Construction materials maker CalPortland Co. announced it has temporarily laid off 94 of the 130 workers at its Colton Cement Plant, citing a steep drop in demand for its products amid a near standstill in new Inland building.

"Cement shipments are off 60 percent from the pre-recession demand," CalPortland President and CEO James Repman said by phone from the company's Glendora headquarters.

The Colton Cement Plant opened in 1891 and is touted by CalPortland as the oldest operating cement plant west of the Rocky Mountains. Officials estimate it pumps $183 million into the local economy during full operations.

At its peak, it produced more than 800,000 tons of cement annually.

CalPortland's cement customers are spread throughout California, Arizona and Nevada. Its primary clientele are makers of concrete, used in the construction of buildings, roads, bridges and other structures.

Affected workers were informed Friday that they will be paid through the end of January. CalPortland is providing outplacement assistance and working with local organizations to help the workers meet family expenses.

Workers who were laid off are those who operate the Colton plant's kilns, used to produce cement, a powdered material created by heating limestone and clay. The cement is used to make concrete.

Kilns at the Colton plant are being shut down until economic conditions improve, the company said.

Repman said about 35 other employees will remain in their jobs at Colton, doing work including packaging and transporting cement made with materials at the company's plant near Palmdale.

"We still have to serve our customers," Repman said.

In a CalPortland statement, a spokesman for the United Steel Workers union, which represents the workers, said the Colton plant has a long history, and its work force "is seen as family."

"Many of our employees are second- and third-generation, sometimes working at the same time as their grandfather, father, brother, sister and/or spouse," said union representative Dennis Carlson, a Colton plant worker whose father also worked there for 35 years.

"These are excellent manufacturing jobs with high wages and excellent benefits," Carlson said. "These are jobs that have been recommended to friends, neighbors and children for more than 118 years."

Jobs at the plant pay hourly wages averaging $21.50 to $22, and all employees have full medical benefits, according to CalPortland.

The Colton layoffs are just the latest among thousands of Inland construction jobs lost in the recession, a trend that first hit residential building in the second half of 2007 as demand for housing plummeted. That has since led to a sharp downturn in new commercial projects aimed at serving those new households.

Data released last week by the California Employment Development Department put the Inland region's construction-related work force at 69,200 as of October. That was a drop of 18.7 percent -- 15,900 jobs -- from October 2008.

Mark Knorringa, CEO of the Riverside County Chapter of the Southern California Building Industry Association, said his organization has several members dealing with drops in demand for concrete, cement and other supplies. Those companies have lost revenues and shed workers as projects have dried up.

While companies doing government infrastructure projects are holding up relatively well, housing construction in the Inland area is off 90 percent from 2006-07 levels, before the recession hit.

Repman said the Colton layoffs will not affect the company's non-cement operations in the Inland area. The company has plants in San Bernardino, Ontario and Thousand Palms, producing materials such as gravel and ready-mix concrete.