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02-01-21 | Feature

Maintaining Sustainability in Unmaintained Landscapes

Courtney Campbell Causeway
by Jonathan H. Toner, ASLA, ISA, Terra Tectonics design group, Inc.

The Courtney Campbell Causeway in West Central, Florida, connects the city of Clearwater in Pinellas County to the City of Tampa in Hillsborough County and is the northernmost bridge across Old Tampa Bay. Landscape Architect firm, Terra Tectonics, was chosen to design the landscape for a transportation project that would connect the bridge and causeway to a nearby expressway and state road. Most of the Florida friendly-sustainable landscape was designated to be unmaintained. Therefore, the landscape selections had to be chosen for their durability and ability to survive the first three years of weed stage, before the intended plants took over and settled in. The environment is subjected to salt spray during the winter and spring storm events and all plantings had to have some sort of salt tolerance as well.
The Courtney Campbell Causeway in West Central, Florida, connects the city of Clearwater in Pinellas County to the City of Tampa in Hillsborough County and is the northernmost bridge across Old Tampa Bay. Landscape Architect firm, Terra Tectonics, was chosen to design the landscape for a transportation project that would connect the bridge and causeway to a nearby expressway and state road. Most of the Florida friendly-sustainable landscape was designated to be unmaintained. Therefore, the landscape selections had to be chosen for their durability and ability to survive the first three years of weed stage, before the intended plants took over and settled in. The environment is subjected to salt spray during the winter and spring storm events and all plantings had to have some sort of salt tolerance as well.
The plantings were chosen to provide a variety of looks, but importantly, Palms were selected as this is an important tourist area during winter months. Sea Grape and Muhly grass plantings are also seen here at the frontage road along the causeway at an underpass.
A low maintenance plant palette that would be self-sustainable and resistant to the urban conditions in the area was selected and included flowering trees such as crape myrtle and indigenous coniferous trees like southern slash pine. Bald cypress trees were planted in the infield areas of the roadway interchange at a detention pond due to their tolerance to salt and resistance to drought and wind.

The Tampa Airport Interchange in Hillsborough County, Florida, has been 16 years in the making for Landscape Architect firm Terra Tectonics, from design concepts to final construction, and now eight years after installation.

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This Florida Department of Transportation (FDOT) project is a link between the communities of Pinellas County and Hillsborough County, right under the runways of Tampa International Airport, in the City of Tampa, Florida. It connects the Courtney Campbell Causeway Bridge with the Veterans Expressway to the north and I- 275 to the south. The project was a multi-level road widening and additional lanes linkage.

The landscape architectural project has two main components, the salt-tolerant causeway plantings along Tampa Bay and the interior roadway streetscape within the medians. The plantings along the seawall portion had to be not only salt tolerant but were selected to be a natural buffer between the roadway facility and the adjacent residential area. The plantings in the interior portions were required to be placed to allow for roadway visibility not only at the time of planting but throughout the lifespan of the plants. This was taken care of by proper setbacks and plant species at the right locations that would not grow out into the roadway areas. Understory plantings of saw palmetto (SERENOA repens) was utilized in large areas due to its dense growth habit, shading out weeds and for drought and pollution tolerance. Live oaks (QUERCUS virginiana) were also used frequently as well as sabal palms (SABAL palmetto). These are all native plantings and very durable and sustainable for this type of urban design environment.

Planting design was developed to include an irrigation system designed to synchronize with the City of Tampa Parks department's radio-controlled irrigation system. All of the proposed plantings are designed to be irrigated. However, only a small portion of the plantings are actually maintained and those are by a private entity for an entrance to a hotel and facilities. The remaining landscape receives zero maintenance and was designed for that usability. Knowing that it was to be non-maintained, the plant selection and spacings were developed to allow for the shading out of undesirable weeds that are inevitable after a new landscape is planted. It was thought of as a 5-year landscape maturity project. It has been 8 years since construction completion and is now thriving. As the plantings grow, the understory plants were selected for shade tolerance as well as less soil moisture due to the tree uptake of that moisture from tree roots.

The landscape was designed to be sustainable by use of appropriate plant materials for the conditions of the site. The site is in west central Florida in the Tampa Bay area. Salt tolerance was an important consideration due to the proximity to Tampa Bay and occasional winter storms which will push salt spray across the Pinellas Peninsula well inshore. This has occurred a few times since the project was installed with one memorable spring "no-name storm" which burned the budding leaves off the Cypress trees all along the west side. The other fact for sustainability is the primary use of native plantings that would naturally occur in the location. These are both salt tolerant as well as wind resistant and drought resistant. Even though the plantings are drought resistant there is an irrigation system to supplement natural rainfall. This is an artificial environment, especially on areas of 2:1 roadway slopes and spaced between lanes of roadway, and some that are used for swales. The irrigation system was designed to establish plantings for the first three years.

Sustainability comes down to knowing the local environment, climate soil types and then what the project type is, such as this with high temperatures and pollution due to the roadway environment. Mimicking nature and how the original site might have been is also a keep to sustainable planting design. Trying to place back what might have been in the region, in a more architectural manner, will generally lead to success and sustainability.

As seen in LASN magazine, January 2021.

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