Geotechnical engineering and services firm Geotechnology Inc. and its exploration team recently helped solve a long-standing mystery about the legendary “lost” English Cave in St. Louis.

“We were contacted by Bill Kranz, who represents the English Cave Community Garden Committee, in 2019 about our interest in supporting their efforts,” says Jim Howe, Geotechnology Exploration president.

Experts believe the cave, named for St. Lewis brewer Ezra English, measures about 350-feet-long by 25- to 35-feet-wide. It’s thought to sit about 50 to 60 feet below the surface. English, in the 1840s, used the cave as an underground beer garden and entertainment complex. Over decades, the cave served commercial purposes, including for lagering beer, storing wine, farming mushrooms — even bowling. The last recorded use of the cave for commercial purposes was in 1919. After that time, entrances of the cave were sealed and the property above the cave went vacant.

In the 100 years since, many details about the cave — including the cave’s exact location and where the entrance or entrances were — were lost to time.

“As a firm with deep roots in St. Louis,” Howe adds, “we offered to do some pro bono drilling and project planning services to get the project off the ground. I enjoyed meeting the English Cave team and appreciated their determination and drive to rediscover this historic feature in the heart of South St. Louis.”

Descriptions recorded around 1905 led the Benton Park Neighborhood Association to suspect that a large part of the cave was located under their English Cave Community Garden. The association formed the English Cave Recovery Project, which subsequently attracted many supporters throughout Missouri who were interested in the underground landmark.

Two of the most notable financial donors were the Meramec Valley Grotto and the Missouri Speleological Survey. The garden’s actual owner, the Gateway Greening Land Trust Inc., also endorsed the drill plan.

After many years of planning, the English Cave Recovery Project engaged Geotechnology for exploration drilling services. Geotechnology used a Geoprobe 3230DT tracked for the project, due to the rig’s low-impact on the garden and the surroundings.

The team’s first attempt at drilling a nearly 5-inch hole hit limestone bedrock at 16 feet. However, as crews went deeper, the core barrel hit a sand-filled void in the rock that bound up the bit. After freeing the bit, they cased the 5-inch hole and continued the project with a 2.75-inch hole. At 50 feet, the drilling tools broke through into a void. They had found English Cave.

And, there was some luck involved. If the drill location had been 2 feet to the west, the drill would have remained in the rock wall, missing the cave altogether.

Geotechnology’s crew drilled a second successful hole southeast of the original bore and reached the top of the cave at a similar depth.

The bores gave plenty of access for a researcher, Ken Boyko of the Missouri University of Science and Technology, to drop a LIDAR scanning device into the cave. The post-doctoral fellow in geological engineering used the device, which creates high-definition laser scans, to create a digital map of the cave, shedding new light on a 100-year-old mystery.

Geotechnology Inc. offers a range of consulting services in applied earth and environmental sciences, including geophysics, water resource management, geotechnical and environmental engineering, materials testing and drilling. For more than 30 years, the company has provided expertise on thousands of major construction projects in the Midwest and Mid-South. Geotechnology is ranked in ENR’s Top 500 Design Firms in 2019. The St. Louis-based company has 10 offices in Missouri, Illinois, Kansas, Ohio, Kentucky, Tennessee, Mississippi and Arkansas. For more information, visit www.geotechnology.com.