A 138-foot tall NEON tower at the Jones Ecological Research Center in Georgia is typical of the towers being constructed to help researchers monitor the conditions of the ecology in dozens of locations across the United States. Skip Sowards/NEON
A project to develop comprehensive data about climate, biodiversity, and land use changes involves constructing identical stations in 96 vastly differing sites.
October 15, 2013—When complete, the National Ecological Observatory Network (NEON) will include 106 observational stations in 96 disparate sites across the United States, including the remote, permafrost slopes of Healy, Alaska, the lava formations in Hawaii, and the soft, saturated soils at the Guanica Forest in Puerto Rico.
Engineers working on the project face a tall challenge: disturb virtually nothing beyond the station’s small footprint during construction and ensure that all of the stations are almost identical.
NEON is an ambitious 30-year program to collect a vast array of data concerning climate change, land use changes, biodiversity, and population dynamics. Taken together, this data will present a comprehensive picture of how the climate is changing at the sites over decades and what impacts those changes are having on ecology.
Sixty of the sites are on land; 36 sites are aquatic. Of the 60 land sites, 40 of those are being designed to be relocated several times during the 30-year span of the project after a number of years that has yet to be determined. Whenever possible, the stations are wired into the electrical grid—as many as 5 mi away—and employ wired communications links for data transmission.
Because of the sensitive measurements to be taken during the project, it is extremely important to scientists at NEON that the sites not be disturbed during construction and that the stations are placed so that they achieve accurate measurements. The firm Leo A Daly, in Omaha, Nebraska, is providing site design services.
“They want to go into areas that are mostly remote,” says Basant Satpathy, P.E., S.E., an associate and senior structural project engineer for Leo A Daly. “They are undisturbed, and they can preserve the environment while they are monitoring the quality of air, water, soil, and [the] chemical composition of all the components that go into it.
“The sites have been very different from one end to the other,” he adds. “When we go to northern Alaska, there has been permafrost—frozen ground as far down as you can go. Other extremes have been on top of the lava sediments they have in Hawaii. Other areas are very unstable, as in Puerto Rico, where they have areas that literally saturate with rain and become very unstable.”
Micro-construction equipment helps the team access the site,
which must remain as undisturbed as possible. Access paths to
the site can be 8 ft wide during construction but must be no more
than 4 ft wide afterward. Skip Sowards/NEON
The team has little leeway to alter the proposed site or the station layout. Their goal is to never remove a tree to gain access to the remote sites. “I go to every site with a survey crew and a geotechnical crew,” explains Elizabeth A. Hunter, P.E., AICP, LEED-AP BD+C, the NEON project manager for Leo A Daly. “I help them figure out how we can get in there without damaging anything and do the drilling we need to do to get the report that we need. There are some places where we end up having to haul in everything by hand. We will hand auger or we’ll do seismic testing or ground-penetrating radar to help verify the results of the tests we did a couple hundred feet away.”
Each site requires a steel tower, a small instrument hut, and several smaller sensors and instruments. The towers are designed to extend 32.8 ft above the local tree canopy as it is projected to be in 30 years; the tallest will be 300 ft. The towers are designed by Paul J. Ford and Company, of Columbus, Ohio.
The towers are 6.5 ft by 6.5 ft at their tops with a foundation that cannot exceed 8 ft by 8 ft, and result in no exposed construction materials. The 11 ft long tower segments are brought to each site via a narrow access paths and assembled in place, according to Christian Thompson, P.E., A.M.ASCE, NEON’s assistant director of facilities and civil construction.
“It’s shipped in pieces and basically stick-built in the field,” he says. “We don’t have the freedom and room to build these things and then ship them in sections and stack them with a crane,” Thompson says. “At the end of the day, the biggest challenge with this project is that we’re trying to get in and get out with the least amount of damage possible, so we are not compromising the future science that will be taking place.”
NEON extensively vetted a list of contractors to find those able to meet the strict requirements. Access paths to the remote sites are eventually set at 4 ft wide, but during construction can be as wide as 8 ft, Thompson says.
“They get no more than 8 feet across to do all of this work—installing micropiles, if need be, excavating foundations, bringing in concrete. You name it; they have an 8-foot working area—at most—to make this happen,” Thompson says.
NEON has completed 15 tower sites, with sensors and instruments installed at approximately 4 of those, Thompson says. The project is currently working on as many as five sites concurrently, and plans are to ramp that figure up to seven in 2014. A field supervisor at each site verifies that the exacting specifications are met.
The projects involve essentially the same setups replicated 60 times, Thompson says. “But each one is unique in its own ways: the foundation and designs that have to be implemented, the means and methods on how we build it.
“It’s a challenge,” he says, “but it’s a fun challenge.”