system accomplished
System Accomplished focuses on unique design or installation problems and how they were solved.
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BoRRego SolAR
This 2.3-megawatt photovoltaic system
sits on a landfill site in Easthampton, Mass.
Walk Softly for Landfill PV
50 March/April 2012 SOLAR TODAY solartoday.org
When Joe Harrison of Borrego Solar took on the job of building a 2.3-megawatt photovoltaic (PV)
system on a landfill site in Easthampton, Mass.,
he had to figure out how to move many tons
of concrete without punching through the
40-mm (1.6-inch) rubber membrane covering
the decomposed garbage.
The membrane prevents uncontrolled out-
gassing of flammable (and carbon-intensive)
methane. The 12-acre site is too small for eco-
nomical harvesting of the methane for fuel, so
it uses a typical passive venting system. Instead
of footings, the PV array would sit on non-pen-
etrating concrete bumpers weighing 5,000 lb
( 2,273 kg) each. Protected only by 12 inches
( 30 cm) of topsoil, the rubber was rated at 10 psi
( 7 newtons/cm2). To carry the weight of heavy
trucks, Harrison’s crew built a reinforced road
down the middle of the site, using a geosyn-
thetic membrane covered with dirt. From there
the bumpers were moved into place using a
loader with rubberized tracks, giving an unladen
ground pressure of about 4 psi ( 3 N/cm2).
The PV array is bolted to non-penetrating
concrete bumpers — weighing 5,000 lb
( 2,273 kg) each — to avoid breaking through
a 40-mm (1.6-inch) rubber membrane
covering the decomposed garbage.
