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Site restrictions, requirements challenge Highway 90 project

The new Clark Oil gas station/convenience store in Biloxi may look like any other business of that kind, but there’s more there than meets the eye. It’s presently Biloxi’s only station on U.S. 90, and it was built by complicated design and engineering standards to protect it against hurricanes. The business’ owner is Jon Frank Clark of Waynesboro.

Vicksburg architect Paul Ingram and structural engineer Gary Rogers of Advanced Engineering Resources in Madison are responsible for making the project a reality.

“The complexity of the project is what makes it interesting,” Ingram said. “At first I looked at the site and told the client I could not do it because of the low, small site and the flood elevation requirements. But, the client said ‘get it done.’”

Ingram says the city was helpful, but FEMA’s new flood maps were slow coming out, and the city was told to add four feet to the old maps’ 12 feet-above-sea-level standard for new construction. Built to that specification, the store would have been sitting at 16 feet.

“I said ‘that’s it,’” the architect recalls. “The parking would have been too steep — people would fall down. It would not have been good.”

However, city officials — Ingram singles out Steve Stickler as being great to work with — came back with the suggestions to build the facility to 12 feet and flood proof the additional four feet to prevent water intrusion.

“That’s the design. We followed the pre-Katrina FEMA manual for coastal construction,” he said. “Working with the engineer, we had to come up with a building that would not float out of the ground.”

That requirement resulted in eight-inch thick walls of cast concrete around the building. The only gaps are the front door and the fire exit. Ingram researched far and wide to find exit doors made of solid steel with gasket seals. This effort was further complicated by a desire to have the front door look aesthetically pleasing. It has a fabrication of sheet metal that is stored and brought out and bolted in place before storms. An emergency plan must be in the store to instruct employees on how to get the building ready for impending storms.

“We tried to make the store look good and still be water proof,” he said. “There is brick veneer around the water proofing.”

Also, the building must be heavy enough not to float away. Anchors were drilled into the ground 16 feet to lock the foundation to the ground. There are concrete slabs on the roof to add weight and prevent fire, plus applications to resist 140 mile-per-hour winds.

Interior cast concrete steps lead to a third exterior door on an elevated landing that serves a dual purpose. It can be used as an escape hatch for anyone left in the building after flooding begins. It is also used as a landing for the power meter. An escape hatch on the roof provides another way of exiting the building and a way to service the roof-mounted central heating and air unit.

Other features include a valve on the sewer line to prevent flood water pushing it into the building and seals around all electrical outlets.

Rogers has worked with Ingram on other convenience store projects but none compared to this one. He says it was a good exercise in thinking creatively, something engineers do not always get to do.

“Just following the formula is usually our job as engineers, limiting our creativity,” Rogers said. “I had to learn a lot about the science behind what we did for this project. I enjoyed doing it.”

But the project was not without challenges. “The greatest challenge of this project by far,” he said, “was calculation of flood loading for which the structure had to be designed. It’s not like still water. Flood loadings are more complex because of the wave action. The waves add dynamic stress to the water pressure.”

Another challenge for this engineer with almost 30 years experience was figuring out how to account for the pressure water creates when it flows into a structure.

“This is not something taught in school,” Rogers said. “I got my hands on all the documents I could find, and I called one of the authors. He was very helpful and able to give me some perspective.”

The project, as presented to Ingram and Rogers by the City of Biloxi, didn’t comply with anything that was written down. The combination of requirements and site reality is not covered by existing construction manuals. Therefore, Rogers says the unusual circumstances of the design will be applicable to a few projects in a small area and perhaps have academic interest.

“You can’t say it’s just a gas station, but no one walking into it will know the engineering involved,” he added.

The need for flood-proof fuel dispensers presented a big obstacle. This requirement protects the federal government from insurance claims. Ingram researched and could not find them.

“We had to write in the emergency operations procedures that the business will remove the electrical parts or that it won’t file a claim,” Ingram said. “I don’t know what the owner will do about that.”

This convenience store is different from the hundreds he’s designed. He says he had to research and look all over the place for everything for this one.

“A typical convenience store costs $250 a square foot. I can’t tell you right now what this project cost,” he said. “I learned a lot from it.”

Contact MBJ contributing writer Lynn Lofton at llofton656@aol.com.

About Lynn Lofton

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