-8 feet of limestone and sediment between the homes resting above the cave and the cave’s ceiling. Geotechnical drilling was conducted, and core samples were taken around the cave’s entrance. The geotechnical under- takings were part of the due diligence process in the discovery of the cave, as well as an effort to obtain additional geotechnical information to better understand the geology surrounding the cave. The core analysis was important to help determine if there were additional voids surrounding the cave in the county right- of-way which would impact the mitigation process. The analysis was also necessary to ensure shallow voids did not exist in areas where heavy equipment would be staged during the construction phase. Several voids were encountered in the borings, but they were considered common and expected in the geographic region. These voids may be empty air space, but more likely, they are a clay-filled pocket in the underlying rock formation. The boring logs indicated no significant voids at shallow depths or less than ten feet below surface elevation. Boring B-1 discovered a void at a depth of 13 feet below surface elevation extending to a depth of 20 feet. Williamson County’s structural engineers do not feel this void will impact future mitigation efforts or pose any safety concerns with regards to future construction activities. Recorded material strength properties were highly variable. This variability in rock quality and strength was anticipated and consistent with mapped geologic formations in this region. Williamson County has not yet received a finalized report from the structural engineers, but it should contain options for pos- sible mitigation efforts. Williamson County is working with the Texas Commission on Environmental Quality to choose the best plan forward to protect people and the environment. Editor’s Note: In between our print issues, the WWDR Team prepares an electronic newsletter called E-News Flash . Based on readership, this was the most popular E-News Flash article of the month. Get in on the action and subscribe today at : www.worldwidedrillingresource.com