The largest project ever undertaken to measure the pulse of this nation's environment is taking shape. More than 250 employees from the National Ecological Observatory Network (NEON) have embarked on a project to create an observatory that will study, for the next 30 years, the impacts of climate change, land use change, and invasive species on the ecology at 106 sites across the United States.
Funded by the National Science Foundation, NEON will gather and synthesize data collected from these sites, which have been strategically selected to represent different regions of vegetation, landforms, climate, and ecosystems. Thousands of sensors affixed to towers and located in the soil and nearby streams will collect data including temperature, precipitation, solar radiation, air pressure, humidity, wind speed and direction, nutrient quantity, and greenhouse gases.
The data, which will be uploaded to an information management system, will then be available online to the public. Obtaining this kind of data over a long-term period is critical to improving ecological forecast models. It also will enable a virtual network of researchers and environmental managers to collaborate, coordinate research, and address ecological challenges at regional, national, and continental scales by providing comparable information across sites and regions.
NEON and international architecture/engineering firm LEO A DALY, which is providing civil design, engineering, site analysis, and coordination of all survey and geotechnical design services, have been collaborating since 2007 to build the massive network. Their biggest challenge is designing and constructing the infrastructure without disturbing the ecology.
The project is being built under unusually strict guidelines – each tower must cause little-to-no impact on its surrounding ecosystem, and the infrastructure must last the duration of the study without experiencing measurable change. Some sites are permanent, designed to collect data for 30-plus years, while other sites stay in place for five to seven years before being relocated.
Scientists originally envisioned small, lightweight towers built using shovels and picks. NEON sites, however, feature much larger and heavier towers because of the instrumentation they hold and safety concerns for those working on the towers. After several rounds of discussion, scientists and engineers reached an important compromise – the largest piece of equipment to be used on each site would be a Bobcat-like compact tractor. All aspects of each site design were based on this agreement and requirements were developed. They included:
- Access paths must not exceed 7 feet in width during construction and no wider than 4 feet for site operations.
- Each tower foundation can extend only 2 feet beyond the edge of the tower. Tower foundations must be less than 8 feet by 8 feet, a challenge because some towers are more than 200 feet tall.
- Each instrument hut foundation can extend only 3 feet beyond the edge of the hut.
- Excess material must be packaged and carefully removed from the site without disturbing the ground.
Every site goes from design drawings (created by LEO A DALY engineers) to post-construction checks. While each site offers unique challenges, this is the general process:
- Site work is conducted with a careful layout of access routes. Every tree's location is surveyed so that access paths and power runs can be designed around them.
- Construction documents are reviewed by NEON scientists, civil engineers, and facilities teams at different stages of completion.
- Drawings go out to bid; contractors engage in Q&A with NEON.
- A contractor is selected, followed by a preconstruction meeting that requires the contractor to provide the means and methods that will be used to meet the strict disturbance guidelines.
- A pre-vegetation survey is completed prior to the arrival of construction crews, providing an ecosystem baseline.
- Construction begins with boundary delineation. Once everything is marked, scientists visit the site for review and approval before construction activities begin. Changes are made, if necessary.
A NEON field supervisor is present during each day of construction. The supervisor ensures the work is performed in accordance with the drawings and the approved construction limits. Many challenges impact the process, including the restriction on machinery, remote conditions, lack of electricity, below-grade obstacles, site accessibility, and cost. Despite these challenges, 23 sites – 14 terrestrial and nine aquatic – have been built so far. The entire project is slated for completion in 2017.
Elizabeth Hunter, Basant Kumar Satpathy, Jay Srinivasan, and Aaron Filipi are with LEO A DALY. Christian Thompson is interim assistant director, Facilities and Civil Construction, with NEON Inc. (www.neoninc.org).