Some of the benefits of nonmetallic junction boxes over metal boxes are that because they don't corrode when out in the elements they can last longer; their non-conductive nature eliminates any potential shock hazard; and the PVC material offers less resistance than metal in cutting cable holes for conduit entrance.
The Immokolee Wastewater Treatment Plant near Naples, Fla., took advantage of these attributes recently with nonmetallic junction boxes manufactured by Midwest Plastic Fabricators (MPF), Aurora, Ohio. As you can see in this photo, the company's 20-inch × 18-inch × 8-inch PVC junction box fits as a water-tight liner into the traffic-rated concrete hand-hole and provides access for wire pulling and connection for the underground conduit system and remote service equipment. The shoebox-style lid has a gasket and is attached with stainless steel fasteners.
These products were designed by applying CNC technology and PVC material to make enclosures, cabinets and boxes for conduit and control systems. A complete size range up to 48-inch is available. The box has been tested and conforms to UL and NEMA 4X requirements. MPF sells these junction boxes and other nonmetallic products through a network of 28 manufacturer representative firms located throughout the United States to more than 2,100 electrical distributors.