Contacts
Advertisement










Advertisement

Advertisement

Advertisement

Advertisement

Advertisement

Advertisement

Advertisement

Advertisement

Advertisement

Advertisement

Highway Artscape: The Interstate 5 / SR-54 Project

By Tom Ham, Caltrans District Landscape Architect; Project Designer, Catalina Flores




The design team, after careful considerable, elected to use highway art to cover inert materials and stabilize soil and slopes, while presenting attractive, decorative materials—colored gravel, recycled glass, decomposed granite, cobbles and sand.
virtuallawn.gif

A unique challenge of landscape architecture is the design of large vehicular expanses, such as modern freeways and accompanying public roadsides. These vehicular spaces are different of course from more static environments. Drivers get only a glimpse of these landscapes as they quickly move past them.






Before renovation the slopes near the highway were eroded and denuded of vegetation, the result of the soil’s high salinity.


Caltrans landscape architects have evolved design themes for these spaces. Initially, it was the use of native plant materials—trees, shrubs and herbaceous ground covers of the 1950s (yes, lots of ice plants), to a mix of drought-tolerant native species in the 1970. Then came the popular xeriscape era of the late 1970s and ’80s when reclaimed water use, drip irrigation and water management became more and more a necessity of highway planting projects statewide.

Other strategies, such as mulching, usually with organic bark or wood chips, were also part of reducing water consumption. The mulches were effective but needed reapplication every few years.






The Interstate 5 and Route 54 interchange in Southern California is traveled by millions every month, I-5 being one of the main freeways to Mexico, a few miles to the south, and SR 54 a major connector to I-805 to the east. The interchange is adjacent to the Chula Vista Nature Center, featuring interpretive displays, native plant and animal species of the adjacent Sweetwater Marsh Wildlife Refuge and the Pacific Coast ocean community. These elements inspired the project’s theme.


Soil amendments along roadsides were usually not practical, because of the high cost of amending these large planting areas. Seeding of native species have always been used with great success, but these types of roadsides are not always practical because of the potential for roadside fires when these areas become very dry. Then there is the ever-present issue of homeless encampments and security of adjacent properties prone to unmanaged wildscapes.

More recently, as the increasing cost of maintenance, water and a highway planting budget competing with highway safety projects (safety is always a higher priority), there was a need for Caltrans landscape architects to design affordable, attractive, context-sensitive roadsides with low water requirements and low maintenance requirements.






The slopes were sprayed with filtered fabric and gravel poured into the aluminum staked forms. The aluminum edging is used to separate areas and the filter fabric allows water filtration and abates weed.


The Interstate 5 and State Route 54 interchange in Southern California is traveled by millions every month, I-5 being one of the main freeways to Mexico, a few miles to the south, and SR 54 being a major arterial connector to I-805 to the east. This major interchange is adjacent to the Chula Vista Nature Center, which features interpretive displays featuring native plant and animal species of the adjacent Sweetwater Marsh Wildlife Refuge and the Pacific Coast ocean community.

This interchange was previously planted with salt-tolerant trees, shrubs and shrub ground covers. Still, this landscape died from the high soil salinity from the adjacent Sweetwater Marsh.






All rock material—gravels, decomposed granite, cobbles, and sand—was quarried from Utah and Arizona. No artificial color was added to the rock.


In 2006, an alternate design—”Ecotheme”—more in keeping with the adjacent Sweetwater Coastal Marsh, was implemented. Inert materials like decorative rock and organic mulches, recycled colored glass from bottles, decomposed granite and sand were placed over the saline soil areas. Areas of less salinity were planted with low maintenance native species.

Faced with eroded slopes and unsightly bare areas, the design team, after considerable investigation, decided to use the concept of highway art to improve conditions. The highway art would provide a cover for inert materials, stabilize soil and slopes, while presenting attractive, decorative materials—colored gravel, recycled glass, decomposed granite, cobbles and sand. Caltrans landscape architects partnered with the nearby Chula Vista Nature Center to select the appropriate sea shells, marsh birds and plant art shapes to depict in giant scale at the interchange using the colored decorative rocks and recycled glass. As the art was to be done in very large scale, the designers had to do actual-size art mock-ups on the slopes and view them from the perspective of motorists or trolley riders “in the field.” The placement of these flat artistic shapes on freeway slopes required exaggerating the shapes and proportions to read properly from a moving vehicle.













































Preliminary design concepts depicting different forms of coastal life such as white egrets, sea snails, shells, and star fish. These shapes were designed on a grid formed by squared meter units, first drawn to scale, then laid out on site.


The colored rock aggregates, 1/2 to 1.5 inch diameter, were dry spread approximately four inch in depth over a filter fabric weed barrier secured with metal stakes. A metal border with metal stakes were used to separate each of the colored rock shapes. (Don’t use aluminum, as vandals will stolen it.) Glass mirror shards were sprinkled over the “rock beach,” which gives the look of a shimmering tide washing over a tropical island with real palms growing in plastic lined planting pockets (to keep the salt out).

With any luck, this highway planting should last 20 to 30 years with minimal touch-ups and almost no watering required, except for the islands.






Planting berms, created by excavating onsite soils, were installed on the top flat part of slopes, covered with plastic liners, then topped with imported soil. Palms were planted in the top soil of the berms with perforated plastic piping installed for drainage.



      Give us your feedback.


Comments

April 23, 2014, 11:16 am EST

Website problems, report a bug.
Copyright © 2014 Landscape Communications Inc.