Abstract: At approximately 1:30 p.m. on Tuesday July 23, 2002, Employees #1, 2, 3, and 4, all construction/maintenance workers, were lining a section of a 4-ft to 5-ft deep cement irrigation canal that had been drained of water, with a product called Dura Form (polyurethane-elastomer/geotextile composite). The Dura Form was being tested to determine how well it worked to prevent the loss of water. The composite material was made from two rolls of material, an absorbent polyester cloth and a porous polypropylene material. The materials were brought together by rollers and pulled through a puddle of polyurethane elastomeric. The cloth was thoroughly impregnated with resin, then cut and laid across half of the canals' with, and a second sheet covers the other half. The sheets overlapped one another. The material was then smoothed using a paint roller to seal the seams. The resin acted as an adhesive, causing the liner to stick to the sides of the canal. All four employees were working at a moderate to heavy work rate in the full sun in temperatures of 104 degrees Fahrenheit, while wearing street clothes under their Tyvek suits. None of the employees were provided adequate rest breaks and proper amounts of liquids to hydrate their bodies. Employee #1 was hospitalized and treated for heat exhaustion and an inflamed pancreas due to heat stress. Employees #2 and #3 were taken to the hospital and treated for heat exhaustion. Employee #4 was taken to the hospital and was treated for dehydration.