The installation
of a permeable surface in a parking area at a newly developed Florida recreation
spot is helping park managers provide an aesthetically pleasing look to the lot,
while providing optimal onsite stormwater retention.
Ferndale Preserve
is a 192-acre park in Ferndale, FL, located on the western shore of Lake Apopka
in the central part of the state. The park, which is slated to open around the
beginning of 2009, has three trails that offer vistas of Lake Apopka: a 2.5-mile
nature and hiking trail, a 2.9-mile equestrian trail, and a 1.6-mile unpaved
multipurpose trail. On a clear day, one can see downtown
Orlando.
The former orange
grove is being restored to a long-leaf pine and wiregrass ecosystem.
Long-needled and large-coned trees characterize such an ecosystem with wiregrass
as primary ground cover on a sand hill system with native wildflowers dispersed
throughout.
“If you’ve ever
driven through part of the Ocala National Forest, that’s what it would look like
with sparsely populated tall trees,” says Tom Eicher, manager of parks and
trails for Lake County. “Although these aren’t going to start that way, that’s
what we’re aiming for.”
Ferndale
Preserve’s history dates back before the 1940s, when the land had been converted
into a citrus grove. Part of it had been used for a truck farm in the 1940s,
says Eicher.
“The property was
basically agricultural, so everything that originally had been there had been
wiped out,” he explains.
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Grass grows through the spaces in the porous mat. |
At Ferndale
Preserve, visitors may be able to spot one of 110 species birds; 40 types of
butterflies; animals such as the pine snake, gopher tortoise, bobcat, river
otter, American alligator, box turtle, and fence lizard; and many native plants,
including an endangered small tree species, the silver
buckthorn.
Plans call for a
fishing pier and observation tower on Lake Apopka, a scenic pavilion overlook
and a short boardwalk through the wet deciduous woodland.
The county has
several goals before opening the park, including establishing portable
sanitation and building an education pavilion. It also wants to establish grass
in the parking area, which was surfaced with 26,000 square feet of Soil
Retentions’ Drivable Grass.
Drivable Grass, a
concrete-based flexible and permeable pavement product, allows stormwater to
filter through into the subsurface. In areas such as Florida, which can be prone
to drought, the stormwater is retained on the property and in Florida’s high
water table.
The product is
designed to flex and conform to irregular ground surface contours along
predefined linear grooves. Root penetration takes place through premanufactured
holes and cracks down into the subgrade soil.
The mat’s porous
nature allows moisture to filter into the underlying soil, increasing onsite
stormwater storage, and minimizing offsite water flow.
“Last summer, when
it was wicked hot, our contractors put the Drivable Grass down. They did
everything they were supposed to do: They hydroseeded it, they watered it a
couple of times,” says Eicher. “But they didn’t water enough, waiting for summer
rains, and we never got them last year. Then we did get some [rain]—all of a
sudden, we got two inches in two hours and the hydroseeding washed
away.
“So they came in
and tried it again. We had the same thing happen again, so we decided to wait
until fall [2007] and throw some annual ryegrass in there to get something
established, then come back in during the growing season, which started in
spring, and replant.”
County officials
are waiting for that grass to come up.
“In the meantime,
we’ve got a temporary watering system in case the weather doesn’t help us out,”
says Eicher. As of late spring, the weather was still rather
dry.
Ferndale Preserve
sits atop a ridge. The parking lot elevation is about 90 feet above sea level.
From there, the land slopes up to the highest point east toward Lake Apopka,
where there is an elevation change of about 165 feet, offering the scenic
vistas. The property then drops down to about 65 to 70 feet at Lake
Apopka.
“The parking lot
itself is on the back side of the hill,” says Eicher. Therefore, stormwater
concerns are not affiliated with runoff, but rather, potential flooding issues
in the parking area.
The Drivable Grass
installation went smoothly, Eicher notes. “Basically, it was getting the parking
lot graded to where we wanted, putting down the base material that was required
for the Drivable Grass, and mowing it,” he says. “It really wasn’t that
difficult.”
The Drivable Grass
mats installed measure 2 feet by 4 feet and weigh about 95 pounds apiece. Soil
Retention has since switched to a 2-foot-square mat, primarily because of the
weight, Eicher notes.
Eicher describes
the appearance and function of the mats as such: “If you take a cupcake tin and
turn it upside down, and in between the areas of the raised portion of the
cupcake tin, you’ve got holes—that’s where the water seeps
through.”
Drivable Grass
allows contaminants, such as vehicle drippings, to filter through the aggregates
installed below the product.
The grass grows
in-between what are called “muffins.”
“You put organic
material around the raised portion—the ‘muffin’—and that also helps grass grow
and gives it something else to grow into,” says Eicher.
This option was
selected for the lot based on testing that Soil Retention had performed by
driving fire trucks on the product, says Eicher.
“We know with the
equestrian trails, people are going to be pulling in with larger-than-normal
trucks, pulling trailers with horses,” he says. “We had the added weight there
that we normally don’t see in our parks, and we wanted to do something without
creating huge retention ponds.”
The park features
a few small retention ponds, but Eicher says they exist primarily to help
collect some of the runoff from the concrete driveway; Drivable Grass is favored
because it helps to create a pervious area for stormwater.
“This was the only
option that really made sense,” says Eicher. “The area getting into the park is
relatively soft sand, and if we did anything other than asphalt, people would be
getting stuck and there would be problems. We contemplated just having grass,
but that wouldn’t hold up, especially in the soft sand.”
Eicher notes that
Ferndale Preserve may ultimately not have enough parking spaces and the county
may have to purchase adjacent lots.
This is the first
time the county has used Drivable Grass. The project stayed within budget, and
the product has proven to be an appropriate benchmark for future consideration,
Eicher says.
Other than having
to cut the grass after it grows, the Drivable Grass requires no other
maintenance, says Eicher.
“It should give us
the look for a place that’s called a preserve,” he says. “We think it’s going to
be beautiful.”