By Stephen Enzweiler
Special to the NKyTribune
When the bishop of the Catholic Diocese of Covington, Camillus Paul Maes, sank the blade of his shovel into the earth in April 1894 to break ground for Covington’s new St. Mary’s Cathedral, he had high hopes that construction would commence quickly and proceed without incident. He and architect Leon Coquard had spent the previous two years meticulously planning the project, with Maes purchasing properties upon which to build the new cathedral, and Coquard pumping out volumes of detailed drawings in order to meet the bishop’s broad vision for the magnificent Gothic structure he hoped to build.
Bishop Camillus Paul Maes, circa 1885. Courtesy of the Archives of the Diocese of Covington.
In the weeks that followed, engineers and workmen began surveying and excavating the ground according to the architect’s plans to make way for construction of the foundation. Steam shovels and heavy equipment moved in, transforming the site into a beehive of activity. Coquard’s plans called for them to dig down 25 feet along the foundation perimeters, where piers could be sunk that would support the massive weight of the cathedral structure. But as larger and larger buckets of earth were scooped out, supervising civil engineer Willis Kennedy noticed a problem. While hoping to find stable ground for construction, he found instead only a wet, marshy soil with layers of sand and clay. He knew immediately it was the type of soil upon which no cathedral could be built.
The soil Kennedy encountered was sediment that had been laid down during the latter part of the Pleistocene Epoch or last Ice Age. As the ice sheets receded one to two million years ago, floodplains of rivers and creeks across Northern Kentucky filled with what are called Quaternary sediments, which consist mostly of silts, sands, gravel and clay. In his excavations, Kennedy had found them throughout the construction site down to 60 feet below the surface; but he knew these layers could go as deep as 100 feet or more.
Kennedy broke the news to a stunned Bishop Maes as best he could. The ground was what engineers called a “compressible” soil, one that was not uniform throughout and could never support the weight of a massive building. Yet, he tried to reassure the bishop that there were a few things he could still try in hope of resolving the problem. Nevertheless, he could not guarantee that any of them would work.
Louis Frederic Gustave Bouscaren, the engineer who conducted the soil load-bearing test that ultimately concluded that the cathedral could be built. Source: Ancestry.com
A frustrated Maes wrote to Leon Coquard and explained what Kennedy had found. “It is impossible for me to say just what should be done,” the puzzled architect penned in reply. “I have allowed about 2½ tons per square foot of footing. Of course, this will not do if you have the bottom which you describe.”
“The whole lot is endless and bottomless sand!” the good bishop lamented. “The men who worked it … assure me it is the same all over, for blocks and blocks.” For the first time, it seemed that a new site, though a less favorable location, may have to be selected. The only “fix” was an engineering method called “preloading and vertical drain.” This method essentially consisted of squeezing the soil with a fill material so that residual ground water could be drained away. By eliminating the water, the soil could be strengthened.
The “apparatus” that Bouscaren constructed to measure the compression of a given weight into the soil. After a sketch made by Bishop Maes.
For this, Bishop Maes contacted Gustave Bouscaren, a Paris-trained civil engineer working in Cincinnati, whom the Enquirer said “had the reputation of being one of the great civil engineers of America.” He worked for Cincinnati Southern Railway for 25 years, held patents for dozens of inventions, and built some of the bridges spanning the Ohio River. He also was a consulting engineer for large-scale projects in Texas and New York and was once appointed by President Cleveland to evaluate the Brooklyn Bridge. “He was very conscientious of his work,” the Enquirer went on to say, “and was noted for his strictness in requiring contractors to live up to the specifications.”
After inspecting the cathedral site, Bouscaren sent his report to Bishop Maes: “The material at the bottom of the pits … is fine sand with a thin stratum of clay. It is a compressible formation which should not be loaded more than one and a half tons to the square foot.” The load capacity turned out to be about half of what Coquard had originally calculated. Bouscaren further recommended that borings be made to a depth of 25-30 feet below the bottom of the existing pits to test the soil.
