The Pensacola airport hasn’t had a proper stormwater pond in nearly 70 years.

What is known as the Airport pond is actually a borrow pit -- “basically a hole in the ground that’s been there since the 1940s” as city engineer Derrik Owens calls it --  that has been used as a holding pond for stormwater runoff.

Last month the city accepted a grant that will change that.

What was a 32-acre hole in the ground will become a properly engineered stormwater retention pond, thanks to $2.7 million from the Florida Department of Transportation and the National Fish and Wildlife Foundation.

It is one of three stormwater projects coincidentally announced together that aim to improve water quality and stormwater management in the city. One will be in Gaberonne Swamp in roughly the same Cordova Park/Scenic Heights neighborhood; the other will be at Corrine Jones Park on Government Street.

The stormwater pond behind Cordova Square shopping complex also connects to the Airport Pond, through the 12th Avenue drainage system. Making sure that airport pond is properly engineered is critical.

The grant project won’t change the footprint of the pond that much, Owens said, but it will properly dredge the pond, slope the sides and increase its holding capacity by 30 percent. It also, Owens said, will have enough capacity that it can be used to provide “compensatory” or offsite mitigation treatment for the construction of the new Pensacola Bay bridge.

“(It’s depth now) varies, 25 to 35 feet, it could be 40 feet in some areas. It’s really irregular,” Owens said.

And it will be engineered to a 100-year rain event standard, Owens said, which “statistically for this area is 13.44 inches within 24 hours.”

The epic rainfall of April 29-30 dropped by some measurements 26 inches on the area in a 24-hour period, putting it in the 250- to 400-year storm event category, Owens said.

The current city standard is that such ponds be engineered to a minimum 25-year event for new construction.

The airport pond could be constructed to a threshold of a 250-year flood event, but it would, as Owens points out, double or triple the footprint of the pond and “take up an enormous amount of airport property.

“That’s not really even a consideration because it’s not practical or feasible to do that.

“I was talking to this gentleman the other day and he had a good example. He was like, just because they make cars that go 250 miles an hour, should we design roadways for that? Well no because it’s not practical and feasible to do that because how many people drive 250 miles per hour on the road? You might have one every now and then. It was a good example and it’s just not something that we find ourselves looking at from a practicality standpoint.”

The city contracted with Hatch Mott McDonald for $21,000 to perform a forensic engineering analysis of the collapse of Piedmont Road in the rain event. That report should be ready by mid-June.

The 48-inch reinforced concrete pipe under Piedmont Road should have had a 60-70- year minimum lifespan, Owens said. Historical records show Piedmont Road was built around 1960-1961, Owens said.

The parking lot at Roger Scott Tennis Center on June 10. Photo credit/Shannon Nickinson.

That pipe also is fed by a 30-inch line that runs under Roger Scott Tennis Center.

On a contour map, Piedmont Road is the floor of a valley through that neighborhood, draining to Bayou Boulevard and ultimately Bayou Texar.

And though rainfall has caused problems at the Roger Scott complex in the past, Owens said nothing like the collapse of Piedmont has “ever happened according to our records from what we can tell.”

The April storm, Owens said, “did reveal that our system can’t take 27 inches of water so we know that, but it’s not designed for that and its not practical or feasible to design for those volumes of water. We will use it as a learning tool as much as possible and if it has revealed weaknesses in the system, we will be addressing those because like I said it helps with fall-ins on road issues, so it helps us head those off in the future so when we do get high rainfall, hopefully we can prevent fall-ins of roadways and things like that.”

At the June 12 Pensacola City Council meeting, members will recommend that the mayor set a date on or before July 16 for an "educational symposium" about city and county stormwater plans.

"The City shall review the results of the city's post-storm event engineering reports, invite the county to join us to review their findings and set the next steps for improvement to our stormwater system," the agenda for the meeting reads.

Here is a summary of two other key projects in the pipeline:

Gaberonne Swamp: At $1.8 million in state funding, with $1.2 million in local match. It will include work on a pond near Langley Avenue and Scenic Highway intersection, a new pond off Spanish Trail and an education kiosk at Pensacola Bay Bluffs Park. The ponds will divert stormwater into Gaberonne swamp to help nutrients settle out of it before it flows ultimately into Escambia Bay. That improve water quality and reduces the nutrients that feed algae blooms and damage marine life.

Government Street: A $2,106,500 grant from the National Fish and Wildlife Foundation will put a stormwater pond on West Government Street in part of Corrine Jones Park. It will be improve water quality in Pensacola Bay and helped alleviate flooding in the neighborhood. It will be landscaped and designed in a fashion similar to the pond at Admiral Mason Park on Bayfront Parkway, with walking trails, benches, fountains, aquatic plants, bicycle rack, lighting and other amenities.

“I am going after more NFWF money,” said Mayor Ashton Hayward. “They have criteria for projects that focus on stormwater and water quality and that’s the reason we were able to get that grant over here for Corrine Jones.”

The lead photo is credited to Jim Edds @ExtremeStorms on Twitter.

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