Work has to go on and repairs have to be made, even when subfreezing temperatures make things nasty for construction and public works crews. For rental centers, this is an opportunity to supply a variety of winter tools and equipment. You can actually extend the working season for many construction projects, if you have the right equipment.

Relatively new on the construction scene are portable machines designed specifically to thaw frozen ground. Your best prospects: concrete contractors, utility contractors and public works departments, but also look for plumbers, parks departments, building contractors, sign companies and cemeteries.

Ground heater components include a portable generator that powers a boiler that heats propylene glycol heat-transfer fluid. The fluid, heated to a temperature of about 180 degrees Fahrenheit, is circulated through hoses laid on the ground in loops placed about 2 feet apart, or in other configurations to conform to different job sites. Heat radiated from the hoses thaws the ground.

Depending on the size of the unit used and other factors, as much as 6,000 feet of ground can be thawed to a depth of 24 inches in 48 hours, says Sue Meekhof, Ground Heaters, Spring Lake, Mich. Twelve inches more can be thawed in another 24 hours. Thawing times vary with ground temperature, moisture content of the frozen ground, air temperature, wind and the efficiency of the insulation cover.

For faster, deeper thaws in concentrated areas, heating rods are inserted in holes drilled in the ground. Fluid circulates to the rods and back through the system.

"Ground heaters are especially applicable for concrete work because temperature is critical for proper curing of concrete," says Meekhof.

Ground heaters can thaw surfaces and preheat forms before concrete is poured. When concrete is spread over heating loops, warming continues during curing.

Excavating contractors can extend the work season by renting machines outfitted for cold-weather work.

Special buckets and teeth for digging in extremely hard and frozen ground are available for backhoes and mini-excavators, says Jim Mitchell of John Deere Construction Equipment, Moline, Ill.

Snow removal blades made of carbon, and heat-treated and tempered steel and blades with carbide insert bits last longer than conventional blades. Scarifier blades with rotating carbide bits cut grooves in ice-packed roads.

For trenchers, heavy-duty digging chain and special teeth, including carbide bit inserts, effectively cut through frozen ground, says Marty Piel, Charles Machine Works (Ditch Witch), Perry, Okla. Frost equipment can replace standard teeth and chain for cold-weather work.

Telecommunications companies, electrical and natural gas utilities, utility contractors, municipal street and utility departments, and road building contractors frequently do excavating and trenching in cold weather.

Trenching through frozen ground is slower, but special teeth and chain make trenching possible throughout the winter. Trenchers equipped with frost chain and teeth bring higher rental rates.

Mike Hubbard, Vermeer Manufacturing Co., Pella, Iowa, says larger, more powerful trenchers are required to cut through frost. Easy-start options, including dual batteries, are useful for machines rented in cold weather, he adds.

Tents to serve as temporary shelters, portable heaters and mobile lighting equipment are other items needed for winter construction and maintenance work.

Marc Messner, president of Horizontal Drilling Technologies, a company specializing in horizontal directional drilling for utility and environmental markets, says when he has a crew working in extreme cold, he rents a tent to place over the drill frame and rents heaters to warm the crew and equipment.