On June 25th, at a spot beneath where the cathedral’s north tower now is, shafts were sunk to 35 feet below the pits to a total depth of 60 feet below street level. But the results of the soil sampling turned into more bad news for Bishop Maes. They showed the same mix of sand, gravel, yellow and blue clays as everywhere else. Maes complained to Coquard it was “too deep to reach it for foundations and unfit for draining.” But Gustave Bouscaren wasn’t about to give up on the site.
Architect Leon Coquard’s blueprint showing the redrawn foundation piers. The view is from inside the cathedral looking toward the sanctuary at left, and the Blessed Sacrament Chapel at right. Courtesy of the Archives of the Diocese of Covington.
In the bottom of an excavated pit, Bouscaren erected a wooden apparatus designed to measure how much a given weight would sink into the soil. It was an eight-foot-high oak timber, spiked at the bottom and topped with thick oak plates one foot square and capable of holding up to twelve thousand pounds. Bouscaren established a reference elevation and placed 3,500 pounds of weight on the top plate. The idea was to see how much the oak timber sank over time, which would tell him how much weight the soil could support per square foot. This information would, in turn, tell Leon Coquard how he needed to adjust the pier design to correctly account for cathedral weight and to avoid potential shifting or sinking of the structure.
Bouscaren put Kennedy in charge of taking the readings. After five hours he observed the oak timber barely sank at all. Then he put an additional weight on it until it reached 6,470 pounds. That night, a heavy rain fell over Covington, saturating the pit where Bouscaren’s apparatus was and completely filling the pit with water. For two more days, Kennedy continued to take readings until the timber stopped sinking. In the end, under more than three tons of weight, the platform had depressed only 0.05 inches over a four-day period.
Bouscaren, however, was not satisfied with the numbers. “The settling of the soil under a load … is somewhat more favorable than I had anticipated, but the result is not yet conclusive.” So, he directed Kennedy to increase the weight to 8,000 pounds and take another series of readings the following day. In his final determination, Bouscaren wrote Maes that “the result of the test only justifies a maximum allowance of three thousand pounds per square foot.”
Leon Coquard had proposed to simply increase the size of the piers to accommodate any additional weight. But Bishop Maes replied that he felt “perfectly satisfied” that there was no need of increasing their size. “My advice is to figure it to the full 3,000 pounds allowed by Bouscaren. We are perfectly safe in doing so . . .” Coquard agreed, and set about redesigning the piers. The redrawn plans arrived in the bishop’s hands not too long after, and construction was able to resume by the end of July 1894.
Construction of the cathedral façade in Spring 1909. Bouscaren’s load test had been conducted in a pit dug beneath the north tower at left. The towers were not added because Bishop Maes judged that ornamentation took priority over their construction. Courtesy of the Archives of the Diocese of Covington
On January 27, 1901, the finished St. Mary’s Cathedral was dedicated by Bishop Maes to his great relief and to the delight of the people of Covington. Eight years later, the weight issue came up again when architect David Davis was contracted to erect the cathedral’s façade and bell towers. It was judged that the façade, with the planned towers, could be constructed safely under the known soil conditions. However, after the façade was finished, Maes decided that ornamentation – statues and sculptures – were more important than finishing the upper bell towers, which could be left to a later date.
It has been nearly 127 years since Bishop Maes turned over that first shovelful of dirt and was confronted by the “endless and bottomless sand.” Since that day, St. Mary’s Cathedral Basilica of the Assumption has undergone many periodic maintenance and restoration efforts, but the structure itself remains essentially as square and plumb as the day it was built. The faith of Bishop Maes, the diligence of Gustave Bouscaren, and the genius of Leon Coquard are a testament to the ingenuity of men who had the faith, drive and creative vision to construct a Gothic masterpiece that will last for centuries to come.
Stephen Enzweiler is a writer and author. He is a former columnist for the Kentucky Enquirer and is the Cathedral Historian at St. Mary’s Cathedral Basilica of the Assumption in Covington, Ky.
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We should forever be indebted to Bouscaren’s genius. This was a fascinating article. Thanks. Steve.