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Monday, July 27, 2009

Location of Stormwater Runoff Leaves Resident "Across the Big Pond"

The location of the retention pond for the V.O. Dobbins Community Center renovations on Louis Street in Riverview has raised the eyebrow of a nearby resident.

Jack Pierce says one day, "right out of a clear blue sky," he noticed what looked like a long, rectangular ditch right across the street from his Louis Street home.

"We saw them digging it one day," he says, "but we didn't what it was for, or if they were going to leave it open like it was. When I asked one of the fellows working over there what it was, he told us it was for holding rainwater."

What Mr. Pierce saw, is the latest eco-friendly process to keep land from being flooded. It is commonly referred to as a retention pond, usually built to catch excess stormwater runoff from parking lots and construction projects. If it is working correctly, a retention pond holds excess storm water from a heavy rain just long enough so it will flow into a small pipe that connects it to the nearest storm water drain, whose pipe is much larger. The resulting "damming" effect holds the water in the pond for a few hours while it goes into the drainage system and not onto nearby land. Almost every municipality requires builders to install these ponds on the downslopes of new buildings and parking lots. Often, new construction will upset the normal flow of excess storm water, and often sends that excess water into previously unflooded places like nearby basements, crawl spaces, and low spots in streets.

When the Dobbins Center was Douglass High School, the building was "grandfathered" from having to install a retention pond. Once the building was approved for renovation though, that "grandfather" rule did not apply anymore, and new rules requiring a retention pond went into effect.

But it's not the pond itself that concerns Jack Pierce. It's an unwanted by-product of the standing water that may be left behind as the pond slowly drains into the stormwater drainage system.


"We're concerned that standing water that has not flowed out of the pond yet could breed mosquitoes," says Mr. Pierce. "We have not had any problems with the bugs yet because we haven't had that much rain, but if you give them a habitat like standing water, they're drawn to it. We're worried that we won't be able to enjoy our yards if the mosquitoes establish a breeding ground in any water that's left in the pond."

"And then, what about the appearance of the pond?" he wondered out loud. "Will we have to come outside and stare at that hole in the ground all the time?"

"Mr. Pierce has legitimate concerns about the retention pond," says Chris McCartt, Kingsport's Development Service Manager and Assistant to the City Manager. "I wish there were any other place to put that pond, but if you look at the lay of the land and the way the slope is, water flow from Lincoln/MLK and the railroad tracks, slopes downward through Riverview towards the Holston River. We had to put the pond down from the building in the direction of the river, but near enough to the construction site and the parking lot to catch the excess runoff from heavy rains."

"We will be monitoring for bugs, especially mosquitoes," he says. "One of the good things is, that this is a retention pond, not a detention pond. A detention pond normally holds the excess storm water and lets it seep into the ground without drainage into the stormwater system. As this water leaves, it might leave little pockets, but those will either evaporate or sift into the ground quickly."

"We are also considering landscaping for the retention pond," Mr. McCartt added. "Another good thing about retention ponds, is they lend themselves to landscaping with shrubs, bushes and decorative plants. A detention pond retains too much water for those types of plants to work."

Storm water runoff has always been problematic for Riverview. Longtime residents say problems with excess water after heavy rains date back to the early days of the neighborhood. The community was built over the site of a former chemical dump for nearby industries, and as some chemical wastes hardened, seeping water moving towards the water table was obstructed by the the new barrier. That water frequently seeped back to the surface and flooded backyards and storm drains.

Upgrades to the storm water drainage system along Carver, Louis, Dunbar, Lincoln and Douglass Streets helped to move the excess rain water along somewhat, but heavy rains still produced flooding. Wheatley Street was the last new street added to the neighborhood, and as a result, does not experience the standing water the other streets have.

Apparently, without the retention pond, the V.O. Dobbins renovations would intensify many of the flooding problems the neighborhood has suffered in the past.

"We may also be forced to build another retention pond on the other side of the building," says Mr. McCartt. "The other one may not be as big as the present one, but when you look at the additional parking lot we have to build at the new Headstart classrooms, you have to start figuring up your drainage calculations and once they hit a certain point, you have to start thinking of how to capture that water also."

What should local residents do, if they notice more mosquitoes than normal?

"Just call City Hall," Mr. McCartt says. "Let us know, and if we find out the mosquitos are coming from the retention pond, then we will act quickly to spray for them. There is also a tablet you can drop into standing water that poisons the larvae immediately. Residents just need to let the building manager Mark Kilgore know, and he'll take a look at it and do the right thing if they're coming from the pond."

Mr. McCartt visited the pond to personally hear Mr. Pierce's concerns.

"I feel confident that Chris will take care of any problem we might have," says Mr. Pierce. "They've always been pretty good about looking into anything we have a problem about. I realize the pond has to go someplace and we were surprised to see it right across the street from us, but I feel the city won't let us down if problems come out of it."