Electrical Subcontractor Interstate Electrical Services

The 6-MW ground-mount photovoltaic solar array is located on the 50-acre Shaffer landfill site, a former industrial complex and rail yard that once contained high amounts of hazardous materials. The project’s location and tight schedule required several advance planning considerations.

The design called for a ballasted panel system, so the U.S. Environmental Protection Agency expressed concern about preserving the landfill cap’s integrity and the stability of its 20-degree slopes. Specification of lightweight materials and low-ground weight equipment was necessary to address those concerns.

Much of the construction needed to take place during winter with heavy snows threatening to cause delays from January to May. To maintain construction progress, build access roads and perform installations, the project team rented a modified snowcat from a nearby ski lodge to keep the site clear and help maneuver components into position.

Assembly of the solar panel racking was performed around the clock in a local warehouse, allowing that part of the project to proceed independently of weather conditions. A customized transport structure protected completed panels as they were shipped to the landfill for installation.

Interconnection of the panels presented a major safety challenge during the powering up phase. The project team rigorously checked and verified the system as well as potential shock and trip hazards prior to startup. The team also developed a fire safety program that provided information on photovoltaic systems so that informed decisions could be made to ensure safe operations.

Another safety challenge involved the slope and the style of panel settings. The panels were set four at a time on panelization beams, a different arrangement than standard one-panel mounts.

The Shaffer Landfill Solar site is a revenue generating facility for the client. Capital Dynamics sells the power generated from the solar panels to the town of Billerica. Now operational, the landfill solar energy system has reduced electric bills for Billerica’s residents and businesses by 10%. As a dividend, the town gained $3 million in guaranteed tax revenue, thanks to reductions in energy generation costs.